According to the Montana Natural Resource Information System, groundwater provides 94 percent of Montana's rural domestic water supply and 39 percent of the public water supply. The MBMG has over 80 active projects related to surface water and ground water in Montana and focuses on issues critical to water use in agricultural, domestic, fisheries, municipal, and industrial applications.
The demand for abundant clean ground water grows with the approval of each new subdivision. The Bureau is participating in several projects related to the increasing demand for ground water in new developments and the cumulative impact of septic systems in existing developments. Many areas of Montana have seen a change from agricultural land use to subdivisions and shopping centers. This often means that the irrigated land that was providing recharge to ground water is converted to residential areas with runoff control that actually reduces recharge and adds high demands on ground-water discharge. Such change often has dramatic effects on ground-water flow and quality that are just recently being realized. Of course, the demand for ground water also increases for every year of the drought. Surface-water shortages for agricultural purposes or for drought-stricken communities are being replaced by wells, increasing reliance on the ground-water supply.
Ground-water flow and quality respond to many influences, both man-made and natural. Several long-term monitoring programs are underway—some for over 30 years now—that provide data for decision makers to address natural and human influences on ground water and geothermal resources, evaluate reclamation in hard-rock and coal mines, and mitigate the effects of the sustained drought. Some of these programs include monitoring the geothermal area near Yellowstone National Park, the Berkeley Pit and underground workings in Butte, coal strip mines and coalbed-methane fields in southeastern Montana, Big Muddy Creek in the northeast, and post-reclamation monitoring for several hard-rock mines in western Montana.