Average Annual Unimpaired Flow

Values in Cubic Feet Per Second
  • Source: Cal-Adapt. Data: Routed Unimpaired Projected Streamflows (Scripps Institution of Oceanography), Unimpaired Historical Flows (1922-2014) (California Department of Water Resources).
  • Four models have been selected by California’s Climate Action Team Research Working Group as priority models for research contributing to California’s Fourth Climate Change Assessment. Projected future climate from these four models can be described as producing:
    • A warm/dry simulation (HadGEM2-ES)
    • A cooler/wetter simulation (CNRM-CM5)
    • An average simulation (CanESM2)
    • The model simulation that is most unlike the first three for the best coverage of different possibilities (MIROC5)

Runoff Midpoint

Values in Cubic Feet Per Second
How to use? 
  • Source: Cal-Adapt. Data: Routed Unimpaired Projected Streamflows (Scripps Institution of Oceanography), Unimpaired Historical Flows (1922-2014) (California Department of Water Resources).
  • Four models have been selected by California’s Climate Action Team Research Working Group as priority models for research contributing to California’s Fourth Climate Change Assessment. Projected future climate from these four models can be described as producing:
    • A warm/dry simulation (HadGEM2-ES)
    • A cooler/wetter simulation (CNRM-CM5)
    • An average simulation (CanESM2)
    • The model simulation that is most unlike the first three for the best coverage of different possibilities (MIROC5)

About

As temperatures increase and snowpack diminishes, streamflows are also projected to shift in their timing. Of particular concern in California is the spring snowmelt, which feeds streamflow when it is needed most for irrigation and energy purposes. This tool enables the user to explore the timing and magnitude of streamflow in selected months of the water-year, which runs from October 1 to September 30 (i.e., water year 2018 runs from October 1, 2017 to September 30, 2018).

Because California’s major watersheds have been altered by large-scale projects such as dams and diversions, which enable human management of water to meet needs related to agriculture, urban uses, energy, and ecology, it would be misleading to do a straight comparison of “observed” streamflows at a given point. This obstacle is overcome through calculation of natural or “unimpaired” flows, which are what would occur if flows were not subjected to storage in reservoirs or to diversions (e.g., irrigation, power generation, water supply).

Data Sources

scripps logo

Routed Unimpaired Projected Streamflows at 11 Locations in California

Scripps Institution Of Oceanography - University of California, San Diego

Projected, bias corrected streamflow (1950-2099) is generated through first routing runoff results of the Variable Infiltration Capacity (VIC) model driven by the temperature and precipitation (daily time steps, 1/16 degree grid) LOCA projections. Then, the streamflows are bias-corrected based on California's Department of Water Resources’ Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014.

university of washington logo

Unimpaired Historical Flows (1922-2014)

California Department of Water Resources

California's Department of Water Resources summarizes their estimates of natural, unimpaired flows for all areas in the Central Valley tributary to the Sacramento-San Joaquin Delta for water years 1922-2014 in a report entitled Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014.

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