Subjects -> EARTH SCIENCES (Total: 771 journals)
    - EARTH SCIENCES (527 journals)
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HYDROLOGY (29 journals)

Showing 1 - 32 of 32 Journals sorted alphabetically
Águas Subterrâneas     Open Access   (Followers: 1)
Anais Hidrográficos     Open Access   (Followers: 1)
Bulletin of Marine Science     Full-text available via subscription   (Followers: 9)
Discover Water     Open Access   (Followers: 1)
Ecohydrology     Hybrid Journal   (Followers: 13)
Ecohydrology & Hydrobiology     Full-text available via subscription   (Followers: 5)
Geology, Ecology, and Landscapes     Open Access   (Followers: 1)
Hidrobiológica     Open Access  
Hydrobiology     Open Access   (Followers: 16)
Hydrological Sciences Journal - Journal des Sciences Hydrologiques     Full-text available via subscription   (Followers: 22)
Hydrology     Open Access   (Followers: 7)
HydroResearch     Open Access   (Followers: 1)
Hydrosphere. Hazard processes and phenomena     Open Access  
International Hydrographic Review     Open Access   (Followers: 7)
International Journal of Hydrology Science and Technology     Hybrid Journal   (Followers: 7)
Journal of Contaminant Hydrology     Hybrid Journal   (Followers: 23)
Journal of Hydrogeology and Hydrologic Engineering     Hybrid Journal   (Followers: 9)
Journal of Hydrology     Hybrid Journal   (Followers: 74)
Journal of Hydrology (New Zealand)     Full-text available via subscription   (Followers: 7)
Journal of Hydrology : Regional Studies     Open Access   (Followers: 22)
Journal of Hydrology and Hydromechanics     Open Access   (Followers: 5)
Journal of Hydrology and Meteorology     Open Access   (Followers: 40)
Journal of Hydrology X     Open Access   (Followers: 6)
Journal of Limnology     Open Access   (Followers: 6)
Open Journal of Modern Hydrology     Open Access   (Followers: 6)
Proceedings of the International Association of Hydrological Sciences     Open Access   (Followers: 2)
Regional Studies in Marine Science     Hybrid Journal   (Followers: 2)
Russian Meteorology and Hydrology     Hybrid Journal   (Followers: 3)
Shuiwen dizhi gongcheng dizhi / Hydrogeology & Engineering Geology     Open Access   (Followers: 14)
Water Conservation Science and Engineering     Hybrid Journal  
Water Environment and Technology     Hybrid Journal   (Followers: 21)
Water Security     Hybrid Journal   (Followers: 6)
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Journal of Hydrology and Hydromechanics
Journal Prestige (SJR): 0.599
Citation Impact (citeScore): 2
Number of Followers: 5  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0042-790X - ISSN (Online) 1338-4333
Published by Sciendo Homepage  [389 journals]
  • Flow resistance at lowland and mountainous rivers

    • Abstract: This study initially examines the various sources of flow resistance in sand-bed (lowland) and gravel-bed (mountainous) rivers along with the limitations of traditional estimation methods. The nondimensional hydraulic geometry approach, relating dimensionless flow discharge (q*) to the Darcy-Weisbach friction factor (f), has demonstrated good performance for both river types, covering shallow to moderately deep flows. However, accuracy in estimating f is affected by simplifications like assuming uniform and deep flow, neglecting bed load transport and vegetation effects, which require further evaluation. To address these issues, the proposed method is evaluated using data from four sand-bed rivers in Slovakia (with vegetation), and three gravel-bed rivers in Iran (dominated by cobbles and boulders). Bedforms prove to be significant resistance sources in all studied rivers. The approach yields separate predictors for each river type, showing a satisfactory agreement between observed and calculated values within a maximum deviation of ±20% error bands. These predictors are further validated using field data and established equations from rivers with similar physiographic characteristics. Results indicate the method performs well in predicting flow resistance in sand-bed rivers, slightly overestimating overall (+40%). It effectively captures riverbed features and vegetation influence under small-scale roughness conditions. However, the predictor’s validity for gravel-bed rivers is somewhat limited due to high variability in water-surface profiles, making it challenging to accurately capture flow dynamics under large-scale roughness conditions. Addressing complex characteristics of gravel-bed riverbeds, including boulders and local energy extraction, is crucial for improving the estimation of water-surface profile variations and flow resistance using the hydraulic geometry approach.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Impact of biochar particle size and feedstock type on hydro-physical
           properties of sandy soil

