GROUND-WATER / SURFACE-WATER INVESTIGATIONS IN MONTANA

ABSTRACT: Ground-water/surface-water interactions are complex in the irrigated intermountain basins of Montana. In these basins, excess water from flood irrigation percolates to alluvial aquifers and may eventually contribute to streamflow. Water consumption in some of these basins is increasing as new irrigation wells pump ground water from the shallow aquifers, and as inefficient, flood-irrigation systems are converted to sprinkler irrigation, with subsequent increases in irrigated acreages. The Montana Department of Natural Resources and Conservation has conducted hydrology and return-flow studies in the Beaverhead, North Fork Blackfoot, and Smith river basins in west and west-central Montana. The intent of the studies is to characterize the interactions of ground water and surface water in these basins by intensively monitoring surface-water flows and ground-water levels. The results from these studies are being provided to water managers and policy makers so that they may use the information when making water management decisions. KEY TERMS: water management, return flow, irrigation well, alluvial aquifers