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Frontiers in Water
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  This is an Open Access Journal Open Access journal
ISSN (Online) 2624-9375
Published by Frontiers Media Homepage  [96 journals]
  • Hydrogeochemical characterization of groundwater in a coastal area,
           central western Senegal

    • Authors: Seyni Ndoye, Mathias Diedhiou, Helene Celle, Serigne Faye, Mohammed Baalousha, Philippe Le Coustumer
      Abstract: One of the most serious problems affecting coastal aquifers is seawater intrusion. Senegal is currently facing an increased demand for freshwater resources due to population growth and economic development in coastal areas. In areas affected by saltwater contamination, chloride concentrations as high as 8880 mg/L were measured in groundwater samples taken from wells near the coastal zone, indicating deterioration in water quality. Our study aims to identify the zones of degradation of the water quality by determining the chemical composition of groundwater and the geochemical processes controlling the chemical patterns. Hydrogeochemical (Piper and Chadha diagrams, chloroalkaline indices, normalized bivariate plots) and multivariate statistical (Hierarchical cluster analyses) techniques were used. Forty-two groundwater samples were collected and analyzed for concentrations of major and some minor ions, electrical conductivity (EC), total dissolved solids (TDS), temperature, and pH. From samples we were able to establish a diagnosis of the very heterogeneous quality of the groundwater in this area. The average pH of the groundwater is 7.6 and about 80% of the groundwater samples have a TDS below 1000 mg/L. On the other hand, the EC values are very heterogeneous with very high conductivities in coastal areas. Approximately, 80% of the groundwater samples have a TDS less than 1000 mg/L and EC values are very heterogeneous. The dominant water types in the study area are Na-Cl water type (less than 10% of the samples) characteristic of the spatial evolution of groundwater salinization from west to east, mixed Ca-Mg-Cl due to fresh water/salt water contact and Ca-Mg-HCO3 water-type (nearly 56% of the samples) to the east. A hydrogeochemical zonation of the aquifer, based on the presence of different water families allows us to visualize the highly degraded (west), mixed (center) and healthy (east) zones. Chloroalkaline indices and normalized bivariate plots show that the chemistry of groundwater is controlled mainly by water-rock interaction and evaporation processes. As water-rock interaction processes, dissolution of carbonate and evaporite, weathering of silicate, ions exchange regulates major ion chemistry.
      PubDate: 2023-01-26T00:00:00Z
  • Willing to have, willing to help, or ready to own—Determinants of
           variants of stewardship social practices around Blue-Green Infrastructure
           in dense urban communities|Introduction|Methods|Results|Discussion

    • Authors: Jessica Lamond, Glyn Everett
      Abstract: IntroductionThere is increasing acceptance of the desirability of involving communities in stewardship activities around urban blue-green infrastructure (BGI) to generate acceptance, reduce vandalism and decrease the maintenance burden on authorities. However, little is yet known about the willingness of communities to engage in such stewardship, or the drivers to participate in activities.MethodsThis research adopted a practice lens and firstly defined three variants of BGI stewardship associated with passive acceptance, active care for and ownership of BGI. Secondly, the research conceptualized these practices within a complex of pro-environmental practices communities could perform. Through a face-to-face household survey in a dense UK urban area, the research sought to identify the prevalence of these variants of practice, their associations with other pro-environmental practices and the meanings, resources and competencies that drive a household's willingness to engage.ResultsThe research found different willingness for the three variants with passive most popular and ownership least. Meanings associated with BGI stewardship practice appeared to differ in crucial respects from other pro-environmental practices and were most associated with water-management rather than climate concern, however some place-based motivations were also involved. Practical resource and competency considerations also affected willingness to perform active stewardship and ownership variants.DiscussionThe research concluded that promoting the water-management aspects of BGI for all variants, along with facilitation of engagement with more active variants, could increase interest in BGI stewardship participation.
      PubDate: 2023-01-26T00:00:00Z
  • Flood frequency and flood intensity changes in the post embankment period
           in the Kosi sub-basin India: Impact of location, caste, and class on the
           flood vulnerability of the marginal communities