    • Abstract: Biochar, as an organic amendment, could positively change soil properties, especially soil with low organic matter and/or poor structure. Biochar application in sandy soil with low organic matter could be an effective tool for improving hydro-physical parameters of the soil economically and ecologically as well. The effect on bulk density, particle density, porosity, saturated hydraulic conductivity and available water content for plants of two biochar types applied at three different particle sizes in a sandy soil was examined. The results confirmed previous studies, showing decreased bulk density, particle density and saturated hydraulic conductivity and partially increased available water content for plants and porosity. Both biochar type and particle size affected the studied soil hydro-physical parameters. After analysis and comparison of two different types of biochar and three particle sizes, the most effective treatment for sandy soil was proved by the biochar produced from willow with the smallest particle size (<125 µm).
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Effects of the application of biochar on the soil erosion of plots of
           sloping agricultural and with silt loam soil

    • Abstract: The application of biochar is considered to be a beneficial strategy for improving soil ecosystem services. The objectives of this study are to evaluate the differences in the soil erosion of silt loam soil with or without the application of biochar and to compare the impact of the application of biochar on soil erosion for different agricultural practices, namely, bare soil, silage corn, and sown peas. Specifically, the physically-based EROSION 3D model was used to estimate the soil erosion of small plots of sloping agricultural land. In considering various combinations of agricultural practices and rainfalls with different durations and intensities, several scenarios were used to assess the impact of the application of biochar on soil erosion.The results of this study demonstrate that the highest mean values of mean soil erosion in the case study area were simulated without using any biochar on bare soil. The values of the mean soil erosion were reduced with the use of biochar. The effect of the application of biochar was shown for all types of agricultural practices; above all, it reduced soil erosion that occurred above high values (over 30 t ha–1). Although the application and reapplication of biochar showed promise in reducing soil erosion, further research is needed to gain a deeper understanding of its total effects.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Sensitivity of runoff due to changes in the characteristics of the water
           balance in the Danube River region

    • Abstract: Climate change is presently a widely discussed subject in relation to alterations in water storage capacity and the components of the hydrological balance within catchment areas. This research study was directed at two main objectives: 1. The indirect estimation of long-term mean annual runoff using an empirical model; 2. The determination of changes in the annual runoff regime of fifty Danube sub-basins. Monthly areal precipitation, discharges, and air temperature data from 1961 to 1990 were collected for selected headwater sub-basins of the Danube River. In the first part, Turc-type empirical equations for the estimation of the long-term average annual runoff R in the Danube basin were employed. The parameters of the empirical equations were determined through nonlinear regression. Given the underestimation of the actual (territorial, balance) evapotranspiration ET values determined from the balance equation, the precipitation totals were corrected by +10%. With a 10% increase in precipitation, the values of balance ET reached the values ET determined by the Budyko–Zubenok–Konstantinov method. In the second part, fifty equations for the estimation of changes in the average annual runoff, depending on increases in the air temperature and changes in the annual precipitation separately for each of the 50 sub-basins, were established. In conclusion, the results suggest that, on average, a 100 mm increase in the average annual rainfall in the Danube River headwater sub-basins, will cause a 50 mm increase in outflow, and a 1 °C increase in the average annual air temperature will lead to a 12 mm decrease in runoff.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Inverse task of pollution spreading – Localization of source in
           extensive open channel network structure

