rss_2.0Journal of Hydrology and Hydromechanics FeedSciendo RSS Feed for Journal of Hydrology and Hydromechanicshttps://sciendo.com/journal/JOHHhttps://www.sciendo.comJournal of Hydrology and Hydromechanics Feedhttps://sciendo-parsed.s3.eu-central-1.amazonaws.com/65c4e38bc8e72413086599d2/cover-image.jpghttps://sciendo.com/journal/JOHH140216Testing sensitivity of BILAN and GR2M models to climate conditions in the Gambia River Basinhttps://sciendo.com/article/10.2478/johh-2023-0044<abstract> <title style='display:none'>Abstract</title> <p>This study investigates the performance of two lumped hydrological models, BILAN and GR2M, in simulating runoff across six catchments in the Gambia River Basin (Senegal) over a 30-year period employing a 7-year sliding window under different climatic conditions. The results revealed differences in overall performance and variable sensitivity of the models to hydrological conditions and calibration period lengths, stemming from their different structure and complexity. In particular, the BILAN model, which is based on a more complex set of parameters, showed better overall results in simulating dry conditions, while the GR2M model had superior performance in wet conditions. The study emphasized the importance of the length of the calibration period on model performance and on the reduction of uncertainty in the results. Extended calibration periods for both models narrowed the range of the Kling-Gupta Efficiency (KGE) values and reduced the loss of performance during the parameter transfer from calibration to validation. For the BILAN model, a longer calibration period also significantly reduced the variability of performance metric values. Conversely, for the GR2M model, the variability rate did not decrease with the length of the calibration periods. Testing both models under variable conditions underscored the crucial role of comprehending model structure, hydrological sensitivity, and calibration strategy effects on simulation accuracy and uncertainty for reliable results.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00442024-02-08T00:00:00.000+00:00Spectral analysis of oscillatory wind wave parameters in fetch-limited deep-water conditions at a small reservoir and their prediction: Case Study of the Hulín Reservoir in the Czech Republichttps://sciendo.com/article/10.2478/johh-2023-0042<abstract> <title style='display:none'>Abstract</title> <p>The dams and banks of small water reservoirs face significant erosion from wind-generated oscillatory waves. Proper design of structure height is crucial to protect such banks against erosion, considering the maximum characteristics of wind waves. Long-term measurements at the Hulín reservoir revealed that the wave spectrum aligns best with the Bretschneider type. This spectrum serves as a basis for simulating oscillatory waves and their impact on shore protection structure design. Empirical models were evaluated using wind and wave data from Hulín reservoir in the Czech Republic. The measured wind speeds attained a maximum of 8 m/s, and wave heights reached up to 15 cm. The Bretschneider (SMB) empirical formula provided the most accurate estimation of wave height (<italic>H</italic><sub>m</sub><sub>0</sub>), with an average underestimate of RMSE = 0.038 m. On the other hand, Wilson revisited (WIL rev.) performed less effectively, with an average RMSE = 0.304 m. For wave period (<italic>T</italic>) estimation, Bretschneider (SMB) yielded the best results, with an average RMSE = 0.062 s. Conversely, Wilson revisited (WIL rev.) showed poorer performance, with an average underestimate of RMSE = 2.196 s. The discrepancy between the empirical formulas and measured values, particularly in underestimating <italic>H</italic><sub>m</sub><sub>0</sub>, can be attributed to inaccurate determination of fetch length and wind speed.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00422024-02-08T00:00:00.000+00:00A 1-dimensional-two-layer transient drift-flux model for hydraulic transport pipelines: modelling and experiments of bed layer erosion and density wave amplificationhttps://sciendo.com/article/10.2478/johh-2023-0039<abstract> <title style='display:none'>Abstract</title> <p>Hydraulic transport pipelines in the dredging, mining and deep sea mining are designed using steady-state methods. However, these methods cannot predict density wave formation. Density waves form a risk for pipeline blockages, therefore there is a need to understand and preferably be able to model the process. The density waves studied in this research are caused by a stationary sediment deposit in the pipeline. This article explores the development of a new transient design model, based on 1-dimensional-two-layer Driftflux CFD. The two layers model the exchange of sediment between the turbulent suspension, and a stationary bed layer, and can therefore model density wave amplification. An empirical erosion-sedimentation closure relationship is applied to model the sediment exchange between the two layers, and is calibrated using experiments. The final model is also validated against a second experiment, specifically for density wave amplification. The experiments and the model show good agreement on the erosion of a stationary bed layer and the growth rate of a density wave and the amplitude of the density wave.