    • Authors: Ranjeet Kumar Sahani, Shrinivas Badiger, Abhishek Samrat, Siddhartha Krishnan
      Abstract: The overall precipitation in the state of Bihar, India is showing a decreasing trend both annually and seasonally, and yet extreme flood events are on the rise. The Kosi river embankments built to safeguard communities against flood risk are a product of socio-political and historical events in the past, but have resulted in differential impacts on those living inside and outside these embankments. The geomorphology of the river Kosi also makes it highly susceptible to recurring floods because it forms one of the largest inland deltas in North Bihar. Flood protection structures such as embankments exacerbate the magnitude of floods by jacketing the heavy sediment load and thus raising the riverbeds and exacerbating the intensity and duration of floods. Our paper employs an interdisciplinary approach to analysing both the biophysical and socio-institutional causalities of increasing flood events. From the quantitative analysis of rainfall data, we find that the daily, as well as monthly rainfall alone are not responsible for extreme flood events. The extreme rainfall events in the summer monsoon also do not increase the odds of flooding. Therefore, we conclude that precipitation alone is not the main factor affecting community's vulnerabilities but, a combination of socio-institutional factors including spatial location with respect to the embankment, class and caste of these communities. Our statistical analysis correlating daily and monthly gridded rainfall to the occurrences of flooding at the district level suggest that there are fewer flood events in the presence of the embankments across all years. However, primary data from household interviews and field observations confirm that the frequency and intensity of floods have increased in the post-embankment period. We found that the breaching of the river embankments is one of the major factors responsible for floods outside of the embankments. Kosi's marginalized communities perceive that they have become more vulnerable to flood risk in the post-embankment period with a declining standard of living in the Kosi villages caused by lack of proper roads, economic opportunities, educational institutions, public utilities and healthcare facilities, especially in areas with embankments.
      PubDate: 2023-01-26T00:00:00Z
  • Evaluation of wastewater surveillance for SARS-CoV-2 in Massachusetts
           correctional facilities, 2020–2022|Introduction|Materials and

    • Authors: R. Monina Klevens, Cristin C. W. Young, Scott W. Olesen, Anthony Osinski, Daniel Church, Jennifer Muten, Lori Chou, Tami Segal, Kevin Cranston
      Abstract: IntroductionCorrectional facilities have environmental, resource, and organizational factors that facilitate SARS-CoV-2 transmission and challenge clinical testing of staff and residents. In Massachusetts, multiple state prisons implemented wastewater surveillance for strategic testing of individuals and isolation of COVID-19 cases early in the course of infection, as recommended by the Centers for Disease Control and Prevention (CDC). Our objective was to quantify the correlation of COVID-19 cases with facility-level wastewater surveillance compared to standard case surveillance in towns in closest geographic proximity to participating correctional facilities.Materials and methodsAvailable data included number of reported COVID-19 cases in residents from each of eight participating facilities (labeled A-H for anonymity), wastewater viral concentrations at each facility, and COVID-19 cases reported to routine surveillance in towns geographically nearest each facility. We selected data from December 2020-February 2022. Spearman's rank correlation was calculated at each facility to assess agreement between town cases and facility resident cases, and between wastewater concentrations and facility resident cases. We considered a correlation of ≤0.3 as weak and ≥0.6 as strong.ResultsFacilities housed a mean of 502 individuals (range 54–1,184) with mean staffing of 341 (range 53–547). In 7/8 facilities, the town/resident cases correlation coefficients (ρ) were statistically significant (range 0.22–0.65); in all facilities, the wastewater/facility resident cases correlations were statistically significant (range 0.57–0.82). Consistently, ρ values were higher for facility-specific wastewater/resident cases than for town/resident cases: A (0.65, 0.80), B (0.59, 0.81), C (0.55, 0.70), D (0.61, 0.82), E (0.46, 0.62), F (0.51, 0.70), and H (0.22, 0.57).ConclusionWe conclude that wastewater surveillance for SARS-CoV-2 can provide an additional signal to objectively supplement existing COVID-19 clinical surveillance for the early detection of cases and infection control efforts at correctional facilities.
      PubDate: 2023-01-26T00:00:00Z
  • Mountaintop removal coal mining impacts on structural and functional
           indicators in Central Appalachian streams

