BUILDING STRONG ® Dworshak SOR # Transition to Refill Stephen Hall P.E., Reservoir Regulation Walla Walla District USACE

BUILDING STRONG ® SOR # Requested full power-house discharge from Dworshak from May 12 th 2009 to May 17 th 2009 as needed to achieve 100 kcfs flow at Lower Granite Dam. The COE response was a compromise between requested SOR flows and minimum discharge for a higher probability of refill.

BUILDING STRONG ® Time Line of TMT Meetings April 8 th TMT Meeting – April 1 st forecast = 99% normal (2.66 MAF), estimated discharge during refill = 5 to 6 kcfs. Discharging maximum amount (110% TDG) for flood control based on Grand Coulee Flood control shift and increasing water supply forecast April 22 nd TMT Meeting – Initiated discussion on transition to refill with two options. Salmon Managers requested maximum discharge through the end of April. COE accepted the Salmon Manager request. April 29 th TMT Meeting – Based on a decline in National Weather Service Ensamble Streamflow Prediction forecasted volume (2.4 MAF) COE expressed concern regarding refill. The Flood Control Refill Curve (FCRC) was intersected on April 18 th. FCRC provides 95% chance of refill by 30 June. Salmon Managers request maximum discharge through April 30 th then a reduction to full powerhouse (10.6 kcfs) through May 6 th. COE accepted the Salmon Manager request.

BUILDING STRONG ® Time Line of TMT Meetings cont. May 5th RCC Communication with Salmon Managers – COE reduced discharge from 10.6 kcfs to 7.5 kcfs per agreement with Salmon Managers with a further plan to make further reductions on May 6 th. May 6 th TMT Meeting – COE expressed increasing concern with refill flexibility (little remaining volume above minimum discharge). Based on ESP and other data, with Salmon Manager agreement, COE reduced to minimum discharge on May 6 th. May 12 15:23 SOR sent to Reservoir Control Center (RCC) by Salmon Managers May 13 th TMT Meeting – COE present ESP refill information, explained the significant departure from FCRC curve, and historical analysis of similar years/conditions to express significant concern regarding refill based on the SOR. COE decided to implement a compromise operation resulting in a gradual reduction in discharge over the next 5 days.

BUILDING STRONG ® The next few slides are the information presented at TMT including: Water Supply Forecast ESP Traces with refill volumes

BUILDING STRONG ® Forecast Uncertainty = +/- 400 KAF ESP Forecast change = KAF

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® COE Decision was based on: Fish Needs – described in SOR Risk to Refill –ESP Trace information –Flood Control Refill Curve computations –Historical Analysis – 4 of 12 similar years would not refill –Water supply forecast uncertainty

BUILDING STRONG ® Lessons from SOR & JTS Memo Balance between refill and spring augmentation is difficult, especially with high uncertainty in future events. Raises valid question “If we could go back in time, would we do anything different based on what we did know or could have known?” We cannot use hind sight (observed runoff) to question real-time decisions. We need to communicate forecast AND the uncertainty associated with the forecast

BUILDING STRONG ® Questions