Lake Isabella water level chart
By Michael, independent developer behind zovo.one. Latest CDEC month October 2026.
CDEC's latest monthly storage figure for Lake Isabella is 139,008 acre-feet, for October 2026, 24 percent of its 568,000 acre-foot capacity. It is the 36th highest of the 73 October figures from 1954 to 2026.
Where October 2026 sits in 74 years of readings
CDEC's latest monthly storage figure for Lake Isabella is 139,008 acre-feet for October 2026. That is 24 percent of its 568,000 acre-foot capacity.
The file holds 73 October figures from 1954 to 2026. This one is the 36th highest of them. The average October figure across those years is 146,781 acre-feet, so the lake holds 95 percent of its average for the month.
Across every month from January 1954 on, 334 of 873 months were lower than today. That is 38 percent of those months.
The record low and the record high
The lowest monthly figure since January 1954 is 344 acre-feet, in February 1954. The highest is 628,177 acre-feet, in June 1983. That high is above the capacity CDEC lists today.
CDEC lists 1953 as the year Lake Isabella first filled. So the ranks, the average and the record low on this page count months from January 1954 on. That boundary is ours, not CDEC's. The file itself starts in October 1952. Its lowest figure, 300 acre-feet in August 1953, comes from before that boundary, so the comparisons leave it out.
How to read this chart
The line is storage, the volume of water in the reservoir, in acre-feet. It is not the surface elevation. CDEC publishes storage as one figure per month back to the start of the record, which is why this chart uses it. The dashed line is the capacity CDEC lists for the reservoir. The dotted line marks January 1954, where the ranks start.
Want today's elevation and percent full rather than the monthly record? The Lake Isabella water level page carries the latest daily CDEC reading.
Questions about the Lake Isabella record
How far back does this chart go? To October 1952, the first month in CDEC's monthly storage file for station ISB. The file carries 888 monthly readings through October 2026.
Is Lake Isabella low for October? It is the 36th highest of 73 October readings, at 95 percent of the October average.
What is the lowest it has been? 344 acre-feet in February 1954, counting from January 1954.
How often does this page update? The build fetches the CDEC file again every day and recomputes each figure. A new month shows up once CDEC publishes it.
Where these numbers come from
Every figure on this page is computed in code from CDEC's monthly reservoir storage file for station ISB. The capacity and the first fill year come from CDEC's reservoir information page for the station. The build drops months that CDEC marks as missing. None of the numbers is typed by hand.
The same chart exists for 11 other California lakes. They are Shasta Lake, Lake Oroville, Lake Berryessa, Folsom Lake, Pine Flat Lake, Millerton Lake, New Melones Lake, Don Pedro Reservoir, San Luis Reservoir, Cachuma Lake and Casitas Reservoir. The California lake levels page covers every reservoir in CDEC's daily storage summary.
Levels are point-in-time readings and can lag real conditions. Confirm ramp and hazard status with the lake operator before heading out. Not affiliated with any government agency. Data is republished from public USGS, CDEC and USBR feeds.