A drainage expert proposed at Brookings storing agricultural drainage water in ponds or wetlands to reuse it for irrigation, which would reduce flooding, chemical runoff and groundwater use, at an estimated cost of $10,000 to $20,000 per acre-foot.
BROOKINGS, South Dakota — Farmers could reduce their reliance on groundwater, mitigate downstream flooding and improve crop yields during droughts by storing their drainage water in a pond or wetland, a speaker proposed at the Eastern South Dakota Water Conference.
Chuck Brandel, a drainage specialist with ISG, an engineering and architecture firm with offices in South Dakota and other states, presented the practice of drainage water recycling to attendees Wednesday at South Dakota State University's McCrory Gardens Education and Visitor Center.
As Brandel explained, the practice capitalizes on water moving through existing networks of perforated pipes buried beneath crop fields, known as drain tile, which farmers install to remove excess water from the soil. Instead of letting that water drain away, drainage water recycling stores it in ponds or wetlands and uses it for irrigation when the producer needs it.
"In some cases, you can gravity-feed the drainage system into a low spot," Brandel told South Dakota Searchlight after the presentation, "and then you pump it back out and put it back on the field."
The specialist said the practice could do a lot for South Dakota, such as reducing downstream flooding and farm-chemical runoff, improving yields by having more water available for irrigation during droughts, and reducing the amount of groundwater used for irrigation. A prior speaker presented a chart showing irrigation accounts for 86% of South Dakota's water use.
Multiple speakers at the conference said South Dakota needs more water to keep up with development and population growth projections. Some of the state's water systems depend on pockets of groundwater known as aquifers.
Brandel said the reduction in groundwater use for irrigation could be substantial if drainage water recycling is widely adopted. "If you build enough storage, you could potentially switch it all over," he said, referring to individual farmers' irrigation.
An Environmental Defense Fund estimate says building a pond, wetland or other storage area for a drainage water recycling system could cost between $10,000 and $20,000 per acre-foot of storage. An acre-foot is the volume of water needed to cover 1 acre of land to a depth of 1 foot. The estimate lists additional costs to install drain tile, irrigation and other parts of the system.
