Abstract: Water poverty has been the focus issue in northwest China for a long time.Taking Ningxia as the study area in this study,the regional water poverty levels were calculated from 2011 to 2015 using the WPI model based on the built evaluation index system of water poverty.The key factors causing the differentiation of water poverty were analyzed by using WPI-Geodetector to reveal the mechanism of water poverty and to give the regional types of water poverty.The results showed as follows:(1) The spatial-temporal variation of water poverty index was significant.Ningxia's WPI value was increased from 0.393 in 2011 to 0.404 in 2015 which indicated an overall slow improvement trend while its regional gap became magnified. (2) The spatial-temporal variation of the leading factors in water poverty was obvious.From the target perspective,the resource system had the biggest impact on water poverty in Ningxia,while its weight was getting smaller.The weight of the environmental system was increasing.The weight of the utilization system was the least.From the index perspective,theq value of annual precipitation and other 10 indicators was always above 0.8.However,the weights of 7 indicators s including annual runoff depth on the Ningxia water poverty were declining.In the regions' point of view,there were 6 indicators in determining water poverty index differentiation with theq value greater than 0.5 for Yinchuan which suggested an urgent need to improve the water-use efficiency,reduce water pressure and to allocate reasonably the ecological water utilization.For Shizuishan City,there were 11 indicators with the q value greater than 0.5 which,objectively indicated the contradiction in the transformation process of the resource-based region.For Wuzhong City,there were also 13 indicators with theq value greater than 0.5 which suggested something needs to be done to enhance water-use efficiency,water-use management and to improve the planning and coordination of water resources.For Guyuan City,there were 4 indicators with the q value being more than 0.5 which suggested a focus on improving water-use facilities and controlling pollution.For Zhongwei City,there were 15 indicators with theq value being more than 0.5 which indicated the efficiency of water use and facilities should be improved. (3) Water poverty regional types were classified.Sharing the sane background of water resources constraints,the study area were divided into 3 types including the pathway (facility level) constrained area,the capacity-utilization (water management andwater efficiency) constrained area and the environment (water-use pressure-ecological environment) constrained area.

Key words: water poverty, spatial-temporal differentiation, leading factors, WPI-Geodetector