The Ukrainian Government started the process of EU water Directives implementation aimed at developing of the River Basin Management Plan for 9 main river catchments. The program SWAT was tested to simulate the water flow of a large plain river with a predominant snow supply. River discharges (12 gauges), snow cover depth (13 stations), and the soft data, including graphically defined surface runoff and MODIS evapotranspiration, were used to calibrate the model. The calibration flowchart, along with a detailed source data description, is proposed to aid with streamflow simulation for the snowmelt-driven watersheds and fill the existing gap of distributed hydrological modeling in the region. The main issues with snow simulation and climate data coverage are discussed. The program SUFI-2 in SWAT-CUP package was used for performing calibration/validation and uncertainty analysis. The statistics (R2, NSE, PBIAS) showed good agreement (NS > 0.7, R2 > 0.75, PBIAS < ±10%) for a major part of the gauges and satisfactory for all of them (NS > 0.5, R2 > 0.6, PBIAS < ±15%), except of two linked upstream outlets. This study provides the basis for further research on water resources, the impacts of climate change, and water quality issues.
The article presents the national methodology for the identification of vulnerable areas to pollution of surface and ground water by nutrients compounds. The designation of nitrate vulnerable zones is an effective tool to reduce the impact of agricultural activities on water pollution by nutrients and is used for managing of diffuse pollution within river basins to achieve “good” ecological status. The analysis of heterogeneity of natural conditions in Ukraine and intensity of agricultural activity allows to determine 3 types of zones which differ in vulnerability: 1. Zones of high risk of water pollution, where nitrogen surplus in soil and washing and periodic washing regime are favorable for the nitrate leaching; 2. Zones of potential water pollution, where a deficient nitrogen balance in soil is observed in conditions of washing and periodic washing regime; 3. Zones of short-term pollution, where positive nitrogen balance in soil is noted by the unwashed water regime. The content of dissolved forms of mineral nitrogen (Nminer) in water and the presence of eutrophication process in the water body were recommended to use as criterias for designation of vulnerable zones. For the small rivers with a Strahler coefficient < 5, the nitrate vulnerable zones designation is recommended using the criterion of the nitrogen mineral forms content with a threshold value of 11,3 mgN/l. For the rivers with a Strahler coefficient ≥ 5, reservoirs, estuaries and coastal waters the designation is carried out on the basis of eutrophication. For the groundwater, it is based on the content of nitrogen mineral forms less than 9,7 mgN/l. This method was developed in Ukraine for the first time.
<p>A comprehensive study of humic substances (HS) in the surface water of Ukraine have been carried out. It reveals the nature of the basic laws of humic substances intake, the spatial-temporal distribution, and the physicochemical processes of the intra-water transformation. The spatial differentiation of the studied parameters largely depends on the zonal-genetic conditions of humus formation. The HS content in the azonal system of cascade of the Dnipro reservoirs, decreases from the upper - the Kyiv - to the lower - the Kakhovka - reservoirs. Based on the coefficient of the HS water migration, which is characterizes their ratio in the water and catchment soils, the zoning of the Ukrainian territory is carried out.</p><p>The basic properties of the surface water HS - polydispersity, solubility, and the effect on the water blooming formation - are studied. It is shown that humic acids (HA) dissolved in water are more highly-molecular and polydisperse in comparison with fulvic acids (FA). Their most fine particle fractions, which content is 50&#8211;65% for HA and about 50% for FA, dominate in the surface water HS. The quantitative characteristics and features of the interphase distribution of HA and FA and the change in their molecular weight in the system &#8220;soil catchment complex - river water &#8211; suspended matter - bottom sediments&#8221; are established.</p><p>It is shown that sorption by suspended substances play a major role in the processes of self-purification of water from humus, while the oxides and hydroxides of Fe, Al, and Mn have the maximum sorption capacity for the HS. Conducting the laboratory experiments, sorption isotherms of the HS are obtained by Fe hydroxides and clay minerals of suspended substances of the Dnipro reservoirs. Also, the study states that among the various natural water factors, the conformational changes of HS are predominantly due to a change in pH.</p><p>Moreover, the quantitative indicators of the HS wash-off from the Prypiat catchment surface, the marshiest river basin in Ukraine, are calculated. The role of different pathways of water flow in the formation of the HS runoff is shown. Based on the data gathered, the material balance of HS within the cascade of the Dnipro reservoirs is calculated, and the role of the Prypiat river as the main source of HS is explained.</p><p>The results of the study indicate that the cascade of the Dnipro reservoirs is a powerful biogeochemical barrier that facilitates the transition of HS and associated with them pollutants from solution phase into bottom sediments, and in the reservoirs with delayed water exchange, FA are characterized not only by the transporting but also accumulating function.</p><p>Finally, the thermodynamic calculations of coexisting forms of HS in water were conducted. It is concluded that in the physicochemical conditions typical for the surface water of Ukraine, water contains 13&#8211;15% of free fulvate ions capable of binding heavy metals, which is an important characteristic for assessing the buffer capacity of water.</p>
The dataset contains long gridded time series of monthly minimum, maximum and mean air temperature and atmospheric precipitation for Ukraine, covering the period of 1946-2020. The dataset was built through the thorough historical climate data processing, which included all mandatory steps: data rescue/digitization of missing values and/or periods in station time series from paper sources, their quality control and homogenization, and interpolation on 0.1x0.1 grid. The station data comprised monthly values of 178 stations for air temperature (for each of three parameters) and 224 stations for atmospheric precipitation. The quality assurance and homogenization were performed by means of the widely used homogenization software HOMER (HOMogEnization in R), while the well-known interpolation software MISH (Meteorological Interpolation based on Surface Homogenized data basis) was used to perform the gridding.
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