THE COLORADO RIVER: INTEGRATING HYDROLOGIC AND MANAGEMENT PERSPECTIVES

Transcription

1 THE COLORADO RIVER: INTEGRATING HYDROLOGIC AND MANAGEMENT PERSPECTIVES Drought Past and Future ANU, Canberra November Rosalind Bark and Bonnie Colby, Kathy Jacobs, Dave Meko, Peter Troch, Connie Woodhouse, Kiyomi Morino, Lana Jones, Matthew Switanek

2 June 2002 Lake Powell John Dohrenwend, USGS March 2003

3 TREE-RING RECONSTRUCTIONS Lees Ferry, , low 5.6MAF in 1977 and high 25.3MAF in average ~ 15 MAF drought, average 9.3 MAF, low 6.2 MAF in 2002 Tree-ring record using remnant wood, AD Mid-1100s: 13 consecutive yrs low flows embedded in dry 62 yr period and no high flows [Meko et al., GRL 2007]. SRP, CAP, etc.

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5 CLIMATE CHANGE Temperature +5 F to +7 F Precipitation Lower Basin declines of ~ 5-10% by 2099 Upper Basin less certain f) transition zone Runoff Declines modeled Reduction in snowpack In models? Appendix U Renewal guidelines post 2026

6 SYSTEM MANAGEMENT MATTERS System management pre-2008 New guidelines reduce the probability of shortage The ICS mechanism further reduces the probability of shortage

7 SHORTAGE MAGNITUDES Circles represent years from 2010, the first year of shortage for both PA and NA, to 2026 PA consistently shows a lower probability and magnitude of shortage than NA

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9 TRIBUTARY STREAMFLOWS Tributary flows can be significant 2005 Lower Basin tributary flows above Lake Mead were 253% of average flows Historically given little attention in river modeling Separating tributary input and providing a probabilistic estimate of flows could improve prediction accuracy Better management: operational tier, shortage declarations, and reservoir balancing Moreover opportunities to enhance forecast skill in Lower Basin

10 BSCP IMPROVING ON NINO3 Basin-specific climate prediction relaxes the spatial constraint inherent in NINO3 Explore the full dimensionality of SST data and a sub-basin s seasonal temp, precip and discharge [Switanek et al, 2008]

11 BASIN-SPECIFIC FORECASTS Nash-Sutcliffe efficiencies: the darker the shading, the more skillful the hindcasts are in comparison to the hydroclimatic mean More skillful at predicting precip, temp and discharge in the Little Colorado River watershed at different time lags than NINO3 and other climate indices [Switanek, Troch and Castro, 2008]

12 CONDITIONED-FORECASTS AND SHORTAGE TRIGGERS 333 kaf 417 kaf 500 kaf

13 ICS storage rights System efficiency ICS Drop 2 Reservoir conserve average 69 KAFY SNWA $115 M, 400 KAF ICS credits accumulate max 300 KAF credits in Mead CAWCD and MWDSC $27.8 M each, 100 KAF credits Tributary conservation ICS SNWA Muddy and Virgin Rivers Extraordinary conservation ICS Irrigation forbearance to preserve system storage Reclamation funded 2 pilot system conservation projects: CA 2006/07 (PVID water) and AZ 2007/08 New program for 2008/09 Imported ICS SNWA Coyote Spring Valley GW, up to 15 KAFY

14 CLIMATE SCIENCE AND ADAPTIVE CAPACITY Time-scales: short-term 24 MSM and long-term CRSS Tree-ring data + BSCP + GRACE initial TWS conditions + decadal prediction = reduced uncertainty about the probability, timing and magnitude of droughts Improved system management Operational tier for management Shortage declaration Mid-year review: operational tier for Lake Powell management More cost-effective adaptation Buy & Dry, water transfers i.e. IID-SDCWA, 45 yrs + 30 yrs, up to 200 kafy DYO: contract terms, pricing, when to exercise, 3rd party impacts Water banking: e.g. AWBA Indian and M&I firming obligations Intentionally created surplus (ICS) activities What if perfect forecasts on frequency, magnitude and duration of drought?

15 MANAGEMENT TIMING AUGUST JANUARY APRIL MAY SEPTEMBER DECEMBER Coordinated Operations Shortage Declarations Projections of Lakes Mead and Powell January 1 elevations Mid-year review of Lake Powell EOWY elevations EXERCISE DRY YEAR OPTION Mid-year review of the effect of ICS releases on Lake Mead EOCY elevations

16 FUTURE WORK Third 2-yr phase Engagement with Upper Basin researchers BSCP in other tributary watersheds Tributary flow tree-ring reconstructions GRACE TWS Integration of enhanced climate science and the design of costeffective adaptation: DYO, banking, ICS Climate change downscaled GCMs and tree-rings

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