PROSPECTS AND PROBLEMS OF USING LOCAL WATER RESOURCES FOR IRRIGATION IN THE BASINS OF SMALL RIVERS OF THE FOREST-STEPPE OF UKRAINE

Abstract

On the example of a separate agricultural farm located in the basin of the small Manzhelia River within the Left Bank Forest Steppe, the approaches to the selection of potential sources of irrigation and the specifics of determining the volumes of local water resources intended to be used for irrigation, as well as the areas of possible irrigation in the absence of existing irrigation systems, are given. The results of the research indicate that the prospects for the development of land irrigation on farmland can be mainly provided subject to the combined use of surface runoff accumulated in ponds on the Manzhelia River and groundwater admissible for extraction, taking into account their quality. It was determined that influenced by a complex of anthropogenic factors, the river runoff sharply decreased compared to natural conditions, and the feeding of river course ponds during the entire low water period occurs only due to lateral inflow. Based on calculations it was determined that in average and low-water years, the volumes of surface and ground inflow to the cascade of ponds for the period from June to September are smaller than evaporation losses. Under such conditions, the use of the river runoff for irrigation is possible only due to the accumulation of flood and, partially, high water runoff. The calculations of flood runoff volume for March - April at the gate of the lower pond indicate the impossibility of using water from it for irrigation in very low-water years, as well as the dependence of runoff use for irrigation in low-water years on the pre-flood filling level of the ponds. It was determined that up to 0.8 million m3 of water can be used for irrigation in medium-water years, and up to 1.4 million m3 in high-water years, which will provide irrigation on an area of 400 and 700 hectares, respectively (having an irrigation rate of 2000 m3/ha). The possibility of installing at least 40 water intake wells within the territory of the farm with a total flow rate of 20-24 thousand m3/day and a total water intake during the irrigation period of about 1.5 million m3 has been substantiated. This will make it possible to irrigate 750 hectares of land having an irrigation rate of 2000 m3/ha, and at least 1000 hectares having an irrigation rate of 1500 m3/ha. It is focused on the mandatory preliminary investigation of water quality for irrigation, which for many small rivers and aquifers is a limiting factor when using local water resources for the construction of irrigation systems.