Suitability and assessment of surface water in the Bereslav reservoir water-intake zone for irrigation purpose

 The aim of the study was to monitor and assess the suitability of surface water in the intake area of the Bereslav Reservoir for irrigation. During the growing season, water mineralization varied from 0.998 to 1.601 g·dm‑3. According to Kostyakov A.N., the water is characterized as slightly mineralized and belongs mainly to group III. According to Alekin O.A., water at the beginning and end of the growing season is classified as sodium sulfate-­chloride class; in July and August, the water chemistry changes to sulfate class of magnesium-­sodium group. Observations of seasonal changes in the main components of mineral composition of water relative to their maximum permissible concentrations revealed an excess of sulfate anion in May and August by 7 and 91 mg·dm‑3, respectively, and in July — almost 1.5 times. In the cation series, the main pollutants were sodium (in combination with potassium), its highest concentration in May was 299 mg·dm‑3, in July it decreased to the maximum permissible value, as well as magnesium, concentration of which in July exceeded the standard by 28 mg·dm‑3. In terms of concentration of sodium chlorides and sulfates, the irrigation water is of satisfactory quality. Actual values of mineral composition of the water and calculated values of irrigation coefficients, considering variability of chemical composition of the water over time, indicate its possible negative impact on ionic equilibrium in soil absorption complex. As a result, in order to maintain ameliorative state of the soils, it is necessary to develop and regularly carry out agrotechnical and agroameliorative measures to prevent salinization processes.