Estimating Groundwater Recharge Using the Oklahoma Mesonet.

Soil moisture data from the Oklahoma Mesonet system are used in research efforts in multiple disciplines in the natural sciences. Using these soil moisture data, along with site-specific hydraulic conductivity functions, estimates of drainage from the soil can be obtained based on unsaturated flow theory. These estimates may prove to be helpful in reducing groundwater-related controversies as well as allowing for more effective water management and planning within the state. Our objective is to determine how well the long-term average drainage rates found using soil moisture data approximate groundwater recharge rates In Oklahoma. The median long-term average drainage rate across the state was found to be 70.5 mm yr-1, which is approximately 8.7% of precipitation. Drainage rates exhibited significant spatial variability but generally decreased from east to west, consistent with the precipitation gradient. A recent global review found that recharge under grasslands averages 8.3% of precipitation, thus providing support for the claim that Mesonet-based drainage rates provide a reasonable approximation of groundwater recharge. Comparisons of the Mesonet-based drainage rates with other independent recharge estimates are ongoing.