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Colorado River Basin Water Supply & Demand Study
Technical Updates

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Updated Technical Reports

    Technical Report B
        Water Supply Assessment

    Technical Report D
        System Reliability Metrics

These reports were initially published in June 2011 under Interim Report No. 1 and have since been updated to reflect the comments received on Interim Report No. 1, technical developments, and the ongoing input of stakeholders.

Technical Report B - Water Supply Assessment and Appendices

This report describes the water supply scenarios and presents the analysis and comparison of those scenarios.

Substantive changes made to this report since its first publication as part of Interim Report No. 1 are noted below by section.

  • Historical Supply (Section 4) – Information related to watershed elevation was added and discussion related to the Pacific Decadal Oscillation and El Nino-Southern Oscillation relationships to streamflow in the Colorado River was expanded. Recent updates to the observed natural flow record for the Colorado River at Lees Ferry resulted in a reclassification of the recent drought.

  • Future Supply under Downscaled GCM Projected Scenario (Section 8) – Evaluated biases in GCM-projected precipitation and temperature and streamflow simulated by the Variable Infiltration Capacity (VIC) hydrology model. Applied a correction to account for the biases in the VIC-simulated streamflows. Additionally, the method to generate daily precipitation and temperature for input to the VIC model was modified. A more in-depth analysis was conducted to better understand 1) the relative sensitivity of results to emission scenarios driving the GCM output, and 2) extreme high annual flows projected under this scenario.

  • Supplemental Water Supply Data and Methods (Appendix B2) – Consolidates discussion previously included in separate appendices.

  • Supplemental Analysis of Future Climate Data (Appendix B3) – New appendix that describes supplemental analysis of biases in GCM-projected precipitation and temperature, and its potential influence on streamflow.

  • VIC Hydrologic Modeling Methods and Simulations (Appendix B4) – Consolidates discussion previously included in separate appendices. A discussion was added to describe the model validation results and the newly applied streamflow bias correction method.

  • Watershed-based Climate and Hydrologic Process Changes (Appendix B6) – Updated watershed-based hydrologic flux figures to be consistent with updates to modeling data sets.

Technical Report D - System Reliability Metrics

This report describes the metrics that have been identified for use in the assessment of the reliability of the system to meet the needs of the resources under future demand and supply scenarios.

Substantive changes made to this report since its first publication as part of Interim Report No. 1 are noted below by section.

  • Water Deliveries Metrics (Section 4) – Metrics have been added including those that measure the ability of the system to satisfy tribal water rights.

  • Water Quality Resources Metrics (Section 6) – Metrics have been added to include the measurement of salinity in the Upper Basin and one additional location in the Lower Basin.

  • Recreational Resources Metrics (Section 8) – Metrics have been developed and added that provide the ability of a quantitative assessment of river and whitewater boating.

  • Ecological Resources Metrics (Section 9) – Metrics have been developed and added for all attributes of interest. In particular, two new groups of metrics were added to the aquatic and riparian habitat attribute of interest, cottonwood recruitment and flow-dependent ecological systems. In addition, metrics described in Interim Report No. 1 were further refined.

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Updated: February 2012