The purpose of research was to study the filtration process during wastewater irrigation in Rostov region to assess the dynamics of soil moisture regime. The research area is located in Kuibyshevskiy district of Rostov region, geomorphologically – on the watershed of the Mius and the Dedov rivers as well as confined to the floodplain terrace of the river Mius. In solving the given problem, the laws of ameliorative underground hydrodynamics which consider filtration in a homogeneous environment were adopted. Irrigation and drainage practices were not implemented previously on the selected site. These research calculations for conditions of the floodplain lands of the Mius river for the first time put into operation allow to conclude that soil soaking with treated wastewater forms the suspended wetting zones at the soil surface. It has been found that within a certain estimated time after suspension, the water layer begins to drop which in turn indicates the air pressure decline with time before the wetting front (the air pressure coefficient decreases with time). At the same time for various soils the lowering time of irrigation water layer to the lower boundary of the root zone changes approximately by a factor of 90, while the total duration of the inter-irrigation period for the same grounds changes only by 2.0–2.5 times. It is noted that after water discharge from land surface, a sharp instability of the wetting front is formed, that is, points that considerably exceed the relatively even wetting surface appear. At the same time the wetting of a soil layer 1.0 m thick occurs within 1–50 hours. Despite the fact that permeability of the 1st and 3rd soil types varies by a factor of 1000, the wetting time of this soil layer differs only by a factor of 3.5–4.0. The results of the conducted research are expedient for calculating the value of irrigation rates of treated wastewater and the time of their supply to the field.
Key words: soaking, ground, soil, wastewater, irrigation, filtration.
