Cooper (Chapman) Lake: 78.0% full as of 2026-02-27

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)
Today 2026-02-27 78.0 436.66 237,593 201,818 258,723 16,077
Yesterday 2026-02-26 78.1 436.67 237,754 201,979 258,723 16,082
2 days ago 2026-02-25 78.2 436.69 238,076 202,301 258,723 16,094
1 week ago 2026-02-20 78.9 436.81 240,011 204,236 258,723 16,163
1 month ago 2026-01-27 69.8 435.30 216,322 180,547 258,723 15,162
3 months ago 2025-11-27 76.9 436.48 234,709 198,934 258,723 15,973
6 months ago 2025-08-27 90.9 438.66 270,897 235,122 258,723 17,227
1 year ago 2025-02-27 99.4 439.92 293,060 257,285 258,723 17,952
*

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 2026-02-27 17:00 436.64 440.00 -3.36 below flood pool
1 hour prior 2026-02-27 16:00 436.65 440.00 -3.35 below flood pool
2 hours prior 2026-02-27 15:00 436.64 440.00 -3.36 below flood pool
6 hours prior 2026-02-27 11:00 436.65 440.00 -3.35 below flood pool
12 hours prior 2026-02-27 05:00 436.65 440.00 -3.35 below flood pool
24 hours prior 2026-02-26 17:00 436.67 440.00 -3.33 below flood pool
48 hours prior 2026-02-25 17:00 436.68 440.00 -3.32 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

Lake Location