Data / Open datasets / Western Terminal Lakes
Western Terminal Lakes
Monthly open-water area for 19 series on 18 western lakes and reservoirs, January 2019 to September 2026, next to gauge-derived area where a published area table exists. Great Salt Lake has two series, one for each arm.
Published now: Version 1.0: Kaggle (7 series on 6 lakes in version 1.0). Version 1.1: Zenodo, Kaggle, Hugging Face (19 series on 18 lakes in version 1.1).
- Status
- Released
- Version / DOI
- Published 2026-10-10. Version 1.1, DOI 10.5281/zenodo.23045007.
- Coverage
- 19 series on 18 lakes in version 1.1. Seven terminal-lake series: Great Salt Lake (north and south arms), Salton Sea, Mono Lake, Pyramid Lake, Walker Lake and Lake Abert. Twelve reservoirs and lakes: Mead, Powell, Elephant Butte, Falcon, Flaming Gorge, Amistad, Blue Mesa, Upper Klamath, Choke Canyon, Lahontan, American Falls and Corpus Christi.
- Tables
- Water table: open-water area. Surface table: surface classes for Great Salt Lake and Salton Sea are planned for a later version.
- Period
- January 2019 to September 2026
- Resolution
- Lake by month, from Sentinel-2 imagery
- Free updates
- Latest gauge reading in the live feed: 24 October 2026. The monthly table in the published version 1.1 covers through September 2026. The live feed is newer data from the API. It can change and is not part of the cited version.
- After the release
- Provisional months after 2026-09 are available through the API with
include=provisional. They can change and are not covered by the DOI. - Weekly lake watch
- Planned. Not available yet. Paid plans start January 1, 2027.
- Formats
- CSV and Parquet tables; reference outlines as GeoJSON
- Coordinate system
- Areas measured in an equal-area projection.
- Access
- Free and paid
- License
- CC BY 4.0, with upstream attribution below
- API and MCP
- Lake list with a free key. Monthly values from the published package are served.
Download and API key
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In the download
Version 1.1, published on Zenodo, Hugging Face and Kaggle: the monthly area table for 19 series (CSV and Parquet), the lake outlines (GeoJSON), one WebP preview of each series for each summer, 2019 to 2026, the citation and the data dictionary. The Kaggle copy also has the notebook.
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With a free API key
Full-size Sentinel-2 composites, from
GET /v1/lakes/{lake}/imagery. The MCP tool isget_lake_imagery.
Not in this download, free through the API: full-size summer satellite images of all 18 lakes and reservoirs, 2019 to 2026. Get a free key.
Download the data Create a free account
Sample rows
month | water_area_km2 | area_low_km2 | area_high_km2 | quality_flag |
|---|---|---|---|---|
2025-04 | 1905.9 | 1905.9 | 2029.0 | ok |
2025-05 | 1935.2 | 1935.2 | 2053.4 | ok |
2025-06 | 1866.8 | 1866.8 | 1965.6 | ok |
2025-07 | 1829.1 | 1829.1 | 1904.1 | ok |
2025-08 | 1790.5 | 1790.5 | 1876.9 | ok |
2025-09 | 1791.5 | 1791.5 | 1885.5 | ok |
2025-10 | 1899.8 | 1899.8 | 2042.2 | ok |
2025-11 | 1744.5 | 1744.5 | 1918.7 | ok |
2025-12 | 1843.2 | 1843.2 | 2025.7 | ok |
2026-01 | 1892.6 | 1892.6 | 2186.7 | ok |
2026-02 | 1814.2 | 1814.2 | 2051.7 | ok |
2026-03 | 1867.5 | 1867.5 | 2020.8 | ok |
2026-04 | 1855.7 | 1855.7 | 1978.5 | ok |
2026-05 | 1845.0 | 1845.0 | 1942.4 | ok |
2026-06 | 1803.9 | 1803.9 | 1890.4 | ok |
2026-07 | 1770.6 | 1770.6 | 1866.5 | ok |
2026-08 | 1756.1 | 1756.1 | 1845.6 | ok |
2026-09 | 1734.9 | 1734.9 | 1837.3 | ok |
Rows from the Western Terminal Lakes 1.1 table (lake_monthly.csv). Area is rounded to 0.1 km² for the table. Not for water-rights, legal or engineering decisions.
Yearly pictures
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July 2019
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July 2020
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July 2021
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July 2022
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July 2023
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July 2024
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July 2025
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July 2026
July preview each year, Great Salt Lake south arm. The download has one preview for each of the 19 series and each summer, 2019 to 2026. Four of them still show cloud or sun glint over part of the lake: Choke Canyon Reservoir and Lake Corpus Christi, 2019 and 2020.
Try it
Great Salt Lake, south arm, in September 2026: 1734.9 km².
