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Showing 1 - 200 of 3120 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 8)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 26, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 90, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 30, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 378, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 26, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 237, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
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Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
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Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 5)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 7)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 140, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 27, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 4)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 9, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 23, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 26, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 6, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 4)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 13)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 26, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 9, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 12)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 12)
Advances in Digestive Medicine     Open Access   (Followers: 7)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 6)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Ecological Research     Full-text available via subscription   (Followers: 47, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 9)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 46, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 52, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 17, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 27)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 10)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 23)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 9, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 7)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 371, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 9, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 31, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 16)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 45, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 338, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 433, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 42, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 56, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 9, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 49, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 48, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 48, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 42, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 9, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 31, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 45, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 207, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 61, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 24, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 26, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 36, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 60, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 14)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 36, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 173, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 12)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 176, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)

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Journal Cover Advances in Water Resources
  [SJR: 2.408]   [H-I: 94]   [45 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0309-1708
   Published by Elsevier Homepage  [3123 journals]
  • Global estimation of long-term persistence in annual river runoff
    • Authors: Y. Markonis; Y. Moustakis; C. Nasika; P. Sychova; P. Dimitriadis; M. Hanel; P. Máca; S.M. Papalexiou
      Pages: 1 - 12
      Abstract: Publication date: March 2018
      Source:Advances in Water Resources, Volume 113
      Author(s): Y. Markonis, Y. Moustakis, C. Nasika, P. Sychova, P. Dimitriadis, M. Hanel, P. Máca, S.M. Papalexiou
      Long-term persistence (LTP) of annual river runoff is a topic of ongoing hydrological research, due to its implications to water resources management. Here, we estimate its strength, measured by the Hurst coefficient H, in 696 annual, globally distributed, streamflow records with at least 80 years of data. We use three estimation methods (maximum likelihood estimator, Whittle estimator and least squares variance) resulting in similar mean values of H close to 0.65. Subsequently, we explore potential factors influencing H by two linear (Spearman's rank correlation, multiple linear regression) and two non-linear (self-organizing maps, random forests) techniques. Catchment area is found to be crucial for medium to larger watersheds, while climatic controls, such as aridity index, have higher impact to smaller ones. Our findings indicate that long-term persistence is weaker than found in other studies, suggesting that enhanced LTP is encountered in large-catchment rivers, were the effect of spatial aggregation is more intense. However, we also show that the estimated values of H can be reproduced by a short-term persistence stochastic model such as an auto-regressive AR(1) process. A direct consequence is that some of the most common methods for the estimation of H coefficient, might not be suitable for discriminating short- and long-term persistence even in long observational records.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.003
      Issue No: Vol. 113 (2018)
  • Emulsification kinetics during quasi-miscible flow in dead-end pores
    • Authors: M. Broens; E. Unsal
      Pages: 13 - 22
      Abstract: Publication date: March 2018
      Source:Advances in Water Resources, Volume 113
      Author(s): M. Broens, E. Unsal
      Microemulsions have found applications as carriers for the transport of solutes through various porous media. They are commonly pre-prepared in bulk form, and then injected into the medium. The preparation is done by actively mixing the surfactant, water and oil, and then allowing the mixture to stagnate until equilibrium is reached. The resulting microemulsion characteristics of the surfactant/oil/water system are studied at equilibrium conditions, and perfect mixing is assumed. But in applications like subsurface remediation and enhanced oil recovery, microemulsion formation may occur in the pore space. Surfactant solutions are injected into the ground to solubilize and/or mobilize the non-aqueous phase liquids (NAPLs) by in-situ emulsification. Flow dynamics and emulsification kinetics are coupled, which also contributes to in-situ mixing. In this study, we investigated the nature of such coupling for a quasi-miscible fluid system in a conductive channel with dead-end extensions. A microfluidic setup was used, where an aqueous solution of an anionic, internal olefin sulfonate 20–24 (IOS) surfactant was injected into n-decane saturated glass micromodel. The oil phase was coloured using a solvatochromatic dye allowing for direct visualization of the aqueous and oil phases as well as their microemulsions under fluorescent light. Presence of both conductive and stagnant dead-end channels in a single pore system made it possible to isolate different transport mechanisms from each other but also allowed to study the transitions from one to the other. In the conductive channel, the surfactant was carried with flow, and emulsification was controlled by the localized flow dynamics. In the stagnant zones, the driving force of the mass transfer was driven by the chemical concentration gradient. Some of the equilibrium phase behaviour characteristics of the surfactant/oil/water system were recognisable during the quasi-miscible displacement. However, the equilibrium tests alone were not sufficient to predict the emulsification process under dynamic conditions.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.001
      Issue No: Vol. 113 (2018)
  • Effects of fracture surface roughness and shear displacement on
           geometrical and hydraulic properties of three-dimensional crossed rock
           fracture models
    • Authors: Na Huang; Richeng Liu; Yujing Jiang; Bo Li; Liyuan Yu
      Pages: 30 - 41
      Abstract: Publication date: March 2018
      Source:Advances in Water Resources, Volume 113
      Author(s): Na Huang, Richeng Liu, Yujing Jiang, Bo Li, Liyuan Yu
      While shear-flow behavior through fractured media has been so far studied at single fracture scale, a numerical analysis of the shear effect on the hydraulic response of 3D crossed fracture model is presented. The analysis was based on a series of crossed fracture models, in which the effects of fracture surface roughness and shear displacement were considered. The rough fracture surfaces were generated using the modified successive random additions (SRA) algorithm. The shear displacement was applied on one fracture, and at the same time another fracture shifted along with the upper and lower surfaces of the sheared fracture. The simulation results reveal the development and variation of preferential flow paths through the model during the shear, accompanied by the change of the flow rate ratios between two flow planes at the outlet boundary. The average contact area accounts for approximately 5–27% of the fracture planes during shear, but the actual calculated flow area is about 38–55% of the fracture planes, which is much smaller than the noncontact area. The equivalent permeability will either increase or decrease as shear displacement increases from 0 to 4 mm, depending on the aperture distribution of intersection part between two fractures. When the shear displacement continuously increases by up to 20 mm, the equivalent permeability increases sharply first, and then keeps increasing with a lower gradient. The equivalent permeability of rough fractured model is about 26–80% of that calculated from the parallel plate model, and the equivalent permeability in the direction perpendicular to shear direction is approximately 1.31–3.67 times larger than that in the direction parallel to shear direction. These results can provide a fundamental understanding of fluid flow through crossed fracture model under shear.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.005
      Issue No: Vol. 113 (2018)
  • Predicting the impact of land management decisions on overland flow
           generation: Implications for cesium migration in forested Fukushima
    • Authors: Erica R. Siirila-Woodburn; Carl I. Steefel; Kenneth H. Williams; Jens T. Birkholzer
      Pages: 42 - 54
      Abstract: Publication date: Available online 9 January 2018
      Source:Advances in Water Resources
      Author(s): Erica R. Siirila-Woodburn, Carl I. Steefel, Kenneth H. Williams, Jens T. Birkholzer
      The effects of land use and land cover (LULC) change on environmental systems across the land surface's “critical zone” are highly uncertain, often making prediction and risk management decision difficult. In a series of numerical experiments with an integrated hydrologic model, overland flow generation is quantified for both present day and forest thinning scenarios. A typhoon storm event in a watershed near the Fukushima Dai-ichi Nuclear Power Plant is used as an example application in which the interplay between LULC change and overland flow generation is important given that sediment-bound radionuclides may cause secondary contamination via surface water transport. Results illustrate the nonlinearity of the integrated system spanning from the deep groundwater to the atmosphere, and provide quantitative tools when determining the tradeoffs of different risk-mitigation strategies.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.008
      Issue No: Vol. 113 (2018)
  • River banks and channel axis curvature: Effects on the longitudinal
           dispersion in alluvial rivers
    • Authors: Stefano Lanzoni; Amena Ferdousi; Nicoletta Tambroni
      Pages: 55 - 72
      Abstract: Publication date: March 2018
      Source:Advances in Water Resources, Volume 113
      Author(s): Stefano Lanzoni, Amena Ferdousi, Nicoletta Tambroni
      The fate and transport of soluble contaminants released in natural streams are strongly dependent on the spatial variations of the flow field and of the bed topography. These variations are essentially related to the presence of the channel banks and to the planform configuration of the channel. Large velocity gradients arise near to the channel banks, where the flow depth decreases to zero. Moreover, single thread alluvial rivers are seldom straight, and usually exhibit meandering planforms and a bed topography that deviates from the plane configuration. Channel axis curvature and movable bed deformations drive secondary helical currents which enhance both cross sectional velocity gradients and transverse mixing, thus crucially influencing longitudinal dispersion. The present contribution sets up a rational framework which, assuming mild sloping banks and taking advantage of the weakly meandering character often exhibited by natural streams, leads to an analytical estimate of the contribution to longitudinal dispersion associated with spatial non-uniformities of the flow field. The resulting relationship stems from a physics-based modeling of the flow in natural rivers, and expresses the bend averaged longitudinal dispersion coefficient as a function of the relevant hydraulic and morphologic parameters. The treatment of the problem is river specific, since it relies on an explicit spatial description, although linearized, of flow field that establishes in the investigated river. Comparison with field data available from tracer tests supports the robustness of the proposed framework, given also the complexity of the processes that affect dispersion dynamics in real streams.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.10.033
