Analysis of design parameters of drainage systems for the conditions of Ukraine by mathematical modeling

Abstract

Goal. To study the conditions for increasing the efficiency of water regulation on reclaimed lands in Ukraine in the conditions of modern climatic changes. The object of the study was double-acting drainage systems that could perform the function of both drainage and provide plants with moisture throughout the growing season. Methods. A series of computational experiments was conducted for different soil conditions (peat, loam, sandy loam, and sandy) of Ukraine using Richards mathematical model and the procedure for determining the permissible parameters of drainage systems (depth of laying and inter-drainage distance) under different modes, when the critical function was drainage or water supply. In particular, they considered both multilayer models of the studied soils and their individual layers. The determination of the change in the moisture transfer coefficient from the head level was also investigated. For this purpose, the following forms of dependencies were used, which were upper and lower approximations of laboratory-defined values. Results. Modeling showed that the greatest inter-day distances (> 50 m) were characteristic of peat soils, while for meadow black soils of loamy composition, they did not exceed 6–11 m. For sandy and sandy loam soils, the distance varied within 11–50 m. According to the simulation results, in the case of evapotranspiration (ET) at the level of 2 mm/day at the beginning of the growing season, providing moisture consumption was possible for most of the soils under consideration, however, according to ET = 10 mm/day during the period of the highest moisture consumption — only for peat and part of sandy loam soils. Conclusions. The obtained results of modeling indicated that the optimal parameters differed significantly depending on the type of soil and the level of moisture consumption of crops, and in some cases, the implementation of the double function was limited.