Revised On: Feb. 20, 2024 - 4:25 p.m.

The site is located in the southern portion of the Upper Hassayampa Basin in the Central Highlands Hydrologic Province. The Upper Hassayampa Basin encompasses approximately 740 square miles and includes relatively small alluvial sub basins. The Basin is bounded on the north by the Weaver Mountains, on the northwest by the Date Creek Mountains, on the south by the Vulture Mountains, and on the east by the Bradshaw Mountains. Elevations in the basin range from 2,000 feet above mean sea level (amsl) in the valley to more than 7,000 feet amsl at the mountain ridges.

The Hassayampa River watershed drains an area of approximately 1,470 square miles in central Arizona. The headwaters originate in the Bradshaw Mountains, and flows southward through the Upper Hassayampa Basin to the Gila River near Phoenix. Most of the runoff infiltrates into the subsurface before reaching the Hassayampa River. Perennial flow occurs at several locations within the Hassayampa River watershed but not within the site. 

Approximately seven miles south of Wickenburg, the Hassayampa River enters the broad Hassayampa Plain where the river crosses a major fault (the Narrows) which is down-thrown to the south and virtually all of the runoff from the Hassayampa River infiltrates into the bed of the river. The main water-bearing units of the Upper Hassayampa Basin are the basin fill deposits, which consist of gravel, sand, silt, and clay. Along the Hassayampa River, the granitic intrusive or volcanic rock is overlain by a thin accumulation of alluvial deposits.

Depth to groundwater within the Upper Hassayampa Basin ranges from a few feet along the Hassayampa River and other major drainages, to more than 800 feet in the middle portion of the basin. The regional direction of groundwater flow is generally south approximately parallel to the axis of the Hassayampa River. Depth to groundwater within the vicinity of the site ranges from a few feet to about 50 feet.