The impact of plant water uptake and recharge on groundwater level at a site in the Loess Plateau of China

Shallow groundwater in unconsolidated sediments represents a substantial water resource in the Chinese Loess Plateau. However, prior to development of the water supply for agriculture, annual and seasonal fluctuation of the recharge mechanism should be clarified. Since the region is arid, the effect of plant water uptake on groundwater fluctuation must also be assessed. A study was therefore undertaken to clarify groundwater recharge together with interaction between the plant ecosystem and shallow groundwater at a field site in the Loess Plateau of China. Observations showed that recharge response of the groundwater level (GWL) was limited except for intensive rainfall during the rainy season. The main recharge to the groundwater occurred from horizontal inflow from focused recharge at the upstream end of the site. Fluctuation of the GWL produced by plant water uptake was monitored during the growing season. For seasonal fluctuation of GWL, temperature was most important, while for diurnal fluctuation of GWL during the growing season, solar radiation was most important. During the growing season, the GWL declined during the daylight hours and recovered during the night. The diurnal fluctuation was well synchronized with the solar radiation, consistent with plant-water uptake by shrubs surrounding one of the observation wells.