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00392024-02-08T00:00:00.000+00:00Soil moisture regime in lowland forests – quantity and availability of waterhttps://sciendo.com/article/10.2478/johh-2023-0037<abstract> <title style='display:none'>Abstract</title> <p>Water is one of the key ecological factors that has a great impact to development and productivity of lowland species such as <italic>Quercus robur</italic>. This paper deals with water regime influence to site conditions of these species and how actually changeable soil moisture affects <italic>Q. robur</italic>. Studied area includes a protective embankment built on the river bank in order to eliminate flooding effect, which means that all needs for water these associations provide from rainfalls and groundwater. Water regime was monitored during two critical years (extremely dry and extremely wet) on four soil types – Planosol, Fluvisol and Gleysol that belong to hydromorphic (three experimental plots) and Chernozem which belongs to automorphic soils (three experimental plots), respectively. It was studied the distribution of rainfalls and groundwater during the growing seasons and how it affects total and available water amount in the soil. The main focus should be given to available water, because it is located in capillary pores and plants can utilize it. Bearing in mind rainfalls makes just 15–20% of the total water amount in the soil it is much more significant to evaluate its proportion in available water. Based on obtained results, we can deduce that much more suitable site conditions for <italic>Q. robur</italic> are present on hydromorphic soils due to much greater proportion of groundwater.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00372024-02-08T00:00:00.000+00:00Experimental investigation of scour downstream of a type A trapezoidal piano key weir under free and submerged flow conditionshttps://sciendo.com/article/10.2478/johh-2023-0041<abstract> <title style='display:none'>Abstract</title> <p>In this paper, the scour downstream of a trapezoidal Piano key weir (PKW) is investigated under free and submerged flow conditions. For this purpose, an experimental model was used in a laboratory channel with a length of 10 m, width of 0.75 m, and height of 0.8 m at various discharges and tailwater depths. The results showed an increase and decrease in the maximum scour depth with an increase in the discharge and submergence ratio, respectively. In addition, increasing the particle Froude number enhanced the geometric features of the scour hole downstream of the PKW. The rate of bed changes slowed down over time. The average values of maximum scour depth, the distance of the maximum scour depth from the weir toe, maximum scour hole length and weir toe scour depth increased in the free flow compared to the submerged flow. The scour hole volume and scour hole area in the submerged flow were less compared to the free flow. The average maximum level of the sedimentary ridge in the free flow is less than the submerged flow. New equations for calculating the geometric characteristics of the scour hole downstream of the trapezoidal PKW are presented with acceptable accuracy.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00412024-02-08T00:00:00.000+00:00Uncertainty analysis of discharge coefficient predicted for rectangular side weir using machine learning methodshttps://sciendo.com/article/10.2478/johh-2023-0043<abstract> <title style='display:none'>Abstract</title> <p>The present study used three machine learning models, including Least Square Support Vector Regression (LSSVR) and two non-parametric models, namely, Quantile Regression Forest (QRF) and Gaussian Process Regression (GPR), to quantify uncertainty and precisely predict the side weir discharge coefficient (Cd) in rectangular channels. So, 15 input structures were examined to develop the models. The results revealed that the machine learning models used in the study offered better accuracy compared to the classical equations. While the LSSVR and QRF models provided a good prediction performance, the GPR slightly outperformed them. The best input structure that was developed included all four dimensionless parameters. Sensitivity analysis was conducted to identify the effective parameters. To evaluate the uncertainty in the predictions, the LSSVR, QRF, and GPR were used to generate prediction intervals (PI), which quantify the uncertainty coupled with point prediction. Among the implemented models, the GPR and LSSVR models provided more reliable results based on PI width and the percentage of observed data covered by PI. According to point prediction and uncertainty analysis, it was concluded that the GPR model had a lower uncertainty and could be successfully used to predict Cd.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00432024-02-08T00:00:00.000+00:00Simulation and prediction of water temperature in a water transfer channel during winter periods using a new approach based on the wavelet noise reduction-deep learning methodhttps://sciendo.com/article/10.2478/johh-2023-0036<abstract> <title style='display:none'>Abstract</title> <p>In winter, the water transfer channel of the Middle Route of South-to-North Water Transfer Project (MR-StNWTP) in China always encounters ice problems. The preciously simulation and prediction of water temperature is essential for analyzing the ice condition, which is important for the safety control of the water transfer channel in winter. Due to the difference of specific heat between water and air, when the air temperature rises and falls dramatically, the range of change of water temperature is relatively small and has a lag, which often affects the accuracy of simulation and prediction of water temperature based on air temperature. In the present study, a new approach for simulating and predicting water temperature in water transfer channels in winter has been proposed. By coupling the neural network theory to equations describing water temperature, a model has been developed for predicting water temperature. The temperature data of prototype observations in winter are preprocessed through the wavelet decomposition and noise reduction. Then, the wavelet soft threshold denoising method is used to eliminate the fluctuation of certain temperature data of prototype observations, and the corresponding water temperature is calculated afterward. Compared to calculation results using both general neural network and multiple regression approaches, the calculation results using the proposed model agree well with those of prototype measurements and can effectively improve the accuracy of prediction of water temperature.