ИСТИНА

The correlation of climatic and anthropogenic factors in the change of river flow and runoff from catchment areas, as well as water quality in various natural and economic conditions, is considered. Climatic and man-induced changes of hydrological characteristics are closely interrelated and often affect the runoff not directly, but indirectly through relief, soil, and biota. That is why it is impossible to separate definitely the contribution of climatic and anthropogenic factors to changes of hydrological characteristics and one has to be satisfied with relative estimates, which are generally performed by the deviations from some basic values (for example, from the normal annual discharge, the average long-term runoff or runoff of some other period, from the MPC, background characteristics of the environment and target quality indicators) calculated by different methods, among which water balance methods, methods of water management statistics, reconstruction of conditionally natural runoff for a period of intensive anthropogenic impacts and its comparison with the actual runoff. The contribution of climatic and anthropogenic factors to changes in the annual and seasonal runoff of a number of Russian rivers, the surface slope runoff in the southern part of Russia, as well as the water quality of the Russian rivers and reservoirs, are estimated. It is shown that the role of natural and man-induced factors in modern changes in the quantity and quality of water resources varies widely depending on specific conditions. But in general, in most cases, the contribution of both of them is significant, which is important to keep in mind performing hydrological and water management calculations. Some measures, mainly preventive, aimed to reduce the negative anthropogenic impact on water resources are proposed.