Latest month in the table. It can be a reading flagged as low confidence.
| Month | Water area km2 | Area low km2 | Area high km2 | Quality flag |
|---|---|---|---|---|
2026-05 | 1845.0 | 1845.0 | 1942.4 | ok |
2026-06 | 1803.9 | 1803.9 | 1890.4 | ok |
2026-07 | 1770.6 | 1770.6 | 1866.5 | ok |
2026-08 | 1756.1 | 1756.1 | 1845.6 | ok |
2026-09 | 1734.9 | 1734.9 | 1837.3 | ok |
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Download the data
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Western Terminal Lakes
Monthly open-water area of western lakes and reservoirs, with an uncertainty range. Version 1.1, 19 series on 18 lakes.
Citable copy (Zenodo) · Dataset (Kaggle) · Run the notebook (Kaggle) · Discussion (Kaggle) · Load in Python (Hugging Face)
What the data shows
4 findings from the published version.
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Great Salt Lake's south arm: July open water was 12% lower in 2026 than in July 2019.
Great Salt Lake south arm open-water area fell from 2017.2 km2 in July 2019 to 1770.6 km2 in July 2026 (loss 246.5 km2, 12.2 percent).
Breakdown
For great-salt-lake-south, water_area_km2 is 2017.2 in 2019-07 and 1770.6 in 2026-07. That is a loss of 246.5 km2, or 12.2 percent of the July 2019 area. This compares July 2019 with July 2026. July water_area_km2 values are 2019 2017.2; 2020 1968.7; 2021 1816.8; 2022 1743.3; 2023 1919.5; 2024 1956.3; 2025 1829.1; 2026 1770.6. Low-confidence Julys: none.
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Great Salt Lake's north arm: July open water was 16% lower in 2026 than in July 2019.
Great Salt Lake north arm open-water area fell from 1369.9 km2 in July 2019 to 1149.3 km2 in July 2026 (loss 220.6 km2, 16.1 percent).
Breakdown
For great-salt-lake-north, water_area_km2 is 1369.9 in 2019-07 and 1149.3 in 2026-07. The loss is 220.6 km2, or 16.1 percent. This compares July 2019 with July 2026. July water_area_km2 values are 2019 1369.9; 2020 1350.3; 2021 1169.2; 2022 1181.5; 2023 1228.2; 2024 1203.7; 2025 1231.6; 2026 1149.3. Low-confidence Julys: none.
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Salton Sea: July open water was 9% lower in 2026 than in July 2019.
Salton Sea open-water area fell from 850.4 km2 in July 2019 to 772.0 km2 in July 2026 (loss 78.3 km2, 9.2 percent).
Breakdown
For salton-sea, water_area_km2 is 850.4 in 2019-07 and 772.0 in 2026-07. The loss is 78.3 km2, or 9.2 percent of the July 2019 area. This compares July 2019 with July 2026. July water_area_km2 values are 2019 850.4; 2020 840.5; 2021 842.1; 2022 824.1; 2023 811.4; 2024 814.2; 2025 792.6; 2026 772.0. Low-confidence Julys: none.
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Lake Abert: July open water was 7% lower in 2026 than in July 2019.
Lake Abert open-water area fell from 128.0 km2 in July 2019 to 119.5 km2 in July 2026 (loss 8.5 km2, 6.7 percent).
Breakdown
For lake-abert, water_area_km2 is 128.0 in 2019-07 and 119.5 in 2026-07. That is a loss of 8.5 km2, or 6.7 percent. This compares July 2019 with July 2026. July water_area_km2 values are 2019 128.0; 2020 110.0; 2021 81.7; 2022 136.4; 2023 110.1; 2024 129.6; 2025 131.8; 2026 119.5. Low-confidence Julys: 2022, 2023. An earlier published table for these two Julys showed a gain. This table shows a loss.
What it is for
- Intended use
- Tracking long-term change in the size of western lakes and reservoirs, comparing lakes on one definition, and checking satellite area against gauge-derived area.
- How the tables fit
- The water table reports open-water area. Surface classes for Great Salt Lake and Salton Sea are planned for a later version.
- Not intended for
- Legal shoreline or boundary determinations, lake volume without gauge data, navigation, or dust-emission, air-quality, or health estimates. The planned potential emissive surface value is a screening label for dust-prone surface conditions. It does not measure dust.
The 19 series on 18 lakes
This table and map show all 19 series on 18 lakes: the seven terminal-lake series, then the 12 reservoirs and lakes added in version 1.1. All of them are in lake_monthly.csv in the download.
