ESTIMATING GROUNDWATER RECHARGE USING THE OKLAHOMA MESONET

Groundwater serves as a crucial source of water for citizens, agriculture, and industry in Oklahoma, but there has been no large-scale study of groundwater recharge in Oklahoma in the past 30 years. What Oklahoma does have, however, is the Oklahoma Mesonet, a world class network of environmental monitoring stations located in every single county. Our objective is to utilize this unique network to estimate groundwater recharge. Site and depth specific soil hydraulic conductivity functions, K(θ), were estimated using the Rosetta pedotransfer function. Daily soil moisture data from Mesonet stations were then used with these K(θ) functions and the Buckingham-Darcy equation to calculate drainage at the 60 cm soil depth. This method was applied to five sites in central Oklahoma and returned an average annual drainage value of 70 mm yr^-1 or 8.3% of mean annual precipitation, similar to recharge estimates from prior studies in the region. Daily drainage values were compared to groundwater levels in monitoring wells adjacent to Mesonet sites, and increases in drainage preceded subsequent rises in the water table, days or even months later depending on the site. These results demonstrate the plausibility of the proposed method for recharge estimation and highlight the significant role of the soil in mediating the groundwater recharge process.