Unnatural Data - Summer 2021

Wild and Scenic Big Sioux

Created in 1968, the National Wild and Scenic Rivers System preserves stretches of free-flowing rivers possessing outstanding natural, cultural and recreational values. Designation to the system safeguards the character of these rivers, while recognizing the potential for appropriate development. 12,000 miles of rivers are now designated as part of the system. If that seems like  a lot, consider this: In the United States there are over 250,000 rivers, totaling about 3,500,000 miles of channel. South Dakota has about 9,500 miles of rivers, and 93 miles -the Missouri River National Recreation River, in the southeast part of the state- have been designated under the national rivers system. An inventory of potential additions to the system is called the Nationwide Rivers Inventory (NRI). This list includes more than 3,200 free-flowing river segments from around the country that retain significant natural or cultural values. A 23-mile segment of the Big Sioux River that stretches from the Dells of the Big Sioux to the I-90 bridge just north of Sioux Falls, is part of this inventory.

Hypoxia Update

Pollution from the Big Sioux River and its watershed is carried into the Missouri River and by the Missouri into the Mississippi, before ultimately settling into the Gulf of Mexico. The large quantity of pollution that accumulates from runoff in the Mississippi River basin has created a so-called dead zone, or hypoxia zone, an area of low to no oxygen that can kill fish and other marine life. Scientists predict this summer’s dead zone will be approximately 4,880 square miles, a bit smaller than the state of Connecticut. This area is smaller than the five-year-average of 5,400 square miles, though more than double the long-term goal (target is 1,900 square miles) set by the Gulf of Mexico Hypoxia Task Force. According to one hypoxia researcher, “Each year, the forecasts are reported to be bigger or smaller than some long-term average, when in fact the long-term average is not acceptable. Large reductions are called for in the federal-state action plans that have been in place for almost 20 years. Clearly, something different needs to be done in the watershed to actually reduce the nutrient loads and reduce the size of the dead zone.”

Water Problems in Des Moines  

In 2020, Des Moines, Iowa was unable to use the Des Moines River for 110 days to supply citizens with water because large amounts of toxic algae polluted the river. That issue, coupled with high levels of nitrates in the river, has forced Des Moines’ water utility to invest many millions of dollars to treat water and find additional sources of potable water. “If you look at the total load of nutrients, if you look at the cyanobacteria blooms in Saylorville Reservoir and the microcystin concentrations at our intake in the last two years, they're shocking,” said Ted Corrigan, CEO of Des Moines water utility. According to scientists, blue-green algae fed by fertilizer and manure runoff are the main source of the toxins in Iowa rivers. These foul-smelling toxins can cause skin rashes, intestinal problems, and in severe cases, liver damage. The toxins can quickly kill dogs and other animals that drink the contaminated water.

Parched Places

South Dakota and the Big Sioux basin aren’t the only places suffering from drought and remarkably hot weather that is attributed to climate change. Nearly 89 percent of nine western states are in some form of drought. A recent South Dakota report indicated that 94 percent of the state is affected by drought.  Ground water levels in the Big Sioux Basin and Skunk Creek Basin north of Sioux Falls are at their lowest levels for this time of year in 17 years of record-keeping. During June 2021, typically a high flow month, Big Sioux discharge into the Missouri River ranged between 950 and 1200 Cubic Feet per Second (CFS). In 2018, the overall annual daily average for discharge into the Missouri River was 5703 CFS.