BUTTE COUNTY, S.D. — Hidden among the dusty roads and cow pastures of northwestern South Dakota lies a new threat to ranchers – rising salinity in the water supply worsening the effects of an already stressful drought.
Researchers at South Dakota Mines have been sampling stock dams, which are man-made, earthen impoundments for collecting and holding water, since 2018.
Their results are concerning – a dramatic jump in the percentage of stock dams with salt concentrations well over the safe limit for livestock.
Only 3% of sampled stock dams had salinity measured over 2,500 microsiemens in 2019, compared to 31% in 2021.
“In 2019, we had no impoundment over 4,000 microsiemens [per centimeter],” says Ph. D. graduate student Patrick Kozak. “That is all consumable by livestock and wildlife with minor irritations but no major problems. Starting in 2021, when we got out this year, we started running into impoundments that were over 10- to 15,000 microsiemens.”
Kozak says around 15,000 microsiemens and above becomes lethal for cattle over time.
A microsiemen is a measurement of electrical conductivity. Measuring the conductivity tells the researchers how salty the water is.
But why is the salt there in the first place?
Around 65 million years ago, much of the Midwest was at the bottom of the ocean.
Over time, due to regional uplift, it dried out – similar to the Great Salt Lake in Utah or the Salton Sea in California.
What got left behind was a concentration of salt, which is covered over and becomes the new bedrock.
Gradually, as that bedrock is exposed, it becomes soil – allowing those salts and evaporite deposits to flow out.
Stock dams are in drainage areas – catching water flowing from rain and snow melt – allowing these salts to accumulate over time. The concentration then increases as the water evaporates.
With virtually no naturally existing surface water year-round in this area, stock dams are a critical source of water for cattle – meaning the situation could have a potentially devastating economic impact in northwestern and western South Dakota.
In northwestern South Dakota alone, there are 77,000 similar dams – 24% of which have gone dry since September 2020.
The problem, however, isn’t unique to South Dakota.
In recent weeks, abnormally high temperatures – including extreme, record-breaking heat across parts of the western U.S. – deteriorated drought conditions and further depleted soil moisture.
“In the western United States, where you’re in a water-scarce area, you run into situations where you have these types of soils…and you will have salinity…and if you have stock dams or surface water, you can get these collections and this increase – and that happens in locations across the western United States,” Kozak says.
Their study hopes to provide crucial information to stakeholders to help them make educated decisions on how to manage the situation when it occurs – before the next drought.
“Some of the producers will have multiple [stock dams] on their own land, and I would hope that we could help them know what would be an efficient way to potentially save the ones that are most beneficial for their needs and not repair or utilize resources they could be using for something else in fixing something that’s not going to be utilizable by the cattle,” Dr. Kunza says.
The team from Mines includes Dr. Lisa Kunza, associate professor of chemistry, biology, and health sciences; Dr. Tejo Bheemasetti, a civil engineer specializing in geotechnical engineering; Ph. D. graduate student Patrick Kozak; and undergraduate students Darin Archibald (civil/environmental engineering) and Lee Wuertz (biology).
“We’re here as a university to support the students and help them grow, understand, and participate in these collaborative efforts with the whole goal that we can aid in giving solutions or helping people come up with the solutions that would be beneficial to them,” Dr. Kunza says.
The interdisciplinary group of scientists getting the opportunity to do hands-on research, build bonds with the community, and make a difference.
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