Changes of soil salinity and ground waters at the rice systems in Sivash lowland after irrigation cease

Abstract

The aim of the article is to submit data about ground water table and soil salinity of the rice irrigated systems at the Sivash seashore in Nyzhnegorsky district of Crimea in 2017–2018 which is 4–5 years from irrigation cease. It was found that many soil cover patterns with salt-affected solonetz at the rice system were leached from salts to the depth about 3–3.5 m by flooding irrigation during half a century. In 2017–2018 ground water tables were deeper than the critical depth. Ground water mineralization is characterized by mosaic spatial distribution, varying from 1.9 to 7.4 g/l with a tendency to growth as ground water depth increases. Depression funnel of ground water table was formed at the seashore. The bottom water drive is up to 0.8–1.6 m relatively sea level. The first symptoms of the salinity returning in grounds of vadose zone were found: (1) appearance of calcium and magnesium chlorides in pore solutions of formally no saline or weakly saline horizons; (2) increasing trend of sodium and chloride ion activity measured in pastes with moisture 50% (w) at the dynamic plots in 2018 as compared with 2017; (3) frequency of grounds with clustered gypsum crystals is increased.