Groundwater Recharge in Shallow Water Table Conditions

Abstract

A disproportionate increase or decrease in water table in response to minor water input or drainage is observed in shallow water table conditions inside drainage lysimeters. This increase occurs because the capillary fringe of the shallow water table reaches up to or near the surface (Wieringermeer effect). The correlations between water table level changes and rainfall, seepage irrigation, drip irrigation, and drainage were analyzed. Correlations with rainfall, seepage irrigation, and drainage were high (R2 ranged from 0.46 to 0.97). Drip irrigation had low correlations due to the low rates of application (R2 ranged from 0.26-0.44). Conventional methods of calculating recharge such as multiplying the specific yield with the water table fluctuations cannot be used for Wieringermeer effect situations. A method using water balance data and soil moisture at different depths in the lysimeters was developed to estimate recharge and upflux. The recharge results were used to develop the apparent specific yield (Sya), which could be used to calculate consequent recharge events from water table fluctuations data. Combining the water tables fluctuations relationships developed with Sya value will allow the prediction of recharge from rainfall and irrigation events without the need for soil moisture equipment.