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Preparing for Oklahoma’s Future: Estimating Groundwater Recharge Rates

Preparing for Oklahoma’s Future: Estimating Groundwater Recharge Rates class="plain kssattr-atfieldname-text kssattr-templateId-newsitem_view kssattr-macro-text-field-view">

A doctoral student at Oklahoma State University, recently published her research on estimating potential groundwater recharge rates statewide.

Briana Wyatt, a doctoral student studying soil science, spent the last two years studying soil moisture data from the Oklahoma Mesonet and using that data to estimate statewide annual and long-term average groundwater recharge rates.

The Oklahoma Mesonet is a network of 121 environmental monitoring stations across the state with at least one station in each county. This network provides researchers access to statewide environmental data.  While most groundwater research is conducted on a single aquifer spanning a few years, through the use of the Mesonet, Wyatt’s research allows long-term potential recharge estimates to be made for aquifers across the entire state.

“Over 35% of all water used in Oklahoma comes from groundwater sources, and the majority of those withdrawals are used for irrigated agriculture. Extensive pumping from aquifers has led to declines in groundwater in many areas of the state, specifically in the Panhandle. In order to preserve these resources and ensure their sustainability for the future, it is essential to know how much water is being returned to groundwater systems,” explained Wyatt on the importance of monitoring groundwater recharge rates for proper water management practices.

Rural residents and agricultural producers statewide are well aware of groundwater declines. Irrigating farmers have had to dramatically increase their efficiency in irrigation techniques to protect Oklahoma water resources.   Chandler Henderson, a third-generation farmer in Cimarron County, explained several ways farmers in the Oklahoma panhandle, as well as other parts of the state, are working to use water more efficiently. These farmers are implementing techniques like converting center-pivot sprinklers from high and wide-spaced drops to low and narrow-spaced drops, as well as changing from spraying the water out in a fan to spraying it straight down to decrease evaporation. Another way farmers are increasing their water use efficiency is by implementing drip irrigation. Through drip irrigation there is no water lost to evaporation and water usage is decreased by 66%, on average. Though farmers are working to improve water resource management practices, there is still a great need to be able to estimate groundwater recharge rates.

“The problem we face with these changes is the cost of labor and supplies needed to convert everything. Drip irrigation costs $1,800 an acre, which is more than the average price of land, but we have to do whatever it takes to raise crops with less water. Farmers already adjust planted acres each year based on groundwater declines, but being able to estimate groundwater recharge from year to year would allow us to be make more informed decisions based on how much water is available,” said Henderson.

Other rural Oklahoma residents, who depend on groundwater resources, are concerned by the demands placed upon aquifers by municipalities and the potential negative impacts of depleted groundwater resources. Chris Horton, a rural Caddo county resident, explains his concern for the depleting Rush Springs Aquifer.

“Landowners have sold water rights to these municipalities, resulting in numerous wells being drilled to tap into this fresh water resource.  These municipalities are pumping large quantities of water, and the demands placed upon the aquifer are continually increasing.  Although a replenishing aquifer, the Rush Springs aquifer replenishes at a very low rate.  It is a concern for me and my rural neighbors whether our interests will be sacrificed for municipalities and metropolitan areas. 
“The value of rural residents’ property and their livelihoods are dependent upon protecting rural water resources and water rights.  It is therefore imperative that landowners and the state take an active role in monitoring aquifer levels to ensure no more water is being used than can be replaced,” said Horton.

Irrigating farmers, rural residents, and municipalities alike rely greatly on Oklahoma groundwater resources. The future of these resources will determine the future of Oklahoma. The ability to estimate groundwater recharge rates will allow Oklahomans to improve water resources management while better preparing for the future.  Wyatt’s research makes estimating potential groundwater recharge possible by combining long-term Mesonet soil moisture data with soil properties from across the state. This produces drainage rates, which are considered to be an upper limit to groundwater recharge.

This project determined that average annual drainage rates for the years 1998-2014 ranged from 0.2 – 10.5 inches per year.  A hydrological model, HYDRUS-1D, was used to validate the drainage estimates for certain sites. The project’s results showed that in many cases drainage rates were estimated with reasonable accuracy and are indicative of potential groundwater recharge rates.

Wyatt first became involved in the project in the fall of 2013 when she began her master’s program. Her major advisor, Tyson Ochsner, an associate professor in applied soil physics, developed the initial proposal and earned funding for the project through the USGS 104b program. Wyatt worked on the project for just under two years during her master’s program. She then spent an additional six months improving upon the research before submitting her work for publication.

Wyatt’s paper will be published as an open access paper soon; search for the citation below or check our Publications page in the near future.
Wyatt, B.M., T.E. Ochsner, C.A. Fiebrich, C.R. Neel, and D.S. Wallace. 2017. Useful drainage estimates obtained from a large-scale soil moisture monitoring network by applying the unit-gradient assumption. Vadose Zone J. [take a "first look"]