Spatiotemporal dynamics of meteorological and soil droughts and their effects on water use efficiency in the Ningxia-Inner Mongolia Irrigation District

QIAN Jialin; FENG Xiong; BU Lingxin; ZHANG Shutong; FENG Kepeng

doi:10.13522/j.cnki.ggps.2025184

Abstract：[Objective]The Ningxia-Inner Mongolia Irrigation District,spanning Ningxia and Inner Mongolia Autonomous Regions,is a large irrigation district in Northern China,where drought is the primary constraint to agricultural production.This analyzes the spatiotemporal dynamics of meteorological and soil drought,as well as their effects on water use efficiency(WUE)in this region.[Method]Long-term experimental data measured from 1989 to 2018 were integrated,which include in-situ data and global land surface satellite(GLASS)data,standardized precipitation evapotranspiration index-grid data and global land evaporation Amsterdam Model v3.5.Soil moisture anomaly index(SMAI)was used to characterize soil drought.We also analyzed the spatiotemporal variation in GPP,ET,SPEI and SMAI,as well as their relationships with WUE.[Result]① During the study period,monthly drought showed significant fluctuation,while quarterly drought fluctuated more smoothly;annual meteorological drought showed a decreasing trend.SMAI fluctuated notably but presented an increasing trend.②Spatially,mean WUE was high in central area of the district and low at the edges.Mean GPP and ET were high in the Ningxia section than in the Inner Mongolia section;crucially,the increasing rate of GPP in Ningxia was faster than that of ET,leading to a significant increase in mean WUE in the Ningxia section.③ Correlation analysis revealed that annual SPEI was negatively correlated with WUE,while annual SMAI was positively correlated with WUE,both at significant levels.The relationship between monthly SPEI and WUE was complicated:positively correlated in May,and negatively correlated in July and September,all at significant levels.④ WUE showed a strong response to monthly SPEI but with a 7-month lag,and a weak response to SMAI with a lag of 5 and 7 months.In the Inner Mongolia section,the negative response of WUE to monthly SPEI could lag by over 12 months,alluding that meteorological drought had a more pronounced impact on WUE than soil drought.[Conclusion]Meteorological drought is the dominant factor influencing WUE in the Ningxia-Inner Mongolia Irrigation District,and its lagged effect significantly enhances WUE.Compared to meteorological drought,soil drought has a small and more complex impact on WUE.These findings can help develop drought-resistance strategies and improve water use efficiency in the district.