    • Abstract: This paper is focused on the problem of the pollutant source localisation in streams in other words the solution of the inverse problem of pollution spreading with in an extensive open channel network structure, i.e. in a complex system of rivers, channels and creeks in natural catchments or sewer systems in urban catchments. The design of the overall localisation procedure is based on the requirement that the entire localization system be operative and fast enough to enable quick operative interventions and help prevent the spread of pollution. The proposed model, as well as, the overall localisation procedure was calibrated and tested on a real sewer system, which represents in this case an extensive open channel network structure with free surface flow. The test results are successful and confirmed applicability of proposed localization tool in simple real conditions. However, the localisation procedure has pros and cons, which are discussed in the paper.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Using feature engineering and machine learning in FAO reference
           evapotranspiration estimation

    • Abstract: The authors of this study investigated the use of machine learning (ML) and feature engineering (FE) techniques to accurately determine FAO reference evapotranspiration (ETo) with a minimal number of climate variables being measured. The recommended techniques for areas with insufficient measurements are based solely on daily temperature readings. Various ML methods were tested to evaluate how sophisticated an ML algorithm is for this task necessary. The main emphasis was on feature engineering, which involves converting raw variables into inputs better suited for ML algorithms, resulting in improved results. FE methods for estimating evapotranspiration include approximations of clear-sky solar radiation based on altitude and Julian day, approximate relative humidity and wind velocity, a categorical month variable, and variables interactions. The authors confirmed that the ability of ML in such tasks is not solely dependent on choosing the suitable algorithm but also on this frequently ignored step. The results of computational experiments are presented, accompanied by a comparison of the proposed method against standard ETo empiric equations. Machine learning methods, mainly due to the transformation of raw variables using FE, provided better results than traditional empirical methods and sophisticated ML algorithms without FE. In addition, the authors tested the applicability of the developed models in the broader area to evaluate the possibility of their generalizability. The potential of this approach to deliver improved predictions, reduced input requirements, and increased efficiency holds interesting promise for optimizing water management strategies, irrigation planning, and decision-making within the agricultural sector.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Changes in crack width on the surface of heavy soils during drought,
           determined by precise measurement and calculation

    • Abstract: In heavy soils, changes in humidity incur soil volume changes. In the horizontal plane, these are manifested by cracks formation and in the vertical plane by the movement of the soil surface. Cracks have a significant impact on hydrodynamics of the soil profile. The work is based on the hypothesis that soil volume changes depend on both the content of clay particles in soil and soil volumetric moisture. The aim of the work is to measure and analyze the changes in the width of the cracks and their reaction to the changes in volumetric soil moisture. One of the objectives of the work was to design a simple tool for accurate measurement and calculation of the crack width on the soil surface. For the study of crack width, a soil profile in an area on the East Slovakia Lowland was selected. The profile was examined under conditions of extreme drought, at the turn of July and August 2022. Crack width varied between 1.0 cm and 3.3 cm. The calculation procedure was evaluated as satisfactory for estimating the change in crack width on the soil surface.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Spatial and temporal variability of saturated areas during rainfall-runoff

    • Abstract: Spatially distributed hydrological model Mike SHE was used as a diagnostic tool to provide information on possible overland flow source areas in the mountain catchment of Jalovecký Creek (area 22.2 km2, elevation range 820–2178 m a.s.l.) during different rainfall-runoff events. Selected events represented a sequence of several smaller, consecutive events, a flash flood event and two large events caused by frontal precipitation. Simulation of hourly runoff was better for runoff events caused by heavy rainfalls of longer duration than for the flash flood or consecutive smaller runoff events. Higher soil moisture was simulated near the streamflow network and larger possibly saturated areas were located mainly in the upper parts of mountain valleys. The most pronounced increase in the areal extent of possibly saturated areas (from 6.5% to 68.6% of the catchment area) was simulated for the event with high peak discharge divided by a short rainfall interruption. Rainfall depth exceeding 100 mm caused a large increase in the potentially saturated areas that covered subsequently half of the catchment area or more. A maximum integral connectivity scale representing the average distance over which individual pixels were connected varied for the selected events between 45 and 6327 m.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Special issue dedicated to 70th anniversary of foundation of Institute of
           Hydrology, Slovak Academy of Sciences, Bratislava, Slovakia

    • PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • The testing of a multivariate probabilistic framework for reservoir safety
           evaluation and flood risks assessment in Slovakia: A study on the Parná
           and Belá Rivers

    • Abstract: Intense floods represent a challenge to risk management. While they are multivariate in their nature, they are often studied in practice from univariate perspectives. Classical frequency analyses, which establish a relation between the peak flow or volume and the frequency of exceedance, may lead to improper risk estimations and mitigations. Therefore, it is necessary to study floods as multivariate stochastic events having mutually correlated characteristics, such as peak flood flow, corresponding volume and duration. The joint distribution properties of these characteristics play an important role in the assessment of flood risk and reservoir safety evaluation. In addition, the study of flood hydrographs is useful because of the inherent dependencies among their practice-relevant characteristics present on-site and in the regional records. This study aims to provide risk analysts with a consistent multivariate probabilistic framework using a copula-based approach. The framework respects and describes the dependence structures among the flood peaks, volumes, and durations of observed and synthetic control flood hydrographs. The seasonality of flood generation is respected by separate analyses of floods in the summer and winter seasons. A control flood hydrograph is understood as a theoretical/synthetic discharge hydrograph, which is determined by the flood peak with the chosen probability of exceedance, the corresponding volume, and the time duration with the corresponding probability. The framework comprises five steps: 1. Separation of the observed hydrographs, 2. Analysis of the flood characteristics and their dependence, 3. Modelling the marginal distributions, 4. A copula-based approach for modelling joint distributions of the flood peaks, volumes and durations, 5. Construction of synthetic flood hydrographs. The flood risk assessment and reservoir safety evaluation are described by hydrograph analyses and the conditional joint probabilities of the exceedance of the flood volume and duration conditioned on flood peak. The proposed multivariate probabilistic framework was tested and demonstrated based on data from two contrasting catchments in Slovakia. Based on the findings, the study affirms that the trivariate copula-based approach is a practical option for assessing flood risks and for reservoir safety.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Evaluation of precipitation measurements using a standard rain gauge in
           relation to data from a precision lysimeter

    • Abstract: The construction of modern lysimeters with a precise weighing system made it possible to achieve an unprecedented accuracy of precipitation measurement. This study compares two methods of measuring precipitation in the conditions of the humid continental climate of the Eastern Slovakian Lowland (Slovakia): measurement using a standard tipping-bucket rain gauge vs. precision weighable lysimeter. Data from the lysimeter were used as a reference measurement. The comparison period lasted four years (2019–2022). Only liquid rainfall was compared. The rain gauge was found to underestimate precipitation compared to the lysimeter. Cumulative precipitation for the entire monitored period captured by the rain gauge was 2.8% lower compared to lysimeter measurements. When comparing hourly and daily totals of precipitation and precipitation events, a very high degree of agreement was detected (r2 > 0.99; RMSE from 0.22 to 0.51 mm h–1). A comparison based on precipitation intensity showed a decreasing trend in measurement accuracy with increasing precipitation intensity. This tendency has an exponential course. With increasing intensity of precipitation, increasing intensity of wind was also recorded. In order to correct measurement errors, simple correction method was proposed, which helped to partially eliminate the inaccuracies of the rain gauge measurement.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Monthly stream temperatures along the Danube River: Statistical analysis
           and predictive modelling with incremental climate change scenarios

