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Marana High Plains Effluent Recharge

Study status:  Active 

The Marana High Plains Effluent Recharge Project (MHPERP) was constructed in 2002 by the Pima County Regional Flood Control District in cooperation with the Bureau of Reclamation, Arizona Water Protection Fund, Cortaro-Marana Irrigation District and the Town of Marana.  The project is located along the Santa Cruz River, in Section 33 of Township 11 South, Range 11 East in the Avra Valley sub-basin of the Tucson Active Management Area (TAMA).  The facility is one component of a regional water resource, flood control, environmental protection and enhancement, and recreation program (the Northwest TAMA Replenishment Program) that is sponsored by more than a dozen local, state and federal entities.  Facility operations have been ongoing since February 2003.

MHPERP is a multi-purpose facility designed to recharge treated effluent from the Santa Cruz River into the local groundwater aquifer, while simultaneously investigating wildlife habitat associated with recharge facilities.  The overall objectives for the project include the following:

  • To recharge up to 600 acre-feet of water per year while maintaining significant infiltration rates in basins having side slopes vegetated with emergent plants and riparian trees and in basins fully vegetated with native grasses tolerant of periodic flooding;
  • To provide trails, descriptive literature, and interpretive signs describing the project operation.  Trails at the project site may eventually be linked to a longer river trail network that is scheduled to be built along the Santa Cruz River;
  • To revegetate the area outside the recharge basins with plants that will improve wildlife habitat value and , once established, could survive if the recharge activities cease;
  • To characterize wildlife, aquatic macroinvertebrates, and vegetative resources associated with an important effluent-dominated stream; and
  • To identify and monitor the biological effects that have resulted from establishing other habitat types that are now rare to the area (e.g., marsh, grassland), and increase the aerial extent of riparian vegetation.

The MHPERP facility is comprised of one settling basin (equalization basin) and four spreading basins (recharge cells), totaling 4.5 acres of recharge area.  Water is delivered to the project via the “oxbow” channel, a remnant channel of the Santa Cruz River from when the riverbed was less incised and the channel meandered back and forth across the floodplain.  A berm consisting of streambed materials is used to divert some of the effluent flowing down the Santa Cruz River into the oxbow channel.  Sources of the effluent are the Roger Road and Ina Road Wastewater Treatment Plants, which are located approximately 15 miles and 10 miles upstream of the diversion structure respectively.  The effluent flows along the oxbow channel for about one mile before reaching MHPERP.