    • Authors: Roger A. Burke, Ken M. Fritz, Brent R. Johnson, Rachel Price
      Abstract: Mountaintop removal coal mining (MTR) has been a major source of landscape change in the Central Appalachians of the United States (US). Changes in stream hydrology, channel geomorphology and water quality caused by MTR coal mining can lead to severe impairment of stream ecological integrity. The objective of the Clean Water Act (CWA) is to restore and maintain the ecological integrity of the Nation's waters. Sensitive, readily measured indicators of ecosystem structure and function are needed for the assessment of stream ecological integrity. Most CWA assessments rely on structural indicators; inclusion of functional indicators could make these assessments more holistic and effective. The goals of this study were: (1) test the efficacy of selected carbon (C) and nitrogen (N) cycling and microbial structural and functional indicators for assessing MTR coal mining impacts on streams; (2) determine whether indicators respond to impacts in a predictable manner; and (3) determine if functional indicators are less likely to change than are structural indicators in response to stressors associated with MTR coal mining. The structural indicators are water quality and sediment organic matter concentrations, and the functional indicators relate to microbial activity and biofilm production. Seasonal measurements were conducted over the course of a year in streams draining small MTR-impacted and forested watersheds in the Twentymile Creek watershed of West Virginia (WV). Five of the eight structural parameters measured had significant responses, with all means greater in the MTR-impacted streams than in the forested streams. These responses resulted from changes in source or augmentation of the original source of the C and N structural parameters because of MTR coal mining. Nitrate concentration and the stable carbon isotopic ratio of dissolved inorganic carbon were the most effective indicators evaluated in this study. Only three of the fourteen functional indicators measured had significant responses to MTR coal mining, with all means greater in the forested streams than in the MTR-impacted streams. These results suggest that stressors associated with MTR coal mining caused reduction in some aspects of microbial cycling, but resource subsidies may have counterbalanced some of the inhibition leading to no observable change in most of the functional indicators. The detritus base, which is thought to confer functional stability, was likely sustained in the MTR-impacted streams by channel storage and/or leaf litter inputs from their largely intact riparian zones. Overall, our results largely support the hypothesis that certain functional processes are more resistant to stress induced change than structural properties but also suggest the difficulty of identifying suitable functional indicators for ecological integrity assessment.
      PubDate: 2023-01-19T00:00:00Z
  • Sample size requirements for riverbank macrolitter characterization

    • Authors: Sjoukje I. de Lange, Yvette Mellink, Paul Vriend, Paolo F. Tasseron, Finn Begemann, Rahel Hauk, Heleen Aalderink, Eric Hamers, Peter Jansson, Nonna Joosse, Ansje J. Löhr, Romi Lotcheris, Louise Schreyers, Vivien Vos, Tim H. M. van Emmerik
      Abstract: Anthropogenic litter is omnipresent in terrestrial and freshwater systems, and can have major economic and ecological impacts. Monitoring and modeling of anthropogenic litter comes with large uncertainties due to the wide variety of litter characteristics, including size, mass, and item type. It is unclear as to what the effect of sample set size is on the reliability and representativeness of litter item statistics. Reliable item statistics are needed to (1) improve monitoring strategies, (2) parameterize litter in transport models, and (3) convert litter counts to mass for stock and flux calculations. In this paper, we quantify sample set size requirement for riverbank litter characterization, using a database of more than 14,000 macrolitter items (>0.5 cm), sampled for 1 year at eight riverbank locations along the Dutch Rhine, IJssel, and Meuse rivers. We use this database to perform a Monte Carlo based bootstrap analysis on the item statistics, to determine the relation between sample size and variability in the mean and median values. Based on this, we present sample set size requirements, corresponding to selected uncertainty and confidence levels. Optima between sampling effort and information gain is suggested (depending on the acceptable uncertainty level), which is a function of litter type heterogeneity. We found that the heterogeneity of the characteristics of litter items varies between different litter categories, and demonstrate that the minimum required sample set size depends on the heterogeneity of the litter category. This implies that more items of heterogeneous litter categories need to be sampled than of heterogeneous item categories to reach the same uncertainty level in item statistics. For example, to describe the mean mass the heterogeneous category soft fragments (>2.5 cm) with 90% confidence, 990 items were needed, while only 39 items were needed for the uniform category metal bottle caps. Finally, we use the heterogeneity within litter categories to assess the sample size requirements for each river system. All data collected for this study are freely available, and may form the basis of an open access global database which can be used by scientists, practitioners, and policymakers to improve future monitoring strategies and modeling efforts.
      PubDate: 2023-01-19T00:00:00Z
  • Editorial: Identifying hotspots of hydro-hazards under global change

