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Corn+Soybean Digest

Farmers use reservoirs to collect water, use in irrigation pivots

An onfarm water reservoir in northeast Kansas collects surface and subsurface drainage water from farm fields and recycles it for irrigation The practice allows irrigation in regions where midsummer droughts routinely cut yields but groundwater is limited or expensive
<p>An on-farm water reservoir in northeast Kansas collects surface and subsurface drainage water from farm fields and recycles it for irrigation. The practice allows irrigation in regions where mid-summer droughts routinely cut yields, but groundwater is limited or expensive.</p>

Keith Grimm hates to let valuable water drain away. So the Hiawatha, Kan., farmer and his two brothers collect runoff in reservoirs at field edges, then pump it back onto crops through center pivots.

Farm ponds are nothing new, of course. But now, innovative growers are linking on-farm water storage to drainage and irrigation systems to recycle water and nutrients. “We’re catching water during the winter and spring and storing it for when we need it,” says Grimm, 30, who is also the owner of MWI, an irrigation company.

The practice allows irrigation in regions where mid-summer droughts routinely push down yields but groundwater is limited or expensive, says Danny Rogers, Kansas State University agricultural engineer. 

Eastern Kansas, for example, has little groundwater, but gets 30 to 40 inches of annual rainfall, offering “lots of opportunity to capture surface water,” Rogers says.

Seeking drought protection

“It seems like every year, it quits raining in July,” Grimm says. Heat and drought push down corn yield potential from 200 bushels per acre “to 125 bushels in about three weeks.”

Just 3 or 4 inches of irrigation water during these dry spells boost corn yields by 50 to 75 bushels per acre, he says. In a typical year, the Grimms’ dryland corn averages 150 bushels per acre, while their irrigated corn yields 210 to 230 bushels per acre. Even during good weather in 2014, irrigation was an advantage, Grimm says. Their dryland corn averaged 200 bushels per acre, while their irrigated ground produced 240 to 270 bushels per acre.

The hitch: Water supply. “There are only small pockets of groundwater where we can put in wells,” Grimm says. It is also difficult to obtain permits to divert stream water, so most of the time, reservoirs are their only option.


Catching water

Inspired by their dad, who installed one of the first pond-and-pivot setups in northeast Kansas in 1997, the brothers now irrigate just under 500 acres of cropland from four, 8- to 20-foot-deep reservoirs at field edges.

Ranging in size from four to 10 acres, the basins are designed to store 4 to 7 inches of water per irrigated acre. On the Grimms’ farm, underground flow from seepage tiles on side hills and tile outlets on blocked terraces fill the basins by early spring.

The size of an irrigation pond depends on the terrain and soil, how much water drains from the watershed and the number of acres needing irrigation. In the eastern Kansas hill country, where annual runoff averages 6 to 10 inches per acre, it takes two watershed acres to supply one acre of cropland with 4 or 5 inches of irrigation, Grimm says.

In wetter areas of the Corn Belt, where per-acre water yields are greater, smaller watersheds are adequate for midsummer droughts. Asmall well can supplement the pond, he adds.

Opportunities east of the Mississippi

Heavily tiled regions of the Corn Belt also show potential for harvesting and recycling drainage water, says Larry Brown, Ohio State University agricultural engineer. Ohio’s heavy, silty clay soils have high runoff potential if not properly drained.

Brown and the USDA-ARS are doing research in the Maumee River watershed in northwest Ohio on wetland reservoir subirrigation (WRSI) systems, which include a drainage reservoir plus a constructed wetland for water treatment. During the summer, reservoir water is pumped back into closely spaced drain lines to irrigate crops. This technique takes advantage of existing drainage tile, Brown says. It’s also up to 30% more water efficient than overhead irrigation because of less evaporation and runoff.

Even in the eastern Corn Belt, eliminating crop water stress can boost corn yields 30% or more, Brown says. On Bill Shininger’s farm in Fulton County, Ohio, the yield advantage for subirrigation during the past decade has averaged 53 bushels per acre for corn and 9 bushels per acre for soybeans.

Shininger’s WRSI system includes a 20-acre field with subsurface drains on 15-foot spacings, which empty into a 1.57-acre reservoir holding 2.3 million gallons of water. A 1.4-acre wetland can hold an additional 1 million gallons of water.

Impounding drainage water can also cut nitrate losses from cropland by as much as 50%, Brown says. Water quality issues are front and center now, he adds. “Anything we can do to capture and recycle drainage water is a plus for the environment.”


Water storage economics

The cost to build an irrigation reservoir depends on size. Earthwork expenses range from $30,000 to $100,000, Grimm says. Permitting requirements, which vary by state, can add significant cost.

There are plenty of situations in which growers have marginal ground, such as land close to creeks, says Jeremy Meiners, vice-president of Agrem, an agricultural water management company in Anchor, Ill. If the land is naturally sloped, “digging costs are lower and it can be quite cheap, just the cost of the dam.”

If prime cropland has to be used for water storage, a reservoir doesn’t always pay. However, “there’s a lot of value in harvesting and storing water,” Meiners says.

Rogers agrees: “If you sacrifice three or four acres of cropland to irrigate 125 acres, that might be a good tradeoff.”

Climate change influences the economics of reservoirs too, Rogers says. In eastern Kansas, climate models predict fewer – but larger – rainfall events. On thinner soils, stormwater irrigation from reservoirs can boost yields.

Rogers sees many areas of the country where a reservoir system would be feasible, particularly where productive soils experience mid-summer drought and the terrain lends itself to capturing water. Today, only a few thousand acres of Kansas cropland are watered from on-farm reservoirs, “but there’s potential for a lot more,” he says.

Does an irrigation reservoir make sense on your farm?

Ask yourself the following questions:

  • Is a cheaper source of irrigation water available?
  • Is there an existing farm pond that could be adapted for irrigation?
  • Is there a suitable reservoir site close to the field?
  • What is the irrigation method?
  • What is the estimated amount of runoff and subsurface drainage that could be harvested, and how many cropland acres can be irrigated by this amount of water?
  • What is the value of the land that will be used for water storage?
  • Will the reservoir take good cropland out of production?
  • What are the potential yield and revenue increases from irrigation?

Sources: Jeremy Meiners, Agrem; Danny Rogers, Kansas State University; Larry Brown, Ohio State University

Sharing water storage, helping the environment

Kent Grimm and his neighbor share an irrigation water reservoir. The 7-acre pond, which holds about 60 acre-feet of water, is located between their fields, collecting drainage water from both farms.

It takes a little more management to run two center pivots out of the same reservoir, says the Hiawatha, Kan., corn and soybean grower. He and his neighbor coordinate their rotations each year, so one of their fields is in corn and the other in soybeans. Pump flow meters track each grower’s water use. In a typical year, Grimm applies 4 to 5 inches of water per acre.

Even in wetter years, irrigation boosts yields in northeast Kansas. “We figure we get even more yield boost in a good year than in a poor year,” he says.

Reservoirs also slash non-point pollution, Grimm adds, capturing sediment, nutrients and ag chemicals. One of his reservoirs drains 600 acres of cropland. “Not a lot of water leaves the farm. It’s one way we farmers can help the environment.”

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