Groundwater Recharge from Floods in the a Hyper- Arid Floodplain.

Floods are important sources of ground water recharge in most of the world’s arid lands. Flood spreading (River overflowing) is one of the suitable methods for flood management and water harvesting that increases the groundwater recharge. However, information on the relationship between the flood water and ground water recharge is limited. The objective of this study was to determine the relationship between the flood water depth and the height of ground water level rise using lysimeters and numeric modeling in the floodplain of the Tarim River in Northwest China. The experimental results suggested that the rise in the height of the ground water table was closely related to the flood water ponding depth, ground water depth responded quickly after flooding due to the high infiltration rate in the floodplain of Tarim River. The water table falling velocity was significantly less than the water table rising velocity. If the initial groundwater table was deeper, the variation in the depth of water table rise was smaller and the water table falling velocity was slower. The numerical simulation results showed good agreement with observed data, with a determination coefficient (R²) of 0.87 and a root mean square error (RMSE) of 63.91 cm. A good relationship (R²=0.79) between height of water table rise and the initial groundwater table depth, initial soil water content, and flood water depth, was established. Considering natural and artificial flood frequency are related to flood time interval, a relationship (R²=0.89) between height of water table rise and the initial groundwater table depth, flood time interval, initial soil water content, and flood water depth was developed. These results can enhance the understanding of flood recharge characteristics in the hyper-arid floodplain.

Keywords: Arid land; Flood; Ground water recharge; Inland river; Lysimeter