      Issue No: Vol. 113 (2018)
  • Long-term morphological developments of river channels separated by a
           longitudinal training wall
    • Authors: T.B. Le; A. Crosato; W.S.J. Uijttewaal
      Pages: 73 - 85
      Abstract: Publication date: Available online 9 January 2018
      Source:Advances in Water Resources
      Author(s): T.B. Le, A. Crosato, W.S.J. Uijttewaal
      Rivers have been trained for centuries by channel narrowing and straightening. This caused important damages to their ecosystems, particularly around the bank areas. We analyse here the possibility to train rivers in a new way by subdividing their channel in main and ecological channel with a longitudinal training wall. The effectiveness of longitudinal training walls in achieving this goal and their long-term effects on the river morphology have not been thoroughly investigated yet. In particular, studies that assess the stability of the two parallel channels separated by the training wall are still lacking. This work studies the long-term morphological developments of river channels subdivided by a longitudinal training wall in the presence of steady alternate bars. This type of bars, common in alluvial rivers, alters the flow field and the sediment transport direction and might affect the stability of the bifurcating system. The work comprises both laboratory experiments and numerical simulations (Delft3D). The results show that a system of parallel channels divided by a longitudinal training wall has the tendency to become unstable. An important factor is found to be the location of the upstream termination of the longitudinal wall with respect to a neighboring steady bar. The relative widths of the two parallel channels separated by the wall and variable discharge do not substantially change the final evolution of the system.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.007
      Issue No: Vol. 113 (2018)
  • On the stability of river bifurcations created by longitudinal training
           walls. Numerical investigation
    • Authors: T.B. Le; A. Crosato; E. Mosselman; W.S.J. Uijttewaal
      Pages: 112 - 125
      Abstract: Publication date: Available online 17 January 2018
      Source:Advances in Water Resources
      Author(s): T.B. Le, A. Crosato, E. Mosselman, W.S.J. Uijttewaal
      To maintain a navigable channel and improve high-flow conveyance, engineers have recently proposed constructing longitudinal training walls as an alternative to the traditional transverse groynes. However, previous work has shown that the system of parallel channels created by a longitudinal training wall might be unstable in rivers with alternate bars. Many questions remain unanswered, particularly whether a stable system can be obtained by carefully designing the bifurcation point. This work analyses the stability of the bifurcating system created by a thin longitudinal wall in sand-bed rivers with alternate bars or point bars. The methodology includes performing 102 numerical tests using the Delft3D code to reproduce an idealized low-land river, either straight or meandering. The results show that the system of parallel channels separated by a training wall may indeed become unstable. An important factor is found to be the location of the bifurcation point with respect to a neighboring bar or point bar. The same trends are observed for both constant and variable discharge, in straight and meandering channels. The results suggest that cyclic growth and decline of the bifurcating channels may arise as inherent system behavior, without the need of any additional external forcing. We explain this from changes in the relationship between sediment transport ratio and discharge ratio as the bifurcation evolves. This cyclic behavior can be regarded as a form of system stability and can be obtained by carefully placing the starting point of the longitudinal training wall, and thus the bifurcation point, near the top of a bar.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.012
      Issue No: Vol. 113 (2018)
  • Water and sediment temperature dynamics in shallow tidal environments: the
           role of the heat flux at the sediment-water interface
    • Authors: M. Pivato; L. Carniello; J. Gardner; S. Silvestri; M. Marani
      Pages: 126 - 140
      Abstract: Publication date: Available online 11 January 2018
      Source:Advances in Water Resources
      Author(s): M. Pivato, L. Carniello, J. Gardner, S. Silvestri, M. Marani
      In the present study, we investigate the energy flux at the sediment-water interface and the relevance of the heat exchanged between water and sediment for the water temperature dynamics in shallow coastal environments. Water and sediment temperature data collected in the Venice lagoon show that, in shallow, temperate lagoons, temperature is uniform within the water column, and enabled us to estimate the net heat flux at the sediment-water interface. We modeled this flux as the sum of a conductive component and of the solar radiation reaching the bottom, finding the latter being negligible. We developed a “point” model to describe the temperature dynamics of the sediment-water continuum driven by vertical energy transfer. We applied the model considering conditions characterized by negligible advection, obtaining satisfactory results. We found that the heat exchange between water and sediment is crucial for describing sediment temperature but plays a minor role on the water temperature.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.009
      Issue No: Vol. 113 (2018)
  • Suspended sediment assessment by combining sound attenuation and
           backscatter measurements – analytical method and experimental validation
    • Authors: Massimo Guerrero; Vittorio Di Federico
      Pages: 167 - 179
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Massimo Guerrero, Vittorio Di Federico
      The use of acoustic techniques has become common for estimating suspended sediment in water environments. An emitted beam propagates into water producing backscatter and attenuation, which depend on scattering particles concentration and size distribution. Unfortunately, the actual particles size distribution (PSD) may largely affect the accuracy of concentration quantification through the unknown coefficients of backscattering strength, ks 2 , and normalized attenuation, ζs . This issue was partially solved by applying the multi-frequency approach. Despite this possibility, a relevant scientific and practical question remains regarding the possibility of using acoustic methods to investigate poorly sorted sediment in the spectrum ranging from clay to fine sand. The aim of this study is to investigate the possibility of combining the measurement of sound attenuation and backscatter to determine ζs for the suspended particles and the corresponding concentration. The proposed method is moderately dependent from actual PSD, thus relaxing the need of frequent calibrations to account for changes in ks 2 and ζs coefficients. Laboratory tests were conducted under controlled conditions to validate this measurement technique. With respect to existing approaches, the developed method more accurately estimates the concentration of suspended particles ranging from clay to fine sand and, at the same time, gives an indication on their actual PSD.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.020
      Issue No: Vol. 113 (2018)
  • Anomalous Behaviors During Infiltration Into Heterogeneous Porous Media
    • Authors: F.D.A. Aarão Reis; D. Bolster; V.R. Voller
      Pages: 180 - 188
      Abstract: Publication date: Available online 11 January 2018
      Source:Advances in Water Resources
      Author(s): F.D.A. Aarão Reis, D. Bolster, V.R. Voller
      Flow and transport in heterogeneous porous media often exhibit anomalous behavior. A physical analog example is the uni-directional infiltration of a viscous liquid into a horizontal oriented Hele-Shaw cell containing through thickness flow obstacles; a system designed to mimic a gravel/sand medium with impervious inclusions. When there are no obstacles present or the obstacles form a multi-repeating pattern, the change of the length of infiltration F with time t tends to follow a Fickian like scaling, F ∼ t 1 2 . In the presence of obstacle fields laid out as Sierpinski carpet fractals, infiltration is anomalous, i.e., F ∼ tn, n ≠ 1/2. Here, we study infiltration into such Hele-Shaw cells. First we investigate infiltration into a square cell containing one fractal carpet and make the observation that it is possible to generate both sub (n < 1/2) and super (n > 1/2) diffusive behaviors within identical heterogeneity configurations. We show that this can be explained in terms of a scaling analysis developed from results of random-walk simulations in fractal obstacles; a result indicating that the nature of the domain boundary controls the exponent n of the resulting anomalous transport. Further, we investigate infiltration into a rectangular cell containing several repeats of a given Sierpinski carpet. At very early times, before the liquid encounters any obstacles, the infiltration is Fickian. When the liquid encounters the first (smallest scale) obstacle the infiltration sharply transitions to sub-diffusive. Subsequently, around the time where the liquid has sampled all of the heterogeneity length scales in the system, there is a rapid transition back to Fickian behavior. An explanation for this second transition is obtained by developing a simplified infiltration model based on the definition of a representative averaged hydraulic conductivity.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.010
      Issue No: Vol. 113 (2018)
  • Efficient analytical implementation of the DOT Riemann solver for the de
           Saint Venant-Exner morphodynamic model
    • Authors: F. Carraro; A. Valiani; V. Caleffi
      Pages: 189 - 201
      Abstract: Publication date: Available online 11 January 2018
      Source:Advances in Water Resources
      Author(s): F. Carraro, A. Valiani, V. Caleffi
      Within the framework of the de Saint Venant equations coupled with the Exner equation for morphodynamic evolution, this work presents a new efficient implementation of the Dumbser-Osher-Toro (DOT) scheme for non-conservative problems. The DOT path-conservative scheme is a robust upwind method based on a complete Riemann solver, but it has the drawback of requiring expensive numerical computations. Indeed, to compute the non-linear time evolution in each time step, the DOT scheme requires numerical computation of the flux matrix eigenstructure (the totality of eigenvalues and eigenvectors) several times at each cell edge. In this work, an analytical and compact formulation of the eigenstructure for the de Saint Venant-Exner (dSVE) model is introduced and tested in terms of numerical efficiency and stability. Using the original DOT and PRICE-C (a very efficient FORCE-type method) as reference methods, we present a convergence analysis (error against CPU time) to study the performance of the DOT method with our new analytical implementation of eigenstructure calculations (A-DOT). In particular, the numerical performance of the three methods is tested in three test cases: a movable bed Riemann problem with analytical solution; a problem with smooth analytical solution; a test in which the water flow is characterised by subcritical and supercritical regions. For a given target error, the A-DOT method is always the most efficient choice. Finally, two experimental data sets and different transport formulae are considered to test the A-DOT model in more practical case studies.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.011
      Issue No: Vol. 113 (2018)
  • Patterns of precipitation and soil moisture extremes in Texas, US: A
           complex network analysis
    • Authors: Alexander Y. Sun; Youlong Xia; Todd G. Caldwell; Zengchao Hao
      Pages: 203 - 213
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Alexander Y. Sun, Youlong Xia, Todd G. Caldwell, Zengchao Hao
