Climate Change/Variability and Reservoir Operations 2007 CWEMF Stu Townsley Chief, Water Management
Mount Action Curve Funding Public Awareness Time
Corps Authority Section 7 of the 1944 Flood Control Act 33 CFR 208.11 Authoring legislation for water resource projects If Federal dollars for flood damage reduction, then Corps has responsibility But Corps does not own water, just reservoir space
Corps Flood Control 35 reservoirs (Corps e.g., Pine Flat, Isabella; Section 7 e.g., Shasta, Folsom, Oroville) Total storage ~ average annual runoff Flood space is seasonal Basic operation: reserve space, store when flows above targets, release soonest possible Operation governed by Flood Control Diagram For most part diagrams unchanged from authorization 50+ years
Historic data needs Streamflow for reservoir system Snow accumulation and melt patterns Irrigation and spreading demands Peak flow/volume duration curves Does history give enough information to establish reliable trends for future flood operations?
Pine Flat Flood Control Diagram Typical snowmelt influenced rule curve
1000000 900000 800000 Rainflood Space 700000 600000 500000 400000 300000 Flood Space Conditional Flood Space =f(snowpack, demands) Rain Flood Flood Control 200000 100000 0 Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Developed from historical record (look-back) Conditional space dependent on 120B, irrigation demands Operation based on observed data (rainfall, snow pillows)
Pine Flat Operations WY 2006 WY 2005 WY 2004 WY 1997
Potential Flood Implications Literature suggests Warmer regime, about the same annual precipitation Smaller snowpack,, earlier melt, flow shift Greater storm variability/intensity Implications? Need more rainflood space? Allow earlier fill?
Climate adjusted diagram? 1000000 900000 800000 700000 600000 500000 400000 300000 200000 100000 Rainflood Space Flood Space Conditional Space 0 1-Aug 1-Sep 1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul Jury still out takes studies to resolve!
Updating diagrams in the real world Current Corps policy revisit every decade Project enhancement, e.g., Folsom, Terminus To date, only minor revisions to release rate of change limits, low flow enhancements Likely requires full EIS, maybe Congressional reauthorization big deal, big cost
What next? Climate models downscaled - better spatial and temporal resolution Establish temperature/weather to runoff relationship Forecast accuracy metrics Confidence limits Risk-based
Collaborative process with partners Climate modelers establish site-specific specific trends Operations modelers dynamic tools DWR financially responsible Water users help build political case Environmental interests ditto Goal: dynamic, transparent process for rule curve updates with a system perspective
Systems approach Watershed Engineered Economic Environmental Governmental Supported by: 12 Actions for Change 2007 Army Civil Works Legislative Program
The critical piece Discrete Kernel - How to get ALL the popcorn to pop? Supply/economic modeling to establish a strong case for integrating climate change/variability into tools for better flood damage reduction
Questions?