Analysis of the variability of the irrigation properties of the waters of the Kuchurgansky and Baraboysky reservoirs

Abstract

The purpose research is: in the evaluation of the irrigation properties of the waters of the Kuchurgansky and Baraboy reservoirs and their variability during the warm period of the year according to the data of hydrochemical observations of the Odesa Regional Department of Water Resources in 2010–2020 using different methods; comparing the possibilities of irrigation salinization and salinization of soils when using the waters of the considered water bodies for irrigation; in the practical processing of the proposed improvement of the methodology of DSTU 2730:2015 based on the detailed typification of irrigation waters. Methods. The analysis of the empirical material for the presence of gross errors, the determination of the statistical characteristics of the series of observations and the parameters of the laws of the distribution of water quality indicators was performed using the methods of mathematical statistics. Results. The sources of water reservoirs in the south of the Odesa region are usually the Danube and the Dniester, whose waters correspond to irrigation conditions. However, the mixing of the Danube or Dniester waters with the waters of natural sources of water reservoirs usually leads to a change in the properties of water masses, not for the better. An example can be the Sasyk reservoir, the waters of which, after mixing with the waters of the Danube, are suitable for irrigating only light, well-permeable and drained soils. Whereas the Danube waters are suitable for watering all types of soil. The article discusses various known methods of irrigation water assessment. A detailed typification of irrigation water and, based on it, improvement of the DSTU 2730:2015 methodology are proposed. An assessment of the water quality of the Kuchurgansky and Baraboy reservoirs was carried out according to the considered methods. It was found that the irrigation properties of the waters of these reservoirs differ significantly. Kuchurgan reservoir: water mineralization during 90 % of the warm period (WP) is in the range of 1–3 g/dm3; according to A. M. Kostyakov's classification, these are waters with "increased danger" of salinity (category 3); the amount of toxic salts in chloride ion equivalents varies in the range of 5.4–43 mg‑eq/dm3; water of subtype IIb (84 % WP); the waters are suitable for watering light, well-permeable and drained soils; the magnesium content contributes to salinization during 70–75 % of WP. Baraboy reservoir: water mineralization does not exceed 1 g/dm3; according to Kostyakov A. M., a "careful approach" (category 2) is needed during watering during 71 % of the TP and in 29% – "good" water (category 1); the amount of toxic salts in chloride ion equivalents varies in the range of 1.0–5.0 mg‑eq/dm3; the ratio of the main ions refers to subtypes IIa (53%) and IIb (41 %); according to Bezdnina S. Ya., waters belong to category I with a probability of 65 % during the WP and to category II – 35 %; the amount of magnesium has a harmful effect on the soil during 53 % of the WP. Conclusions. The waters of the Kuchurgansky and Baraboysky reservoirs are suitable for splicing, but require a careful approach due to the possibility of magnesium salinization. The waters of the Baraboy reservoir have better irrigation properties, they are suitable for watering most types of soil, the water of Kuchurgansky – only for watering light, well-permeable and drained soils.