Hydrologic assessment and computer model application in the Upper Santa Cruz River Basin, Santa Cruz County, Arizona

Abstract

A two-phase study of the Upper Santa Cruz River Basin consisting of a hydrologic assessment and the application of a computer model to the area is presented. Groundwater occurs in Older and Younger Alluvium units, is held under unconfined conditions, and is of good quality. The Finite-Difference Three-Dimensional Groundwater Flow Model (MODFLOW) is applied to the study area in order to simulate the hydrologic system. A water budget and conceptual model is developed to aid in model input and calibration. A steady-state analysis for the system is performed for 1965 in order to calibrate model parameters and produce initial conditions for the transient analysis. A transient analysis is performed to verify model response over the period 1965-1980 in which stresses to the system are changing. Model-produced trends and water levels are consistent with observed data, indicating the model's utility for predictive analysis of the system.