Quality of water and chemistry of bottom sediment in the Rillito Creek basin, Tucson, Arizona, 1986-92

Abstract

Controlled artificial recharge of surface runoff is being considered as a water-management technique to address the problem of ground-water overdraft in Rillito Creek basin, Arizona. Surface-water, ground-water, and bottom-sediment data were collected from August 25, 1986, through March 13,1992, to provide information that would be needed to plan and manage artificial recharge operations. Suspended-sediment concentrations in streams generally increased with increases in streamflow and were highest during the summer. The surface water is a calcium and bicarbonate type, and the ground water is a calcium, sodium, and bicarbonate type. Total recoverable trace elements in surface water that exceeded the State of Arizona maximum contaminant levels for drinking water were barium, cadmium, chromium, lead, and mercury. None of the dissolved trace elements in surface water exceeded the drinking-water standards. The median values for dissolved activities of gross beta as strontium-90/yttrium-90 and dissolved gross beta as cesium-137 were lower in ground water than in surface water. Comparisons of trace-element concentrations in bottom sediment with those reported for soils of the western conterminous United States generally indicate similar concentrations for most of the trace elements, with the exceptions of scandium and tin. The maximum concentrations of total nitrite plus nitrate as nitrogen in three ground-water samples exceeded U.S. Environmental Protection Agency maximum contaminant levels for drinking water. Seven organochlorine pesticides were detected in surface-water samples and ten were detected in bottom-sediment samples. Three priority pollutants were detected in surface water, two were detected in ground water, and eleven were detected in bottom sediment. Low concentrations of oil and grease were detected in 7 of 25 surface-water samples.