    • Authors: Maria Pregnolato, Lindsay Beevers, Ioana Popescu
      PubDate: 2023-01-18T00:00:00Z
  • A coupled agent-based model to analyse human-drought feedbacks for
           agropastoralists in dryland regions

    • Authors: Ileen N. Streefkerk, Jens de Bruijn, Toon Haer, Anne F. Van Loon, Edisson A. Quichimbo, Marthe Wens, Khalid Hassaballah, Jeroen C. J. H. Aerts
      Abstract: Drought is a persistent hazard that impacts the environment, people's livelihoods, access to education and food security. Adaptation choices made by people can influence the propagation of this drought hazard. However, few drought models incorporate adaptive behavior and feedbacks between adaptations and drought. In this research, we present a dynamic drought adaptation modeling framework, ADOPT-AP, which combines socio-hydrological and agent-based modeling approaches. This approach is applied to agropastoral communities in dryland regions in Kenya. We couple the spatially explicit hydrological Dryland Water Partitioning (DRYP) model with a behavioral model capable of simulating different bounded rational behavioral theories (ADOPT). The results demonstrate that agropastoralists respond differently to drought due to differences in (perceptions of) their hydrological environment. Downstream communities are impacted more heavily and implement more short-term adaptation measures than upstream communities in the same catchment. Additional drivers of drought adaptation concern socio-economic factors such as wealth and distance to wells. We show that the uptake of drought adaptation influences soil moisture (positively through irrigation) and groundwater (negatively through abstraction) and, thus, the drought propagation through the hydrological cycle.
      PubDate: 2023-01-13T00:00:00Z
  • Institutional levels of water management in the Colorado River basin
           region: A macro-historical geographic review

    • Authors: James L. Wescoat
      Abstract: Complex water-stressed basins like the Colorado River in North America have multiple institutional levels of water management. Each institutional level is characterized by rules, organizations, and spatial jurisdictions that developed over decades to centuries to shape a dynamic multi-level system. After introducing the concept of institutional levels, and its relationship to geographic scales, this paper employs systematic bibliographic search methods to review their development in the Colorado River basin region. Results begin with the community level of water management from prehistoric Indian water cultures to early Hispanic water communities, 19th century water communities, and 20th century water organizations. Conflict among water communities shaped the state level of constitutional authority over water rights administration during the 19th century. Competition among states led in the 20th century to the interstate level of apportionment that often paralleled federal and tribal level water development policies, eventually leading to the international level of treaty relations between the U.S. and Mexico. This macro-historical geographic progression from institutions that were relatively small in size and early in time to those at higher levels and more recent in time offers insights into the multi-level institutional logic of the “law of the river” in the Colorado River basin region.
      PubDate: 2023-01-11T00:00:00Z
  • On the transferability of snowmelt runoff model parameters: Discharge
           modeling in the Chandra-Bhaga Basin, western Himalaya