      Understanding of the spatial and temporal dynamics of extreme precipitation not only improves prediction skills, but also helps to prioritize hazard mitigation efforts. This study seeks to enhance the understanding of spatiotemporal covariation patterns embedded in precipitation (P) and soil moisture (SM) by using an event-based, complex-network-theoretic approach. Events concurrences are quantified using a nonparametric event synchronization measure, and spatial patterns of hydroclimate variables are analyzed by using several network measures and a community detection algorithm. SM–P coupling is examined using a directional event coincidence analysis measure that takes the order of event occurrences into account. The complex network approach is demonstrated for Texas, US, a region possessing a rich set of hydroclimate features and is frequented by catastrophic flooding. Gridded daily observed P data and simulated SM data are used to create complex networks of P and SM extremes. The uncovered high degree centrality regions and community structures are qualitatively in agreement with the overall existing knowledge of hydroclimate extremes in the study region. Our analyses provide new visual insights on the propagation, connectivity, and synchronicity of P extremes, as well as the SM–P coupling, in this flood-prone region, and can be readily used as a basis for event-driven predictive analytics for other regions.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.12.019
      Issue No: Vol. 112 (2018)
  • Reactive solute transport in an asymmetrical fracture–rock matrix
    • Authors: Renjie Zhou; Hongbin Zhan
      Pages: 224 - 234
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Renjie Zhou, Hongbin Zhan
      The understanding of reactive solute transport in a single fracture–rock matrix system is the foundation of studying transport behavior in the complex fractured porous media. When transport properties are asymmetrically distributed in the adjacent rock matrixes, reactive solute transport has to be considered as a coupled three-domain problem, which is more complex than the symmetric case with identical transport properties in the adjacent rock matrixes. This study deals with the transport problem in a single fracture–rock matrix system with asymmetrical distribution of transport properties in the rock matrixes. Mathematical models are developed for such a problem under the first-type and the third-type boundary conditions to analyze the spatio–temporal concentration and mass distribution in the fracture and rock matrix with the help of Laplace transform technique and de Hoog numerical inverse Laplace algorithm. The newly acquired solutions are then tested extensively against previous analytical and numerical solutions and are proven to be robust and accurate. Furthermore, a water flushing phase is imposed on the left boundary of system after a certain time. The diffusive mass exchange along the fracture/rock matrixes interfaces and the relative masses stored in each of three domains (fracture, upper rock matrix, and lower rock matrix) after the water flushing provide great insights of transport with asymmetric distribution of transport properties. This study has the following findings: 1) Asymmetric distribution of transport properties imposes greater controls on solute transport in the rock matrixes. However, transport in the fracture is mildly influenced. 2) The mass stored in the fracture responses quickly to water flushing, while the mass stored in the rock matrix is much less sensitive to the water flushing. 3) The diffusive mass exchange during the water flushing phase has similar patterns under symmetric and asymmetric cases. 4) The characteristic distance which refers to the zero diffusion between the fracture and the rock matrix during the water flushing phase is closely associated with dispersive process in the fracture.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.12.021
      Issue No: Vol. 112 (2018)
  • Typecasting catchments: Classification, directionality, and the pursuit of
    • Authors: Tyler Smith; Lucy Marshall; Brian McGlynn
      Pages: 245 - 253
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Tyler Smith, Lucy Marshall, Brian McGlynn
      Catchment classification poses a significant challenge to hydrology and hydrologic modeling, restricting widespread transfer of knowledge from well-studied sites. The identification of important physical, climatological, or hydrologic attributes (to varying degrees depending on application/data availability) has traditionally been the focus for catchment classification. Classification approaches are regularly assessed with regard to their ability to provide suitable hydrologic predictions – commonly by transferring fitted hydrologic parameters at a data-rich catchment to a data-poor catchment deemed similar by the classification. While such approaches to hydrology's grand challenges are intuitive, they often ignore the most uncertain aspect of the process – the model itself. We explore catchment classification and parameter transferability and the concept of universal donor/acceptor catchments. We identify the implications of the assumption that the transfer of parameters between “similar” catchments is reciprocal (i.e., non-directional). These concepts are considered through three case studies situated across multiple gradients that include model complexity, process description, and site characteristics. Case study results highlight that some catchments are more successfully used as donor catchments and others are better suited as acceptor catchments. These results were observed for both black-box and process consistent hydrologic models, as well as for differing levels of catchment similarity. Therefore, we suggest that similarity does not adequately satisfy the underlying assumptions being made in parameter regionalization approaches regardless of model appropriateness. Furthermore, we suggest that the directionality of parameter transfer is an important factor in determining the success of parameter regionalization approaches.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.12.020
      Issue No: Vol. 112 (2018)
  • Impact of bimodal textural heterogeneity and connectivity on flow and
           transport through unsaturated mine waste rock
    • Authors: Willemijn M. Appels; Andrew M. Ireson; S. Lee Barbour
      Pages: 254 - 265
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Willemijn M. Appels, Andrew M. Ireson, S. Lee Barbour
      Mine waste rock dumps have highly variable flowpaths caused by contrasting textures and geometry of materials laid down during the ‘plug dumping’ process. Numerical experiments were conducted to investigate how these characteristics control unsaturated zone flow and transport. Hypothetical profiles of inner-lift structure were generated with multiple point statistics and populated with hydraulic parameters of a finer and coarser material. Early arrival of water and solutes at the bottom of the lifts was observed after spring snowmelt. The leaching efficiency, a measure of the proportion of a resident solute that is flushed out of the rock via infiltrating snowmelt or rainfall, was consistently high, but modified by the structure and texture of the lift. Under high rates of net percolation during snowmelt, preferential flow was generated in coarse textured part of the rock, and solutes in the fine textured parts of the rock remained stagnant. Under lower rates of net percolation during the summer and fall, finer materialswere flushed too, and the spatial variability of solute concentration in the lift was reduced. Layering of lifts leads to lower flow rates at depth, minimizing preferential flow and increased leaching of resident solutes. These findings highlight the limited role of large scale connected geometries on focusing flow and transport under dynamic surface net percolation conditions. As such, our findings agree with recent numerical results from soil studies with Gaussian connected geometries as well as recent experimental findings, emphasizing the dominant role of matrix flow and high leaching efficiency in large waste rock dumps.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.12.008
      Issue No: Vol. 112 (2018)
  • Partitioning uncertainty in streamflow projections under nonstationary
           model conditions
    • Authors: Ila Chawla; P.P. Mujumdar
      Pages: 266 - 282
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Ila Chawla, P.P. Mujumdar
      Assessing the impacts of Land Use (LU) and climate change on future streamflow projections is necessary for efficient management of water resources. However, model projections are burdened with significant uncertainty arising from various sources. Most of the previous studies have considered climate models and scenarios as major sources of uncertainty, but uncertainties introduced by land use change and hydrologic model assumptions are rarely investigated. In this paper an attempt is made to segregate the contribution from (i) general circulation models (GCMs), (ii) emission scenarios, (iii) land use scenarios, (iv) stationarity assumption of the hydrologic model, and (v) internal variability of the processes, to overall uncertainty in streamflow projections using analysis of variance (ANOVA) approach. Generally, most of the impact assessment studies are carried out with unchanging hydrologic model parameters in future. It is, however, necessary to address the nonstationarity in model parameters with changing land use and climate. In this paper, a regression based methodology is presented to obtain the hydrologic model parameters with changing land use and climate scenarios in future. The Upper Ganga Basin (UGB) in India is used as a case study to demonstrate the methodology. The semi-distributed Variable Infiltration Capacity (VIC) model is set-up over the basin, under nonstationary conditions. Results indicate that model parameters vary with time, thereby invalidating the often-used assumption of model stationarity. The streamflow in UGB under the nonstationary model condition is found to reduce in future. The flows are also found to be sensitive to changes in land use. Segregation results suggest that model stationarity assumption and GCMs along with their interactions with emission scenarios, act as dominant sources of uncertainty. This paper provides a generalized framework for hydrologists to examine stationarity assumption of models before considering them for future streamflow projections and segregate the contribution of various sources to the uncertainty.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.10.013
      Issue No: Vol. 112 (2018)
  • On the representation of subsea aquitards in models of offshore fresh
    • Authors: S.C. Solórzano-Rivas; A.D. Werner
      Pages: 283 - 294
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): S.C. Solórzano-Rivas, A.D. Werner
      Fresh groundwater is widespread globally in offshore aquifers, and is particularly dependent on the properties of offshore aquitards, which inhibit seawater-freshwater mixing thereby allowing offshore freshwater to persist. However, little is known of the salinity distribution in subsea aquitards, especially in relation to the offshore freshwater distribution. This is critical for the application of recent analytical solutions to subsea freshwater extent given requisite assumptions about aquitard salinity. In this paper, we use numerical simulation to explore the extent of offshore freshwater in simplified situations of subsea aquifers and overlying aquitards, including in relation to the upward leakage of freshwater. The results show that available analytical solutions significantly overestimate the offshore extent of upwelling freshwater due to the presumption of seawater in the aquitard, whereas the seawater wedge toe is less sensitive to the assumed aquitard salinity. We also explore the use of implicit, conductance-based representations of the aquitard (i.e., using the popular SEAWAT code), and find that SEAWAT's implicit approach (i.e., GHB package) can represent the offshore distance of upwelling freshwater using a novel parameterization strategy. The results show that an estimate of the upward freshwater flow that is required to freshen the aquitard is associated with the dimensionless Rayleigh number, whereby the critical Rayleigh number that distinguishes fresh and saline regions (based on the position of the 0.5 isochlor) within the aquitard is approximately 2.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2017.11.025
      Issue No: Vol. 112 (2018)
  • Comparative analysis of the apparent saturation hysteresis approach and
           the domain theory of hysteresis in respect of prediction of scanning
           curves and air entrapment
    • Authors: A. Beriozkin; Y. Mualem
      Abstract: Publication date: Available online 3 February 2018
      Source:Advances in Water Resources
      Author(s): A. Beriozkin, Y. Mualem
      This study theoretically analyzes the concept of apparent saturation hysteresis, combined with the Scott et al. (1983) scaling approach, as suggested by Parker & Lenhard (1987), to account for the effect of air entrapment and release on the soil water hysteresis. We found that the theory of Parker & Lenhard (1987) is comprised of some mutually canceling mathematical operations, and when cleared of the superfluous intermediate calculations, their model reduces to the original Scott et al.’s (1983) scaling method, supplemented with the requirement of closure of scanning loops. Our analysis reveals that actually there is no effect of their technique of accounting for the entrapped air on the final prediction of the effective saturation (or water content) scanning curves. Our consideration indicates that the use of the Land (1968) formula for assessing the amount of entrapped air is in disaccord with the apparent saturation concept as introduced by Parker & Lenhard (1987). In this paper, a proper routine is suggested for predicting hysteretic scanning curves of any order, given the two measured main curves, in the complete hysteretic domain and some verification tests are carried out versus measured results. Accordingly, explicit closed-form formulae for direct prediction (with no need of intermediate calculation) of scanning curves up to the third order are derived to sustain our analysis.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.016