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00362024-02-08T00:00:00.000+00:00Heat-induced alterations in moisture-dependent repellency of water-repellent forest soils: A laboratory approach with Japanese Andosolshttps://sciendo.com/article/10.2478/johh-2023-0035<abstract> <title style='display:none'>Abstract</title> <p>Soil water repellency (SWR) is a phenomenon that prevents the spontaneous wetting of numerous forest soils. It is a moisture-dependent characteristic, which disappears when soil moisture reaches near saturation. The heat generated during forest fires affects soil characteristics including SWR. The possibility of heat influencing moisture-dependent repellency (MDR) is not well understood. The present study aimed to investigate the effects of different heating temperatures (H<sub>T</sub>) and exposure durations (E<sub>D</sub>) on MDR using water-repellent Japanese Cedar (CED) and Japanese Cypress (CYP) forest soils. Soil samples collected from 0–5 cm depth were exposed to heat separately at 50, 100, and 150 °C (<italic>H</italic><sub>T</sub>) for 1 h and 2 h durations (<italic>E</italic><sub>D</sub>). The MDR of heated and non-heated soils was determined using the water drop penetration time (WDPT) test in a drying process. During the drying process of the tested soils, SWR appeared and then increased with drying to reach an extreme level (WDPT ≥3600 s) that persisted for a range of decreasing moisture contents, and declined to be non-repellent again (WDPT = 0 s). The critical moisture content at which soils become water-repellent with drying (CMC), the highest and the lowest moisture contents when soils showed maximum SWR (HMC<sub>max</sub> and LMCmax, respectively), and the integrated area below the MDR curve (S<sub>WR</sub>) decreased with increasing H<sub>T</sub> in both CED and CYP soils. The moisture content at which soils become non-repellent again during drying, MCNR, was independent of the type of soil and heat treatment. The range of moisture contents between HMC<sub>max</sub> and LMCmax, where soils show maximum SWR during drying, decreased with increasing HT, from 50 to 150 °C in CED and from 100–150 °C in CYP. The SWR showed strong positive linear correlations with CMC and HMC<sub>max</sub>. The heat generated during wildfires can alter the MDR and all the related repellency parameters of water-repellent forest soils. SWR prevails over a narrower range of moisture contents in heated soil compared with non-heated soils. Further investigations with higher temperature levels using different soil types would be important for a comprehensive understanding of the heat impacts on MDR.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00352024-02-08T00:00:00.000+00:00Numerical investigation of dam break flow over erodible beds with diverse substrate level variationshttps://sciendo.com/article/10.2478/johh-2023-0040<abstract> <title style='display:none'>Abstract</title> <p>This study aimed to comprehensively investigate the influence of substrate level difference and material composition on dam break wave evolution over two different erodible beds. Utilizing the Volume of Fluid (VOF) method, we tracked free surface advection and reproduced wave evolution using experimental data from the literature. For model validation, a comprehensive sensitivity analysis encompassed mesh resolution, turbulence simulation methods, and bed load transport equations. The implementation of Large Eddy Simulation (LES), non-equilibrium sediment flux, and van Rijn’s (1984) bed load formula yielded higher accuracy compared to alternative approaches. The findings emphasize the significant effect of substrate level difference and material composition on dam break morphodynamic characteristics. Decreasing substrate level disparity led to reduced flow velocity, wavefront progression, free surface height, substrate erosion, and other pertinent parameters. Initial air entrapment proved substantial at the wavefront, illustrating pronounced air-water interaction along the bottom interface. The Shields parameter experienced a one-third reduction as substrate level difference quadrupled, with the highest near-bed concentration observed at the wavefront. This research provides fresh insights into the complex interplay of factors governing dam break wave propagation and morphological changes, advancing our comprehension of this intricate phenomenon.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00402024-02-08T00:00:00.000+00:00Tree morphology dependent transpiration reduction function of for landfill cover restorationhttps://sciendo.com/article/10.2478/johh-2023-0038<abstract> <title style='display:none'>Abstract</title> <p>Changes in hydrological processes and water resources required to sustain vegetation for ecological restoration of landfill covers and post mining sites in arid environments pose challenges in the context of extended droughts. Knowledge of actual threshold and wilting suction values based on tree morphological feature or plant age is essential for understanding the variation of root water uptake with drought stress and numerically predict the pore water pressure profile in root zone. The objective of this study is to quantify the transpiration reduction function (TRF; in terms of stomatal conductance (SC) and xylem sap flow (SF)) of <italic>Schefflera arboricola,</italic> considering the effects of tree morphology. Continuous drought condition was applied on the plant quantified with leaf area index (LAI) values at 0.5, 2 and 3.5, wherein each LAI represent tree age. The soil matric suction (ψ) and