Lower Snake River Weekly Report 4/24/17

Steelhead (hatchery and wild) movement in the lower Snake River, over Lower Granite Dam are as follows:

Totals on 4/23/17.

2017:  7009

2016:  5155

10-yr avg:  8247

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Wild Steelhead:

2017:  2875

2016: 2876

10-yr avg:  3074

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While high flows help juveniles to return to the ocean quicker, which helps their survival, it also means that more water needs to be spilled.  Currently there is more water flowing than the turbines can handle, so quite a bit of flow is being spilled.  Spill produces dissolved gases in the river which are toxic to juveniles and adults.  The US Army Corps tries to manage the Total Dissolved Gases (TDG) at each dam and keep it below 120%.  Lower Granite Dam is currently producing levels around ~109%.  Ice Harbor is ~119% and sometimes up to 122%.  Smolt mortality can be expected because of this.