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About the Tool

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

The following list of datasets were used to create this tool. Download data visualized in the charts by clicking the Download Chart button. For more download options follow the links below.


  • The Adaptation Clearinghouse is the State of California's consolidated searchable database of resources for local, regional and statewide climate adaptation planning and decision-making.

  • California's Fourth Climate Change Assessment advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors.

Related Cal-Adapt Tools


  • An introduction to climate data, models, and projections.

  • Frequently asked questions about Cal-Adapt's tools and data.