Water Resources Portfolio

Metropolitan Domestic Water Improvement District (District) has long understood the importance of effectively and efficiently managing its water resources. The District’s Long Range Water Resources Plan for each of the District’s six active service areas gives a snapshot of the District’s projected water demands compared to available renewable supplies (Central Arizona Project (CAP) water, effluent, and remediated water) and groundwater availability and outlines the District’s strategy to manage water resources for the next 50 years..

Groundwater – Groundwater is the current sole source of water for District customers. Metro Main has 26 active wells that pump water from the aquifer underneath the Cañada del Oro Wash and Rillito River. Water from the wells is placed in storage tanks or reservoirs. The water is then pressurized to move underground through pipes to reach customers. The Metro Hub service area has 5 wells that pump water beneath the ground along Sabino Canyon Creek and Tanque Verde Wash. The Metro Southwest service area has 5 wells that pump groundwater that originates from mountain front recharge and minor streamflow along the Black Wash. 

Other Water Sources – Based on the Arizona Groundwater Management Code and the assured water supply designations for Metro Main and Metro Southwest – Diablo Village, the District has sought to use a renewable water source to reduce its dependency upon groundwater in these service areas. Other water sources, including Central Arizona Project (CAP) water and recycled water, are considered renewable water sources. These other water sources can help stabilize the aquifer and reduce the use of groundwater.

Central Arizona Project (CAP) Water – The District has an annual allocation of 13,460 acre-feet (approximately 4.4 billion gallons) of CAP water. The District has primarily looked at replenishing CAP water by pursuing projects in which the water is recharged by spreading basins (direct recharge projects) and in which CAP water is used in lieu of groundwater by farms (groundwater savings projects). In fact, the District helped initiate the Northwest Replenishment Program, an effort to recharge CAP water in northwest metropolitan Tucson. The first project under that Program, the Avra Valley Recharge Project (AVRP), was the first recharge project using spreading basins in Pima County and was done in partnership with CAP and BKW Farms.
 
From 1996 to 2021, the District has stored 200,690 acre-feet of water at AVRP through its CAP water recharge efforts. While the District uses credits on an annual basis to meet a portion of customer demand, the District has a balance of 31,000 acre-feet of CAP credits in its “account” as of January 1, 2017.
 
Over the years, the District has pursued how to bring CAP water to the various service areas. The District has partnered with the Town of Marana and the Town of Oro Valley to design and construct the Northwest Recharge, Recovery, and Delivery System (NWRRDS) that will recover a portion of the respective water provider’s CAP allocation stored in Avra Valley and provide a means to convey this water to the Marana Water, Oro Valley Water, and Metro Main service areas. This will reduce the amount of groundwater that is pumped to meet customer demands, reduce the ongoing decline in groundwater levels in the aquifer, and will ensure water resource availability for current and future customers. 

Recycled Water – The District has an entitlement to approximately 4,000 acre-feet of effluent generated from the Metro Main and Metro Hub service areas based on an Intergovernmental Agreement (IGA) with the City of Tucson.  The District has worked with other regional water providers to establish a joint managed effluent recharge project in the Santa Cruz River that allows the District to obtain 95% credit for the effluent recharged, which could range from 450 to 950 credits annually after the cuts associated with the managed in-channel recharge facility are taken into account.
 
Another use for the District’s effluent allocation is to utilize reclaimed water through a wheeling agreement with Tucson Water to replace groundwater irrigation for large turf facilities in the District. This would require utilizing a reclaimed system and construction of a delivery system to move the reclaimed water where it may be needed. The District constructed a reclamation line that can deliver approximately 250 acre-feet of reclaimed water to the Omni Tucson National’s new nine golf holes and replace groundwater irrigation to that facility starting by December of 2023. The use of reclaimed water will help to reduce the decline of the groundwater table.

Water Usage – Metro Main customers used 6,993 acre-feet (2.3 billion gallons) of water in 2021. While all the water was pumped from wells, most of it was calculated as recovered CAP water based on the credits the District accrued through its recharge efforts. Metro Hub customers used 811 acre-feet (264 million gallons) of water in 2021. Metro Southwest customers used 525 acre-feet (171 million gallons) of water in 2021. Wheeling agreements with Tucson Water at Diablo Village and Lazy B enable the District to meet a portion of customer demand with renewable water resources.

Avra Valley Recharge Project (AVRP) and Recharge CAP Allocation – In 2010, the District Board approved the use of recharge as the initial treatment method for its CAP water allocation. Recharge was seen as a less expensive alternative with lower capital but still as effective as a treatment plant. The District’s CAP allocation would be recharged in Avra Valley, which the District had entered an agreement in 2009 with CAP to acquire. The acquisition was completed in January 2011. 

Northwest Recharge, Recovery & Delivery System (NWRRDS) – NWRRDS will use wells to recover CAP water that has been recharged at AVRP and then delivers it through a 13-mile transmission line to be blended with groundwater at the Herb Johnson Reservoir. This approach is similar to Tucson Water’s usage of their Central and Southern Avra Valley recharge facilities. The Project is estimated to cost about $36 million, though the District’s cost will be substantially less due to approved intergovernmental agreements with the Towns of Oro Valley and Marana who will participate as proportional funding Partners in this program. The District will operate NWRRDS. Marana and Oro Valley will have capacity rights, and pay for capital and operational costs based on respective proportional capacities.
 
In April 2014, the Board approved a 10-year timeline to accomplish the three major components of the Project – Land Acquisition, Design, and Construction. The timeline ensures that the Project can be accomplished efficiently but also with the least financial impact on customers.