Causal regularities of effect of urban systems on condition of hydro ecosystem of Dnieper river

Abstract

Under conditions of uncontrolled increase of anthropogenic impact in use of water resources and intensity of contamination, it becomes necessary to develop and comply with water conservation measures, use environmentally friendly technologies and introduce adapted conservation measures. Emphasis was made on the fact that the influence of urban systems lead to the transformation of floodplains, destruction of river hydro ecosystem and significant deterioration of the water management and recreational values. The situation is aggravated by the operation of outdated and inefficient water discharge and water treatment systems. It leads to systematic contamination of the urban system of suburban river basin with sewage surface runoff and distribution of pollutants outside/upriver. The results of the study of process of the impact of sewage surface runoff from the urban system Kherson city on the condition of the lower Dnieper hydro ecosystems in the suburban area of the river and outside/upriver were shown. The model of the system research of causal relation “coming of water (stage I) → surface sewage runoff (stage II) → condition of the hydro ecosystem (stage III)” was offered. The seasonal nature of intensity of precipitation effects, which causes acceleration of hazardous erosion in territory of urban systems, which is a consequence of systemic diffuse pollution in suburban basin of the Dnieper River, was determinted. The hydrochemical properties of sewage runoff, which have significant seasonal dynamics, were determined. It was justified by the change in volume of water use in economic and domestic purposes. The intensity of the impact of surface runoff of the urban system of Kherson city on the hydro ecosystem of the Dnieper River at 100- and 300-meter area upriver was determined: the 100-meter area is “very polluted” (class VI) – “extremely polluted” (class VII); the 300-meter area is “polluted” (class V) – “very polluted” (class VI). It was found that the main pollutant that leads to deterioration in the quality of the water in the Dnieper River is the significant excess of petroleum products. Hydrochemical values of sewage discharges in accordance with needs for fishery exceed the MPC values 4 times. It proved the unsatisfactory ecological condition of the hydro ecosystem of the lower Dnieper river in the urban system and outside/upriver. It was proved that reusing of treated sewage surface water of Kherson city can provide irrigation for growing crops at the area of 9468 ha. The application of the suggested complex model of research and the establishment of causality of the impact of the urban system on the ecological condition of the hydrosystem of the rivers shall allow to carry out spatial differentiation of protection measures regarding reduction of the negative impact of sewage surface runoff on surface water condition and it shall improve obtaining of crop yields on irrigated land due to the reuse of sewage surface water.