    • Abstract: The aim of the study is to analyse changes and predict the course of mean monthly water temperatures of the Danube River at various locations for the future. The first part of the study involves conducting a statistical analysis of the annual and monthly average air temperatures, water temperatures, and discharges along the Danube River. The study examines long-term trends, changes in the trends, and multiannual variability in the time series. The second part of the study focuses on simulating the average monthly water temperatures using Seasonal Autoregressive Integrated Moving Average (SARIMA) models and nonlinear regression models (NonL), based on two RCP based incremental mean monthly air temperature scenarios. To assess the impact of future climate on stream temperatures, the historical long-term average of the monthly water temperature (1990–2020) was compared with scenarios S1 (2041–2070) and S2 (2071–2100). The simulation results from the two stochastic models, the SARIMA and NonL, showed that in scenario S1, the Danube River’s average monthly water temperature is projected to increase by 0.81/0.82°C (Passau), 0.55/0.71°C (Bratislava), and 0.68/0.56°C (Reni). In scenario S2, the models predict higher increases: 2.83/2.50°C (Passau), 2.06/2.46°C (Bratislava), and 2.52/1.90°C (Reni). Overall, the SARIMA model proved to be more stable and effective in simulating the increase in monthly water temperatures in the Danube River.
      PubDate: Tue, 14 Nov 2023 00:00:00 GMT
  • Stable isotopes of oxygen and hydrogen in precipitation and river water in

    • Abstract: The article presents the first comprehensive evaluation of the isotopic composition of precipitation and runoff in Georgia. It is based on data from the monitoring of δ18O and δ2H in monthly precipitation at eleven precipitation stations and monthly runoff from five large, mostly nested catchments in Georgia, collected between the years 2013 and 2022. The data represent different climatic and altitudinal conditions ranging from the wet western part of Georgia affected by the Black Sea to the dry eastern part of the county presumably affected also by the air masses from the Caspian Sea. Specific conditions affecting the isotopic composition of precipitation and river water seem to occur close to the main ridge of the Greater Caucasus Mountains. We defined the National Meteoric Water Line (NMWL) and the National River Water Line (NRWL) for Georgia as well as the Local Meteoric Water Lines (LMWLs) and River Water Lines (RWLs) for individual precipitation stations and river gauges and investigated their slopes and intercepts. Altitude gradients of δ18O and δ2H in the rivers were similar to those in precipitation (–0.16‰ and –1.2‰ per 100 m of altitude for δ18O and δ2H, respectively). The rivers were supplied from precipitation of the colder part of the year (November/December to March/April) while the isotopic composition of precipitation in the remaining warmer part of the year was clearly detached from that of the rivers. The isotopic signal in precipitation was dampened in the rivers by a factor of 5–6. The scaled line-conditioned excess (lc-excess*) did not indicate any significant deviations of river waters from meteorological conditions in the catchments.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Effect of eucalyptus on blue and green water availability and discharge in
           the tropical highlands: An interpretation of available literature

    • Abstract: The highlands serve as water towers for the blue water in the surrounding area, with often insufficient rainfall for rainfed crops. The population is growing in the highlands, changing the hydrology and blue and green water availability. One of the changes that affect the highlands of Ethiopia is the rapidly expanding areas of small patches of eucalyptus on farmers fields. This manuscript aims to sort through the limited available literature and develop a water balance model as a starting point to discuss how hydrology is affected by increased acreage of eucalyptus in the highlands. We find some evidence in the literature that patches of eucalyptus during the dry phase may withdraw water from the subsoil up to twice the rate of evapotranspiration when the soil water is not limited. Since saturation excess generates surface runoff in the subhumid and humid highlands, water withdrawn during the dry phase should be made up before the area with eucalyptus becomes hydraulically active. The amount of water that can be removed from storage by eucalyptus is greater in areas with a long dry monsoon phase than in temperate climates for the same increase in trees. We also found, as expected, that the eucalyptus water balance model, as developed in this paper, was not valid for areas in semi-arid and arid regions. Soil crusting and water repellency might induce infiltration excess runoff. A tentative implication is that since most blue water is produced in the areas with the highest rainfall, eucalyptus in subhumid and humid monsoon regions will affect the blue water supply downstream but not the plant available green water although shading will decrease yield in the immediate surroundings of the eucalyptus trees.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Multi-criteria evaluation for parameter uncertainty assessment and
           ensemble runoff forecasting in a snow-dominated basin

    • Abstract: The increase in global temperatures undesirably affects the ever-growing world population and reveals the significance of hydrology science. Hydrological models might estimate spatial and temporal variability in hydrological components at the basin scale, which is critical for efficient water resource management. Satellite data sets with enhanced snow mapping with high spatial and temporal resolutions have been developed. The potential of these satellite data sets is evaluated in this study for multi-criteria evaluation of a conceptual hydrological model to improve model performance and reduce uncertainty.The upstream part of the transboundary Coruh River is selected for this study because snowmelt contributes a significant portion of the streamflow feeding major reservoirs during the spring and early summer months. The region’s snow cover dynamic has been analyzed using a combination of two satellite products. Hydrologic modeling is performed using the HBV model for the 2003–2015 water years (01 Oct–30 Sep). The Monte Carlo method is used for multi-criteria optimization exploiting satellite snow cover data besides runoff data. The sensitivity and uncertainty analysis on the model parameters indicate that multi-criteria calibration effectively reduces the uncertainty of the parameters and increases the model performance. Moreover, ensemble runoff forecasts are generated with several best model parameters using 1-day and 2-day lead time numerical weather prediction data for the snowmelt period (March–June) of the 2015 water year.The results indicate that the use of multiple remote sensing products in combination better represents the snow-covered area for the region. Additionally, including these data sets into hydrological models enhances the representation of hydrological components while reducing runoff prediction uncertainty.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Influence of boulder array on the near-bed turbulent flow characteristics
           in a gravel bed stream - An experimental investigation

    • Abstract: The present study aims to focus the turbulent flow characteristics over arrays of submerged boulders in a gravel bed stream. Round shaped boulders of diameter, Dc = 6 cm were staggered over a gravel bed stream (d50 = 4 cm) with varying boulder-to-boulder spacing and the flows over the arrays were studied experimentally. The flow measurements were carried out by an acoustic Doppler velocimeter and the double averaging methodology (DAM) was applied. The results of large spacing boulder array reveals near-bed velocity deficit within 1Dc upstream to 5Dc downstream of the boulder and no influence on the approaching velocity was observed after 5Dc corroborating the recovery of boundary layer. In case of medium and small spacing boulder array, the velocity deficit is significant at all locations. The shear stress distributions depict development of high and low bed shear stresses causing redistributions of the local bed shear stress. The higher magnitude of shear stress is observed at the boulder crest whereas; the secondary peak near the gravel bed crest is attributed to the skin shear stress on the individual boulder. Moreover, the present research contributes to our understanding that the boulder array on a rough bed stream leads to higher turbulent intensity at the boulder crest level.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Comparative analysis of numerical solutions of 2D unsteady dambreak waves
           using FVM and SPH method

    • Abstract: This work presents a comparison of two-dimensional numerical solutions of unsteady free surface flow. This is a simulation of the dam-break wave with different configurations using based-mesh finite volume method and meshless smoothed particle hydrodynamics (SPH). Two well-known approaches, widely used in the computational fluid dynamics (CFD). These techniques have proven their robustness in the numerical treatment of such conservation laws. The main goal is to check the ability of the SPH method and the first order finite volume HLLC solver to reproduce the numerical solutions of the 2D shallow water equations. Based on many benchmark tests, one investigates the effect of the topographic variation along the x and y directions on behavior of the numerical solutions namely at the wet-dry front. The comparison between the simulated results, the analytical solutions and the experimental measurements shows a good correlation, although the finite volume approach remains more advantageous in terms of accuracy and the CPU time.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Simplified dispersion analysis based on dye tests at a small stream

