A team of research faculty and students at South Dakota Mines has been tracking salinity content in 70 stock dams across 12 watersheds in two northwestern South Dakota counties over the past two years  Their study, funded by the Bureau of Land Management, shows an alarming trend of increasing salinity in the stock dam water during the ongoing drought of 2021. In some cases, the salt concentrations of the water is high enough to cause adverse health effects for livestock and wildlife. In a handful of stock dams, the salinity is high enough to be lethal.

“We hope the information will help the people who matter the most, and that’s the livestock producers in this scenario,” said Lisa Kunza, Ph.D., associate professor of chemistry, biology and health sciences at South Dakota Mines. “Our producers need decent water to give to their cattle, and this trend could exacerbate the water shortages they are already facing. We hope our students can foster this collaborative effort to help local ranchers and land managers understand this problem, know their options and find solutions.” 

Sampling done by the team of student researchers in Butte and Harding counties showed low salinity levels during the wetter years of 2018-19. But in times of drought, such as the first half of 2021, many stock dams begin to dry up, and this evaporation caused increased salinity. Researchers can estimate the amount of salt in water by testing its electrical conductivity. Water with higher salt content is more conductive.

Electrical conductivity measurements of less than 5,000 microsiemens per centimeter (µS/cm) are relatively safe water levels for livestock consumption. “This year, we have seen a 19 percent increase in stock dams with conductivity over 5,000 µS/cm [none in 2019] and 6 percent of those stock dams over 11,000 µS/cm. We see salinity increase as the drought continues and as many of these impoundments dry up,” said Patrick Kozak, a Ph.D. graduate student at South Dakota Mines who is conducting the research.  

Stock dams are common for livestock producers across the American West to make sure their animals have access to water. In northwestern South Dakota alone, there are 77,000 stock dams. These small earthen dams catch water during rain events and snowmelt in the spring, allowing for water availability through the rest of the year. Many of these dams were constructed between the 1930s and 1990s, and some are abandoned or not being utilized by the cattle due to water quality. During droughts, the water can dry and up and disappear leaving the producers without water.

In the Upper Great Plains, stock dams are often located in soils formed from ancient seafloor. These soils can contain elevated amounts of remaining salts from the evaporated seawater. These salts are dissolved and transported downstream to collect in stock dams, riparian areas and other low-lying regions. Over time, the salts accumulate and become more and more concentrated. “People are starting to notice white spots and salt crusting around stock dams and along streams and drainages where it hasn’t been before, and we are doing this study to get a better understanding of what is happening,” said Kozak.

The team is looking to expand its research to a broader area in the Great Plains region. They hope to provide information to help local ranchers and government land managers to make the best decisions to support and protect livestock and wildlife.

—Excerpts from the South Dakota Mines News