A shallow water table fluctuation model in response to precipitation with consideration of unsaturated gravitational flow

A precise estimation of groundwater fluctuation is studied by considering delayed recharge flux (DRF) and unsaturated zone drainage (UZD). Both DRF and UZD are due to gravitational flow impeded in the unsaturated zone, which may nonnegligibly affect groundwater level changes. In the validation, a previous model without the consideration of unsaturated flow is benchmarked. The model is calibrated using multiyear groundwater data, and consistent model parameter statistics are obtained and validated. The estimation capability of the new model is superior to the benchmarked model as indicated by the significantly improved representation of groundwater level with physically interpretable model parameters.