The space - time distribution of chinese semi - ari d region surface water is n ' t even , the differences in a year are obvious ; the differences of underground water between years are not so obvious as surface water , but it still has a decreasing tendency , especially in shanxi and sha ' anxi provinces . there is a significant linear correlation between the precipitation and water resources in semi - arid region , the dynamic regularity of water resources is basically same as the dynamic regularity of precipitation 半干旱地区地表水资源时空分布不均匀，年内分配差别大，地下水资源年际间变化率不大，但总体有减少的趋势，尤以陕西和山西突出。半干旱地区降水量与水资源量线性相关显著，降水量的变化规律基本上与水资源量的变化规律吻合。
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