USGS Work at the Fort Belknap Indian Reservation: 1965 Summary

By Wyoming-Montana Water Science Center

The following summary highlights the U.S. Geological Survey’s work at the Fort Belknap Indian Reservation during the 1950s and 1960s.

The investigation resulted in a 1965 publication by Alverson, which documented the study's findings and conclusions.

Open Report

Objectives of investigation

Determine the possibility of obtaining adequate supplies of groundwater of good quality for domestic and stock-watering purposes
Examine the extensive gravelly terraces and other potential aquifers around the north flank of the Little Rocky Mountains as possible sources of irrigation water

Publication

The report provides a lengthy description of the major geology of the Milk River valley including the lands of the Fort Belknap Indian Community and their capacity to bear and transport water.

Groundwater highlights

Water table (distance to groundwater) ranges in depth from a few feet below the surface in the Milk River valley alluvium to more than 100 feet deep in the Judith River formation. Water yields from groundwater wells are generally low, but adequate for domestic and stock-watering use.
Groundwater quality from wells varies from highly mineralized to excellent, with many wells in the Milk River valley having been abandoned because of alkalinity.
Artesian well conditions occur within aquifers around the Little Rocky Mountains including sandstone aquifers in the Judith River, Eagle and Kootenai formations as well as the Ellis group, and Mission Canyon Limestone. Artesian wells range from 50 to more than 300 feet in depth, have varying water quality, and can discharge up to 150 gallons per minute.