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. Plain Language Summary Although there are a few available methods that can be applied for estimating groundwater level based on the precipitation time series, the methods are mostly limited when incorporating unsaturated gravitational flow. The hydraulics of the unsaturated zone is affected significantly by seasonally varying climatic condition (especially in temperate regions); and therefore, the pattern of water table (WT) response is different for different climatic periods. The authors believe that there have been almost no studies that address this issue. The purpose of this study is to develop a mathematical model that is more versatile in representing various water table responses to precipitation. An additional objective of the study is to show that the effect of the unsaturated gravitational flow variable on climatic conditions must be included in water table estimations.