Presentations 2016

Salinization and waterlogging of irrigated agricultural land is a serious threat in Central Asia and especially in the Aral Sea basin. Salinization is coped with by pre-season leaching and excessive irrigations. However, massive water applications cause rising groundwater tables of few decimeters till few meters from the soil surface. Too shallow groundwater can be a barrier for leaching of salts from the soil root zone. A study is conducted in the Khorezm Region of the Aral Sea Basin, where the objective is to assess the efficiency of soil leaching to reduce harmful salts. HYDRUS-1D was used to model vertical soil root-zone moisture and salinity dynamics, accounting for shallow groundwater, which by far prevails over lateral flow. Long term groundwater table and salinity, soil texture and salinity, and other factors that drive soil salinization and waterlogging, have been collected over the period of 2003 – 2014. Simulation covered most crops grown in the province, cotton, winter wheat and vegetables. Inverse modeling was used to calibrate the model for each of the crops. The results show a substantial contribution of moisture from shallow groundwater in the range of 23 – 30 % depending on groundwater levels, to the total crop water requirements. The leaching procedure caused relocation, but not removal, of salts within the 1.5-m profile and maintains the high groundwater table problem. Evaporation, causes the capillary rise and 40 % increase of salts in loamy soils and tripled in sandy soils within the top 80-cm soil layers during the crop growth season. Research results also showed that, improving irrigation and drainage management will lead to alleviation of the land degradation.