Cooper (Chapman) Lake: 73.2% full as of 2026-09-10

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 2026-09-10 73.2 435.87 225,083 189,308 258,723 15,573
1 day prior 2026-09-09 73.4 435.91 225,706 189,931 258,723 15,601
2 days prior 2026-09-08 73.7 435.95 226,331 190,556 258,723 15,629
1 week prior 2026-09-03 74.8 436.14 229,313 193,538 258,723 15,758
1 month prior 2026-08-10 81.6 437.24 247,014 211,239 258,723 16,410
3 months prior 2026-06-10 86.5 438.00 259,652 223,877 258,723 16,847
6 months prior 2026-03-10 77.5 436.58 236,309 200,534 258,723 16,031
1 year prior 2025-09-10 89.1 438.39 266,267 230,492 258,723 17,072
*

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 2026-09-10 23:00 435.85 440.00 -4.15 below flood pool
1 hour prior 2026-09-10 22:00 435.84 440.00 -4.16 below flood pool
2 hours prior 2026-09-10 21:00 435.84 440.00 -4.16 below flood pool
6 hours prior 2026-09-10 17:00 435.93 440.00 -4.07 below flood pool
12 hours prior 2026-09-10 11:00 435.88 440.00 -4.12 below flood pool
24 hours prior 2026-09-09 23:00 435.89 440.00 -4.11 below flood pool
48 hours prior 2026-09-08 23:00 435.93 440.00 -4.07 below flood pool
*

Data is provisional and subject to revision.

Additional Information

Impoundment date 1991-01-01
Vertical datum NGVD29
Dead pool elevation 415.50 ft above NGVD29
Emergency spillway crest elevation 446.20 ft above NGVD29
Flood pool elevation 446.20 ft above NGVD29
Maximum design elevation 459.50 ft above NGVD29
Top of dam elevation 464.50 ft above NGVD29
Conservation pool elevation 440.00 ft above NGVD29
Data download (CSV) period of record, last one year, last 30 days

Elevation-Area-Capacity Curves

1991-01-01 (source: USGS)
2007-07-01 (source: TWDB) : GIS Data
2022-07-01 (source: TWDB) : GIS Data
Data Source USGS:07342495
USGS Monitoring Location USGS:07342495

Lake Location