Dynamics of Irrigation Quality of Irrigation and Drainage-Wastewater of the Nizhne-Don Irrigation System in 1972 and 2019–2021

Abstract

Purpose: to assess the dynamics of the irrigation quality of irrigation water from the main canal and drainage wastewater (DWW) from the outlet collectors using the example of the Nizhne-Don irrigation system (NDIS) to justify the sustainability of their environmental safety. Materials and methods. The objects of the study were DWW from the TsS, K-3, LS-2 and MKL-7 collectors, water from the Tsimlyansk reservoir supplied to the Nizhne-Don main canal (NDMC). The subject of the study was the hydrochemical indicators of the DWW in 1972 and 2019–2021, and the comparative irrigation characteristics of the waters. Results. Comparison of water irrigation characteristics from NDMC in 1972 and 2019 showed an increase in sulfate salinity by about 35 %. The irrigation coefficient according to H. Stebler (Ka) has decreased from 43.24 to 28.15 since 1972, while the irrigation water quality from NDMC remains good (Ka > 18). In 1972, the average value of the irrigation coefficient (Ka) of DWW during the irrigation period in the K-3 collector was 2.98, in LS-2 – 4.14, in TsS – 5.54, in MKL-7 – 22.96. In 2019–2021 – 10.44; 14.85; 12.62; 11.61 respectively. Conclusions. The irrigation quality of the Don irrigation water from the NDMC has now deteriorated compared to 1972 by 1.54 times. Over the fifty-year period of operation of the NDIS, the irrigation quality of the DWW in the collectors K-3, LS-2 and TsS increased by 2–3.5 times. Irrigation water quality in the MKL-7 collector decreased by 2 times. It has been proven that the use of fresh irrigation water for irrigation contributes to a sustainable increase in the environmental safety of DWW. The need to reuse DWW for irrigation should be decided at the regional level based on the economic feasibility of the cost of cleaning and transporting water to the irrigation system.