ABSTRACT

Water shortages are common in the Musselshell River Basin. Water shortages could be decreased by increasing water-storage capacity. Increased storage would allow better control of the tuning of surface water flows, thereby improving the usability of available water. Many efforts have been made to identify and investigate possible new water-storage locations. Several abandoned underground coal mines in the Bull Mountains south of Roundup have been suggested as possible off-stream reservoir sites.

Water-level data indicate the mines are, for the most part, hydrologically isolated from one another. Water samples from the mines contain water dominated by sodium and sulfate ions, with dissolved solid concentrations ranging from about 1,300 to 5,200 milligrams per liter.

Due to water quality concerns, the larger mines (Republic No. 2, Roundup No. 3 east and west, and Prescott), are not considered viable reservoirs at the present time. However, the smaller mines that are located nearest the Musselshell River (Republic No. 1, Jeffrey, and Republic No. 4) contain water of such quality and quantity as to be usable in a limited fashion to supplement river flow or for direct irrigation use. Potential impacts to nearby private wells would have to be strongly considered and mitigated as necessary.