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California Reservoirs - Drought Status Percentiles
| Change Date: |
Percentile |
Drought Monitor Category |
|
0.00 - 0.02 |
D4 |
Drought - Exceptional |
0.02 - 0.05 |
D3 |
Drought - Extreme |
0.05 - 0.10 |
D2 |
Drought - Severe |
0.10 - 0.20 |
D1 |
Drought - Moderate |
0.20 - 0.30 |
D0 |
Abnormally Dry |
0.30 + |
N |
Normal |
Notes:
Data is preliminary and subject to change. The end-of-month storage values are collected from the California Dept. of Water Resources' RES and STORAGEM reports, and other sources. See: http://cdec4gov.water.ca.gov/cgi-progs/reservoirs/RES and http://cdec4gov.water.ca.gov/cgi-progs/reservoirs/STORAGEM
Background to the Precipitation Drought Status
Reservoir Storage percentiles are based on different periods of record, depending on when the reservoir was filled and data availability:
| Reservoir | Period of Record | |
| Trinity | 1/1/1963 - Present | |
| Shasta | 1/1/1954 - Present | |
| Almanor | 1/1/1965 - Present | |
| Oroville | 1/1/1969 - Present | |
| New Bullards Bar | 1/1/1970 - Present | |
| *Lake Tahoe | 1/1/1959 - Present | |
| Folsom | 1/1/1956 - Present | |
| Berryessa | 1/1/1963 - Present | |
| Camanche / Pardee | 1/1/1967 - Present | |
| New don Pedro | 1/1/1974 - Present | |
| New Exchequer | 1/1/1968 - Present | |
| Friant | 1/1/1954 - Present | |
| Pine Flat | 1/1/1956 - Present | |
| Isabella | 1/1/1968 - Present | |
| San Luis | 1/1/1969 - Present | |
| Cachuma | 1/1/1960 - Present | |
| Casitas | 1/1/1970 - Present | |
| Nacimiento / San Antonio | 1/1/1966 - Present | |
| "Statewide" | 1/1/1974 - Present |
Some reservoirs, like New Melones, did not have a long enough period of record to be included.
Camanche and Pardee reservoirs are operated in tandem and so they are combined as one reservoir. Naciminto and San Antonio reservoirs are operated jointly and so they are combined as one reservoir.
The "Statewide" number accounts for more than 64% of California's total water storage in reservoirs. It is computed from an unweighted sum of all the reservoirs listed above.
* Lake Tahoe often drops below the level of the natural rim (as many as 10 times in 50 years for some months). When Lake Tahoe is below the natural rim the stage elevation of the Lake is used to compute a negative storage and a corresponding percentile.