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Ongoing CRB R2O Research
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2008 – 2016 Research
Publication Abstracts

Characterizing Monsoon Precipitation Patterns and Predictability in Arizona

Institution(s): National Center for Atmospheric Research (NCAR)

Years: 2020 – present

PI(s): Towler, Prein

Project scientist(s): NA

Summary: The Lower Colorado River Basin is greatly impacted by the North American Monsoon. However, monsoon precipitation is difficult to predict, and to date there have been no robust forecasting products that provide actionable information. This study explores the potential for seasonal predictions of monsoon precipitation to improve the forecasts of intervening flows into Lake Mead and the projections of downstream water demands used in Reclamation’s short-term and mid-term operations planning. Recent studies, including the Reclamation Science and Technology Program’s Detecting, Interpreting, and Modeling Hydrologic Extremes to Support Flexible Water Management and Planning, have characterized precipitation through weather types (WTs), or predominant synoptic-scale weather patterns that are associated with precipitation over the US. WTs have been developed that are associated with monsoon precipitation anomalies over New Mexico, and have been shown to be useful covariates in predictive risk models geared to water management. This project extends and expands upon work done by the PIs in New Mexico into the domain of Arizona. Historical reanalysis data will be used to develop WTs for sub-regions in Arizona, and potential covariates will be identified and used to develop predictive statistical models.

Expected Completion: Spring 2022

Product(s):

Report documenting procedures and findings; predictive statistical models

Exploration of Robust Planning Techniques in the Colorado River Basin

Institution(s): University of Colorado Boulder, Center for Advanced Decision Support for Water and Environmental Systems (CADSWES)

Years: 2019 – present

PI(s): Kasprzyk, Zagona

Project scientist(s): Bonham

Summary: A major challenge in framing and conducting long-term planning studies in the Colorado River Basin is the extreme uncertainty in projecting future conditions decades into the future. The field of Decision Making under Deep Uncertainty (DMDU) has arisen to develop methods that can systematically account for this extreme (or “deep”) uncertainty. One such method is called Robust Decision Making (RDM), which Reclamation first explored in the 2012 Colorado River Basin Water Supply and Demand Study. A recently-completed study aimed at advancing Reclamation’s understanding of DMDU techniques identified Many Objective Robust Decision Making (MORDM) as a promising approach and piloted the application of MORDM’s initial phases. This new study will apply innovative approaches and technologies to demonstrate additional steps of MORDM in the context of Reclamation’s Colorado River Basin planning needs.

Expected Completion: Fall 2023

Product(s):

PhD dissertation, journal articles, etc. (TBD)

Exploring the Feasibility and Benefits of Incorporating Additional Data Sources into the Colorado Basin River Forecast Center’s Consumptive Use Modeling

Institution(s): RTI International (RTI), Colorado Basin River Forecast Center (CBRFC)

Years: 2019 – present

PI(s): Burkhalter (RTI), Micheletty (RTI)

Project scientist(s): NA

Summary: Reclamation uses streamflow forecasts produced by the Colorado Basin River Forecast Center (CBRFC) in its operations models to project short- and mid-term Colorado River Basin system conditions. The modeling performed by CBRFC to generate the forecasts accounts for many processes such as snow accumulation, snow melt, and consumptive use that impact how much streamflow will reach Reclamation reservoirs. Consumptive use encompasses “measured diversions” and “unmeasured depletions”. Measured diversions are incorporated where water taken from streams is accounted for at sufficiently regular intervals for CBRFC to incorporate the measurements directly into their modeling. Unmeasured depletions, which are a large source of forecast uncertainty, refer to irrigation water that is consumed by entities that do not regularly report detailed water use to the CBRFC. However, Upper Basin states maintain diversion records and perform consumptive use modeling at spatial and temporal resolutions that could improve the consumptive use estimates generated by the CBRFC. This project will choose a pilot watershed to demonstrate how such data from the State of Colorado could be incorporated and determine whether the benefits warrant a wider-scale adoption of revised modeling practices by the CBRFC.

Expected Completion: Fall 2020

Product(s):

Report documenting procedures and findings

Using ICAR and En-GARD to Explore the Implications of Using Different Downscaling Methods to Generate CMIP5-Derived Streamflow Projections

Institution(s): National Center for Atmospheric Research (NCAR)

Years: 2019 – present

PI(s): Gutmann

Project scientist(s): Currier

Summary: Translating temperature and precipitation projections from global climate models (GCMs) into Colorado River Basin streamflow requires multiple intermediate processing and modeling steps. For each of the steps, methodological choices must be made that embed assumptions and affect the final streamflow ensemble. One step in this chain is the downscaling procedure that translates climate variables from the global scale to a smaller spatial scale that is useful for regional studies. Recent studies, including Reclamation’s project Exploring Climate and Hydrology Projections from the Coupled Model Intercomparison Project Phase 5 (CMIP5) Archive, have shown that the choice of downscaling method has a significant impact on results. The current study applies two newly-developed downscaling methods, the Intermediate Complexity Atmospheric Research (ICAR) model and Ensemble Generalized Analog Regression Downscaling (En-GARD), to CMIP5 projections in order to better understand the implications of using different techniques to produce GCM-informed Colorado River Basin streamflow ensembles.

