Recharge and Recovery

Recharge and Recovery are processes by which water is able to infiltrate land surface and recharge the underlying aquifer. Down gradient water production wells capture this water and it is brought back into the drinking water supply. Recharge and recovery can help to minimize lowering aquifer levels and improve water use efficiency. De facto reuse through recharge and recovery has been used since the 1900’s in Flagstaff. De facto reuse occurs within Flagstaff’s urban watershed downstream of the Rio de Flag Water Reclamation Plant where recharge and subsequent recovery take place along the Rio de Flag channel.

After the community uses water it is sent to a treatment facility (Wild Cat Hill or Rio de Flag Water Reclamation Plants). A to A+ quality reclaim water is produced and is allowed to infiltrate the ground surface in locations such as the Rio de Flag channel, first passing through an initial unsaturated zone called the Vadose Zone where it is naturally filtered and eventually down to the aquifer.

recharge and recovery_02

Source: Modified from AWWA Potable Reuse 101

Flagstaff's Urban Water Cycle

  1. Reclaimed and potable water is Six Steps of Recharge and Recovery of the Coconino Aquiferused outdoors. 
  2. Reclaimed water is discharged to the Rio de Flag when demand for reclaimed water is low (non-irrigation seasons). 
  3. Water travels through the vadose zone where it is naturally filtered.
  4. Water reaches the aquifer and co-mingles with existing water in storage.
  5. Water from the aquifer is pumped from production wells located down-gradient of the flow direction in the aquifer.
  6. The Flagstaff USGS estimates that 4% of all water that falls on the ground in and around Flagstaff recharges the aquifer, including snow, rain, stormwater, and any reclaimed and potable water used outdoors.

The Problem

There are currently not enough users of reclaimed water during the non-irrigation months or during monsoon season, commonly August to May, to use all the reclaimed water generated in the city. Water Services is looking at options to make sure excess reclaimed water benefits the Flagstaff community.

Seepage Studies

The City completed a seepage study in 2020 to locate stream beds in Flagstaff where we can re-direct water from the Rio de Flag at Wildcat Hill and Rio de Flag Water Reclamation Plants to recharge the C-aquifer up-gradient of water production wells. The study focused on four sites: Switzer Canyon Wash near Jay Lively Ice Arena, Sinclair and Bow and Arrow washes at Lonetree Road, and the Rio de Flag at the current Rio de Flag WRP (see map). The study conducted by Natural Channel Design is available here.

seepage study mapkey for seepage study map

Groundwater Recharge with Recharge Wells

If the recharge rate through stream beds to the C-Aquifer is too slow the City will investigate using groundwater recharge well technologies to reduce the time it takes to recharge the C-Aquifer. The water still travels to the aquifer through the vadose zone, which is a natural environmental buffer that further cleans reclaimed water before it mixes with the natural raw water in the aquifer.

Aquifer Recharge Graphic (Reclaimed)

Source: Modified from AWWA Potable Reuse 101

Groundwater Recharge with Advanced Treated Water

Advanced treatment of recharge water is an option if the Flagstaff community funds the technology to further clean Class A+ water. At this point Advanced treatment has not been recommended by steering groups associated with Arizona’s adoption of regulations for Direct Potable Reuse since the vadose zone is so effective at further cleaning the Class A+ water. Additionally, the City’s Panel on Compounds of Emerging Concern’s final recommendation is that there is no undue health risk by the City’s continued use of reclaimed water.

Injection wells for website

Source: Modified from AWWA Potable Reuse 101

Relative Costs for Recharge and Recovery

Doller SignBlank SpacerIncrementally discontinue flows* from the Wildcat Hill Wastewater Reclamation Plant  (WRP) and increase flows from the Rio de Flag WRP into the Rio de Flag Wash

Doller SignDoller SignBlank SpacerDiscontinue flows from the Wildcat Hill WRP and recharge groundwater through the injection wells near the Rio de Flag WRP

Doller SignDoller SignDoller SignBlank SpacerFund advanced treatment of Class A+ reclaimed water and increase flows from the Rio def Flag WRP into the Rio de Flag wash

Doller SignDoller SignDoller SignDoller SignBlank SpacerFund advanced treatment of Class A+ reclaimed water and recharge groundwater through injection wells near the Rio de Flag WRP

* Minimum environmental flows would be maintained at Picture Canyon, I-40 wetlands, and Frances Short Pond

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