    • Authors: Parul Vinze, Mohd. Farooq Azam
      Abstract: Snowmelt runoff plays a major role in the glacierized and snow-covered basins in the western Himalaya. Modeling is the most helpful tool to quantify snowmelt contribution in mountainous rivers. However, the model calibration is very difficult because of the scarcity of ground observations in the Himalaya. We applied snowmelt runoff model (SRM) in a reference catchment of Chhota Shigri Glacier in the Chandra-Bhaga Basin, western Himalaya. Three model parameters [temperature lapse rate and recession coefficients (x and y)] among the nine model parameters were constrained using extensive field observations while initial values of other parameters were adopted from previous studies and calibrated, and the model was calibrated and validated against the observed discharge data. The daily discharge was simulated over 2003–2018 for both Chhota Shigri Catchment and Chandra-Bhaga Basin using snow cover area (SCA), precipitation, and temperature as inputs. The simulated mean annual discharges were 1.2 ± 0.2 m3/s and 55.9 ± 12.1 m3/s over 2003–2018 for Chhota Shigri Catchment and Chandra-Bhaga Basin, respectively. The reconstructed discharge was mainly controlled by summer temperature and summer SCA in the Chhota Shigri Catchment and summer SCA and summer precipitation in the Chandra-Bhaga Basin. The decadal comparison showed an increase (11% and 9%) and early onset (10 days and 20 days) of maximum monthly discharge over 2011–2018 compared to 2003–2010 in both catchment and basin scales. The model output is almost equally sensitive to the “degree day factor” and “runoff coefficient for snow” in the Chhota Shigri Catchment and most sensitive to the “runoff coefficient for snow” in the Chandra-Bhaga Basin. Though the SRM parameters were constrained/calibrated in a data-plenty reference catchment of Chhota Shigri Glacier, their application resulted in large discharge overestimation at the basin scale and were not transferable in the same basin i.e., Chandra-Bhaga Basin. Extreme care must be taken while using SRM parameters from other basins.
      PubDate: 2023-01-11T00:00:00Z
  • Impacts on alternate bar geometry and dynamics in a trained sand bed river

    • Authors: Till Branß, Jochen Aberle, Bernd Hentschel
      PubDate: 2023-01-09T00:00:00Z
  • Editorial: (10 years) Water-Energy-Food nexus: Towards knowledge
           synthesis, action prioritization and revitalization of security debates

    • Authors: Mohammad Al-Saidi, Bassel Daher, Nadir Ahmed Elagib
      PubDate: 2023-01-09T00:00:00Z
  • Editorial: Urban drainage in a context of climate and land cover changes

    • Authors: Daniel Jato-Espino, Susanne Charlesworth, João P. Leitão, Juan Pablo Rodríguez Sánchez
      PubDate: 2023-01-06T00:00:00Z
  • Pinpointing drivers of widespread colonization of Legionella pneumophila
           in a green building: Roles of water softener system, expansion tank, and
           reduced occupancy|Introduction|Methods|Results|Discussion

    • Authors: Sayalee Joshi, Rain Richard, Carlos Levya, Joanna Ciol Harrison, Daniella Saetta, Naushita Sharma, Lucas Crane, Noelle Mushro, Lucien Dieter, Grace V. Morgan, Ashley Heida, Bennett Welco, Treavor H. Boyer, Paul Westerhoff, Kerry A. Hamilton
      Abstract: IntroductionLegionella pneumophila is an opportunistic pathogen that is a key contributor to drinking water-associated disease outbreaks in the United States. Prolonged water stagnation periods in building plumbing systems due to low occupancy, especially during building shutdowns, breaks, and holidays, can lead to water quality deterioration and (re)colonization of buildings with L. pneumophila. Water monitoring in buildings typically relies on grab samples with small datasets.MethodsIn this study, a larger dataset was created by sampling a Leadership in Energy and Environmental Design (LEED)-certified data-rich commercial building for L. pneumophila and physical-chemical water quality during the COVID-19 pandemic after reduced building occupancy. A proxy for human occupancy rates using WIFI logins was recorded throughout the study period.ResultsL. pneumophila was observed in grab samples taken throughout the building, where concentrations generally increased with greater distances from the building point of entry to locations throughout the building. Factors conducive to microbial growth were identified in the building including fluctuations in water temperatures, lack of chlorine residual, a low water heater setpoint, colonized water-saving fixtures, prolonged stagnation throughout the building; especially in an expansion tank designed to reduce pressure issues during demand fluctuations, and the presence of oversized softener tanks with ion exchange resin that contributed to chlorine residual removal as well as colonization of the resin with L. pneumophila.DiscussionFlushing and thermal disinfection alone did not resolve the problem, and replacement of the expansion tank ultimately resolved the L. pneumophila issue. As ad-hoc approaches are logistically- and time-intensive, more proactive approaches are needed for informing preventative and corrective actions for reducing the risk of exposure to opportunistic pathogens in the building plumbing.
      PubDate: 2023-01-05T00:00:00Z
  • Continuous high-frequency pesticide monitoring in a small tile-drained
           agricultural stream to reveal diel concentration fluctuations in dry

