Independent project. MeadWatch is not affiliated with, or endorsed by, the U.S. Bureau of Reclamation,
USGS or any water agency. Official figures come from the sources below; anything marked est. is our approximation.
Data
- Lake levels & storage: USBR hydrodata, Lake Mead (site 921), daily. Latest reading ; snapshot taken , refreshed automatically each day.
source
- Forecasts: Reclamation 24-Month Study, end-of-month Lake Mead elevations: .
source
- Lake floor: USGS/USBR Open-File Report 03-320, 30 m surface of the floor of Lake Mead (2001 swath bathymetry + pre-impoundment contours + NED).
source
- Operating rules: 2007 Interim Guidelines, 2019 Drought Contingency Plans, IBWC Minute 323, and the 2027–2028 Operating Guidelines (Aug 2026).
source
- Rivers & canals: OpenStreetMap waterways (via OpenFreeMap tiles), traced from intake to terminus. Lake Havasu has no mapped river centreline, so the river isn’t drawn across it.
The Colorado River Aqueduct is mostly buried conduit that OSM doesn’t carry, so it is drawn through its pumping plants as an approximate route.
Region outlines: US Census counties; irrigation districts are traced approximations.
- Basemap: © OpenStreetMap contributors via OpenFreeMap / OpenMapTiles; terrain from AWS Open Data Terrain Tiles; imagery Sentinel-2 cloudless 2016 by EOX (CC BY 4.0).
How the lake is drawn
Inside the reservoir, the terrain is the USGS lake-floor survey rather than the flat water surface most elevation models record.
Every 30 m cell gets a “spill elevation”: the lowest lake level at which water reaches it from Hoover Dam (cells cut off by a sill stay dry).
The water surface is a flat plane at the chosen elevation, drawn only over cells below it and shaded by depth. Storage and area come from the same grid,
scaled by 0.4% to match USBR’s reported storage today.
How impacts are estimated
- Scheduled cuts by state follow the published rules. For 2021–2026 the app uses the tier Reclamation actually declared each year.
- Splits within a state est.: Arizona’s first 512,000 AF of cuts fall on CAP agriculture and excess water, the rest on CAP cities and tribes;
California’s cut is split 60/30/7/3 among MWD, IID, CVWD and PVID. Mexico’s 2027–28 terms (Minute 334) are not modeled.
- Hoover capacity est.: 2,080 MW × (head ÷ 583 ft)1.15, calibrated to 24-Month Study effective-capacity figures; zero below 950 ft.
- Physical limits: below 950 ft releases are limited to the outlet works; at 895 ft (dead pool) nothing passes Hoover Dam; SNWA’s pumping station reaches ~875 ft.
- Region colour is the largest of: the scheduled cut as a share of the region’s Colorado River supply, half of Hoover’s lost capacity (power-contract holders), or physical risk.
- Populations and acreages are rounded public figures.
Code and data pipeline: see the project README. Feedback and corrections welcome.