The objective of this paper is to identify the level of changes in the ecological status of surface reservoirs of Dnipropetrovsk region under the impact of anthropogenic factors and to find a rationale for the limit loads on aquatic ecosystems, based on a quantitative assessment of their assimilative capacity values using GIS-technologies.To characterize and evaluate economic activity in the river basins of Dnipropetrovsk re- gion, the data of state statistical reporting by the form of 2-TP "Water resources management" of the State Agency for Water Re- sources of Ukraine were used. Parameters characterizing the assimilative capacity of water bodies were determined by taking into consideration the perennial average values of river runoff resources of the priority watercourses of Dnipropetrovsk region in the years with varying degrees of supply: with an average (50%), a low (75%) and a very low (95%) river water content. The main indicators characterizing the assimilative capacity of the water bodies of Dnipropetrovsk region are actual and necessary multiplicity of waste- water dilution, the limit to assimilative capacity of surface reservoirs, index of assimilative capacity utilization of river runoff re- sources of varying degrees of supply. A classification that characterizes the level of assimilative capacity utilization for water bodies is proposed. The level of assimilative capacity utilization of the Dnipro River in the reservoir areas, regardless of the degree of river runoff supply, is estimated as “allowable” . At 95% degree of river runoff supply, the level of assimilative capacity utilization of the Oril and Vovcha Rivers is characterized as “moderate”, the Samara River (after the confluence with the Vovcha River) as “high” and the Ingulets River with tributary the Saksagan River, and the Samara River (before confluence with the Vovcha River) as “veryhigh”. It should be noted that irrespective of the level of river runoff supply, the index of assimilative capacity utilization of the Samara River (before its confluence with the Vovcha River) exceeds the limit value by 19-115 times. For the spatial analysis of hydrological parameters and visualizion of the data in the form of thematic maps, the geoinformation system “Rivers of Dnipropetrovsk region” was developed on the basis of the ESRI ArcGIS Desktop10 software package. Using the geoprocessing tools, on the basis of hydrological indices of 7 priority watercourses for each of the 22 administrative-territorial districts of Dnipropetrovsk region, the main indicators characterizing the assimilative capacity of water resources were calculated and ranked. The use of indicatorscharacterizing the assimilative capacity of river runoff resources allows us to identify the threshold levels of anthropogenic transfor- mation of aquatic ecosystems, develop and implement environmental measures to improve the ecological status and ensure environ- mental safety of surface reservoirs.
The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes