Wetlands and Reduced Recycle Water Discharge

Recycled water purveyors who are finding more customer demand for their product face a potential new environmental challenge. Wetlands created by the discharge of excess recycled water can be adversely impacted as the water diminishes.

“Often times, the discharge provides a water source for wetlands that otherwise would not have been present, especially in the summer months when typically creeks are dry,” said Michael Sweesy, Dudek’s practice manager for natural habitat management and restoration. “Biological resources build up that are likely supporting endangered species habitat.”

Water agencies looking at reducing recycled discharge flows to wetlands could have permitting issues with federal and state agencies and potentially with regional water boards because of a change of discharge, Sweesy said.

Yucaipa Valley Water District Project

Yucaipa Valley Water District faced this issue when it sought to reduce 3 million gallons a day (MGD) discharge of tertiary-treated wastewater into a nearby creek. The District wanted to use the water to support a non-potable water supply blending the effluent with groundwater and untreated state project water.

Dudek conducted for the District hydrology and water use studies to identify the amount of discharge necessary to maintain existing riparian conditions in the creek, which as a result of the discharge supported additional wetlands. Biological surveys included vegetation mapping, wetlands delineation, wildlife surveys and rare plant surveys.

The studies determined that discharge could be cut 53% to 1.6 mgd and maintain existing creek conditions using the blend of groundwater, untreated state project water and wastewater.

Dudek developed a Habitat Management Plan (HMP) to establish monitoring protocols, success criteria, and contingency plans for the vegetation to be supported by the 1.6 mgd discharge. Based on HMP, the U.S. Fish & Wildlife Service agreed there would be no effect on least Bell’s vireo and a section 7 consultation was avoided.

Preparing for Reduced Discharge

Agencies looking at reducing flows to wetlands will likely have permitting issues with federal and state agencies and potentially with regional water boards because of a change of water discharge, Sweesy said. He said recycled water agencies facing this issue should consider the following to successfully manage potential permitting issues:

  • Prepare a vegetation monitoring plan that will establish how deeply rooted the native species are and how much water – or little water – they will need to survive.
  • Know the depth of groundwater table to see whether native species roots can access that water source.
  • Develop a water budget to define how much water needs to be left in drainage to maintain habitat while still allowing for reduced discharge so the recycled water can go to customers.