Recycled water for augmenting urban streams in mediterranean-climate regions: a potential approach for riparian ecosystem enhancement

AbstractThe scarcity of water in mediterranean-climate regions makes flow management in the rehabilitation of urban streams problematic. To explore potential applications of using recycled water for stream enhancement, we examine streams in the San Francisco Bay Area of California, USA, to characterize: (a) historic flow regimes at the regional scale, (b) potential unintended ecological effects and (c) specific issues related to recycled water. We analysed historic flow regimes in five basins, performed a streamflow augmentation experiment and monitored benthic macroinvertebrates above and below a recycled-water discharge. Streamflow augmentation with recycled water can provide improved aesthetics and aquatic habitat, but there are caveats to consider. Implications of inputs of recycled water in streams, whether direct or indirect, require detailed analysis of trade-offs. Augmentation is unlikely to harm the ecology of urban streams that are now just barely flowing perennially with pools of stagnant, cont...