  • Review:Large eddy simulations of sediment entrainment induced by a
           lock-exchange gravity current
    • Authors: Foteini Kyrousi; A. Leonardi; F. Roman; V. Armenio; F. Zanello; J. Zordan; C. Juez; L. Falcomer
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Water Resources
      Author(s): Foteini Kyrousi, A. Leonardi, F. Roman, V. Armenio, F. Zanello, J. Zordan, C. Juez, L. Falcomer
      Large Eddy simulations of lock-exchange gravity currents propagating over a mobile reach are presented. The numerical setting allows to investigate the sediment pick up induced by the currents and to study the underlying mechanisms leading to sediment entrainment for different Grashof numbers and grain sizes. First, the velocity field and the bed shear-stress distribution are investigated, along with turbulent structures formed in the flow, before the current reaches the mobile bed. Then, during the propagation of the current above the erodible section of the bed the contour plots of the entrained material are presented as well as the time evolution of the areas covered by the current and by the sediment at this section. The numerical outcomes are compared with experimental data showing a very good agreement. Overall, the study confirms that sediment pick up is prevalent at the head of the current where the strongest turbulence occurs. Further, above the mobile reach of the bed, settling process seems to be of minor importance, with the entrained material being advected downstream by the current. Additionally, the study shows that, although shear stress is the main mechanism that sets particles in motion, turbulent bursts as well as vertical velocity fluctuations are also necessary to counteract the falling velocity of the particles and maintain them into suspension. Finally, the analysis of the stability conditions of the current shows that, from one side, sediment concentration gives a negligible contribution to the stability of the front of the current and from the other side, the stability conditions provided by the current do not allow sediments to move into the ambient fluid.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.02.002
  • Pore-level Influence of Micro-fracture Parameters on Visco-capillary
           Behavior of Two-phase Displacements in Porous Media
    • Authors: M.R. Rokhforouz; H.A. Akhlaghi Amiri
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Water Resources
      Author(s): M.R. Rokhforouz, H.A. Akhlaghi Amiri
      In this work, coupled Cahn-Hilliard phase field and Navier–Stokes equations were solved using finite element method to address the effects of micro-fracture and its characterizations on water-oil displacements in a heterogeneous porous medium. Sensitivity studies at a wide range of viscosity ratios (M) and capillary numbers (Ca), and the resultant log Ca–log M stability phase diagram, revealed that in both media, with/without fracture, the three regimes of viscous fingering, capillary fingering and stable displacement similarly occur. However, presence of the fracture caused water channeling phenomenon which resulted in reduction of the number of active fingers and hence the final oil recovery factor. At high Ca (especially in the stable regime, with log Ca≥-2.5 and log M≥0), recovery factor for the fractured medium was relatively identical with the non-fractured one. At log M≥0, the fracture was fully swept, but flow instabilities were observed inside the fracture at lower M values, especially for log Ca>-4.6. In the case of the fractured medium at log Ca=-4.6 and log M=0 (capillary dominant flow), it is observed that the primary breakthrough took place by a finger progressed through the matrix, not those channeled through the fracture. Geometrical properties of the fracture, including length, aperture and orientation, highly affected both displacement profile and efficiency. The fracture length inversely influenced the oil recovery factor. It was observed that there is a critical fracture width (almost half of the medium average pore diameter) at which the recovery factor of the medium during displacement is minimum, compared to the media having thinner and thicker fractures. Minor channeling effect in the media with thinner fracture and larger fracture swept volume as well as high fracture/matrix cross flow in the media with thicker fracture were detected as the main cause of this non-monotonic behavior. In the models with thick fractures (with the thickness higher than the average pore diameter), considerable trapped oil volumes were observed inside the fracture at low M values. The fracture orientation had the most impressive effect on oil recovery compared to the other studied parameters; where the oil recovery factor incremented more than 20% as the fracture rotated 90° from flow direction. Due to the dominant effect of the channeling phenomenon, the change in the medium wettability from slightly oil-wet to slightly water-wet, did not considerably affect the displacement profile in the fractured medium. However, oil recovery factor increased as the medium became more water-wet. The fracture area was fully swept by the injected water in the oil-wet and neutral-wet media. However, flow instabilities were observed inside the fracture of the water-wet medium due to counter-current imbibition between fracture/matrix. Micro-scale mechanisms of pore doublet effect, interface coalesce, snap-off and reverse movements were captured during the studied unstable displacements.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.030
  • Improving the ecohydrological and economic efficiency of Small Hydropower
           Plants with water diversion
    • Authors: Pierre Razurel; Lorenzo Gorla; Stefania Tron; Amin Niayifar; Benoît Crouzy; Paolo Perona
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Water Resources
      Author(s): Pierre Razurel, Lorenzo Gorla, Stefania Tron, Amin Niayifar, Benoît Crouzy, Paolo Perona
      Water exploitation for energy production from Small Hydropower Plant (SHP) is increasing despite human pressure on freshwater already being very intense in several countries. Preserving natural rivers thus requires deeper understanding of the global (i.e., ecological and economic) efficiency of flow-diversion practice. In this work, we show that the global efficiency of SHP river intakes can be improved by non-proportional flow-redistribution policies. This innovative dynamic water allocation defines the fraction of water released to the river as a nonlinear function of river runoff. Three swiss SHP case studies are considered to systematically test the global performance of such policies, under both present and future hydroclimatic regimes. The environmental efficiency is plotted versus the economic efficiency showing that efficient solutions align along a (Pareto) frontier, which is entirely formed by non-proportional policies. On the contrary, other commonly used distribution policies generally lie below the Pareto frontier. This confirms the existence of better policies based on non-proportional redistribution, which should be considered in relation to implementation and operational costs. Our results recommend abandoning static (e.g., constant-minimal-flow) policies in favour of non-proportional dynamic ones towards a more sustainable use of the water resource, also considering changing hydroclimatic scenarios.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.029
  • The solution of the dam-break problem in the Porous Shallow water
    • Authors: Luca Cozzolino; Veronica Pepe; Luigi Cimorelli; Andrea D'Aniello; Renata Della Morte; Domenico Pianese
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Water Resources
      Author(s): Luca Cozzolino, Veronica Pepe, Luigi Cimorelli, Andrea D'Aniello, Renata Della Morte, Domenico Pianese
      The Porous Shallow water Equations are commonly used to evaluate the propagation of flooding waves in the urban environment. These equations may exhibit not only classic shocks, rarefactions, and contact discontinuities, as in the ordinary two-dimensional Shallow water Equations, but also special discontinuities at abrupt porosity jumps. In this paper, an appropriate parameterization of the stationary weak solutions of one-dimensional Porous Shallow water Equations supplies the inner structure of the porosity jumps. The exact solution of the corresponding dam-break problem is presented, and six different wave configurations are individuated, proving that the solution exists and it is unique for given initial conditions and geometric characteristics. These results can be used as a benchmark in order to validate one- and two-dimensional numerical models for the solution of the Porous Shallow water Equations. In addition, it is presented a novel Finite Volume scheme where the porosity jumps are taken into account by means of a variables reconstruction approach. The dam-break results supplied by this numerical scheme are compared with the exact dam-break results, showing the promising capabilities of this numerical approach. Finally, the advantages of the novel porosity jump definition are shown by comparison with other definitions available in the literature, demonstrating its advantages, and the issues raising in real world applications are discussed.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.026
  • Pilot Points Method for Conditioning Multiple-Point Statistical Facies
           Simulation on Flow Data
    • Authors: Wei Ma; Behnam Jafarpour
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Water Resources
      Author(s): Wei Ma, Behnam Jafarpour
      We propose a new pilot points method for conditioning discrete multiple-point statistical (MPS) facies simulation on dynamic flow data. While conditioning MPS simulation on static hard data is straightforward, their calibration against nonlinear flow data is nontrivial. The proposed method generates conditional models from a conceptual model of geologic connectivity, known as a training image (TI), by strategically placing and estimating pilot points. To place pilot points, a score map is generated based on three sources of information: (i) the uncertainty in facies distribution, (ii) the model response sensitivity information, and (iii) the observed flow data. Once the pilot points are placed, the facies values at these points are inferred from production data and then are used, along with available hard data at well locations, to simulate a new set of conditional facies realizations. While facies estimation at the pilot points can be performed using different inversion algorithms, in this study the ensemble smoother (ES) is adopted to update permeability maps from production data, which are then used to statistically infer facies types at the pilot point locations. The developed method combines the information in the flow data and the TI by using the former to infer facies values at selected locations away from the wells and the latter to ensure consistent facies structure and connectivity where away from measurement locations. Several numerical experiments are used to evaluate the performance of the developed method and to discuss its important properties.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.021
  • The blue water footprint of the world's artificial reservoirs for
           hydroelectricity, irrigation, residential and industrial water supply,
           flood protection, fishing and recreation
    • Authors: Rick J. Hogeboom; Luuk Knook; Arjen Y. Hoekstra
      Abstract: Publication date: Available online 2 February 2018
      Source:Advances in Water Resources
      Author(s): Rick J. Hogeboom, Luuk Knook, Arjen Y. Hoekstra
      For centuries, humans have resorted to building dams to gain control over freshwater available for human consumption. Although dams and their reservoirs have made many important contributions to human development, they receive negative attention as well, because of the large amounts of water they can consume through evaporation. We estimate the blue water footprint of the world's artificial reservoirs and attribute it to the purposes hydroelectricity generation, irrigation water supply, residential and industrial water supply, flood protection, fishing and recreation, based on their economic value. We estimate that economic benefits from 2235 reservoirs included in this study amount to 265 × 109 US$ a year, with residential and industrial water supply and hydroelectricity generation as major contributors. The water footprint associated with these benefits is the sum of the water footprint of dam construction (< 1 % contribution) and evaporation from the reservoir's surface area, and globally adds up to 66 × 109 m3 y−1. The largest share of this water footprint (57 %) is located in non-water scarce basins and only 1 % in year-round scarce basins. The primary purposes of a reservoir change with increasing water scarcity, from mainly hydroelectricity generation in non-scarce basins, to residential and industrial water supply, irrigation water supply and flood control in scarcer areas.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.028
  • A functional framework for flow-duration-curve and daily streamflow
           estimation at ungauged sites
    • Authors: Ana I. Requena; Fateh Chebana; Taha B.M.J. Ouarda
      Abstract: Publication date: Available online 1 February 2018
      Source:Advances in Water Resources
