El Dorado Irrigation District (District) revisited the State Water Resources Control Board (State Water Board) water rights order WRO 95-9 which limited District to discharge a minimum 1.0 million gallons per day (mgd) of treated wastewater from the Deer Creek Treatment Plant (DCWWTP) when influent flows equal or exceed 2.5 mgd. The District would like to divert more of the treated wastewater to use as recycled water for landscape irrigation, thereby preserving upstream watershed diversions and potable water for other uses. RBI performed hydrologic and biological investigations of Deer Creek to determine whether reducing the minimum discharge requirement would adversely affect the riparian corridor, aquatic, or terrestrial life downstream. Specifically, RBI:
Based on the findings from this assessment, it was concluded that the DCWWTP minimum discharge requirement could be reduced to 0.5 MGD under all DCWWTP influent flow conditions without adversely affecting the aquatic, terrestrial, or riparian resources of Deer Creek.