Agriculture Affects River Flow Rates

Changes in agriculture affect river flow rates in both rainy and dry times, according to two University of Iowa researchers.

While it may seem obvious that river flow rates in the Midwest can change depending on how heavy or light rainfall is, what's not so clear is how changes in land use can impact these river flows.

"We wanted to know what the relative impacts of precipitation and agricultural practices played in shaping the discharge record that we see today," lead author Gabriele Villarini said in a statement. "Is it an either/or answer or a much more nuanced one?"

"By understanding our past we are better positioned in making meaningful statements about our future," he said.

If researchers can better understand river flows and what factors influence them, they can possibly help mitigate flooding in drought in areas of the United States like Iowa, which experienced many spring and summer floods, including this year, as well as drought like the one in 2012.

Co-author Aaron Strong added that drought results in large economic damage and even loss of life.

In order to determine agriculture's role in the situation, researchers focused on Iowa's 9,000-square-meter Raccoon River in the town of Van Meter. They looked at water discharge level records from 1927-2012, during which time the number of acres used for corn and soybean production greatly increased, roughly doubling over the course of the 20th century.

As predicted, they found that variability in rainfall is responsible for most of the changes in water discharge volumes.

However, the water discharge rates also varied with changes in agricultural practices, as defined by soybean and corn harvested acreage in the Raccoon River watershed. In times of flood, more agriculture exacerbated water flows, whereas less agriculture did the same during droughts.

The authors added that although flood conditions may be exacerbated by increases in agricultural production, this concern "must all be balanced by the private concerns of increased revenue from agricultural production through increased cultivation."

The findings were published in the journal Agriculture, Ecosystems & Environment.