Abstract: Based on the monitoring data of weather station and groundwater observation wells in the study area, this paper comparatively described the relationship between changes in precipitation and groundwater depth in Horqin,Tongliao City and Inner Mongolia,China,at both annual and seasonal scales(March-May for the spring,June-August for the summer,September-November for the fall,December-February the following year for the winter),based on the data of precipitation from 1951 to 2015 in meteorological stations of Zhongqi, Tongliao and Houqi,and the data of ground-water depth in seven groundwater observation wells in the study area during 1951-2015 observed and simulated by Tongliao City Water Bureau,by using Gray System Theory,linear regression,M-K test,the cumulative anomaly analysis and wavelet cycle analysis. The results show as follows:(1)From 1951 to 2015,annual precipitation showed decrease trend of -11.7 mm·(10 a)^-1. Precipitation in spring,autumn and winter increased,with rates of 1.45 mm·(10 a)^-1,1.79 mm·(10 a)^-1 and 0.67 mm·(10 a)^-1, respectively;while precipitation in summer decreased with rate of -18.6 mm·(10 a)^-1.(2)For annual precipitation,there were three distinct periods,2-5 a,7-12 a and 18-31 a,with two peak periods of 26 a and 10 a in Poland figure;there were distinct periods for seasonal precipitation at different time scales.(3)Seasonal and annual changes in groundwater table showed fluctuant increase trends of 0.48 m·(10 a)^-1,0.50 m·(10 a)^-1,0.51 m·(10 a)^-1, 0.48 m·(10 a)^-1 and 0.49 m·(10 a)^-1,respectively.(4)1994 was the demarcation point for the time series of groundwater depth between base period and variation period.(5)Before 1994,the correlation coefficient between groundwater depth and 4-year-lagged precipitation was -0.514;while after 1994,the correlation coefficient of groundwater depth and 8-year-lagged precipitation was -0.527. This indicates that precipitation played an important role in supplying groundwater,and also had a lagging effect on the variation of groundwater depth. Before and after the sudden change of the groundwater level,the lag time was doubled from 4 a to 8 a. In addition,combined with the periodic analysis of precipitation,it is obvious that short periodic precipitation showed more obvious effect on groundwater level than long periodic precipitation,but the short periodic precipitation was decreasing. This paper has great significance for establishing a ground water research model which could be applied to the study area,achieving the reasonable exploitation and utilization of groundwater resources,and repairing the ecological environment in the area. However,the variation of groundwater depth is also affected by climate change and human activity,but this paper did not quantitatively account for the effect of climate change and human activity to ground water depth,which need further research.

Key words: Horqin Sandy Area, precipitation, groundwater depth, variation