Year Established: 2014 Start Date: 2014-03-01 End Date: 2015-02-28
Total Federal Funds: $25,000 Total Non-Federal Funds: $50,000
Principal Investigators: Tyson Ochsner, Chris Fiebrich, Chris Neel
Abstract: Statement of critical regional or State water problem: Oklahoma water resource managers need accurate information on groundwater recharge rates to allow more effective water planning and to reduce groundwater related conflicts, but no functional recharge monitoring network exists in Oklahoma, or anywhere else to our knowledge. The statewide Oklahoma Mesonet provides a uniquely rich set of long-term data on hydrometeorological variables which are relevant for recharge estimation, most notably soil moisture. When soil moisture, hydraulic conductivity, and hydraulic gradient are known, drainage from the soil profile can be calculated based on unsaturated flow theory. Groundwater withdrawals that exceed the rate of drainage from the soil profile are not likely to be sustainable in the long term. We have recently completed an intensive measurement campaign to estimate soil hydraulic conductivity functions for the stations of the Oklahoma Mesonet. These new data enable us, for the first time, to calculate drainage rates using Mesonet data. Using year one funding from this program received in August 2013, we have made good progress towards quantifying the relationship between Mesonet-based drainage rates and groundwater recharge rates in western Oklahoma. We have calculated and summarized drainage rates for all the Mesonet sites overlying the Rush Springs and Ogallala aquifers. The median annual drainage rates and previously published groundwater recharge rates for these two aquifers are virtually identical. This exciting discovery suggests that the Mesonet has outstanding potential as a tool for estimating groundwater recharge across Oklahoma. However, we currently lack any independent estimates of groundwater recharge directly co-located with Mesonet sites, so the site-specific level of agreement between recharge and Mesonet-based drainage rate is unknown. Also, we have no knowledge about the extent to which regional scale spatial variability in groundwater recharge is reflected in Mesonet-based drainage rates. There is a critical need for both site-specific and regional scale research to fill these two knowledge gaps. Nature, scope, and objectives of the project: The long-term goal for this team of collaborators is to improve scientific understanding about and inform sustainable management of Oklahoma’s groundwater resources by creating powerful new tools for recharge estimation and mapping. The objective of this proposal is to clarify the relationship between Mesonet-based drainage rates and groundwater recharge rates in western Oklahoma. This is an essential next step in a logical progression of research that will lead us toward our long-term goal. To accomplish our objective we propose the following specific aims (continued from year one): 1. Determine the site-specific level of agreement between Mesonet-based drainage rates and independent estimates of recharge in selected aquifers. Site-specific, independent recharge estimates at Mesonet sites will be obtained for three locations in the Rush Springs aquifer and four in the Ogallala aquifer. 2. Determine the regional level of agreement between Mesonet-based drainage rates and independent regional recharge estimates for western Oklahoma. A Mesonet-based average annual soil drainage rate map will be created for western Oklahoma and compared with a new regional recharge map based on chloride concentrations in groundwater. Statement of results or benefits: This project will contribute directly to the 2014 OWRRI funding priorities for groundwater monitoring, by laying the foundation for an operational statewide groundwater recharge estimation system based on the Mesonet. Our method for estimating drainage has been used in research for decades, but it has never been applied with a regional monitoring network like the Mesonet, thus the proposed work is truly innovative. The successful completion of this project will have impacts far beyond the bounds of Oklahoma. Regional monitoring networks patterned after the Mesonet (e.g. the West Texas Mesonet), as well as national and international soil moisture networks will be able to use the results of this research to guide improved groundwater recharge estimates around the globe.