Climatic Teleconnections for Forecasting Seasonal Water Supply in Reclamation Regions
* Can we identify couplings, or teleconnections, between indices of upwind climate patterns and decision variables that control water supply and flood potential forecasting in the Mid-Pacific (MP) and Pacific Northwest (PN) regions and their Water 2025 hot spots (e.g., Central Valley, Upper Columbia)?
For example, teleconnections involve links between the El Nino/Southern Oscillation (ENSO) and PN-region hydrology. Our research addresses a Water2025 principle: enhancing water usage efficiency to allow existing supplies to be used more effectively.
Results should show that teleconnections offer new information in support of water supply and flood potential forecasts in these regions. Upper Colorado (UC) and Lower Colorado (LC) regions could benefit from an extension of this research framework.
Need and Benefit
The outputs of this research would be improved forecast models of Reclamation decision variables (e.g., seasonal precipitation and runoff) using teleconnections. The outputs address Water 2025 needs of liberating more water and reducing operational costs. Recent research suggests that more water could be allocated given information from teleconnection models, which combine climatologies of geographically separated areas.
Teleconnections in this research involve a signal (e.g., summer index of ENSO) leading a response (e.g., winter index of PN region runoff). There is abundant evidence of "signal-leading-response" teleconnections involving Pacific-Basin climatic phenomena and Western United States hydrologic responses that occur later. The lag between signal and response allows for additional management leverage, with information being provided by the teleconnection lead-signal.
In this research, teleconnections are screened as they involve:
* Seasonal to annual hydrologic responses linked to regional Reclamation decisions
* Indices of conditions in upwind climatic regions observed earlier
Indices are developed using pattern recognition techniques before teleconnection screening. Forecast models can be developed for teleconnection schemes that pass screening. Numerous frameworks for these tasks have been demonstrated, but there has yet to be significant application of teleconnection models in Reclamation.
Application of teleconnections in Reclamation has been hindered by obstacles that are addressed through this research:
* Mechanism-based screening for teleconnections has produced a limited set of schemes that apply well in the PN but not in other Reclamation regions (e.g. summer ENSO indices teleconnect strongly to winter PN hydrology, but not to winter MP hydrology).
* Mechanism-based screening focuses on climate dynamics and not the intended beneficiary of the teleconnection information, leading to teleconnections that involve response variables that are not related to Reclamation's operating decisions.
This research eliminates those obstacles by:
* Screening teleconnections in a decision-framed context
* Allowing the candidate teleconnections to involve pattern-based indices rather than mechanism-based indices
Consequently, the research output is designed to be readily used by Reclamation.
Recent research has demonstrated the feasibility of this framework through an application involving California reservoir operations and teleconnections involving North Pacific climatic patterns (Brekke 2003). The decisions of CVP autumn storage-carryover targeting and delivery-year water allocation were used to frame that research. One teleconnection involving an index of North Pacific atmospheric circulation and water-year inflow variations at Folsom Lake and Lake Shasta offered average-annual inflow forecast improvements that amounted to 36 percent and 15 percent of storage capacity, respectively, with minimal reliability impacts.
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