Integrated Water Availability Assessments: Upper Colorado River Basin

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Integrated Water Availability Assessments examine water supply, use, and availability. Snow from the Upper Colorado River Basin contributes 92% of the natural streamflow to the entire Colorado River Basin. The UCOL IWAAs will improve our understanding of the water budget, status and trends in water quality and ecological conditions, and ecosystem response to changes in climate and human water use.

Integrated Water Availability Assessments (IWAAs) examine the supply, use, and availability of water.  These assessments evaluate water quantity and quality in both surface and groundwater, as related to human and ecosystem needs and as affected by human and natural influences. When fully implemented, IWAAs will conduct regional water-availability assessments in each of ten medium-sized watersheds selected as Integrated Water Science (IWS) basins. These regional intensive assessments in reference basins form the mechanism to develop and evolve nationally integrated assessment and prediction capacity and applications. 

Map showing the IWAAs and NGWOS study areas in the Upper Colorado River Basin

The Upper Colorado River Basin (UCOL) Integrated Water Availability Assessment (IWAA) is examining the supply, use, and availability of water in the UCOL upstream of Lee's Ferry, Arizona. The UCOL Next Generation Water Observing System (NGWOS) is installing new monitoring equipment and enhancing existing streamgages in the Colorado River Headwaters and Gunnison River subbasins.

The Upper Colorado River Basin (UCOL) was selected as an IWS basin in 2019. IWAAs studies will focus on the area of the UCOL watershed upstream of Lee’s Ferry, Arizona. A smaller sub-basin that includes the Colorado headwaters and Gunnison River Basins is being intensively monitored by the Next Generation Water Observing System (NGWOS).

Most of the precipitation in the UCOL falls as snow, which is a critical source of streamflow throughout the basin and contributes 92% of the natural streamflow to the entire Colorado River Basin (Lukas and Payton, 2020). Snow that falls and accumulates in the UCOL headwaters is eventually delivered to and stored in two major reservoirs - Lake Powell and Lake Mead. These reservoirs serve as critical water supplies for the Lower Colorado River basin. Managing water levels in these reservoirs and planning for future water availability requires an understanding of the processes influencing the magnitude and timing of snowmelt, effects of climate on evapotranspiration losses, and subsequent streamflow response. Hydrologic and climatic conditions, the interactions between the two, and anthropogenic use of freshwater have important implications for water quality and ecological conditions throughout the basin. Working with other projects in the basin, the UCOL IWAAs project will generate improved process understanding of the water budget, status and trends in water quality and ecological conditions, and ecosystem response to changes in climate and anthropogenic use of water in the UCOL. This information will be applied to better inform predictive modeling, water-availability trend and assessment studies, and water management and allocation.

To support these needs, the following priority topics will guide the scope and discovery, evaluation, and synthesis activities that are undertaken as part of IWAAs work in the UCOL: 

  • Linking snowpack to streamflow 
  • Water use and consumption 
  • Groundwater contributions to streamflow 
  • Water-quality trends and assessments 
  • Ecological flows and aquatic habitat 
  • Water-availability under future climate scenarios 

The UCOL IWAAs project is divided into three phases. Phase 1, which began in October of 2020, will last two years and will focus on identifying existing data and modeling tools and strategic planning. Phase 2 of the project will include the development of integrated assessments and predictions, and Phase 3 will focus on product delivery. 

Table showing the timing of the three regional IWAAs phases

The Upper Colorado IWAAs project began in October of 2020, and completion is anticipated by 2030.

Successful completion of the IWAAs Phase 1 discovery and planning tasks requires understanding relevant past and current work in the basin and making data discoverable and usable for Phase 2 activities as well as activities being conducted through other projects working in the basin. The main objectives of Phase 1 of this project can be grouped into two broad categories – (1) data and model compilation and assessment and (2) science plan development.  

Specific objectives related to data and model compilation and assessment include: 

  1. Conducting a retrospective analysis of existing data, water-availability assessments, and prediction tools.
  2. Cataloging and developing an access structure to historic data sets and current observation networks relevant to the topics noted above.  
  3. Creating multi-source harmonized and screened data sets for use in water-availability assessment, model building, and assessment of trends and drivers.  
  4. Development of a streamlined process to provide regular updates to the data sets (#3). 

Objectives related to science planning include: 

  1. Developing detailed monitoring plans such that new data collection in the UCOL NGWOS basin and in the larger UCOL basin will meet the needs of modeling and assessment (including trends) efforts in the UCOL. 
  2. Developing a detailed strategic modeling plan to improve the water-availability integration and prediction capacity for IWAAs core and regionally relevant water-availability components and metrics. 
  3. Creating a detailed strategic plan to improve representation of trends, and identify drivers of those trends, of IWAAs core and external and internal stakeholder-priority availability components. 

Currently underway, Phase 1 is preparing the launching pad from which IWAAs will assess water supply, demand, and the factors that influence water availability in the UCOL toward the eventual delivery of water availability forecasts, both in the region and nationally Successful completion of Phase 1 requires substantial coordination with other projects working in the basin including external partners such as the Bureau of Reclamation to ensure that components of water availability assessments being conducted by those projects are developed in a way that facilitates eventual development of an integrated water availability assessment and prediction capacity.