Seasonal water storage and replenishment of a fractured granitic aquifer using ASR wells

Abstract

The Town of Payson is situated in a mountainous region of central Arizona. The Town is totally reliant on groundwater for the needs of over 15,000 people. Groundwater is accessed from a climate-dependent fractured granite aquifer from 42 wells with an annual demand of 3.1 million cubic meters (m3). As a result of a law, the Arizona Water Settlement Act of 2004, Payson obtained a water right to use 3.7 million m3 of water stored in the nearby Cragin Reservoir. This additional water supply will be used to offset future groundwater pumping as the Town continues to grow. A pipeline to convey the surface water from the reservoir, a new treatment plant, and aquifer storage and recovery (ASR) wells will be added to Payson’s water system. These wells will be used for seasonal and long-term aquifer storage and recovery of the stored surface water and will contribute to a considerable improved management of Payson’s water resources. For the ASR operation, a number of existing production wells will be selected and retrofitted for injection. The treated surface water will be delivered to the ASR wells from the Town’s potable water distribution system for aquifer storage. Base-Load and On-Call ASR wells and their operation will be automated via a SCADA system. Groundwater in the fractured granite aquifer is typified as calcium-bicarbonate and so is the water stored behind the Cragin dam. The use of ASR wells as a managed aquifer recharge (MAR) component is a successful solution for providing potable water to a small community in a cost effective manner.