Influences of Agricultural Irrigation on Regional Salinity Balance in Arid Areas of Northwestern China

抄録

It is widely recognized that saline transfer and distribution are important considerations in arid areas, where salinization is prevalent, not only for sustainable agricultural production but also for regional environmental conservation. This study discusses the saline balance of the irrigation area in the Tarim River basin of northwestern China. Water quality was investigated at irrigation and drainage channels from 2007 to 2011. The regional water balance was calculated using the water supply and drainage volume data owned by the Xayar Water Management Office and its branches. Comparing the quality of irrigation and drainage water, the concentration of cations (except K⁺) in drainage water was found to be 15 times more than that in irrigation water. Based on the estimation of water balance, it was confirmed that only approximately 5% of the irrigation water flowed out as drainage water. The remaining supplied water is used for evapotranspiration, and groundwater recharge was considered. In addition, the output load of K⁺, Ca²⁺, and Mg²⁺ was lower than the input load. However, the output load of Na⁺ increased by approximately 20% of the input load. This indicates that continuous irrigation does not necessarily promote saline transfer and that salinity is retained in groundwater or soil in this region. Finally, because of the substantial exhaustion of Na⁺, it is necessary to consider the influence of increased levels of Na⁺ in downstream drainage areas.