The Effect of Development on Groundwater in the Parker Strip

Abstract

The 14.6 miles of the Colorado River bounded by Parker Dam and Headgate Rock Dam has been referred to as the Parker Strip. This river reach has become a high use recreation area during the past decade with 4,000 permanent residents and as many as 120,000 water enthusiasts on long weekends. The riparian area of the river is heavily clustered with mobile homes, marinas and public beaches. The means of sewage disposal is exclusively via septic tanks. Recent surveys by the Environmental Protection Agency, Arizona State Department of Public Health and the University of Arizona have localized surface water bacteria levels that may indicate a developing groundwater problem. The geohydrology of the area indicates that the septic tanks are located in Post -Pliocene Colorado River deposits. The deposits are quite thin and relatively narrow. Since the deposits are locally derived sands and gravels, the horizontal hydraulic conductivities are such that a relatively short flow time to the river may result. Intensive evaluation of the degradation of the water quality in these deposits is needed to determine if the ground water supply was jeopardized by septic tank systems.