Wastewater‐effluent‐dominated streams as ecosystem‐management tools in a drier climate

Water withdrawals and discharges from municipal wastewater‐treatment plants in semiarid regions result in more urban streams becoming dependent on wastewater effluent for base flows. Such wastewater‐effluent‐dominated streams support perennial‐stream ecosystems that would not otherwise exist. At the same time, ecosystems downstream of effluent discharges can improve water quality, support water re‐use, create habitat, and provide urban amenities. By identifying measures of success for biota, habitat, hydrology, geomorphology, and water quality, water managers can better design, operate, and monitor effluent‐dominated water courses under future climate conditions. This requires the development of clearly defined ecological and social objectives, as well as a better understanding of the consequences of increasing reliance on wastewater effluent to sustain the biota of effluent‐dominated streams. Successful quantification of the costs and benefits of these projects is likely to attract the attention of agencies and communities that have the power to turn the environmental perturbations associated with effluent discharges into new forms of environmental enhancement.