Irrigation Systems Minimally Effect Water Supply

This farm irrigation system along the west side of Old SR 15, just south of Milford, is one of many installed in the area since the summer of 2012 drought. (Photo by Tim Ashley)

This farm irrigation system along the west side of Old SR 15, just south of Milford, is one of many installed in the area since the summer of 2012 drought. (Photo by Tim Ashley)

“We are not Nebraska.” Lyndon Kelley, irrigation specialist with the Purdue University Department of Agricultural and Biological Engineering, spoke the phrase in reference to what he would title a book if he were to write one about how farm irrigation systems affect the local water supply.

Since the summer of 2012, when one of the worst droughts in recent memory gripped the entire Midwest for several weeks, several irrigation systems have been installed and questions have been raised about how they may affect the aquifer or local water supply.

“We all need water and those questions will come up,” Kelley noted.

Some portions of the U.S. to the west, such as Kansas, Colorado and Nebraska, have seen farming irrigation have an adverse affect on the water supply. But Kelley, and other experts, noted comparing northern Indiana with those areas does not provide an accurate picture.

Kelley acknowledged during the summer of 2012, water levels were down because the amount of rainfall was lower and that does affect the water tables. During the summer, the amount of rainfall needed to recharge the water levels typically falls short, he said. But, he added, the water levels average out and “we have a huge amount of water underneath us in this area,” and after it rains, most of it goes down.

“I know it’s hard for people to understand,” he said, but in other states to the west they have to drill further down and are pulling more out of the table for irrigation systems. “They get far less recharge rain than we do, though,” he said, “and much more land there (out west) is irrigated.”

Kelley said the U.S. Geological Survey has river gauging stations set up in various locations to determine if a river’s flow has decreased any.

Mark Basch, head of the water rights and use section of the Indiana Department of Natural Resources Division of Water, said ground water availability in northern Indiana is generally good due to the presence and thickness of unconsolidated glacial deposits such as sand and gravel. “Because northern Indiana receives about 35 to 40 inches of precipitation annually, the impacts of agricultural irrigation on ground water levels are usually minimal and occur primarily during the irrigation season,” he said.

Basch said several factors determine how much an aquifer is affected by agricultural irrigation. He said those include, but are not limited to, the volume of water withdrawn by a high capacity well, the ability of the aquifer to release water, water in storage, the distance from the withdrawal point and the available recharge.

“In Indiana, ground water levels impacted by irrigation pumping typically recover to normal season levels within a few weeks or months after pumping has ceased,” he said. “In some locations where irrigation withdrawals are substantial and recharge is not as prolific, ground water levels may not fully recover until the following spring.”

As of about two weeks ago, IDNR Division of Water has 114 registered significant water withdrawal facilities in the “agricultural irrigation” category in Kosciusko County, according to information provided by Basch. Those facilities include wells and surface water intakes. Basch said a significant water withdrawal facility is defined as having a pumping capacity greater than 100,000 gallons per day.

He said the Division of Water is not anticipating the wells will significantly impact the ground water resource, but division staff are available to document “baseline” water levels for domestic well owners concerned about the pumping. A domestic well owner is protected against the impacts of high capacity ground water pumping if it substantially lowers ground water levels resulting in the failure of a domestic well.

An explanation of the water rights under Indiana’s Water Rights: Emergency Regulation statute is available on the Division of Water’s website.

Basch noted the impacts of ground water withdrawals on lakes are “generally very site specific.” He said high capacity ground water withdrawals in the vicinity of a lake can potentially lower its water level, however, much of the decline may be due to normal seasonal ground water level fluctuations and evaporation. Indiana’s Surface Water Rights Law provides protection to owners of freshwater lakes if a large capacity water withdrawal facility significantly lowers the lake level, resulting in significant environmental harm. A copy of the law is available online.

Dr. Nathan Bosch, director of Kosciusko Lakes and Streams at Grace College, said it is not known for certain yet how much the increased use of groundwater for irrigation may be affecting the local water supply. Although many irrigation systems were running literally everyday for long stretches last summer, some systems were installed during the winter or spring since then and have not been used nearly as extensively yet this year.

Bosch said the springs bringing groundwater into many local lakes are influenced, to some extent, by any practice that pumps groundwater but those could also include drinking water wells and geothermal systems. “At this point, however, we are not sure to what extent these practices are having on specific local lakes,” he said.

Irrigation pulls groundwater from the aquifer system, but “previous research in our region has shown little to no impact of previous levels of groundwater pumping on local aquifer resources,” he said.

Bosch agreed the local area has a much more sustainable aquifer system compared to other parts of the country such as the central plains or desert southwest. “When the replenishment of the aquifer from precipitation is less than the pumping rate, then the aquifer is drained and wells have to be drilled deeper and deeper,” he said.

He noted Kosciusko Lakes and Streams will be researching these issues during the summer months and should know more as the research progresses.

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