Vadose zone characterization pertaining to artificial groundwater recharge, Southern Avra Valley, Arizona

Abstract

The City of Tucson plans to construct a groundwater recharge and recovery facility in southern Avra Valley to infiltrate Central Arizona Project (CAP) water. The Southern Avra Valley Recharge and Recovery Project (SA VSARP) will initially recharge up to 60,000 acre-feet of CAP water per year. Characterization of the vadose zone is important in understanding the behavior of recharged water. Using grain-size distribution data from well cuttings, three lithologic units are defined and a 2-D vertical cross-section is developed in the area of predominant recharge. Soil samples representing each defined lithologic unit are laboratory tested for saturated and unsaturated flow parameters. Soil moisture retention data is fit to the van Genuchten equation to obtain unsaturated flow model parameters. A 1-D unsaturated flow model is developed using VSAFT2 to simulate infiltration of CAP water through the vadose zone.