Spatiotemporal groundwater recharge estimation for the largest rice production region in Sanjiang Plain, Northeast China

Accurate estimation of groundwater recharge is important for sustainable management of water resources in intensively irrigated agriculture. In this study, the water-table fluctuation (WTF) method, combined with statistical regression analysis, was used to understand the spatiotemporal variability of groundwater recharge in the largest rice production farming region on China's Sanjiang Plain. Monthly and annual groundwater recharge rates were estimated using the WTF method and simple kriging, respectively. Average annual recharge volumes were estimated for the entire region using the Thiessen polygon method. The study showed a large spatial and temporal variation of groundwater recharge in the region. Seasonally, the recharge rate was high during the spring and early summer when snowmelt occurred and heavier rainfall was concentrated. Nearly 68% of the total annual recharge took place during the 4 months from April to July. Annually, recharge volumes varied greatly, ranging from 7.9 x 10(8) m(3)/yr (2005) to 9.9 x 10(8) m(3)/yr (2006). There was a large spatial difference in recharge with the highest annual rate (191 mm/yr) in the south and the lowest (9 mm/yr) annual rate in the north. The findings demonstrated that the WTF is simple and very useful for shallow groundwater assessment for such a large alluvial plain.