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Research: SDSU researchers explore automated controlled drainage systems

Wet springs, dry summers. That’s been the trend in eastern South Dakota, and farmers aren’t particularly thrilled. But what if early rains could be saved, and utilized, as relief for a later dry spell?

It may no longer be just wishful thinking. Researchers in South Dakota State University’s Department of Agricultural and Biosystems Engineering are investigating if an emerging technology — automated controlled drainage systems — could hold the answer.

“Controlled drainage has been around for a while and has proven benefits for farmers with tile drainage systems installed in their fields,” said John McMaine, an SDSU associate professor and the Griffith Chair in Agriculture and Water Resources. “Automated controlled drainage takes this technology one step further.”

What are controlled drainage systems?
Controlled drainage structures were developed to add more flexible management for tile drainage (also known as subsurface drainage) systems on cropland in the Midwest, where the systems are widely used. According to a study conducted by Iowa State University, more than 40% of Midwest farm fields utilize tile drainage systems. Although tile drainage is a long-used agricultural practice with many advantages, it is recognized there are also potential detrimental effects the systems can have on the surrounding environment.

Maryam Sahraei is a graduate research assistant in SDSU’s Department of Agricultural and Biosystems Engineering. Her research seeks to understand how farming practices affect downstream water quality.

“My research looks to improve water quality,” Sahraei said. “One of the biggest potential issues is that if outflow from tile drainage contains high levels of nitrate, there is no buffer before this water enters a river or stream.”

While tile drainage systems effectively move water away from the root zone of growing crops, if excess nitrate or soluble phosphorus is present, then they move these excess nutrients into waterways as well.  Scientists have determined that excess nutrients cause algae blooms in downstream water bodies, disrupting the ecosystem’s natural balance and creating unfavorable conditions for water recreation enthusiasts. In addition, algal blooms can cause potential human health issues, as was seen in the 2014 Toledo Water Crisis. In this case, microcystin from a harmful algal bloom contaminated the drinking water for approximately a half million people.

In the Midwest, most waterways eventually find their way to the Mississippi River and eventually, the Gulf of Mexico. There, the detrimental effects of nutrient-laden water are even more bleak.

According to the U.S. Environmental Protection Agency, nitrate from tile-drained fields in the Midwest and other sources — such as leaking septic systems — are a major contributor to hypoxia zones in the Gulf of Mexico. These zones, often referred to as “dead zones,” decreases the available oxygen for aquatic life, contributing to a reduction in the number of harvestable fish and shellfish in the Gulf. Many states (not including South Dakota) along the Mississippi River have been tasked with reducing nutrient loading in the river’s many tributaries.

“How we manage will have an effect on downstream water quality,” Sahraei said. “In this case, if we lose excess nutrients in eastern South Dakota, it may have an effect on water over 1,000 miles away.”

According to previous research, controlled drainage has resulted in a 40-50% nitrate reduction in water being discharged into nearby lakes or rivers. However, Sahraei’s research has also found that nitrate loss varies across drainage outlets, from around 2 mg/L to over 60 mg/L. | READ MORE