Long-term climatic averages of groundwater recharge is derived from high-resolution time-series of baseflow (groundwater discharge) and other components of the hydrologic water balance. In this study numerical modeling is used to disaggregate recharge within the surface and subsurface components of the system. Through numerical modeling, recharge and discharge results are generalized through a combination of spatially distributed runoff, precipitation, and evapotranspiration. Within a distributed modeling context, observed atmospheric states, and radar-derived precipitation is combined with physical characteristics of the terrain to estimate recharge flux to the regional aquifers during over a period of 12 years. The resolution of the precipitation used as model input is 4x4 km resolution and at hourly time steps, which is characteristic of the Stage III NEXRAD radar product. Reanalysis of this product using Oklahoma Mesonet gauges in and around the study area provides a continuous gap-filled product for hydrologic simulation. Potential evapotranspiration is derived from pan and atmospheric state variables, which are evaluated at daily, monthly, and as climatological annual averages. From continuous simulation with high-resolution precipitation, a climatological rate of recharge for the aquifer is constructed and compared to longer-term estimates from stream flow records.

Located in South-Central Oklahoma, the Arbuckle-Simpson Aquifer is the principal source of water for the Cities of Ada and Sulphur and is the source of water for a number of important springs and streams in the region, including those associated with the Chickasaw National Recreational Area. Within the study region, this aquifer provides base flow to the Blue River, Pennington Creek, Mill Creek, Rock Creek, Oil Creek and Sycamore Creek. Estimation of the annual groundwater recharge for the Arbuckle-Simpson Aquifer is accomplished using a water balance approach within the distributed modeling framework.