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February 2007 – Inflow and Outflow, Flycatchers and Chubs: Reservoir Operations and the Endangered Species Act on the Salt and Verde Rivers

  • John Keane
    Senior Environmental Scientist, SRP

  • Ruth Valencia
    Senior Environmental Scientist, SRP

  • Charles Paradzick
    Senior Ecologist, SRP

Water supply reservoirs are essential for large scale human occupation of most of the western US. These reservoirs also by necessity must inundate riparian habitat and change the downstream flow and sediment regimes. SRP operates six reservoirs on the Salt and Verde Rivers to maximize renewable water supplies to the Phoenix area. Reservoir management has become much more complicated and expensive in recent years as SRP and the US Fish and Wildlife Service have worked to recognize water demand imperatives while addressing biological impacts to species under the Endangered Species Act. Past and present issues will be reviewed. Experience on the Salt and Verde so far indicate the following points:

  • Reservoirs can have both positive and negative impacts on a species.
  • It is often difficult to separate (scientifically or politically) the impacts of reservoirs from other factors impacting the species, and cooperating agencies often have conflicting wildlife or fisheries management goals.
  • Lack of data and uncertainty about these complex biological systems are major factors.
  • The public demanding and depending upon these water supplies often has little understanding of either reservoir system impacts or the cost and complications of ESA compliance.

    Announcement (53K pdf)
    Presentation (4.2 MB pdf)

    Download the audio file (7.5M DSS file)
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