Lakes 1.1. Change compares the 2019 and 2026 averages over the same months, January to September, using only months not flagged as low confidence in either year. The months differ by lake and are listed with each one.
| Lake | State | Type | Latest month (km²) | Latest month | Change since 2019 | What the data shows | Details | Free and paid | |||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Great Salt Lake, north arm | Utah | Terminal lake | 1,148.2 2026-09 | 2026-09 | -16.2% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Great Salt Lake, south arm | Utah | Terminal lake | 1,734.9 2026-09 | 2026-09 | -13.4% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Salton Sea | California | Terminal lake | 756.6 2026-09 | 2026-09 | -8.8% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Mono Lake | California | Terminal lake | 178.1 2026-09 | 2026-09 | +0.0% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Pyramid Lake | Nevada | Terminal lake | 415.6 2026-09 | 2026-09 | -0.9% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Walker Lake | Nevada | Terminal lake | 113.6 2026-09 | 2026-09 | -2.8% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Lake Abert | Oregon | Terminal lake | 114.5 2026-09 | 2026-09 | -5.0% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Lake Mead | Nevada and Arizona | Reservoir or lake | 288.1 2026-09 | 2026-09 | -12.6% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Lake Powell | Utah and Arizona | Reservoir or lake | 249.7 2026-09 | 2026-09 | -31.0% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Elephant Butte Reservoir | New Mexico | Reservoir or lake | 8.4 2026-09 | 2026-09 | -33.2% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Falcon Reservoir | Texas | Reservoir or lake | 109.5 2026-09 | 2026-09 | -32.1% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Flaming Gorge Reservoir | Wyoming and Utah | Reservoir or lake | 129.5 2026-09 | 2026-09 | -13.0% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Amistad Reservoir | Texas | Reservoir or lake | 96.7 2026-09 | 2026-09 | -50.9% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Blue Mesa Reservoir | Colorado | Reservoir or lake | 17.6 2026-09 | 2026-09 | -32.9% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Upper Klamath Lake | Oregon | Reservoir or lake | 236.1 2026-09 | 2026-09 | -0.7% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Choke Canyon Reservoir | Texas | Reservoir or lake | 29.6 2026-09 | 2026-09 | -61.6% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Lahontan Reservoir | Nevada | Reservoir or lake | 18.9 2026-09 | 2026-09 | -12.5% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| American Falls Reservoir | Idaho | Reservoir or lake | 65.0 2026-09 | 2026-09 | -19.7% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
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| Lake Corpus Christi | Texas | Reservoir or lake | 64.3 2026-09 | 2026-09 | -47.5% |
Sample rows from |
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Free: monthly water area since 2019, with an uncertainty range, under CC BY 4.0. Weekly water area is planned. It is not available yet. Create a free account |
Need weekly figures for another lake or reservoir? Weekly figures are planned. Request a lake.
Columns: one row per lake (or arm) per month
| Variable | Units | Type | Description | Valid range |
|---|---|---|---|---|
lake_id | none | string | Stable identifier, for example great-salt-lake-north | controlled list |
month | none | string | Calendar month, YYYY-MM | none if missing |
water_area_km2 | km² | float | Open-water area | none if no clear view |
area_low_km2 | km² | float | Low end of the range across the retained water-index methods. | none if missing |
area_high_km2 | km² | float | High end of the range across the retained water-index methods. | none if missing |
seen_fraction | ratio | float | Share of the lake observed | 0 to 1 |
gauge_area_km2 | km² | float | Area from the gauge record, where a gauge exists | none where unavailable |
quality_flag | none | string | Quality flag for the row | controlled list |
Columns: one row per lake per month
| Variable | Units | Type | Description | Valid range |
|---|---|---|---|---|
| lake_id / month | none | string | Same keys as the water table | controlled list |
| shallow_water_km2, wet_salt_km2, dry_salt_km2, playa_km2, vegetation_km2, ice_km2 | km² | float | Area of each surface class on the exposed bed | ≥ 0 |
| unclassified_km2 | km² | float | Exposed area that could not be classified with enough confidence | ≥ 0; classes plus unclassified equal area_exposed_km2 |
| class_confidence_mean | ratio | float | Mean classifier confidence across classified pixels | 0 to 1 |
| mixed_pixel_fraction | ratio | float | Share of pixels near class boundaries | 0 to 1 |
| potential_emissive_km2 | km² | float | Area meeting the screening definition in the method document | ≥ 0 |
| n_scenes / valid_fraction / flag | count / ratio / bitmask | mixed | Same definitions as the water table | see water table |
Sources and required attribution
| Input | Role | License or terms | Attribution |
|---|---|---|---|
| Copernicus Sentinel-2 Level-2A, including its scene classification layer for cloud, shadow, and snow | Measured | Copernicus Sentinel data terms: free, full, and open | Contains modified Copernicus Sentinel data 2019-2026 |