      Author(s): Ana I. Requena, Fateh Chebana, Taha B.M.J. Ouarda
      Flow duration curves (FDC) are used to obtain daily streamflow series at ungauged sites. In this study, functional multiple regression (FMR) is proposed for FDC estimation. Its natural framework for dealing with curves allows obtaining the FDC as a whole instead of a limited number of single points. FMR assessment is performed through a case study in Quebec, Canada. FMR provides a better mean FDC estimation when obtained over sites by considering simultaneously all FDC quantiles in the assessment of each given site. However, traditional regression provides a better mean FDC estimation when obtained over given FDC quantiles by considering all sites in the assessment of each quantile separately. Mean daily streamflow estimation is similar; yet FMR provides an improved estimation for most sites. Furthermore, FMR represents a more suitable framework and provides a number of practical advantages, such as insight into descriptor influence on FDC quantiles. Hence, traditional regression may be preferred if only few FDC quantiles are of interest; whereas FMR would be more suitable if a large number of FDC quantiles is of interest, and therefore to estimate daily streamflows.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.019
  • Attributing uncertainty in streamflow simulations due to variable inputs
           via the Quantile Flow Deviation metric
    • Authors: Syed Abu Shoaib; Lucy Marshall; Ashish Sharma
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Syed Abu Shoaib, Lucy Marshall, Ashish Sharma
      Every model to characterise a real world process is affected by uncertainty. Selecting a suitable model is a vital aspect of engineering planning and design. Observation or input errors make the prediction of modelled responses more uncertain. By way of a recently developed attribution metric, this study is aimed at developing a method for analysing variability in model inputs together with model structure variability to quantify their relative contributions in typical hydrological modelling applications. The Quantile Flow Deviation (QFD) metric is used to assess these alternate sources of uncertainty. The Australian Water Availability Project (AWAP) precipitation data for four different Australian catchments is used to analyse the impact of spatial rainfall variability on simulated streamflow variability via the QFD. The QFD metric attributes the variability in flow ensembles to uncertainty associated with the selection of a model structure and input time series. For the case study catchments, the relative contribution of input uncertainty due to rainfall is higher than that due to potential evapotranspiration, and overall input uncertainty is significant compared to model structure and parameter uncertainty. Overall, this study investigates the propagation of input uncertainty in a daily streamflow modelling scenario and demonstrates how input errors manifest across different streamflow magnitudes.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.022
  • On the modelling of shallow turbidity flows
    • Authors: Valery Yu. Liapidevskii; Denys Dutykh; Marguerite Gisclon
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Valery Yu. Liapidevskii, Denys Dutykh, Marguerite Gisclon
      In this study we investigate shallow turbidity density currents and underflows from mechanical point of view. We propose a simple hyperbolic model for such flows. On one hand, our model is based on very basic conservation principles. On the other hand, the turbulent nature of the flow is also taken into account through the energy dissipation mechanism. Moreover, the mixing with the pure water along with sediments entrainment and deposition processes are considered, which makes the problem dynamically interesting. One of the main advantages of our model is that it requires the specification of only two modeling parameters — the rate of turbulent dissipation and the rate of the pure water entrainment. Consequently, the resulting model turns out to be very simple and self-consistent. This model is validated against several experimental data and several special classes of solutions (such as travelling, self-similar and steady) are constructed. Unsteady simulations show that some special solutions are realized as asymptotic long time states of dynamic trajectories.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.017
  • Elucidating the impact of micro-scale heterogeneous bacterial distribution
           on biodegradation
    • Authors: Susanne I. Schmidt; Jan-Ulrich Kreft; Rae Mackay; Cristian Picioreanu; Martin Thullner
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Susanne I. Schmidt, Jan-Ulrich Kreft, Rae Mackay, Cristian Picioreanu, Martin Thullner
      Groundwater microorganisms hardly ever cover the solid matrix uniformly–instead they form micro-scale colonies. To which extent such colony formation limits the bioavailability and biodegradation of a substrate is poorly understood. We used a high-resolution numerical model of a single pore channel inhabited by bacterial colonies to simulate the transport and biodegradation of organic substrates. These high-resolution 2D simulation results were compared to 1D simulations that were based on effective rate laws for bioavailability-limited biodegradation. We i) quantified the observed bioavailability limitations and ii) evaluated the applicability of previously established effective rate concepts if microorganisms are heterogeneously distributed. Effective bioavailability reductions of up to more than one order of magnitude were observed, showing that the micro-scale aggregation of bacterial cells into colonies can severely restrict the bioavailability of a substrate and reduce in situ degradation rates. Effective rate laws proved applicable for upscaling when using the introduced effective colony sizes.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.013
  • An efficient Bayesian data-worth analysis using a multilevel Monte Carlo
    • Authors: Dan Lu; Daniel Ricciuto; Katherine Evans
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Dan Lu, Daniel Ricciuto, Katherine Evans
      Improving the understanding of subsurface systems and thus reducing prediction uncertainty requires collection of data. As the collection of subsurface data is costly, it is important that the data collection scheme is cost-effective. Design of a cost-effective data collection scheme, i.e., data-worth analysis, requires quantifying model parameter, prediction, and both current and potential data uncertainties. Assessment of these uncertainties in large-scale stochastic subsurface hydrological model simulations using standard Monte Carlo (MC) sampling or surrogate modeling is extremely computationally intensive, sometimes even infeasible. In this work, we propose an efficient Bayesian data-worth analysis using a multilevel Monte Carlo (MLMC) method. Compared to the standard MC that requires a significantly large number of high-fidelity model executions to achieve a prescribed accuracy in estimating expectations, the MLMC can substantially reduce computational costs using multifidelity approximations. Since the Bayesian data-worth analysis involves a great deal of expectation estimation, the cost saving of the MLMC in the assessment can be outstanding. While the proposed MLMC-based data-worth analysis is broadly applicable, we use it for a highly heterogeneous two-phase subsurface flow simulation to select an optimal candidate data set that gives the largest uncertainty reduction in predicting mass flow rates at four production wells. The choices made by the MLMC estimation are validated by the actual measurements of the potential data, and consistent with the standard MC estimation. But compared to the standard MC, the MLMC greatly reduces the computational costs.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.024
  • Reproducing tailing in breakthrough curves: are statistical models equally
           representative and predictive'
    • Authors: Daniele Pedretti; Marco Bianchi
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Daniele Pedretti, Marco Bianchi
      Breakthrough curves (BTCs) observed during tracer tests in highly heterogeneous aquifers display strong tailing. Power laws are popular models for both the empirical fitting of these curves, and the prediction of transport using upscaling models based on best-fitted estimated parameters (e.g. the power law slope or exponent). The predictive capacity of power law based upscaling models can be however questioned due to the difficulties to link model parameters with the aquifers’ physical properties. This work analyzes two aspects that can limit the use of power laws as effective predictive tools: (a) the implication of statistical subsampling, which often render power law undistinguishable from other heavily tailed distributions, such as the logarithmic (LOG); (b) the difficulties to reconcile fitting parameters obtained from models with different formulations, such as the presence of a late-time cutoff in the power law model. Two rigorous and systematic stochastic analyses, one based on benchmark distributions and the other on BTCs obtained from transport simulations, are analyzed. It is found that a power law model without cutoff (PL) results in best-fitted exponents (α PL ) falling in the range of typical experimental values reported in the literature (1.5 < α PL < 4). The PL exponent tends to lower values as the tailing becomes heavier. Strong fluctuations occur when the number of samples is limited, due to the effects of subsampling. On the other hand, when the power law model embeds a cutoff (PLCO), the best-fitted exponent (α CO ) is insensitive to the degree of tailing and to the effects of subsampling and tends to a constant α CO ≈ 1. In the PLCO model, the cutoff rate (λ) is the parameter that fully reproduces the persistence of the tailing and is shown to be inversely correlated to the LOG scale parameter (i.e. with the skewness of the distribution). The theoretical results are consistent with the fitting analysis of a tracer test performed during the MADE-5 experiment. It is shown that a simple mechanistic upscaling model based on the PLCO formulation is able to predict the ensemble of BTCs from the stochastic transport simulations without the need of any fitted parameters. The model embeds the constant α CO  = 1 and relies on a stratified description of the transport mechanisms to estimate λ. The PL fails to reproduce the ensemble of BTCs at late time, while the LOG model provides consistent results as the PLCO model, however without a clear mechanistic link between physical properties and model parameters. It is concluded that, while all parametric models may work equally well (or equally wrong) for the empirical fitting of the experimental BTCs tails due to the effects of subsampling, for predictive purposes this is not true. A careful selection of the proper heavily tailed models and corresponding parameters is required to ensure physically-based transport predictions.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.023
  • Revisiting analytical solutions for steady interface flow in subsea
           aquifers: Aquitard salinity effects
    • Authors: Adrian D. Werner; Neville I. Robinson
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Adrian D. Werner, Neville I. Robinson
      Existing analytical solutions for the distribution of fresh groundwater in subsea aquifers presume that the overlying offshore aquitard, represented implicitly, contains seawater. Here, we consider the case where offshore fresh groundwater is the result of freshwater discharge from onshore aquifers, and neglect paleo-freshwater sources. A recent numerical modelling investigation, involving explicit simulation of the offshore aquitard, demonstrates that offshore aquitards more likely contain freshwater in areas of upward freshwater leakage to the sea. We integrate this finding into the existing analytical solutions by providing an alternative formulation for steady interface flow in subsea aquifers, whereby the salinity in the offshore aquitard can be chosen. The new solution, taking the aquitard salinity as that of freshwater, provides a closer match to numerical modelling results in which the aquitard is represented explicitly.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.002
  • The effect of a microscale fracture on dynamic capillary pressure of
           two-phase flow in porous media
    • Authors: Mingming Tang; Huifang Ma; Shuangfang Lu; Hongbin Zhan; Wenyue Guo
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Mingming Tang, Huifang Ma, Shuangfang Lu, Hongbin Zhan, Wenyue Guo
      Dynamic capillary pressure (DCP) effects, which is vital for predicting multiphase flow behavior in porous media, refers to the injection rate dependence capillary pressure observed during non-equilibrium displacement experiments. However, a clear picture of the effects of microscale fractures on DCP remains elusive. This study quantified the effects of microscale fractures on DCP and simulated pore-scale force and saturation change in fractured porous media using the multiphase lattice Boltzmann method (LBM). Eighteen simulation cases were carried out to calculate DCP as a function of wetting phase saturation. The effects of viscosity ratio and fracture orientation, aperture and length on DCP and DCP coefficient τ were investigated, where τ refers to the ratio of the difference of DCP and static capillary pressure (SCP) over the rate of wetting-phase saturation change versus time. Significant differences in τ values were observed between unfractured and fractured porous media. The τ values of fractured porous media were 1.1  × 104 to 5.68 × 105, which were one or two orders of magnitude lower than those of unfractured porous media with a value of 4 × 106 A horizontal fracture had greater effects on DCP and τ than a vertical fracture, given the same fracture aperture and length. This study suggested that a microscale fracture might result in large magnitude changes in DCP for two-phase flow.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.015