Expected Completion: Spring 2022

Product(s):

Report documenting procedures and findings; journal article(s); streamflow ensembles

Generating and Evaluating Temperature-Conditioned Colorado River Basin Streamflow Ensembles

Institution(s): National Center for Atmospheric Research (NCAR); University of Colorado Boulder (CU)

Years: 2019 – present

PI(s): Towler (NCAR), Rajagopalan (CU)

Project scientist(s): Woodson (CU)

Summary: Colorado River Basin temperatures have warmed in recent decades, climate models agree that the warming trend will continue, and multiple studies have shown that higher temperatures can reduce the amount of streamflow that results from a given amount of precipitation. As such, accounting for this warming trend when generating mid-term (2- to 5-year-out) hydrologic forecasts could produce more skillful streamflow ensembles to support Reclamation’s mid-term operations projections. This study explores the potential for creating temperature-conditioned forecasts by performing an in-depth analysis of the relationships between temperature, precipitation, and streamflow at subbasin scales and combining it with temperature predictions from climate models. The Community Earth System Model (CESM) climate model has been shown to skillfully predict temperatures up to 10 years into the future when the model run uses observations as initial conditions. Skillful temperature predictions can in turn be used to inform sampling or weighting of historical observations when generating projections. The goal of the resulting ensemble is to capture the warming trend rather than treating observations from the cooler historical years in the early 20th century as equally likely to 21st century conditions. Once generated, the ensemble will be tested against current mid-term forecasting methods using the Colorado River Streamflow Forecast Testbed.

Expected Completion: Winter 2020

Product(s):

Report documenting procedures and findings; journal articles; streamflow ensembles

Exploring Climate and Hydrology Projections from the CMIP5 Archive

Institution(s): Jacobs (formerly CH2M) and Scripps Institute of Oceanography (SIO)

Years: 2016 – present

PI(s): Munevar (Jacobs), Pierce (SIO), Cayan (SIO)

Project scientist(s): Das (Jacobs), Cawthorne (Jacobs), Goodrich (SIO)

Summary: The 2016 SECURE Water Act Report’s west-wide assessment of climate projections from phase 5 of the Coupled Model Intercomparison Project (CMIP5) found that a newer generation of climate models suggested an overall wetter future than phase 3 (CMIP3) modeling. The Upper and Lower Colorado Regions of Reclamation commissioned a study to further explore this conclusion and its implications for the Colorado River Basin (CRB). The effort examines the differences between CMIP3 and CMIP5 in temperature and precipitation projections for the CRB at both the native climate model resolution as well as after downscaling, and uses skill metrics to contextualize individual climate models and ensembles. The study also looks at the effects of different bias correction and downscaling techniques at multiple stages of data processing to go from global climate projections to regional streamflow. Additionally, temperature-perturbed hydrologic modeling is performed to understand the potential impacts that warming alone may have on CRB streamflow. The streamflow ensembles resulting from multiple threads of inquiry will be available for use with the CRSS model to assess their impacts on CRB resources.

Expected Completion: Fall 2020

Product(s):

CMIP5 streamflow ensembles

Report describing methods, analysis, and findings

Identifying Future Climatological Ensembles and their Impacts on Colorado River Reservoir Operations

Institution(s): University of Nevada, Las Vegas

Years: 2014 – present

PI(s): Santos, Piechota, Ahmad

Project scientist(s): NA

Summary: The existence of multiple hydrologic projections for the Colorado River Basin (CRB) illustrates an uncertain and highly variable future. This study analyzes the downscaled Coupled Model Intercomparison Project 5 (CMIP5) climate and hydrology projections, along with historical and observed sea surface temperature data, using singular variable decomposition to identify regions of significant correlation in the Pacific Ocean and in the CRB. An inter-model comparison reveals variable regions of significance and correlation magnitudes when all CMIP5 models are analyzed throughout the historical period ending in the year 1999. This goal of this study is to develop a sub-ensemble of climate projections and to determine the differences between sub-ensemble and full-ensemble projections. The results of the study can potentially assist CRB resource managers in determining the applicability of climate and hydrology projections and reduce the uncertainty of future conditions.

Expected Completion: Spring 2021

Product(s):

PhD dissertation

CMIP5 ensembles