Groundwater Levels and Water Quality
The project is designed to recover a blend of Colorado River water and native groundwater. Each year the amount of river water recharged by the City exceeds the amount recovered. As a result water levels elsewhere in Avra Valley are not being negatively affected by the recovery portion of the project.
The quality of the water recovered from this project and delivered to Tucson Water customers will change over time. Initially, it was very similar to the native groundwater. Tucson’s groundwater is hard, meaning it has an alkaline pH. Colorado River water comes mainly from snowmelt, which has a slightly acidic pH. As recharge of Colorado River water continues, the recovered water will become more like river water in terms of pH and mineral content. The City is examining several treatment methods which could be used to modify the recovered water, if necessary, to meet the water quality and water cost goals determined by Tucson Water customers.
It is important to note that the quality of groundwater varies in different locations within the Tucson area and its environs. For instance, total dissolved solids (TDS) levels, which represent mineral content, are lower than Colorado River water in some areas of the aquifer and higher in others.