  • Simulation of dynamic expansion, contraction, and connectivity in a
           mountain stream network
    • Authors: Adam S. Ward; Noah M. Schmadel; Steven M. Wondzell
      Abstract: Publication date: Available online 31 January 2018
      Source:Advances in Water Resources
      Author(s): Adam S. Ward, Noah M. Schmadel, Steven M. Wondzell
      Headwater stream networks expand and contract in response to changes in stream discharge. The changes in the extent of the stream network are also controlled by geologic or geomorphic setting – some reaches go dry even under relatively wet conditions, other reaches remain flowing under relatively dry conditions. While such patterns are well recognized, we currently lack tools to predict the extent of the stream network and the times and locations where the network is dry within large river networks. Here, we develop a perceptual model of the river corridor in a headwater mountainous catchment, translate this into a reduced-complexity mechanistic model, and implement the model to examine connectivity and network extent over an entire water year. Our model agreed reasonably well with our observations, showing that the extent and connectivity of the river network was most sensitive to hydrologic forcing under the lowest discharges (Qgauge < 1 L s−1), that at intermediate discharges (1 L s−1 < Qgauge < 1 L s−1) the extent of the network changed dramatically with changes in discharge, and that under wet conditions (Qgauge > 1 L s−1) the extent of the network was relatively insensitive to hydrologic forcing and was instead determined by the network topology. We do not expect that the specific thresholds observed in this study would be transferable to other catchments with different geology, topology, or hydrologic forcing. However, we expect that the general pattern should be robust: the dominant controls will shift from hydrologic forcing to geologic setting as discharge increases.. Further, our method is readily transferable as the model can be applied with minimal data requirements (a single stream gauge, a digital terrain model, and estimates of hydrogeologic properties) to estimate flow duration or connectivity along the river corridor in unstudied catchments. As the available information increases, the model could be better calibrated to match site-specific observations of network extent, locations of dry reaches, or solute break through curves as demonstrated in this study. Based on the low initial data requirements and ability to later tune the model to a specific site, we suggest example applications of this parsimonious model that may prove useful to both researchers and managers.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.018
  • Impact of small-scale saline tracer heterogeneity on electrical
           resistivity monitoring in fully and partially saturated porous media:
           insights from geoelectrical milli-fluidic experiments
    • Authors: Damien Jougnot; Joaquín Jiménez-Martínez; Raphaël Legendre; Tanguy Le Borgne; Yves Méheust; Niklas Linde
      Abstract: Publication date: Available online 17 January 2018
      Source:Advances in Water Resources
      Author(s): Damien Jougnot, Joaquín Jiménez-Martínez, Raphaël Legendre, Tanguy Le Borgne, Yves Méheust, Niklas Linde
      Time-lapse electrical resistivity tomography (ERT) is a geophysical method widely used to remotely monitor the migration of electrically-conductive tracers and contaminant plumes in the subsurface. Interpretations of time-lapse ERT inversion results are generally based on the assumption of a homogeneous solute concentration below the resolution limits of the tomogram depicting inferred electrical conductivity variations. We suggest that ignoring small-scale solute concentration variability (i.e., at the sub-resolution scale) is a major reason for the often-observed apparent loss of solute mass in ERT tracer studies. To demonstrate this, we developed a geoelectrical milli-fluidic setup where the bulk electric conductivity of a 2D analogous porous medium, consisting of cylindrical grains positioned randomly inside a Hele-Shaw cell, is monitored continuously in time while saline tracer tests are performed through the medium under fully and partially saturated conditions. High resolution images of the porous medium are recorded with a camera at regular time intervals, and provide both the spatial distribution of the fluid phases (aqueous solution and air), and the saline solute concentration field (where the solute consists of a mixture of salt and fluorescein, the latter being used as a proxy for the salt concentration). Effective bulk electrical conductivities computed numerically from the measured solute concentration field and the spatial distributions of fluid phases agree well with the measured bulk conductivities. We find that the effective bulk electrical conductivity is highly influenced by the connectivity of high electrical conductivity regions. The spatial distribution of air, saline tracer fingering, and mixing phenomena drive temporal changes in the effective bulk electrical conductivity by creating preferential paths or barriers for electrical current at the pore-scale. The resulting heterogeneities in the solute concentrations lead to strong anisotropy of the effective bulk electrical conductivity, especially for partially saturated conditions. We highlight how these phenomena contribute to the typically large apparent mass loss observed when conducting field-scale time-lapse ERT.

      PubDate: 2018-02-05T16:57:57Z
      DOI: 10.1016/j.advwatres.2018.01.014
  • Parsimonious nonstationary flood frequency analysis
    • Authors: Jake M. Serago; Richard M. Vogel
      Pages: 1 - 16
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Jake M. Serago, Richard M. Vogel
      There is now widespread awareness of the impact of anthropogenic influences on extreme floods (and droughts) and thus an increasing need for methods to account for such influences when estimating a frequency distribution. We introduce a parsimonious approach to nonstationary flood frequency analysis (NFFA) based on a bivariate regression equation which describes the relationship between annual maximum floods, x, and an exogenous variable which may explain the nonstationary behavior of x. The conditional mean, variance and skewness of both x and y = ln (x) are derived, and combined with numerous common probability distributions including the lognormal, generalized extreme value and log Pearson type III models, resulting in a very simple and general approach to NFFA. Our approach offers several advantages over existing approaches including: parsimony, ease of use, graphical display, prediction intervals, and opportunities for uncertainty analysis. We introduce nonstationary probability plots and document how such plots can be used to assess the improved goodness of fit associated with a NFFA.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.11.026
      Issue No: Vol. 112 (2017)
  • Evaluation of multi-mode CryoSat-2 altimetry data over the Po River
           against in situ data and a hydrodynamic model
    • Authors: Raphael Schneider; Angelica Tarpanelli; Karina Nielsen; Henrik Madsen; Peter Bauer-Gottwein
      Pages: 17 - 26
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Raphael Schneider, Angelica Tarpanelli, Karina Nielsen, Henrik Madsen, Peter Bauer-Gottwein
      Coverage of in situ observations to monitor surface waters is insufficient on the global scale, and decreasing across the globe. Satellite altimetry has become an increasingly important monitoring technology for continental surface waters. The ESA CryoSat-2 altimetry mission, launched in 2010, has two novel features. (i) The radar altimeter instrument on board of CryoSat-2 is operated in three modes; two of them reduce the altimeter footprint by using Delay-Doppler processing. (ii) CryoSat-2 is placed on a distinct orbit with a repeat cycle of 369 days, leading to a drifting ground track pattern. The drifting ground track pattern challenges many common methods of processing satellite altimetry data over rivers. This study evaluates the observation error of CryoSat-2 water level observations over the Po River, Italy, against in situ observations. The average RMSE between CryoSat-2 and in situ observations was found to be 0.38 meters. CryoSat-2 was also shown to be useful for channel roughness calibration in a hydrodynamic model of the Po River. The small across-track distance of CryoSat-2 means that observations are distributed almost continuously along the river. This allowed resolving channel roughness with higher spatial resolution than possible with in situ or virtual station altimetry data. Despite the Po River being extensively monitored, CryoSat-2 still provides added value thanks to its unique spatio-temporal sampling pattern.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.11.027
      Issue No: Vol. 112 (2017)
  • River networks as ecological corridors: A coherent ecohydrological
    • Authors: Andrea Rinaldo; Marino Gatto; Ignacio Rodriguez-Iturbe
      Pages: 27 - 58
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Andrea Rinaldo, Marino Gatto, Ignacio Rodriguez-Iturbe
      This paper draws together several lines of argument to suggest that an ecohydrological framework, i.e. laboratory, field and theoretical approaches focused on hydrologic controls on biota, has contributed substantially to our understanding of the function of river networks as ecological corridors. Such function proves relevant to: the spatial ecology of species; population dynamics and biological invasions; the spread of waterborne disease. As examples, we describe metacommunity predictions of fish diversity patterns in the Mississippi–Missouri basin, geomorphic controls imposed by the fluvial landscape on elevational gradients of species’ richness, the zebra mussel invasion of the same Mississippi–Missouri river system, and the spread of proliferative kidney disease in salmonid fish. We conclude that spatial descriptions of ecological processes in the fluvial landscape, constrained by their specific hydrologic and ecological dynamics and by the ecosystem matrix for interactions, i.e. the directional dispersal embedded in fluvial and host/pathogen mobility networks, have already produced a remarkably broad range of significant results. Notable scientific and practical perspectives are thus open, in the authors’ view, to future developments in ecohydrologic research.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.10.005
      Issue No: Vol. 112 (2017)
  • Quantification of a maximum injection volume of CO2 to avert geomechanical
           perturbations using a compositional fluid flow reservoir simulator
    • Authors: Hojung Jung; Gurpreet Singh; D. Nicolas Espinoza; Mary F. Wheeler
      Pages: 160 - 169
      Abstract: Publication date: February 2018
      Source:Advances in Water Resources, Volume 112
      Author(s): Hojung Jung, Gurpreet Singh, D. Nicolas Espinoza, Mary F. Wheeler
      Subsurface CO2 injection and storage alters formation pressure. Changes of pore pressure may result in fault reactivation and hydraulic fracturing if the pressure exceeds the corresponding thresholds. Most simulation models predict such thresholds utilizing relatively homogeneous reservoir rock models and do not account for CO2 dissolution in the brine phase to calculate pore pressure evolution. This study presents an estimation of reservoir capacity in terms of allowable injection volume and rate utilizing the Frio CO2 injection site in the coast of the Gulf of Mexico as a case study. The work includes laboratory core testing, well-logging data analyses, and reservoir numerical simulation. We built a fine-scale reservoir model of the Frio pilot test in our in-house reservoir simulator IPARS (Integrated Parallel Accurate Reservoir Simulator). We first performed history matching of the pressure transient data of the Frio pilot test, and then used this history-matched reservoir model to investigate the effect of the CO2 dissolution into brine and predict the implications of larger CO2 injection volumes. Our simulation results –including CO2 dissolution– exhibited 33% lower pressure build-up relative to the simulation excluding dissolution. Capillary heterogeneity helps spread the CO2 plume and facilitate early breakthrough. Formation expansivity helps alleviate pore pressure build-up. Simulation results suggest that the injection schedule adopted during the actual pilot test very likely did not affect the mechanical integrity of the storage complex. Fault reactivation requires injection volumes of at least about sixty times larger than the actual injected volume at the same injection rate. Hydraulic fracturing necessitates much larger injection rates than the ones used in the Frio pilot test. Tested rock samples exhibit ductile deformation at in-situ effective stresses. Hence, we do not expect an increase of fault permeability in the Frio sand even in the presence of fault reactivation.