    • Authors: Daniele la Cecilia, Anne Dax, Heinz Ehmann, Margie Koster, Heinz Singer, Christian Stamm
      Abstract: Plant Protection Products (PPPs) pose a threat to surface water quality worldwide. While small streams compose the majority of the stream lengths and are crucial for biodiversity, their exposure patterns to PPPs and transformation products (TPs) are largely understudied in dry periods. This knowledge gap can lead to ineffective monitoring strategies for addressing water quality issues. Here, we focus on two extended dry periods the in-depth analysis of a unique continuous high-frequency (20 min) concentrations dataset for 60 PPPs and TPs. The dataset refers to the monitoring of a small tile-drained agricultural stream over 41 days from May to July in 2019. The overall 2560 concentration data per compound obtained with the on-site mass spectrometer MS2Field platform revealed: (i) surprisingly high maximum concentrations (hundreds to thousands ng/l for some compounds) over extended periods of time, (ii) novel diel fluctuations of concentrations in the order of hundreds of ng/l for some PPPs and TPs, (iii) unexpected high concentrations (up to 220 ng/l) of a legacy compound (the fungicide oxadixyl withdrawn from the Swiss market in 2005). We hypothesized the cause of our findings was rooted in high PPPs levels in the shallow groundwater. To investigate this, we complemented our measurements with the long-term Swiss national monitoring program integrating samples over 14 days at the same location. The continuous long-term measurements found a few PPPs all year-round, thus indicating the presence of persistent contamination sources in the catchment. Next, we collected spatially distributed grab samples in tile drain outlets and stream water on a dry summer day in 2020. The dry-day campaign not only confirmed our hypothesis given the measured high concentrations of PPPs and TPs in tile drain outlets but also highlighted large spatial variability in measured concentrations along the stream. Hereafter, we highlight the questions that different monitoring schemes can answer in dry conditions. This information was relevant to observe for the first time, and thus foresee, the dynamic patterns of PPPs and TPs in the aquatic ecosystem in dry summer conditions, with the latter generally becoming more frequent due to climate change.
      PubDate: 2023-01-04T00:00:00Z
  • A review of the water resources of Ghana in a changing climate and
           anthropogenic stresses

    • Authors: Sampson K. Agodzo, Enoch Bessah, Mexoese Nyatuame
      Abstract: An extensive narrative review approach is adopted to present existing information on the consumptive and non-consumptive uses and their related issues, such as floods and droughts, climate and the environment in Ghana. Total annual rainfall in the country ranges between 800 mm/y (south-east coat) and 2,000 mm/y (south-west coast) with a bimodal and mono-modal patterns in the south and north, respectively. Annual total runoff from the 3 river systems (the Volta river system, the South-western river system and the Coastal river system) in Ghana is estimated at 40 billion m3 out of about 53 billion renewable freshwater resources. Groundwater yields ranges from 6 m3/h in the Volta basin sedimentary formations to 180 m3/h in the limestone formations. It is estimated that the total water withdrawal as a percentage of total renewable water resources is about 2%. At an average per capita consumption of water of 50 l/p/d, estimated daily water demand for the 2021 population of 31 million people stands at about 566 million m3/y. Current water supply systems are overstretched and it is further estimated that about US $ 240 million is required per year as capital expenditure in urban and rural water supply. Moreover, climate change is projected to increase the scarcity of water in future. Wastewater generated through domestic and industrial uses including storm water in urban Ghana is estimated at about 760 million m3/y. Ghana's irrigation potential to reduce climate change impact on agriculture is put at between 0.36 and 2.9 million ha, accounting for about 66.4% of the consumptive water withdrawal. Estimated water demand for cattle, sheep and goats in 2010 was put at about 22 million m3/y. Other services obtained from surface water are the provision of fish (the Volta Lake is estimated to contributes to 16% of total catch in Ghana); hydropower generation accounting for about 40% of total power installed capacity (Akosombo = 1,020 MW, Kpong = 160 MW, and Bui = 404 MW); water transportation (notably on the Volta Lake); tourist attractions [are 550 km Ghana's shoreline that has about 90 lagoons, the Volta Lake, the lower Volta (e.g., Sogakope, Ada) and some other inland waters like Lake Bosumtwi] and wetlands (recognized by RAMSAR convention of 1971) In the legal context, water governance issues are handled by various institutions created by Acts of Parliament.
      PubDate: 2023-01-04T00:00:00Z
  • Past and future evolution of the onshore-offshore groundwater system of a
           carbonate archipelago: The case of the Maltese Islands, central
           Mediterranean Sea

