Climate Change: Multiple Teleconnection Index Based Prediction of Natural Flow
Project ID: 709
Principal Investigator: David Raff
Research Topic: Water Supply Forecasting
Priority Area Assignments: 2010 (Climate Change and Variability Research), 2011 (Climate Change and Variability Research)
Funded Fiscal Years: 2010
* Can teleconnection based forecast models be developed to predict monthly and annual precipitation and streamflow volumes at up to a 12-month lead-time with much better performance than previous models?
Effective management of water resources in the Western United States involves a complex and challenging series of problems that increasingly requires decision-support systems to balance user demands with water supply. A key component of these support systems are accurate and robust forecasts of water availability with sufficient lead-time to allow managers to adjust the scheduling and volume of water delivery. Significant effort in forecasting of water availability over the previous four to five decades has yielded predictive models that provide managers reasonably accurate streamflow forecasts at seasonal (< 3 months) timescales. Longer range streamflow forecasting models have been shown to benefit from the use of teleconnection indices through the research by Reclamation, the National Weather Service (NWS), Natural Resources Conservation Service (NRCS), and others. Despite this research, there is a desire to reduce the uncertainty associated with the teleconnection based forecasts.
Initial investigations show that it is possible to provide western water managers more accurate and usable long lead-time (9+ months) streamflow forecast models by leveraging existing streamflow records and improved understanding of ocean-atmosphere teleconnections in a multiple linear regression approach.
Need and Benefit
Reclamation currently has used and continues to explore the uses of teleconnections for intra-seasonal water supply forecasting (e.g., beginning January 1 forecasting for January 1 to July 31 water supplies) as well as having explored the use of teleconnections for forecasts beginning in the previous fall to estimate water year type (e.g., dry, wet). These forecasts, however, do not provide Reclamation and other managers the lead-time necessary to sufficiently optimize management decisions at the start of the water year.
A decision support system that would include accurate estimates of the streamflow and volume of water input to storage systems managed by Reclamation (in conjunction with other State and Federal Agencies), at lead-times of approximately nine months and using methods accepted by managers and other and stakeholders would dramatically improve decision-making capabilities. The proposed research seeks to develop and demonstrate a model that uses teleconnection indexes with historical streamflow and precipitation data that will provide Reclamation with accurate estimates of streamflow into storage facilities and the uncertainty associated with those estimates. The methods and techniques used in the proposed modeling framework will be universally applicable across Reclamation's area of operation with capabilities at levels not currently available to Reclamation.
The National Oceanic and Atmospheric Administration's Climate Prediction Center defines teleconnection patterns as "recurring, persistent, large-scale [patterns] of pressure and circulation anomalies that span vast geographical areas" that represent "preferred modes of low-frequency (or long time scale) variability" . These important patterns, which can persist for weeks to years, are also associated with periodic behavior and thus represent an "important part of both the interannual and interdecadal variability of the atmospheric circulation." Atmospheric teleconnections are frequently observed as statistical correlations between anomalies in geographically distant and temporally lagged processes, such as sea surface temperature and streamflow. From the perspective of terrestrial hydrology, teleconnections reflect the atmospheric propagation and modulation of anomalies in the exchange of moisture and heat between the ocean and atmosphere, which ultimately influence terrestrial precipitation and temperature regimes at significant geographical distances. The persistent and temporally lagged nature of these teleconnections and the statistical correlations they impart, implies that current knowledge of some climatological feature (e.g., sea surface temperature anomalies) can aid in the prediction of future hydrologic behavior (e.g., streamflow).
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