volumetric water content were measured by embedded sensors in the root zone. Based on the TRF obtained from SC values, a unique threshold suction (<italic>ψ</italic><sub>NTR</sub><sup>t</sup>) ranging from 30 to 50 kPa was identified. Beyond this <italic>ψ</italic><sub>NTR</sub><sup>t</sup>, measured leaf abscisic acid concentration increased up to 35 ng/mL, indicating the start of water stress avoidance mechanism. It is evident that <italic>ψ</italic><sub>NTR</sub><sup>t</sup> is independent of tree morphological parameter- leaf area to root length ratio (LA/RL). On the contrary, a threshold suction (<italic>ψ</italic><sub>SAP</sub><sup>t</sup>), depending on LA/RL ratio, can be determined, indicating the start of xylem cavitation. This <italic>ψ</italic><sub>SAP</sub><sup>t</sup> values ranging from 80 to 500 kPa depending on the LA/RL value, imply that the plant could significantly resist xylem embolization at higher LA/RL. In contrast, the plant with low LA/RL values have less tolerance of drought stress and hence low survivability. The results from this research study can be vital for devising and predicting plant available water in water scarce arid environments by a flux-based approach which is dependent on the tree age.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00382024-02-08T00:00:00.000+00:00Flow resistance at lowland and mountainous rivershttps://sciendo.com/article/10.2478/johh-2023-0023<abstract><title style='display:none'>Abstract</title> <p>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 (<italic>q</italic><sup>*</sup>) to the Darcy-Weisbach friction factor (<italic>f</italic>), has demonstrated good performance for both river types, covering shallow to moderately deep flows. However, accuracy in estimating <italic>f</italic> 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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00232023-11-14T00:00:00.000+00:00Impact of biochar particle size and feedstock type on hydro-physical properties of sandy soilhttps://sciendo.com/article/10.2478/johh-2023-0030<abstract><title style='display:none'>Abstract</title> <p>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 (&lt;125 µm).</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00302023-11-14T00:00:00.000+00:00Effects of the application of biochar on the soil erosion of plots of sloping agricultural and with silt loam soilhttps://sciendo.com/article/10.2478/johh-2023-0026<abstract><title style='display:none'>Abstract</title> <p>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.</p> <p>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<sup>–1</sup>). 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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00262023-11-14T00:00:00.000+00:00Sensitivity of runoff due to changes in the characteristics of the water balance in the Danube River regionhttps://sciendo.com/article/10.2478/johh-2023-0033<abstract><title style='display:none'>Abstract</title> <p>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 <italic>R </italic>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 <italic>ET</italic> values determined from the balance equation, the precipitation totals were corrected by +10%. With a 10% increase in precipitation, the values of balance <italic>ET</italic> reached the values <italic>ET</italic> 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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00332023-11-14T00:00:00.000+00:00Inverse task of pollution spreading – Localization of source in extensive open channel network structurehttps://sciendo.com/article/10.2478/johh-2023-0029<abstract><title style='display:none'>Abstract</title> <p>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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00292023-11-14T00:00:00.000+00:00Using feature engineering and machine learning in FAO reference evapotranspiration estimationhttps://sciendo.com/article/10.2478/johh-2023-0032<abstract><title style='display:none'>Abstract</title> <p>The authors of this study investigated the use of machine learning (ML) and feature engineering (FE) techniques to accurately determine FAO reference evapotranspiration (<italic>ETo</italic>) 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 <italic>ETo</italic> 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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00322023-11-14T00:00:00.000+00:00Changes in crack width on the surface of heavy soils during drought, determined by precise measurement and calculationhttps://sciendo.com/article/10.2478/johh-2023-0034<abstract><title style='display:none'>Abstract</title> <p>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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00342023-11-14T00:00:00.000+00:00Spatial and temporal variability of saturated areas during rainfall-runoff eventshttps://sciendo.com/article/10.2478/johh-2023-0025<abstract><title style='display:none'>Abstract</title> <p>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 km<sup>2</sup>, 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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00252023-11-14T00:00:00.000+00:00Special issue dedicated to 70th anniversary of foundation of Institute of Hydrology, Slovak Academy of Sciences, Bratislava, Slovakiahttps://sciendo.com/article/10.2478/johh-2023-0031ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00312023-11-14T00:00:00.000+00:00The testing of a multivariate probabilistic framework for reservoir safety evaluation and flood risks assessment in Slovakia: A study on the Parná and Belá Rivershttps://sciendo.com/article/10.2478/johh-2023-0027<abstract><title style='display:none'>Abstract</title> <p>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.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/johh-2023-00272023-11-14T00:00:00.000+00:00en-us-1