    • Authors: Michele De Biase, Francesco Chidichimo, Aaron Micallef, Denis Cohen, Carl Gable, Thomas Zwinger
      Abstract: Offshore freshened groundwater (OFG) is groundwater with a salinity below that of seawater that is stored in sub-seafloor sediments and rocks. OFG has been proposed as an alternative solution to relieve water scarcity in coastal regions and to enhance oil recovery. Although OFG has been documented in most continental margins, we still have a poor understanding of the extent and flow characteristics of OFG systems, and their evolution through time. In view of the general absence of appropriate field data, paleohydrogeological models have been used. The majority of these models are based on 2D approaches, and they rarely consider the future evolution of OFG systems, especially in response to predicted climate change. Here we utilize recently acquired geological, geophysical and hydrogeological data from onshore and offshore the Maltese Islands, and employ 2D and 3D numerical models, to: (i) reconstruct the evolution of the onshore-offshore groundwater system during the last 188 ka, (ii) predict the evolution of the OFG system in response to climate-related changes. We show that the mechanisms emplacing OFG include a combination of active meteoric recharge at present as well as at sea-level lowstands. The Maltese onshore-offshore groundwater system is relatively dynamic, with 23% of groundwater being preserved in the last 18 ka. The control of geology is expressed by the more prevalent distribution of OFG north of the Great Fault, which is associated to the occurrence of low permeability units, and the asymmetry of the groundwater lens during the 18 ka lowstand. A 30% decrease in recharge predicted in the coming 100 years will diminish OFG extent by 38%, whereas sea-level rise will play a negligible role. At present the estimated volume of OFG is 1 km3, which could potentially provide an alternative supply of potable water to the Maltese Islands for 75 years. Exploitation of OFG with minimal salinization of onshore groundwater bodies would require locating pumping wells close to the coast.
      PubDate: 2023-01-04T00:00:00Z
  • Transforming citywide sanitation provision: Utility voices on pit emptying
           and transport services in Kenya and Zambia

    • Authors: Claire Grisaffi, Priscillah Oluoch, Eustakia M. Hamuchenje, Jessica Phiri, Gertrude Salano, Lisa Hawkes, Alison Parker
      Abstract: This paper documents the key challenges faced by utilities in sub-Saharan Africa attempting to establish citywide safe manual and semi-mechanized latrine pit emptying, transport and disposal services. The research aims to take a snapshot of utilities at a pivotal point in service development, where initial services have been piloted and the utilities are looking to go to scale. We use the CWIS framework to guide analysis of perspectives of the implementing agencies in Livingstone, Zambia, and Malindi, Kenya, using a secondary data review and 34 key informant interviews. This paper confirms previous findings around the high cost of safe sanitation services in low-income areas, the barriers of emptiability, the engagement of manual pit emptiers and the requirement for investment in supporting systems. Areas for future research were identified, including approaches for service delivery to reduce the decision load on the household, structures of engagement and regulation of pit emptiers, and finally how regulation could support incremental improvements toward full coverage, including the lowest income households. The research documents, for the first time in the region, the challenges of dealing with disgust in establishing these new services and the conflicting role of public utilities as both commercial and social organizations. The current model for private sector delivery of the service is politically viable and reduces the risk and cost burden on the utilities. However, it is likely to leave the utilities unable to scale sanitation to low-income areas.
      PubDate: 2022-12-23T00:00:00Z
  • Index-based impact monitoring of water infrastructures in climate change

