Future of Delta Ag Dependant on Conserving Valuable Resources
By Becky Gillette
The future of the Mississippi Delta’s economic and environmental viability depends on abundant, accessible water of sufficient quality. More than eighty percent of the water used for irrigation, aquaculture and wildlife habitat enhancement comes from the shallow Mississippi River Valley Alluvial (MRVA) aquifer. Over time, pumpage demands have increased leading to long-term water-level declines in the aquifer, says Kay Whittington, PE, director, Office of Land and Water Resources, Mississippi Department of Environmental Quality (MDEQ).
A permit from the MDEQ Permit Board is required before any person can use the waters of the state, with exceptions for domestic use or uses of exempted small quantities. This permit is the primary means for preventing “the waste or unreasonable use, or unreasonable method of use, of water” and promoting “the conservation of such water.”
“Due to concerns about MRVA water level declines, the Permit Board issued the first General Permit for MRVA agricultural wells in 2011, decreasing the permit life from ten to five years and requiring water conservation practices,” says Whittington. “The General Permit was revised in 2016 to include conservation practices proven to be most effective based on research by Mississippi State University and again in 2021 to reduce from three years to one the time allowed to implement the required practices. Under both the 2016 and 2021 general permits, every permit holder is required to verify that the required conservation practices have been implemented. In addition, if one of the practices selected is installation of a flow meter, the permit holder must report the metered water use annually.”
Whittington says they very much appreciate the time, money and effort involved in the continued submission of metered water use data throughout the Delta. It is used by the U.S. Geological Survey along with soils data, precipitation, and crop-type in a water-use model that extrapolates the water use at metered locations to unmetered locations with similar characteristics to estimate the total water use input into the USGS groundwater model each year. This more accurate estimation of total water use has significantly improved the model’s ability to predict water levels that match measured water levels.
“Aquifer levels are generally driven by water use and recharge,” she says. “Growing season precipitation correlates with irrigation water use and non-growing season precipitation and river stages determine recharge. Above average growing season precipitation and the increase in the implementation of irrigation efficiency practices have resulted in a stabilization of water levels in recent years. However, similar patterns have been observed historically and can change rapidly with a decrease in growing season precipitation.”
To adopt policies and develop strategies to ensure sustainable Delta water resources for the future, MDEQ, the Yazoo Mississippi Delta Joint Water Management District (YMD) and the Delta Sustainable Water Resources Task Force (Task Force) must have adequate MRVA water level data. Water levels in over more than MRVA agricultural wells have been measured in April and October of each year since the early 1980s, first by the USGS, then by MDEQ, and, since the early 1990s, by YMD. In 2023 YMD headed up the reading of 450 wells in the Spring and 440 wells in the fall.
“MDEQ is also working with the USGS to update, refine, and utilize the Mississippi Delta portion of an existing regional groundwater flow model developed by USGS,” says Whittington. “This large-scale regional model covers the entire Mississippi embayment and extends through the primary drinking-water aquifers as part of the Mississippi Embayment Regional Aquifer Study. This model will be used to better understand the groundwater flow system, the potential effects of variations in pumping patterns, and to evaluate various water resources management scenarios.”
Through the multi-year Mississippi Alluvial Plain Project initiated in 2016, the USGS collected airborne electromagnetic, magnetic and radiometric data. USGS and MDEQ staff collaborated in analyzing these data, which were then used by USGS modelers to enhance the detailed representation of the hydrogeologic framework in the Delta Inset Model.
Whittington said the improved model has demonstrated sufficient reliability to enable the Task Force to begin to use model scenario simulations to compare the benefits of different potential practices and projects. The USGS, working closely with MDEQ and with feedback from the Task Force, will use the Delta Inset model to predict water levels from the present to 2055 under various sets of conditions.
“A base case will simulate increased pumping due to newly irrigated acres and modeled climate conditions with no change in irrigation practices and no new projects to augment available surface water or to enhance aquifer recharge,” she says. “Other scenarios will assume implementation of specific irrigation efficiency practices or construction of specific projects. Comparison of the results of the different scenarios will help inform Task Force planning and policy considerations.”
At the request of task force organizations, Mississippi State University’s Delta Research and Extension Center hired a Ph.D. to conduct research on irrigation efficiency practices and provide training to producers on the benefits and implementation of the most effective practices. On farm research has shown that the use of computerized hole sizing for poly-pipe, soil moisture sensors and surge valves can reduce water use on furrow-irrigated corn and soybeans by twenty to fifty percent without reducing yields.
In 2017, Congress established and funded the National Center for Alluvial Aquifer Research in Stoneville as a cooperative program between USDA’s Agricultural Research Service and the Mississippi Agricultural and Forestry Experiment Station at Mississippi State University. NCAAR produces and communicates research directed towards the conservation and sustainability of water resources for agriculture that include developing water-efficient cropping systems, improving water capture, improving water distribution systems and irrigation efficiencies, use of water-saving irrigation management options such as improved irrigation scheduling, and developing economic risk assessment tools that enable producers to identify profitable, water-efficient production options.
The Permit Board may delegate authority to any joint water management district to receive, investigate and make recommendations to the board regarding applications for permits. In 1994, the Yazoo Mississippi Delta Joint Water Management District (YMD), began receiving, investigating and making recommendations regarding applications for permits for irrigation, aquaculture and wildlife habitat enhancement surface water diversions and groundwater withdrawals from applicants located within the 17-county service area.
“The permitting process is much easier for farmers in the Delta because YMD is centrally located in Stoneville and has a long history of assisting farmers,” says Whittington. “YMD has made improvements in the permitting process through the years such as the development of an online application document and an online well mapping viewer.
Since the formation of the task force and the continued efforts of MDEQ and YMD, the awareness of the declining water levels and the importance of the permit have improved greatly.”
YMD Executive Director Don Christy, Ph.D., says in the Delta, there are some areas where groundwater levels have declined but have shown some improvement.
“We all need to remember this is a marathon, not a sprint,” says Christy. “So, we need to be vigilant about conservation practices and doing the best we can to reduce groundwater use to continue preserving the water that is in the aquifer. As part of the groundwater permits that the state issues, permit holders may choose among 11 conservation practices to provide the best outcomes for water conservation. These options allow the permittees to pick something that will best fit their circumstances. For example, they can pick irrigation timers, soil moisture sensors, land leveling or center pivot irrigation systems.”
The solutions can also save money. For example, there can be considerable savings from pumping less water. And preservation of groundwater reserves also helps keep ag and the Delta economy healthy.
“Ag is a central part of not only the Delta economy but the Delta way of life,” says Christy. “It is essential that agriculture provides a strong fabric to support most things that happen in the Delta.”
Recently there was a report by the Agricultural Research Center into a groundwater transfer injection pilot project (GTIP) which has been going on for several years outside of Greenwood. Christy says injecting groundwater back into the aquifers is a higher-technology approach to the issue.
“You may see those types of technologies going in at other places in the Delta, not simply in Greenwood, depending on where they could be most suitably used,” says Christy. “However, GTIP technology is potentially expensive and determining who will pay necessary costs and expenses is an issue.”