Substantiation of optimal parameters of horizontal systematic drainage in modern water management and climatic conditions in the south of Ukraine

Changes in the conditions of natural water supply and unsatisfactory technical conditions of horizontal systematic drainage systems have led to their inability to perform the necessary functions in full. In this regard, the issues of determining the optimal parameters of the collector-drainage network (distances between drains, their specific length, and diameters) become relevant. The research work is based on the results of field research on the effectiveness of drainage in the southern region of Ukraine, which includes Ingulets, Kakhovka, North Rogachytsia, Tatarbunary irrigation systems, and the irrigation zone of the North Crimean Canal. Based on the research, a method for determining the optimal parameters of systematic horizontal drainage has been developed and proposed, which takes into account modern precipitation rates, irrigation methods, and irrigation rates for crops.  Optimization of drainage parameters is to determine such parameters, having which the capital investment in construction would be minimal while ensuring the groundwater level is below critical depths. Based on the research results when calculating the distance between drains, nomograms were made to determine the main parameters of the systems of systematic horizontal drainage of the perfect and imperfect types under different water conditions. The calculations were performed for the soils with filtration coefficients from 0.01 to 30 m/day. Based on the analysis of nomograms, it was found that the main factors influencing the distance between drains for horizontal drainage systems are filtration coefficient, drainage rate, and distance to impermeable rocks. Nomograms enable to quickly perform calculations of the main parameters of systematic horizontal drainage systems, taking into account modern conditions of water supply and to specify the estimated cost of system construction.