The main goal of this study is to employ empirical hydrologic models and different types of earth observational datasets to estimate the spatiotemporal distribution of groundwater recharge within the Contiguous United States (CONUS), and compare the values with other data products. The annually averaged recharge values were calculated using a water balance approach, and the recharge map is presented at a spatial scale of 800 meters. The conceptual model used for the water balance, considers the net recharge as the difference between precipitation and the combined values of evapotranspiration (ET) and runoff. The annual averaged soil moisture storage levels were assumed to be at a steady state. The combination of satellite data and other field-scale observations were used to calculate various water balance components. The PRISM climate dataset was used for modeling precipitation. The ET values were estimated using crop coefficient approach recommended by the Food and Agriculture Organization of the United Nations (FAO). Current study tried to use FAO tabular data for crop coefficient in an optimal way to consider the temporal dynamic of crop coefficient based on crop land map. The soil conservation service (SCS) or SCS curve number method was used for calculating direct runoff. The SURRGO soil database and the national cropland data layer (NCDL) were use for calculating CN number. The ET and runoff estimation were benchmarked with other available datasets. The results compared well and provided a comprehensive understanding of the applying empirical equations in using different types of approaches. It is acknowledged that the current method only provides approximate annually averaged estimates for shallow groundwater recharge at the CONUS scale. The current estimates provide valuable insights for building more sophisticated recharge model.
