Configuration of the water table, 1970 and 1992, and water-table change between 1970 and 1992 in the Boise area, Idaho

A comparison of 1970 and 1992 water-table configuration maps for the Boise area shows that the water table has declined about 10 feet in about 90 percent of the area. Declines exceeded 10 feet in about 50 percent of the area, 20 feet in about 10 percent of the area, and 30 feet in about 5 percent of the area. The largest declines were south of the Boise River between the Ridenbaugh and New York Canals. These declines may be caused in part by the decrease in discharge through irrigation canals during the drought of 1987-92. Small water-level rises were mapped in about 10 percent of the area--in the southeastern part of the Boise area and along the Boise River. This comparative study is the first step in reassessing shallow ground-water conditions in the Boise area in more than 20 years. The 1992 water table was mapped using water-level measurements made in about 170 wells.