The Puget-Willamette Lowland regional aquifersystem analysis included the study of the regional aquifer systems underlying western Washington, western Oregon, and a small part of southwestern British Columbia, Canada, for a total study area of about 23,300 square miles. Two major aquifer systems are contained in the study area the Puget Sound aquifer system located in western Washington and southwestern British Columbia, Canada, and the Willamette Lowland aquifer system located in western Oregon and southwestern Washington. The Puget Sound aquifer system study area includes about 17,600 square miles, of which the aquifer system underlies 7,300 square miles; the Willamette Lowland aquifer system study area includes about 5,700 square miles, of which the aquifer system underlies about 3,660 square miles. The aquifer systems provide water for public supply, industrial, and agricultural use. About 984,840 acrefeet, or 1,291 cubic feet per second, was pumped from the aquifer systems during 1990.