| USGS lake-level and storage records, Great Salt Lake elevation-area-volume tables (DOI 10.5066/P9DGG75W) and Great Basin elevation-area-volume tables (DOI 10.5066/P147WRTT) | Gauge-derived area; validation | Public domain; the tables are CC0 | U.S. Geological Survey, with site numbers |
| USGS National Hydrography Dataset | Lake polygons for the outlines of the 12 added lakes. The seven terminal-lake outlines are hand-drawn | Public domain | U.S. Geological Survey |
| Microsoft Planetary Computer | Access path for Sentinel-2 Level-2A | Planetary Computer terms of use; Copernicus Sentinel terms apply to the imagery | none |
| US Bureau of Reclamation records for Lake Mead, Lake Powell, Flaming Gorge, Blue Mesa, Elephant Butte, Lahontan and American Falls | Gauge level and area-capacity tables | US federal agency data. Reclamation marks recent values provisional and may revise them. | US Bureau of Reclamation |
| US Section, International Boundary and Water Commission level records for Amistad and Falcon; Texas Water Development Board figures for Choke Canyon and Lake Corpus Christi | Level records and reservoir figures | US federal agency data (IBWC). The Texas Water Development Board permits copying and asks for acknowledgment, which this table gives. | Water Data for Texas |
| Labeled reference samples | Planned: training and validation of surface classes | Heimdall Research. The held-out validation subset is published with the release under CC BY 4.0, so the accuracy figures can be checked independently. The training set is not published. | none |
| JRC Global Surface Water, Monthly History | Comparison statistics for the 12 added lakes, 2019 to 2021; not redistributed | Free with required citation | Pekel and others (2016), doi:10.1038/nature20584 |
| USGS Saline Lake Ecosystems IWAA lakes; NASA OPERA DSWx-HLS | Planned comparison, not redistributed | CC0; NASA open data | Planned |
How values are produced
Pixels marked as cloud, cloud shadow, thin cirrus, dark area, saturated or no data are dropped. Snow and ice pixels are dropped from November to April. Each month, every clear view of each pixel is combined into a median composite, so partly cloudy days still count, and the share of the outline seen at least once is reported with the value. Water is classified from the composite with spectral water indices. One threshold is chosen for each lake and month, and water area is counted inside a fixed reference outline. The outlines of the seven terminal-lake series are hand-drawn and larger than the lake, so the area includes bays and ponds next to it. Exposed lakebed is not classified in version 1.1. A version using Sentinel-1 radar to fill cloudy and winter months is planned. The low and high area values span the retained water-index methods. A month with no usable view stays blank; nothing is gap-filled. The full method document is published with each release, along with example code for loading the data, mapping it, and reproducing every published summary. The production pipeline that generates it is not part of the release.
How it is checked
- Water: gauge comparison
- Satellite water area against gauge-derived area wherever a USGS lake-level record and elevation-area table exist.
- Water: independent labels
- Planned.
- Surface: class accuracy
- Planned with the surface table. Labeled points for each class, lake, and season, split by place and time. Confusion matrices and per-class accuracy with sample sizes.
- Product comparison
- The 12 added lakes are compared with JRC Global Surface Water for 2019 to 2021, and the four Texas reservoirs with the Texas Water Development Board surface area. The results are in the README in the download. Comparisons with USGS IWAA and NASA OPERA are planned.
- Release rule
- A lake enters the surface table only after its class accuracy is published.
How it compares with existing products
The 12 added lakes are compared with JRC Global Surface Water for 2019 to 2021. Comparisons with USGS IWAA and NASA OPERA are planned. Surface classes for Great Salt Lake and Salton Sea are planned for a later version.
Free and paid access
- Free
- The published files are on Zenodo, Hugging Face and Kaggle, with no sign-up, and the API and MCP server with a free key.
- Paid
- Weekly lake watch for lakes and reservoirs you name is planned. Paid plans start January 1, 2027. See Water observation histories and plans and prices.
How to cite
Heimdall Research (2026). Western Terminal Lakes (Version 1.1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.23045007 Concept DOI https://doi.org/10.5281/zenodo.23045006.
- Versions and corrections
- Version 1.0 (7 series on 6 lakes) is on Kaggle and has no Zenodo DOI. Version 1.1 (19 series on 18 lakes) has DOI https://doi.org/10.5281/zenodo.23045007 and is the first version on Zenodo and Hugging Face. DOI https://doi.org/10.5281/zenodo.23045006 covers all versions. Version 1.1 corrects the version 1.0 areas. The changelog in the download records changes. Report problems through the collaboration form.
- Corrections
- Report a problem through the collaboration form. Confirmed errors are fixed in a new version and noted in the changelog.
- Download
- Zenodo (CSV and Parquet, DOI) · Hugging Face (same files; loads with the
datasetslibrary) · Kaggle (notebook, discussion) · API and MCP with a free account. Downloads need no account. - Use notice
- Not for water-rights, legal or engineering decisions.