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California

California Water Map

Where California stores its water and how it moves it: the state's dams, the aqueducts and canals of its big water systems, and the plants that pump it, make power from it, make it from salt water and recycle it.

By Oren Ben-Joseph · Dams as of Oct 26, 2026

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Largest reservoirs

    How this is made

    The dams are every California dam in the National Inventory of Dams (NID), kept by the U.S. Army Corps of Engineers, as of its latest update. Each dot's size is its reservoir's storage in the NID. Some reservoirs are held back by more than one dam, such as Oroville's saddle dams. The NID lists those under the main dam, and this map counts their storage once, with the main dam.

    The NID rates a dam's hazard potential by what a failure would cost downstream. "High" means a failure would probably cost lives. It is not a rating of the dam's condition.

    The State Water Project is the California Department of Water Resources' (DWR) own centerline of its aqueducts. The other systems are the aqueducts, canals, pipelines and tunnels that OpenStreetMap contributors have drawn, matched by their names or by the named aqueduct they belong to. Where a named canal breaks off and an unnamed canal carries on to the next named piece, as the Delta-Mendota Canal does near Tracy, the unnamed stretch is drawn as part of it. Where OpenStreetMap has no line at all, as for most of the Tehama-Colusa Canal and the Mokelumne Aqueduct, the U.S. Geological Survey's National Hydrography Dataset (NHD) fills it in. A line's card says how much of it came either way. The three Mokelumne Aqueducts run side by side and are drawn as one line.

    The desalination plants are kept by hand, because no one dataset lists them. They take salt out of seawater or out of brackish water: groundwater or river water too salty to drink. Each fact on a plant's card links its source, with the words it was taken from and the date it was checked. Seawater plants are placed where the State Water Board's map of desalination facilities puts them, with its permit. Other plants are placed from an address in their sources, through the U.S. Census Bureau's geocoder, or where OpenStreetMap maps them by name; each card says which. The map shows the plants that operate, are being built, or are approved or planned by their agency, and those no longer operating. It leaves out projects that were denied or never went ahead, such as the Huntington Beach seawater plant, plants the Water Board lists as decommissioned, such as the Morro Bay power plant's, and plants we could not place from a source, such as Torrance's Goldsworthy Desalter and Camarillo's North Pleasant Valley Desalter. Capacities are what each plant can make, not what it makes in a given year; a plant with no capacity in its sources is drawn at the smallest size.

    The local canals are the California Department of Water Resources' centerlines of the major canals that irrigation districts, cities and other local agencies run. Off at first, they load when turned on. Stretches that the aqueducts layer draws already, and lines named for one of its aqueducts, are left out.

    Reservoirs are the lakes and reservoirs that California's dams hold back: for each dam in the National Inventory of Dams with 10 acres or more of surface, the water body that comes near the dam and whose area is close to the dam's own surface area. The outline is OpenStreetMap's where it has one, and otherwise the U.S. Geological Survey's, from the National Hydrography Dataset; each card says which. Reservoirs of 250 acres or more show from a middle zoom, smaller ones only zoomed in close. That takes in natural lakes a dam raises, such as Lake Tahoe. A dam whose basin is dry most of the year, as many flood control dams are, has no outline, and neither does a reservoir that is not in the Inventory of Dams, such as the small lake in Franklin Canyon Park. An outline with no name is named for its dam.

    The hydroelectric plants are the California Energy Commission's list of the state's power plants, those that run on water and are not retired, each sized by the megawatts it can make. Plants that also pump water uphill, to store it or to lift it along an aqueduct, say so on their card. The Commission lists Hoover Dam, on the Colorado River in Nevada, with California's plants; it is left out.

    The pumping plants are the big lifts of the State Water Project, the Central Valley Project and the Colorado River Aqueduct, kept by hand. Each figure on a card links its source, with the words it was taken from. Most State Water Project figures are a row of the Department of Water Resources' Bulletin 132-22; the Department's own site would not open from here, so the cards link a copy at the California Water Library. Each plant is placed where OpenStreetMap maps it by name or at the station named for it in the Department's California Data Exchange Center (CDEC), or, for O'Neill, at the Energy Commission's point for it; its card says which. Plants with no such location are left off: Del Valle, Pearblossom, Red Bluff, Gene and Contra Costa's Old River intake.

    The water recycling plants are those that reported recycled water put to use in the State Water Board's Volumetric Annual Report for the latest year, at the Board's point for each facility, sized by the acre-feet used that year. That is what was used, not what a plant could make. A plant that hands its treated water on to another to purify reports it as a discharge, not a use, so that water is counted at the plant that uses it; where a plant may also report some of the same water as its own use, as Hyperion may, its card says so. Water used for drinking reaches a tap by way of groundwater or a reservoir, not directly.

    Download: Dams (JSON) · Aqueducts (JSON) · Desalination plants (JSON) · Hydroelectric plants (JSON) · Pumping plants (JSON) · Water recycling plants (JSON) · Local canals (JSON) · Reservoirs (JSON) · Smaller reservoirs (JSON). The aqueducts and reservoirs files hold OpenStreetMap data under the Open Database License (ODbL).

    Legend

    Colors are the water systems, as in the Layers panel.

    Zoom in for hydro plants under 100 MW and recycling plants that used under 10,000 acre-feet a year.

    © OpenStreetMap · CARTO
    Dams: National Inventory of Dams, U.S. Army Corps of Engineers · State Water Project: California Department of Water Resources · Desalination plants: our research, one source per fact, placed from the State Water Board, the Census geocoder and OpenStreetMap · Local canals: California Department of Water Resources · Hydroelectric plants: California Energy Commission · Pumping plants: our research, one source per figure, from DWR, the Bureau of Reclamation, the Metropolitan Water District and others, placed from OpenStreetMap, DWR's California Data Exchange Center and the Energy Commission · Water recycling plants: State Water Board · Reservoirs and gaps in the other aqueducts: National Hydrography Dataset, U.S. Geological Survey · Other aqueducts, most reservoirs and basemap © OpenStreetMap contributors (ODbL) · Basemap © CARTO · Map: Leaflet