Lake J.B. Thomas: 37.9% full as of 2025-04-29

The elevation-storage rating curve used to produce the storage hydrograph is made of two segments: (1) the segment up to the conservation pool top (below the red line) is based on measured data, and (2) the segment in the flood pool (above the red line) is an extrapolation from the first segment and shouldn't be relied upon for flood storage information.

Historical Data

Date Percent Full Mean Water Level
(ft) 		Reservoir Storage
(acre-ft) 		Conservation Storage
(acre-ft) 		Conservation Capacity
(acre-ft) 		Surface Area
(acres)
Most recent 2025-04-29 37.9 2,235.90 76,416 75,743 199,931 4,236
1 day prior 2025-04-28 37.9 2,235.93 76,544 75,871 199,931 4,239
2 days prior 2025-04-27 38.0 2,235.95 76,629 75,956 199,931 4,241
1 week prior 2025-04-22 38.2 2,236.04 77,011 76,338 199,931 4,251
1 month prior 2025-03-29 39.1 2,236.45 78,763 78,090 199,931 4,298
3 months prior 2025-01-29 41.3 2,237.47 83,208 82,535 199,931 4,420
6 months prior 2024-10-29 36.2 2,235.12 73,146 72,473 199,931 4,150
1 year prior 2024-04-29 19.4 2,225.66 39,405 38,732 199,931 3,056
*

Percent Full is based on Conservation Storage and Conservation Capacity and doesn't account for storage in flood pool.

**

   Values above, including today's are averaged conditions. For near real-time instantaneous water level, see table below or the interactive map viewer.

Most Recent Instantaneous Water Level

Date/time Water Level
(ft) 		Conservation Pool Elevation
(ft) 		Height Above Conservation Pool
(ft)
Most recent 2025-04-29 22:45 2,235.88 2,258.00 -22.12
1 hour prior 2025-04-29 21:45 2,235.88 2,258.00 -22.12
2 hours prior 2025-04-29 20:45 2,235.88 2,258.00 -22.12
6 hours prior 2025-04-29 16:45 2,235.89 2,258.00 -22.11
12 hours prior 2025-04-29 10:45 2,235.90 2,258.00 -22.10
24 hours prior 2025-04-28 22:45 2,235.91 2,258.00 -22.09
48 hours prior 2025-04-27 22:45 2,235.93 2,258.00 -22.07
*

Data is provisional and subject to revision.

Additional Information

Impoundment date 1952-01-01
Vertical datum NGVD29
Dead pool elevation 2,200.00 ft above NGVD29
Service spillway crest elevation 2,258.00 ft above NGVD29
Emergency spillway crest elevation 2,264.00 ft above NGVD29
Emergency spillway crest elevation 2,267.00 ft above NGVD29
Maximum design elevation 2,275.00 ft above NGVD29
Top of dam elevation 2,280.00 ft above NGVD29
Conservation pool elevation 2,258.00 ft above NGVD29
Data download (CSV) period of record, last one year, last 30 days

Elevation-Area-Capacity Curves

1952-01-01 (source: USGS)
1999-11-01 (source: TWDB) : GIS Data
Data Source USGS:08118000

Lake Location