    • Abstract: The modelling of solid transport in open channels requires good knowledge about parameters related to basic processes such as hydrodynamic dispersion, advection and decay rates. Such parameters are usually determined by dye tests. Numerous tracer studies have been performed on laboratory flumes and natural rivers. However, on-site sampling is often difficult, expensive and needs special apparatus. The main aim of the study was to justify simplified method based on the monitoring of the dye cloud shape in order to determine both longitudinal and transversal dispersion coefficients. In this study, four dye tests were carried out on a small local stream (the Lipkovsky) using Rhodamine WT fluorescein dye as a tracer. The tests were carried out in such a manner that both longitudinal and horizontal transversal dispersion data were obtained. For this purpose, the visually determined extent of the dye cloud was interpreted via the analytical solution of the advection-dispersion equation. The results obtained by this simplified approach indicated that the longitudinal dispersion coefficient Dx = 0.051–0.057 m2/s and the coefficient of horizontal transversal dispersion Dy = 0.00024–0.00027 m2/s. The method was justified by corresponding root mean square error (RMSE) counting RMSE = 0.65–1.02 m for the dye cloud centre, RMSE = 1.87–2.46 m for the head and tail of the cloud and RMSE = 0.025–0.11 m for the cloud width, the Nash-Sutcliffe efficiency coefficients ranged from 0.9 to 0.998. The comparison of these values with empirical formulae and other tracer studies indicated significant overestimation of the mentioned values of Dx, which can be attributed to the uniform velocity distribution along the width of Lipkovsky Stream. Much better agreement was achieved for Dy.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Thermal regime of the Danube Delta and the adjacent lakes

    • Abstract: The Danube Delta is a unique natural object influenced by natural and human factors. According to the available observation and remote sensing data, the features of the water temperature in the Danube Delta, as well as in nearby lakes and the adjacent area of the Black Sea, have been determined. The water temperature in the Danube River was found to be much higher than the air temperature, especially in autumn. Generally, it is also higher than in nearby lakes and the adjacent part of the Black Sea. During 1961–2021 the mean annual water temperature in the Danube Delta increased significantly, especially during the last three decades. It has been determined that water temperature is affected not only by air temperature, but also by water discharge and wind. With a large water discharge the mixing of water is intensified and it causes the decrease of surface water temperature during the main part of the year with the exception of the coldest months. The greatest impact of water discharge on the water temperature is observed in June. The cool breeze in summer months also has some effect on the surface water temperature of the river near the seashore. The results show the potential of remote sensing to track the changes of water temperature along the river and to identify the shallow sections.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
  • Camera-measured velocity distribution in laboratory open-channel flow with
           intense transport of bimodal combined-load

    • Abstract: An extended stereoscopic method, which identifies, and tracks particles based on their colour in solid-liquid flow, is tested for its capability to separately measure velocity distributions of particles of two fractions transported as bimodal sediment mixture in water flow through a laboratory flume. The principle of the tested method extension is a use of colour-based processing of images collected by two high-speed cameras which enables to filter out particles of one fraction from the image and leave particles of the other fraction in the image based on a selected colour hue range. The modified images are then processed by the original stereoscopic method to produce velocity distribution of particles of the individual fraction in the flow. The method extension is first tested in simple vertical flow carrying neutrally buoyant spherical particles of two distinct colours in a recirculation cell. In the next step, lightweight plastic particles of two fractions of different properties (size, shape, density) and colours are introduced to flow through a laboratory flume and velocity distributions of the two fractions are measured separately at flow conditions which mimic intense transport of bimodal combined-load in an open channel. Results exhibit a very good agreement with previous measurements with unimodal sediment in hydraulically similar flow.
      PubDate: Thu, 10 Aug 2023 00:00:00 GMT
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