    • Authors: Shivanand Nalgire, Pennan Chinnasamy
      Abstract: Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA) is currently the largest funded rural development program in India to ensure rural livelihood by providing employment through different activities. Owing to climate change impacts and water scarcity for the last 5 years, approximately more than 70% of activities (budget of 5 billion USD per year) are focused on water issues. For better utilization of resources, MGNREGA has been implementing these works in convergence with many other schemes like the integrated watershed management programme (IWMP), with the aim of restoring rural natural resources, like soil, vegetation, and water. Although the largest Rural Development Scheme in India, the monitoring and evaluation (M&E) does not focus on the actual impact on water resources but only focuses on the amount spent. This can lead to only information on funds spent but does not have much an impact on water resources and earmarking data for monitoring. The recent advancements in remote sensing techniques have provided open access to high-resolution satellite data along with the processing platform. Considering the available technologies and gaps in the existing M&E framework, the current study developed a low-cost, comprehensive, robust, and near real-time M&E framework to assess the impact of water projects. A novel remote sensing-based ecological index (RSEI) has been developed to assess the overall ecological status of land surfaces due to the water infrastructures developed. The performance of RSEI has also been assessed using the secondary data of crop production, which shows excellent results (adjusted R2 value of 82% and Pearson's correlation coefficient of 0.92). In addition, RSEI results were compared against the results of government audits (e.g., by the Comptroller Auditor General of India), wherein RSEI found similar areas of increased water status and crop productivity. The results indicate that the use of the RSEI-based M&E framework will allow for an impact assessment of water infrastructure and also aid to identify the priority areas demanding immediate intervention. Thus, RSEI can be used as a decision support system for stakeholders, including for smooth planning, designing, implementation, monitoring, and evaluation of water infrastructure for combating climate change extremes such as droughts.
      PubDate: 2022-12-22T00:00:00Z
  • Assessment of inland flood hazard sensitivity to hydrological
           intensification in coastal watersheds|Introduction|Methods|Results and

    • Authors: Robert L. Miller
      Abstract: IntroductionIntensification of the hydrologic cycle induced by climate variability and landscape modification is expected to increase the frequency of extreme flood events. Multi-jurisdictional approaches to manage inland flood risks at watershed scales demand the ability to objectively assess not only future flood potentials, but to also set priorities based upon multiple factors such as the stream channels most sensitive to hydrologic stress.MethodsThis study presents a method to estimate flood hazard sensitivities to increasing stormwater runoff due to hydrologic intensification (e.g., urbanization, climate effects) on local and watershed scales. The method is demonstrated in the low-gradient inland watershed regions of southwestern coastal Louisiana, USA. Utilizing highly detailed numerical models from the Federal Emergency Management Agency (FEMA), absolute and relative flood sensitivities were calculated for 45 flood-prone stream channels in the Lafayette, LA region. Channel sensitivities to flood hazards induced by changes in the 10-yr (10% annual exceedance probability) flood flows were quantified by analysis of 485 scenarios developed using a downward counterfactual scaling strategy.Results and discussionRelying entirely upon publicly available numerical models and input datasets, the study revealed key information about the relationship between estimable hydraulic characteristics (e.g., conveyance, resistance, and flow) and absolute and relative flood hazard sensitivity measures on a per-channel basis. Information from the subset of detailed numerical models was efficiently leveraged to provide a regional map of relative flood sensitivities. The methodology is robust and can be applied in very general settings to address the concern of hydrologic intensification in practical flood risk management applications.
      PubDate: 2022-12-22T00:00:00Z
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