      PubDate: 2017-12-27T01:50:49Z
      DOI: 10.1016/j.advwatres.2017.12.003
      Issue No: Vol. 112 (2017)
  • Representative sets of design hydrographs for ungauged catchments: A
           regional approach using probabilistic region memberships
    • Authors: Manuela Irene Brunner; Jan Seibert; Anna-Catherine Favre
      Abstract: Publication date: Available online 24 December 2017
      Source:Advances in Water Resources
      Author(s): Manuela Irene Brunner, Jan Seibert, Anna-Catherine Favre
      Traditional design flood estimation approaches have focused on peak discharges and have often neglected other hydrograph characteristics such as hydrograph volume and shape. Synthetic design hydrograph estimation procedures overcome this deficiency by jointly considering peak discharge, hydrograph volume, and shape. Such procedures have recently been extended to allow for the consideration of process variability within a catchment by a flood-type specific construction of design hydrographs. However, they depend on observed runoff time series and are not directly applicable in ungauged catchments where such series are not available. To obtain reliable flood estimates, there is a need for an approach that allows for the consideration of process variability in the construction of synthetic design hydrographs in ungauged catchments. In this study, we therefore propose an approach that combines a bivariate index flood approach with event-type specific synthetic design hydrograph construction. First, regions of similar flood reactivity are delineated and a classification rule that enables the assignment of ungauged catchments to one of these reactivity regions is established. Second, event-type specific synthetic design hydrographs are constructed using the pooled data divided by event type from the corresponding reactivity region in a bivariate index flood procedure. The approach was tested and validated on a dataset of 163 Swiss catchments. The results indicated that 1) random forest is a suitable classification model for the assignment of an ungauged catchment to one of the reactivity regions, 2) the combination of a bivariate index flood approach and event-type specific synthetic design hydrograph construction enables the consideration of event types in ungauged catchments, and 3) the use of probabilistic class memberships in regional synthetic design hydrograph construction helps to alleviate the problem of misclassification. Event-type specific synthetic design hydrograph sets enable the inclusion of process variability into design flood estimation and can be used as a compromise between single best estimate synthetic design hydrographs and continuous simulation studies.

      PubDate: 2017-12-27T01:50:49Z
      DOI: 10.1016/j.advwatres.2017.12.018
  • A Mixture Theory Approach to Model Co- and Counter-Current Two-Phase Flow
           in Porous Media Accounting for Viscous Coupling
    • Authors: Qiao Andersen; Evje D.C. Standnes
      Abstract: Publication date: Available online 19 December 2017
      Source:Advances in Water Resources
      Author(s): Y. Qiao, P.Ø. Andersen, S. Evje, D.C. Standnes
      It is well known that relative permeabilities can depend on the flow configuration and they are commonly lower during counter-current flow as compared to co-current flow. Conventional models must deal with this by manually changing the relative permeability curves depending on the observed flow regime. In this paper we use a novel two-phase momentum-equation-approach based on general mixture theory to generate effective relative permeabilities where this dependence (and others) is automatically captured. In particular, this formulation includes two viscous coupling effects: (i) viscous drag between the flowing phases and the stagnant porous rock; (ii) viscous drag caused by momentum transfer between the flowing phases. The resulting generalized model will predict that during co-current flow the faster moving fluid accelerates the slow fluid, but is itself decelerated, while for counter-current flow they are both decelerated. The implications of these mechanisms are demonstrated by investigating recovery of oil from a matrix block surrounded by water due to a combination of gravity drainage and spontaneous imbibition, a situation highly relevant for naturally fractured reservoirs. We implement relative permeability data obtained experimentally through co-current flooding experiments and then explore the model behavior for different flow cases ranging from counter-current dominated to co-current dominated. In particular, it is demonstrated how the proposed model seems to offer some possible interesting improvements over conventional modeling by providing generalized mobility functions that automatically are able to capture more correctly different flow regimes for one and the same parameter set.

      PubDate: 2017-12-27T01:50:49Z
  • Tradeoffs between water requirements and yield stability in annual vs.
           perennial crops
    • Authors: Giulia Vico; Nathaniel A. Brunsell
      Abstract: Publication date: Available online 16 December 2017
      Source:Advances in Water Resources
      Author(s): Giulia Vico, Nathaniel A. Brunsell
      Population growth and changes in climate and diets will likely further increase the pressure on agriculture and water resources globally. Currently, staple crops are obtained from annuals plants. A shift towards perennial crops may enhance many ecosystem services, but at the cost of higher water requirements and lower yields. It is still unclear when the advantages of perennial crops overcome their disadvantages and perennial crops are thus a sustainable solution. Here we combine a probabilistic description of the soil water balance and crop development with an extensive dataset of traits of congeneric annuals and perennials to identify the conditions for which perennial crops are more viable than annual ones with reference to yield, yield stability, and effective use of water. We show that the larger and more developed roots of perennial crops allow a better exploitation of soil water resources and a reduction of yield variability with respect to annual species, but their yields remain lower when considering grain crops. Furthermore, perennial crops have higher and more variable irrigation requirements and lower water productivity. These results are important to understand the potential consequences for yield, its stability, and water resource use of a shift from annual to perennial crops and, more generally, if perennial crops may be more resilient than annual crops in the face of climatic fluctuations.
      Graphical abstract image

      PubDate: 2017-12-27T01:50:49Z
      DOI: 10.1016/j.advwatres.2017.12.014
  • Regional-scale analysis of extreme precipitation from short and fragmented
    • Authors: Andrea Libertino; Paola Allamano; Francesco Laio; Pierluigi Claps
      Abstract: Publication date: Available online 16 December 2017
      Source:Advances in Water Resources
      Author(s): Andrea Libertino, Paola Allamano, Francesco Laio, Pierluigi Claps
      Rain gauge is the oldest and most accurate instrument for rainfall measurement, able to provide long series of reliable data. However, rain gauge records are often plagued by gaps, spatio-temporal discontinuities and inhomogeneities that could affect their suitability for a statistical assessment of the characteristics of extreme rainfall. Furthermore, the need to discard the shorter series for obtaining robust estimates leads to ignore a significant amount of information which can be essential, especially when large return periods estimates are sought. This work describes a robust statistical framework for dealing with uneven and fragmented rainfall records on a regional spatial domain. The proposed technique, named “patched kriging” allows one to exploit all the information available from the recorded series, independently of their length, to provide extreme rainfall estimates in ungauged areas. The methodology involves the sequential application of the ordinary kriging equations, producing a homogeneous dataset of synthetic series with uniform lengths. In this way, the errors inherent to any regional statistical estimation can be easily represented in the spatial domain and, possibly, corrected. Furthermore, the homogeneity of the obtained series, provides robustness toward local artefacts during the parameter-estimation phase. The application to a case study in the north-western Italy demonstrates the potential of the methodology and provides a significant base for discussing its advantages over previous techniques.

      PubDate: 2017-12-27T01:50:49Z
      DOI: 10.1016/j.advwatres.2017.12.015
  • Stochastic modeling of wetland-groundwater systems
    • Authors: Leonardo Enrico Bertassello; P. Suresh C. Rao; Jeryang Park; James W. Jawitz; Gianluca Botter
      Abstract: Publication date: Available online 13 December 2017
      Source:Advances in Water Resources
      Author(s): Leonardo Enrico Bertassello, P. Suresh C. Rao, Jeryang Park, James W. Jawitz, Gianluca Botter
      Modeling and data analyses were used in this study to examine the temporal hydrological variability in geographically isolated wetlands (GIWs), as influenced by hydrologic connectivity to shallow groundwater, wetland bathymetry, and subject to stochastic hydro-climatic forcing. We examined the general case of GIWs coupled to shallow groundwater through exfiltration or infiltration across wetland bottom. We also examined limiting case with the wetland stage as the local expression of the shallow groundwater. We derive analytical expressions for the steady-state probability density functions (pdfs) for wetland water storage and stage using few, scaled, physically-based parameters. In addition, we analyze the hydrologic crossing time properties of wetland stage, and the dependence of the mean hydroperiod on climatic and wetland morphologic attributes. Our analyses show that it is crucial to account for shallow groundwater connectivity to fully understand the hydrologic dynamics in wetlands. The application of the model to two different case studies in Florida, jointly with a detailed sensitivity analysis, allowed us to identify the main drivers of hydrologic dynamics in GIWs under different climate and morphologic conditions.

