Eco-hydrological effects of agricultural water-saving in the Yinchuan Plain, Northwest China

In arid and semiarid irrigation area, the systematic influence of agricultural water-saving on eco-hydrological environment remained unclear at a regional scale. Based on long-temporal multisource data, this paper uses the water balance and empirical Bayesian kriging (EBK) methodology to analyze the process and explore the mechanisms of eco-hydrological environment change in the Yinchuan Plain (YCP), an irrigated oasis in the upper reaches of Yellow River along the Silk Road Economic Belt. The results indicate that, after nearly 20 years of water-saving efforts, the total mean groundwater depth in the whole YCP increased 1.03 m in the irrigation period, and the increased depth of groundwater in the irrigation period is 0.70 m greater than the non-irrigation period. Average groundwater total dissolved solute (TDS) increased 5.7%, the increase in the northern YCP 4.2% higher than in the southern YCP, showing a slight tendency of salinization. Different from groundwater, soil salinity increased 3.64% in the southern YCP and decreased 50.57% in the northern YCP, the proportion of salinity area declined from 53.0 to 30.2%, exhibiting a differentiated and generally desalinizing trend. NDVI is increasing and the restoration effect in the northern YCP is more prominent than in the southern YCP. Most notably, the regional ET calculated from water balance in the whole YCP decreased from 883.8 to 453.2 mm (about 45.8%) during the period 2000 ~ 2017. Agricultural water-saving caused by the decreasing amount of water diversion is responsible for the eco-hydrological environment change in the YCP. An effective and rational water allocation and water-saving policy following variation of eco-hydrological circulation in the YCP is urgently needed.