In the Albuquerque metropolitan area of central New Mexico, residential water-supply requirements have historically been met almost exclusively by ground-water withdrawal from the Santa Fe Group aquifer system. The rapid population growth of the metropolitan area from about 262,200 residents in 1960 (Karen D. Thompson, U.S. Census Bureau, written commun., 2002) to about 712,700 residents in 2000 (U.S. Census Bureau, 2001) has resulted in a large increase in the number of municipal-supply wells operated in the region and the total quantity of water they withdraw per year. The largest municipal supplier is the City of Albuquerque, which delivered about 35.8 billion gallons of water to approximately 450,000 people during 1997 (files of the City of Albuquerque) and operates more than 90 municipal-supply wells. Other nearby important suppliers include the City of Rio Rancho and the Town of Bernalillo. The large quantity of ground-water withdrawal in the Albuquerque metropolitan area relative to ground-water recharge has resulted in water-level declines in the Santa Fe Group aquifer system across much of the region. Analysis of the magnitude of and patterns in water-level declines can improve understanding of how the ground-water system responds to withdrawals and how the system might be managed in the future to minimize water-level declines and operating costs of water suppliers.