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Snake River near Murphy Trends 1914 – 2011 1992 – 2011 Liz Cresto August 7, 2012

Snake River near Murphy Trends 1914 – 2011 1992 – 2011 Liz Cresto August 7, 2012. Assignment Index the low flows Look for long term trends Remove IPCO operations Remove flow augmentation Winter flow trends Spring flow trends Look at temperature data how it correlates to flow.

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Snake River near Murphy Trends 1914 – 2011 1992 – 2011 Liz Cresto August 7, 2012

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  1. Snake River near Murphy Trends 1914 – 2011 1992 – 2011 Liz Cresto August 7, 2012

  2. Assignment • Index the low flows • Look for long term trends • Remove IPCO operations • Remove flow augmentation • Winter flow trends • Spring flow trends • Look at temperature data how it correlates to flow

  3. Trend Analysis • Two Time Periods Reviewed • 1914 - 2011 • 1992 – 2011 • Flow Period • Monthly Averages • Average Daily Minimum Flows (not instantaneous)

  4. Factors when Considering Historical Data (not limited to) • Reservoir Construction • Irrigation development (high lift pumpers) • Carryover • Flood Control • Spring Discharge • Travel times at varying flows • Incomplete data sets.

  5. Removed Idaho Power Releases from Milner • Equation: Snake River near Murphy – Snake River at Milner Combined • 3 – Day lag between Milner and Murphy regardless of the flows. • Idaho Power operations removed 1981 -2011. • This was when data was available. • 1992 – 1999 Idaho Power release data was extremely limited.

  6. January Flows

  7. January Flows

  8. July Flows

  9. July Flows

  10. Daily Minimum Flows at Murphy • Snake River near Murphy average daily flows. • No adjustments

  11. Annual minimum average daily flow at Murphy. • Between 1916 and 1975 minimum flows were never below 5600 cfs.

  12. January Average Daily Minimum Flows • February and March show similar trends in approaching the 5600 cfs minimum.

  13. 8 out of the 10 lowest years have occurred since 2002.

  14. July Daily Minimum Flows at Murphy less IPCO and Flow Augmentation • Equation: Snake River near Murphy average daily flows – IPCO – Flow Augmentation from Milner – Bell Rapids. • Was interested in trends in the minimums in July when flow augmentation and Idaho Power releases were common. • Lagged 3 days when Milner flows were < 7,000 cfs. • Lagged 2 days when Milner flows were > 7,000 cfs. • Flow Augmentation releases 1995 - 2011

  15. July flows less IPCO and Flow Augmentation • Spring Discharge can not fully explain declines in the July minimum daily average flows.

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