Responses of Groundwater Recharge and Pumpage to Change in Precipitation in Hebei Plain

The research from 1986 to 2000 into the dynamic processes and interactions among annual precipitation, annual groundwater recharge from rainfall and annual pumpage for agriculture in Hebei plain to the south of Beijing and Tianjin, revealed the negative relationship between the increase or decrease in annual precipitation and the contemporaneous annual groundwater recharge from rainfall and the annual pumpage. In another word, when the annual precipitation decreases, the recharge decreases, but the pumpage increases. However, when the annual precipitation increases, the recharge increases to a relatively great extent, but the pumpage decreases. During the successive years of shortage or abundance of water, if the annual precipitation decreases (or increases) by 10 mm, the water quantity of the regional groundwater system decreases by 7.08 mm (or increases by 7.06 mm) and the corresponding water level falls (rises) by 5.2 cm to 8.7 cm. In the range of the annual precipitation variation from 10 to 320 mm, if the annual precipitation decreases (or increases) by 10%, the water quantity of the regional groundwater system decreases by 7.98% (or increases by 7.67%), the corresponding water level falls (rises) at the same rate. The effect of the precipitation variation both on the decrease in recharge and on the increase in pumpage in the dehumidification season is greater than that on the increase in recharge and on the decrease in pumpage in the increasingly raining season. Therefore, more attention should be paid to some measures that may soften the effect of the precipitation variation on the underground water system in the successive years of shortage of water, which may be of great significance to the stability and security in the underground water supply system in the north of China.