Assessment and forecast of water quality in the River Ingulets irrigation system

Scarcity of water is one of the most important problems of irrigated farming. Safe use of contaminated water and waste-water needs continuous monitoring of the water quality and its influence on the irrigated lands and cultivated crops. The Ingulets irrigation system is one of the main systems, which supplies with water fields of Kherson and Mykolaiv regions of Ukraine. The water is contaminated by the effluent disposals and wastes of the metallurgic factories. The new water quality improvement technique was introduced in the Ingulets irrigation system in 2010. The study is dedicated to agricultural assessment of the Ingulets irrigation system water quality with the new amelioration technique by using the FAO and DSTU 2730-94 criteria. It was established, that water quality in the Ingulets irrigation system is still poor, though it becomes better each year since 201 0 till nowadays. Total dissoluble salts content in the water is 1489-2280 mg/L, toxic ions content in eCI- is 10.49-21.63 me/L, sodium adsorption ratio is 4.33-7.94 me/L, sodium percentage is 46.4-58.9%, magnesium to calcium ratio is 1.03-1.68, power of hydrogen is 7.31-8.72 in the period from 2007 to 2017. So, the Ingulets irrigation system water requires further amelioration to become safe and suitable for irrigation without any restrictions. Short-term forecast of the water quality by using the triple exponential smoothing with handling of the seasonal effects with multiplicative method of the Holt-Winters algorithm showed that significant improvement of the water quality by some criteria should be achieved till 2025: total dissoluble salts content in the water should be 1212 mg/L, toxic ions content in eCI- should be 6.61 me/L, sodium adsorption ratio should be 4.31 me/L, sodium percentage should be 49.3%, magnesium to calcium ratio should be 1.05, power of hydrogen should be 8.05 in 2025.