Unlike a flat prairie, where ground surface conditions are somewhat uniform, the Oak Creek Watershed is located in an area of high relief along the canyon-cut margin of the Colorado Plateau.
Geologic Features That Influence Water Flow
Water flow within a watershed, whether it is in the form of a surface stream or as groundwater, is dependent upon a wide range of geologic features within a drainage basin. No two watersheds are alike. Different rock and soil conditions control the rate at which water moves across the surface and through the subsurface rocks and soil horizons into which the watershed has been carved.
Areas containing impermeable crystalline basement rocks, like the rocks beneath the Prescott area, provide little chance for water to be retained or recharged, and stream runoff is usually quite rapid. On the other hand, porous and poorly consolidated volcanic ash, like that found on parts of the San Francisco volcanic field on the Colorado Plateau, absorb rain and snowmelt like a sponge, and release it downward and outward as relatively steady groundwater recharge without the presence of free-flowing surface streams. Between those two extremes is the thick Paleozoic Era sandstone and carbonate rocks like those found beneath the elevated rocks of the Colorado Plateau, and exposed along the colorful Mogollon Rim cliffs that form the backdrop for the city of Sedona. Those rocks have variable amounts of open pore space within them (porosity), which allows for significant, long-term water storage. Ultimately groundwater will flow through fractures and pore spaces in the rock (permeability) toward the lower elevations. Open spaces, rock fractures, fault zones, and open solution cavities in soluble rocks like limestone can short-circuit water flow and allow local groundwater to flow more rapidly through and beneath a watershed.
Unlike a flat prairie, where ground surface conditions are somewhat uniform, the Oak Creek Watershed is located in an area of high relief along the canyon-cut margin of the Colorado Plateau. The northern surface limit of the watershed lies close to the Interstate 17 entrance to the Flagstaff airport at an elevation of 7,015 feet. It drops to the south through Oak Creek Canyon and Sedona before entering the Verde Valley, where it ultimately joins the Verde River at an elevation of 3,185 feet. The eastern edge of the watershed is the summit of Mormon Mountain at an elevation of 8,450 feet, meaning that the total elevation range within the watershed is 5,265 feet. The highest elevations play a major role in capturing precipitation that is caused by the orographic atmospheric uplift that occurs on the high-standing Colorado Plateau surface. Most of the ultimate recharge and water storage of the Oak Creek Watershed takes place high on the plateau and volcanic peaks to the north of Sedona and the Verde Valley.