To Bill Thomas' way of thinking, re-using his irrigation water is no different than recycling the oil, plastics and scrap metal he uses on his farm, or even his family's discarded aluminum cans. “It's just my mindset to try to re-use everything I can,” says the Greenwood, Miss., cotton grower whose farm spreads between Leflore and Holmes counties.
A June 17 field day on Thomas' farm showcased his tailwater recovery system, which catches irrigation runoff from crop fields and rainfall, and then returns it to his irrigation system.
“It takes a lot of time and money to set up one of these systems, but I want to be ahead of the curve,” he says. “I want to have these systems already in place when the day comes that we have to start paying for all of the water we use on our farm.”
Like many other farming decisions, installing a tailwater recovery system to recapture irrigation runoff and rainfall is a long-term proposition. “I approach it, not as a decision for 10 years, but for 20 years or 40 years or 50 years. It needs to be a long-term decision, but unfortunately farming is such that it's been hard to make these long-term decisions because it has been a year-to-year deal here of late,” he says.
“I'm fortunate that there were several generations ahead of me, allowing me to make these kinds of decisions. I'm simply continuing what my grandfather told me at an early age about conserving your soil, and now water,” he adds.
Thomas' tailwater recovery system recaptures 161 acres of irrigation runoff, bringing it into one storage area, where it is then re-used to irrigate about 50 acres. He's in the process of putting in a second tailwater recovery system to supply recaptured water to another 30-acre field.
“With my new system, I'm going to be re-using water that's now going down into a ditch, and has never been re-lifted before,” he says. “In other words, instead of putting in a new well, I'm going to re-use runoff water from other fields to irrigate my cotton and corn crops.”
Jerry Singleton, Mississippi area Extension agent, says, “Unfortunately, our flood and furrow irrigation systems are not 100 percent efficient, and we do get some runoff. Installing the type of system Bill Thomas is using can substantially improve your irrigation efficiency.”
Jim Thomas, irrigation specialist at Mississippi State University, says Bill Thomas is recapturing most of his irrigation water with his tailwater recovery system. “He would likely lose much more water under a conventional setup without a re-use than what he is losing with this system, even though he may have lowered his distribution efficiency somewhat to gain runoff to help supplement irrigation water.”
Calling the system “a good best management practice for sediment control and irrigation runoff,” Thomas says there are a myriad of ways to handle this type of system, and insure water supplies get up to where they need to be. “It's almost whatever the imagination and the pocketbook allow.”
Designed to supplement irrigation, the system can be tailored to acreage, drainage area, well size, and whether or not a farmer wants to recapture irrigation run-off and/or rainfall. The system can also be used to supplement well water irrigation.
“There are lots of different ways you can go. You can use submersibles, you can use a short-shaft turbine just like your wells, or you can use floating electric centrifugals,” Thomas says. “You can also design it so you can run at least one full irrigation set through, or you can downsize the system some and try to run it continuously. You see all combinations. If you are trying to recapture rainfall, it's probably easier to design it using irrigation sets because you have the opportunity to get a little more water than you would get from just irrigation runoff. Irrigation runoff is going to vary depending on whether you start early and the ground is a little wetter, or whether you start late and it's dry.”
In addition, management can affect the amount of available runoff.
“You can go intermittent or continuous, which also is called re-lift. It's a practice rice growers have done for years to pick up run-off water,” he says. “Typically you want either a sump or a deep spot that you can pull water out of, because you don't want to pull off the bottom particularly, and you don't want to pull right off the surface. If you pull off the surface, you'll get a vortex and you'll start sucking air, and you may tear up your pump.”
While installing a tailwater recovery system isn't cheap, Thomas says the practice may offer a cost-savings benefit to some growers.
“You take a 70-foot lift and compare it to a 10-foot lift, and there is considerable economic savings there. If you are pumping water right next to the hills, or next to the river, where your pumping depths are 10 to 15 feet, the economics may not be that big a factor. But, as you get out here in the middle of the Delta, where your pumping water level depths are greater, you may be able to see tremendous savings on energy and horsepower. Plus, it's a way to conserve water.”
The downside, he says, is that tailwater recovery systems are expensive units to put in. “They don't make them cheap,” Thomas says.