Tailwater Recovery and On-Farm Storage Reservoir: Water Savings

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Publication Number: P3272

Why Save Water Using TWR Systems?

Row-crop irrigation is the primary use of groundwater in the Mississippi Delta region. Currently, withdrawals of water from the aquifer by irrigators is greater than the amount that is recharged (YMD, 2010). Figure 1 shows the Mississippi Delta region and magnitude of aquifer levels above mean sea level. The groundwater levels range from more groundwater (blue and light blue) to less groundwater (red and orange). Water levels in the aquifer under Sunflower and Leflore Counties are denoted with red because agricultural withdrawal is much greater than recharge. The annual groundwater deficit is estimated to be approximately 150,750 acre-feet (YMD, 2010; Barlow and Clark, 2011).

Several options are available for irrigators to reduce groundwater use. First, they can improve the efficiency of their water use, also known as “at-the-tap conservation” or “more crop per drop.” They can achieve this by using technologies including soil-moisture meters, center-pivot irrigation with drop lines and improved nozzles, or furrow irrigation with pipe planner programs with variable-hole-size selection and surge valves. Second, irrigators can use surface water. This can be done by installing a pump on an existing surface water source or by installing a tailwater recovery (TWR) system.

Map of the Mississippi Delta showing ground water levels: the highest levels are in the north, while the lowest are in the center and south. — **Figure 1. Ground water levels in the Mississippi Delta. Groundwater data were provided by Yazoo Mississippi Delta Joint Water Management District.**

In a TWR system, water moves from a riser board pipe, to a TWR ditch, to being pumped from a TWR ditch into OFS, to a pumping station, to furrow irrigation, to field runoff, and the cycle repeats. — **Figure 2. Water movement through a TWR system. Note that not all TWR systems have the same components. Some TWR systems are comprised of only a large TWR ditch and no OFS reservoir.**

Tailwater recovery (TWR) systems store water on the landscape to provide an alternative irrigation source for producers. Water used by irrigators from tailwater recovery systems directly offsets the amount of groundwater withdrawn from the aquifer. Thus, TWR systems are a popular conservation practice in the Mississippi Delta region. It is important to document how much water is saved and lost using TWR systems.

Water gains in tailwater recovery ditches are from precipitation and runoff (precipitation and irrigation runoff). Losses from tailwater recovery ditches are from evaporation, infiltration, overflow, and re-lift. Water gains in on-farm storage reservoirs are from precipitation and TWR ditch overflow and re-lift. Water losses from on-farm storage reservoirs are from evaporation, infiltration, and irrigation. — **Figure 3. Gains and losses of water into and out of TWR systems. Figure from Omer et al. (2017).**

TWR System Water Monitoring Results

Water Budgets

Irrigators can use surface water from TWR systems as an alternative to groundwater. Data from eight locations in the Mississippi Delta region indicate that TWR systems 1) store surface water from October through May; 2) supply irrigators with water from June through July; and 3) lose considerable water to evaporation from August through September.

TWR System Water Budget Results

Currently installed TWR systems have the capacity to offset aquifer depletion by 23,301 acre-feet a year by providing irrigators with an alternative to groundwater. Assuming each of the current TWR systems is installed on an individual farm, 2 percent of the farms in the Mississippi Delta region would reduce the groundwater deficit by 15 percent.

Graph showing water gains (through precipitation, precipitation runoff, and irrigation runoff) and losses (through irrigation, evaporation, infiltration, and surface water overflow) to the system by month. Generally, TWR systems store surface water from October to May, supply irrigators from June to July, and lose considerable water to evaporation from August to September. — **Figure 4. Mean (2013–16) quantity of water for each budget variable and water balance. From Omer et al. (2017).**

For More Information

Consult your county USDA Natural Resources Conservation Service agent for more details on conservation practices.

TWR ditch in winter (January). The ditch is full of water, and the surrounding field is brown.

TWR ditch in spring (March). The ditch is full of water, and the surrounding field is brown and green.

TWR ditch in summer (June). The ditch is full of tall, green weeds, and the surrounding field is green.

TWR ditch in fall (October) The surrounding grass is mostly brown and the ditch is full of water. — **Figure 5. TWR ditch in the Mississippi Delta region across four seasons (from top, January, March, June, and October).**

References

Omer, A. R., Dyer, J., Prince Czarnecki, J. M., Kroger, R., & Allen, P. J. (2017). Development of water budget for tailwater recovery systems in the Lower Mississippi Alluvial Valley. Journal of Irrigation and Drainage Engineering 144(6). https://doi.org/10.1061/(ASCE)IR.1943-4774.0001302

Barlow, J. R., & Clark, B. R. (2011). Simulation of water-use conservation scenarios for the Mississippi Delta using an existing regional groundwater flow model. Reston, VA: U.S. Department of the Interior, U.S. Geological Survey.

YMD (Yazoo Mississippi Delta Joint Water Management District). (2010). Estimated 2010 groundwater use from the Mississippi River Valley Alluvial Aquifer. Stoneville, MS: YMD.

The information given here is for educational purposes only. References to commercial products, trade names, or suppliers are made with the understanding that no endorsement is implied and that no discrimination against other products or suppliers is intended.

Publication 3272 (POD-05-23)

By Austin Omer, PhD, former Extension Associate, and Beth Baker, PhD, Associate Extension Professor, Wildlife, Fisheries, and Aquaculture.

Department: Wildlife, Fisheries & Aquaculture

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