Troubled Waters Start Here
The Missouri River is in trouble.
From the headwaters at Three Forks downstream to Townsend, the Missouri River is designated as dewatered. That just hints at the size of the problem.
Consider all the dewatered rivers flowing into the Missouri River: the Gallatin, Jefferson, Dearborn, Smith, Teton, Musselshell and Yellowstone Rivers. Consider too the dewatered rivers flowing into tributaries of the Missouri, like the Beaverhead, Big Hole, Boulder, Powde, and Tongue Rivers.
The State of Montana designated these rivers, or stretches of these rivers, as "significantly dewatered by man-caused flow depletions," mostly from irrigation, also from dams and other causes.
Smaller streams too have been dewatered, such as Hyalite Creek, South Cottonwood Creek, Bozeman (Sourdough) Creek and Bridger Creek near Bozeman; Tenmile Creek and Prickly Pear Creek that drain into the Helena Valley; and the Little Prickly Pear that joins the Missouri below Holter Dam.
These are examples, not a complete list, of dewatered streams in the state. Montana Fish, Wildlife & Parks compiled the list because water levels affect fisheries, particularly spawning and rearing habitats.
Water deficiencies harm riparian vegetation and wildlife, too.
Furthermore, erosion is a problem.
Erosion strips fertile topsoil, clogs waterways with sediments, carries nitrates and other pollutants into our streams and weakens the soil’s ability to retain moisture and sequester carbon.
Our activities affect sediment production, transport and storage. According to a new study in the journal Geology, the magnitude of erosion caused by our land uses "vastly exceeds erosion rates driven by the largest climate transitions that naturally occur on Earth."
Logging and plowing are the major causes of the human-caused increase in erosion, according to that study.
The loss of vegetative cover caused by logging — whether clear-cutting, thinning or even prescribed burns — exposes soil to the drying effects of sunlight and wind, and this contributes to erosion, increases fire danger and warms water exposed to sunlight.
Soil as sediment pollutes the waterways of Montana.
In agriculture, the loss of fertile soil, fueled mostly by plowing but also by overapplication of chemicals, prompts farmers to convert historically agricultural lands to development. The proposed Black gravel pit south of Gallatin Gateway is just one example.
Modifying streamflows with dams and dredging also increases soil losses.
Channelization of the Missouri River for transportation and flood control dates back into the nineteenth century. Dams for irrigation and power production further alter the natural stream environment and negatively impact the river and riparian habitats.
Yes, the dams also provide water for municipal water systems and recreation.
But the dams directly and negatively affect species now listed under the Endangered Species Act. The Pallid sturgeon and the piping plover are two listed populations negatively affected by the dams on the Missouri River.
But the population of interior least tern has recovered sufficiently to be delisted.
Adequately funded, conservation works!
More cost efficient is prevention. Stop logging national forests lands that protect our watersheds. Require the flow of sufficient water in our streams. Limit polluting runoff. Protect our water!
Anne Millbrooke, of Bozeman, is a historian.
Main sources:
- Kemp, David B., Peter M. Sadler, and Veerle Vanacker. "The human impact on North American erosion, sediment transfer, and storage in a geologic context." Nature Communications, v. 11 (2020), p. 6012 , https://doi.org/10.1038/s41467-020-19744-3.
- Missouri River Recovery Program, https://www.nwo.usace.army.mil/MRRP/.
- Montana Fish, Wildlife & Parks, "Dewatered Streams - Montana," September 15, 2015, http://gis.fwp.mt.gov/arcgis101/rest/directories/arcgisoutput/webResources/metadata/refrnc/dewateredStreams.htm/.
- Penprase, Shanti B., Andrew D. Wickert, Phillip H. Larson, Jimmy J. Wood, Isaac J. Larsen, and Tammy M. Rittenour. "Plow versus Ice Age: Erosion rate variability from glacial−interglacial climate change is an order of magnitude lower than agricultural erosion in the Upper Mississippi River Valley, USA." Geology (2025; online April 3, 2025), https://doi.org/10.1130/G52585.1.