Methodology and data sources

Every number on this site comes from an official agency. We do not estimate, model or copy data from other websites.

Source

Texas reservoirs: Texas Water Development Board, Water Data for Texas. TWDB compiles daily readings from the U.S. Geological Survey, the U.S. Army Corps of Engineers, the U.S. Bureau of Reclamation, the International Boundary and Water Commission and river authorities such as the Lower Colorado River Authority, and publishes one value per reservoir per day, with records going back as far as 1940.

Update frequency

We check for new data every 2 hours. Each page shows the date of the reading. If a reservoir has had no new reading for more than 7 days we mark it as outdated and remove it from search engine indexes until data returns. Recent values are provisional and can be revised by the agency; we download each reservoir's full history again every week to pick up revisions.

Percent full

Percent full is conservation storage divided by conservation capacity, as calculated by TWDB. Storage in the flood pool is not counted, so a reservoir stays at 100% while its level rises above full pool during floods. The statewide figure is total conservation storage divided by total conservation capacity of the reservoirs with data, the same method TWDB uses.

Normal for the date

"Normal" is the average percent full for the same day of the year (±3 days) between 1996 and 2025. The shaded band in the charts is the range between the 10th and 90th percentile of those years. We only show a normal when there are at least 10 years of data for that date.

Other figures

• vs full pool: current elevation minus the top of the conservation pool.
• Changes (24 hours, 7 days, 30 days, 1 year): difference in elevation with the reading of that day, or the closest earlier reading within 3 days.
• Fullest / lowest since: the most recent date, before the last 30 days, when the reservoir was at least as full (or as low) as today.
• Records: highest and lowest daily value in the TWDB record.

Maps and satellite images

The state map uses Leaflet with map data © OpenStreetMap contributors. Each dot is the reservoir's gauge location as published by TWDB.

Satellite views come from NASA GIBS, Harmonized Landsat Sentinel-2 (HLS) at 30 m resolution: Landsat 8/9 (NASA/USGS) and Sentinel-2 (contains modified Copernicus Sentinel data). For each reservoir we show two fixed images of the same area: the clearest one from a date close to its lowest level since 2016 and another close to its highest, picked from our daily records. The caption gives the date and the level that day. Reservoirs whose level has barely changed since 2016 get a single image. Black specks are cloud and shadow masks applied by NASA.

We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Landsat imagery courtesy of NASA and the U.S. Geological Survey. Contains modified Copernicus Sentinel data, processed by NASA as part of the Harmonized Landsat Sentinel-2 (HLS) project. NASA, USGS and the European Union do not endorse this site.

Limitations

Readings are daily, so short spikes during floods may not appear. This site is not affiliated with TWDB or any lake operator. Do not use it for navigation, boating safety or flood decisions: check official notices from the lake operator and the National Weather Service.