Black Rock’s diversion of 3500 cubic feet per second (CFS) of water from the pool behind Priest Rapids dam would deplete instream flows in the Hanford Reach.  Hanford Reach is the only (non-tidal) free-flowing section of the Columbia River in Washington and is home to a wild, naturally spawning population of endangered Chinook salmon.  President Clinton designated Hanford Reach as a national monument in 2000.  (See the U.S. Fish and Wildlife Service website: Hanford Reach National Monument.) 

It is not yet known how much water is needed to restore and maintain healthy instream flows in the Hanford Reach.  In 2004, various parties, including dam operators, tribes and fishery agencies entered into the “Vernita Bar Agreement” to regulate flows, particularly discharges from upstream dams, to protect salmon spawning and rearing in the Hanford Reach.  In March 2006, the Washington legislature authorized a study of Hanford Reach instream flows, to be published in July 2007.  (ESSB 6581)

In addition, the 2000 presidential proclamation establishing the Hanford Reach National Monument explicitly reserved “sufficient water to fulfill the purposes” of the monument, including fisheries protection.  These federal reserved water rights “could be a significant constraint on new diversions upstream of the Hanford Reach.” (National Academy of Sciences, 2004. For more on this study, click here.)

The science of instream (river) flows instructs that it is the dynamic nature of rivers that keeps them healthy.  Thus, it is important to protect a range of flows from high to low, to ensure ecological integrity.  High or “bank-full” flows provide channel maintenance functions, such as creating river bars and riffle-pool sequences that are critical to salmon-spawning.  (Poff, N.L., et al., “Natural Flow Regime, “BioScience, December 1997)  High flows may also serve an important pollution-dilution function in the Hanford Reach.

By skimming the top off of high flows in the Columbia River, Black Rock’s year-round, round-the-clock diversion of water from above Hanford Reach could have far-reaching, negative impacts on instream flows in this critical reach of the River.

Next:   Tying Up the Region’s Water