Recharge from ephemeral streams : case study in Arizona

Abstract

Infiltration losses and recharge to groundwater at a section of Rillito Creek at Tucson, Arizona, were analyzed using data from two flood events in December 1959 and January 1960. Assuming infiltration losses are a function of stream discharge and using empirical equations developed by the U.S. Geological Survey, infiltration loss at the section was estimated to be 2.24 x 10⁶ m³/km. Estimates of recharge were obtained by two indirect methods: (1) A deconvolution integral in which the impulse response function is derived from the one-dimensional diffusion equation and the output functions are based on well hydrographs. The recharge values ranged between 1.41 x 10⁶ m³/km and 2.07 x 10⁶ m³/km depending on values of aquifer diffusivity obtained from the literature (al = 6,000 m²/day and (α₂ = 3,000 m²/day). (2) A groundwater mound method gave a recharge value ranging between 0.86 x 10⁶ m³/km and 1.29 x 10⁶ m³/km depending on the effective porosity values (0.10, 0.15). Over all, an average of 70 percent of transmission losses reached and recharged the groundwater reservoir. However, this figure should not be generalized because recharge conditions are favorable in the Rillito Creek area.