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The State of California is experiencing one of the most severe droughts on record, which has implications for citizens of California and beyond. Many State, Federal, and Tribal agencies make routine observations of the water cycle. This website graphically visualizes these data to help understand the effect of drought on rivers, streams, lakes, and reservoirs. Below, learn more about water use and changes in the water cycle due to the current drought in California.
The data presented here are drawn from free and publicly accessible sources. In addition, the analytical, graphical, and software tools used are open-source and available for public re-use.
For more information about drought and science-based decision making in California, visit the USGS California Water Science Center webpage.
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Drought reduces snowpack and results in decreased reservoir volume.
Here, the effect of drought on 56 of California's more than 700 reservoirs is shown through time.
Reservoir volume as a percent of total capacity
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Reservoir volume (as a percent of total capacity) |
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California reservoirs sorted by elevation |
Percent total reservoir volume animated since 2011. Bar widths are proportional to maximum capacity. On the map, circles are proportional to reservoir volume. Data providers: U.S. Drought Monitor, U.S. Bureau of Reclamation, U.S. Army Corps of Engineers, and more; reservoir data accessed from the CA Data Exchange.
Changes in reservoir volume impact the surface area of reservoirs. Above, Landsat imagery was used to estimate the change in surface area from August 2011 to August 2014 for two of California's largest reservoirs, Shasta Reservoir and Trinity Lake, both located just under 200 miles northwest of Sacramento, CA. The outlets of the two reservoirs are located approximately 15 miles apart. These reservoirs provide water for irrigation, hydroelectric power, drinking water, ecosystem management, and flood control.
Snowpack in California is the primary source of water to reservoirs that serve drinking water, agriculture, and hydroelectric needs.
For any given year, less wintertime snowpack results in lower reservoir levels, and less water for consumptive use.
In 2014, California received only a fraction of its normal precipitation and snow pack, with the State now facing three years of devastating drought (California Department of Water Resources).
Current streamflow (y-axis) is plotted against the historical (since 1980) median streamflow (x-axis) for this day of year. Axes are log-scaled. Mouse over streams on the plot (blue circles), and on map (colored according to flow; red is well below normal flow, dark blue is well above normal flow) for more information.