      PubDate: 2017-12-27T01:50:49Z
      DOI: 10.1016/j.advwatres.2017.12.007
  • Simultaneous identification of a contaminant source and hydraulic
           conductivity via the restart normal-score ensemble Kalman filter
    • Authors: Teng Xu; J. Jaime Gómez-Hernández
      Abstract: Publication date: Available online 11 December 2017
      Source:Advances in Water Resources
      Author(s): Teng Xu, J. Jaime Gómez-Hernández
      Detecting where and when a contaminant entered an aquifer from observations downgradient of the source is a difficult task; this identification becomes more challenging when the uncertainty about the spatial distribution of hydraulic conductivity is accounted for. In this paper, we have implemented an application of the restart normal-score ensemble Kalman filter (NS-EnKF) for the simultaneous identification of a contaminant source and the spatially variable hydraulic conductivity in an aquifer. The method is capable of providing estimates of the spatial location, initial release time, the duration of the release and the mass load of a point-contamination event, plus the spatial distribution of hydraulic conductivity together with an assessment of the estimation uncertainty of all the parameters. The method has been applied in synthetic aquifers exhibiting both Gaussian and non-Gaussian patterns. The identification is made possible by assimilating in time both piezometric head and concentration observations from an array of observation wells. The method is demonstrated in three different synthetic scenarios that combine hydraulic conductivities with unimodal and bimodal histograms, and releases in high and low conductivity zones. The results prove that the specific implementation of the EnKF is capable of recovering the source parameters with some uncertainty and of recovering the main patterns of heterogeneity of the hydraulic conductivity fields by assimilating a sufficient number of state variable observations. The proposed approach is an important step towards contaminant source identification in real aquifers, which may have logconductivity spatial distributions with either Gaussian or non-Gaussian features, yet, it is still far from practical applications since the transport parameters, the external sinks and sources and the initial and boundary conditions are assumed known.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.12.011
  • Hydrologic responses to restored wildfire regimes revealed by soil
           moisture-vegetation relationships
    • Authors: Gabrielle Boisramé; Sally Thompson; Scott Stephens
      Abstract: Publication date: Available online 9 December 2017
      Source:Advances in Water Resources
      Author(s): Gabrielle Boisramé, Sally Thompson, Scott Stephens
      Many forested mountain watersheds worldwide evolved with frequent fire, which Twentieth Century fire suppression activities eliminated, resulting in unnaturally dense forests with high water demand. Restoration of pre-suppression forest composition and structure through a variety of management activities could improve forest resilience and water yields. This study explores the potential for “managed wildfire”, whereby naturally ignited fires are allowed to burn, to alter the water balance. Interest in this type of managed wildfire is increasing, yet its long-term effects on water balance are uncertain. We use soil moisture as a spatially-distributed hydrologic indicator to assess the influence of vegetation, fire history and landscape position on water availability in the Illilouette Creek Basin in Yosemite National Park. Over 6000 manual surface soil moisture measurements were made over a period of three years, and supplemented with continuous soil moisture measurements over the top 1m of soil in three sites. Random forest and linear mixed effects models showed a dominant effect of vegetation type and history of vegetation change on measured soil moisture. Contemporary and historical vegetation maps were used to upscale the soil moisture observations to the basin and infer soil moisture under fire-suppressed conditions. Little change in basin-averaged soil moisture was inferred due to managed wildfire, but the results indicated that large localized increases in soil moisture had occurred, which could have important impacts on local ecology or downstream flows.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.12.009
  • An advanced analytical solution for pressure build-up during CO2 injection
           into infinite saline aquifers: The role of compressibility
    • Authors: Haiqing Wu; Bing Bai; Xiaochun Li
      Abstract: Publication date: Available online 9 December 2017
      Source:Advances in Water Resources
      Author(s): Haiqing Wu, Bing Bai, Xiaochun Li
      Existing analytical or approximate solutions that are appropriate for describing the migration mechanics of CO2 and the evolution of fluid pressure in reservoirs do not consider the high compressibility of CO2, which reduces their calculation accuracy and application value. Therefore, this work first derives a new governing equation that represents the movement of complex fluids in reservoirs, based on the equation of continuity and the generalized Darcy's law. A more rigorous definition of the coefficient of compressibility of fluid is then presented, and a power function model (PFM) that characterizes the relationship between the physical properties of CO2 and the pressure is derived. Meanwhile, to avoid the difficulty of determining the saturation of fluids, a method that directly assumes the average relative permeability of each fluid phase in different fluid domains is proposed, based on the theory of gradual change. An advanced analytical solution is obtained that includes both the partial miscibility and the compressibility of CO2 and brine in evaluating the evolution of fluid pressure by integrating within different regions. Finally, two typical sample analyses are used to verify the reliability, improved nature and universality of this new analytical solution. Based on the physical characteristics and the results calculated for the examples, this work elaborates the concept and basis of partitioning for use in further work.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.12.010
  • Hydraulic Tomography of Discrete Networks of Conduits and Fractures in a
           Karstic Aquifer by Using a Deterministic Inversion Algorithm
    • Authors: P. Fischer; A. Jardani; N. Lecoq
      Abstract: Publication date: Available online 6 December 2017
      Source:Advances in Water Resources
      Author(s): P. Fischer, A. Jardani, N. Lecoq
      In this paper we present a novel inverse modeling method called Discrete Network Deterministic Inversion (DNDI) for mapping the geometry and property of the discrete network of conduits and fractures in the karstified aquifers. The DNDI algorithm is based on a coupled discrete-continuum concept to simulate numerically water flows in a model and a deterministic optimization algorithm to invert a set of observed piezometric data recorded during multiple pumping tests. In this method, the model is partioned in subspaces piloted by a set of parameters (matrix transmissivity, and network local direction and equivalent transmissivity) that are considered as unknown. In this way the deterministic optimization process can iteratively correct the geometry of the network and the values of the properties, until it converges to a global network geometry in a solution model able to reproduce the set of data. An uncertainty analysis of this result can be performed from the maps of posterior uncertainties on the network geometry or on the property values. This method has been successfully tested for three different theoretical and simplified study cases with hydraulic responses data generated from hypothetical karstic models with an increasing complexity of the network geometry, and of the matrix heterogeneity.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.11.029
  • Modeling chemical gradients in sediments under losing and gaining flow
           conditions: the GRADIENT code
    • Authors: Fulvio Boano; Natalie De Falco; Shai Arnon
      Abstract: Publication date: Available online 6 December 2017
      Source:Advances in Water Resources
      Author(s): Fulvio Boano, Natalie De Falco, Shai Arnon
      Interfaces between sediments and water bodies often represent biochemical hotspots for nutrient reactions and are characterized by steep concentration gradients of different reactive solutes. Vertical profiles of these concentrations are routinely collected to obtain information on nutrient dynamics, and simple codes have been developed to analyze these profiles and determine the magnitude and distribution of reaction rates within sediments. However, existing publicly available codes do not consider the potential contribution of water flow in the sediments to nutrient transport, and their applications to field sites with significant water-borne nutrient fluxes may lead to large errors in the estimated reaction rates. To fill this gap, the present work presents GRADIENT, a novel algorithm to evaluate distributions of reaction rates from observed concentration profiles. GRADIENT is a Matlab code that extends a previously published framework to include the role of nutrient advection, and provides robust estimates of reaction rates in sediments with significant water flow. This work discusses the theoretical basis of the method and shows its performance by comparing the results to a series of synthetic data and to laboratory experiments. The results clearly show that in systems with losing or gaining fluxes, the inclusion of such fluxes is critical for estimating local and overall reaction rates in sediments.

      PubDate: 2017-12-12T16:29:37Z
      DOI: 10.1016/j.advwatres.2017.12.002
  • Pore-network model of evaporation-induced salt precipitation in porous
           media: the effect of correlations and heterogeneity
    • Authors: Hassan Dashtian; Nima Shokri Muhammad Sahimi
      Abstract: Publication date: Available online 5 December 2017
      Source:Advances in Water Resources
      Author(s): Hassan Dashtian, Nima Shokri, Muhammad Sahimi
      Salt transport and precipitation in porous media constitute a set of complex and fascinating phenomena that are of considerable interest to several important problems, ranging from storage of CO2 in geological formations, to soil fertility, and protection of pavements and roads, as well as historical monuments. The phenomena occur at the pore scale and are greatly influenced by the heterogeneity of the pore space morphology. We present a pore-network (PN) model to study the phenomena. Vapor diffusion, capillary effect at the brine-vapor interface, flow of brine, and transport of salt and its precipitation in the pores that plug the pores partially or completely are all accounted for. The drying process is modeled by the invasion percolation, while transport of salt in brine is accounted for by the convective-diffusion equation. We demonstrate that the drying patterns, the clustering and connectivity of the pore throats in which salt precipitation occurs, the saturation distribution, and the drying rate are all strongly dependent upon the pore-size distribution, the correlations among the pore sizes, and the anisotropy of the pore space caused by stratification that most natural porous media contain. In particular, if the strata are more or less parallel to the direction of injection of the gas that dries out the pore space (air, for example) and/or causes salt precipitation (CO2, for example), the drying rate increases significantly. Moreover, salt tends to precipitate in clusters of neighboring pores that are parallel to the open surface of the porous medium.

      PubDate: 2017-12-12T16:29:37Z
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