McMullen Valley is in western Arizona about 80 miles northwest of Phoenix (fig. 1). The valley, which is about 48 miles long and 15 miles wide, is bordered on the south by the Harquahala and Little Harquahala Mountains, on the north by the Harcuvar Mountains, and on the west by the Granite Wash Mountains. The major stream in the area is Centennial Wash, an ephemeral tributary of the Gila River; the wash leaves McMullen Valley through Harrisburg Valley at the southwest edge of the area. The groundwater reservoir is the only dependable source of water in McMullen Valley (fig. 1). and it is important that this supply be managed properly in order to obtain the maximum benefit. Therefore, a comprehensive knowledge of all the factors that affect the ground-water reservoir is necessary.
Ground-water conditions in McMullen valley, Maricopa, Yuma and Yavapai Counties, Arizona