Improved assessment and forecasting of irrigation water quality

Purpose. Improvement of methodological approaches to assessing and forecasting the quality of irrigation water, taking into account its temporal variability, based on the analysis of irrigation properties of river waters in Odesa region. Methods. Statistical, mathematical modelling and forecasting. Results. The following are proposed: a methodology for assessing the risk of water quality deterioration and its forecasting during future irrigation, detailed typification of irrigation waters, improvement of the methodology for assessing the risk of soil salinization during irrigation (DSTU 2730:2015). It has been established that the assessment and forecast of irrigation water quality must be carried out taking into account the variability of their composition and properties over time. It has been shown that the use of average values ​​of indicators for the previous period of time can lead to errors in assessing the quality of irrigation water. It is recommended to consider the risk of water quality deterioration for a separate indicator as the provision of the norm for this indicator. It is proposed, based on the experience of EU countries, to limit the risk of water quality deterioration to 10%. It is indicated that a significant drawback of the methodology for assessing the risk of soil salinization in DSTU 2730:2015 is the need to analyze hypothetical toxic salts in irrigation waters for each calculation of the classification indicator, which is very inconvenient when analyzing observation data for long periods of time. It is proposed to eliminate this drawback by using detailed typification of irrigation waters with a specific set of hypothetical salts in each of their subtypes, which allows providing formulas for calculating the е(rCl–) indicator for these subtypes of water. It is indicated that the simplification of mass calculations allows determining the parameters of the distribution law of the е(rCl–) indicator and assessing the risk of deterioration of water quality for different types of soils. It was established that in the conditions of the Odessa region, the risk of sodium salinization of the soil during irrigation can be assessed using the ratio of sodium and calcium concentrations (kNa1). A significant part of the study is devoted to the testing and refinement of the proposed methods for assessing and forecasting irrigation water characteristics. The main results of the work were obtained for the first time in the domestic practice of environmental research. Conclusions. Domestic methodological approaches to assessing and forecasting the quality of irrigation water require further development, especially in terms of taking into account the variability of these waters over time. Further research should also be directed at substantiating the limitation of the risks of water quality deterioration, since the European level of 10% adopted in the article is indicative.