Executive Update: Hydrologic Conditions in California

Executive Update

Hydrologic Conditions in California (04/01/2015)

Northern Sierra Precipitation Accumulation (1)
Rainfall & Snow Water Content (in inches)
 
Water Year Amount to Date (since Oct. 1, 2014): 31.65      
Average to Date: 41.60      
Percent of Average to Date: 76 %  
Average for the Water Year (Oct. 1 through Sep. 30) 50.00      
Percent of Average for the Water Year (Oct. 1 through Sep. 30) 63 %  

(1) Northern Sierra (Sacramento, Feather, Yuba, and American River Basins)

Snowpack Water Content
Region
Water Content
(in inches)
%
Avg to Date
%
April 1 Avg (2)
Northern Sierra 1.50                   5                   5                  
Central Sierra 1.70                   6                   6                  
Southern Sierra 1.30                   5                   5                  
Statewide 1.50                   5                   5                  

(2) April 1 is the date of normal maximum accumulation for the season.

Forecast of Regional Water Supply Indices (3)
Index Value Year Type
8 River Index for March (in 1000 AF)841       n/a
Sacramento Valley Water Year Type Index (40-30-30) @ 50%4.1       Critical
Sacramento Valley Water Year Type Index (40-30-30) @ 90%3.9       Critical
San Joaquin Valley Water Year Type Index (60-20-20) @ 50%0.8       Critical
San Joaquin Valley Water Year Type Index (60-20-20) @ 75%0.7       Critical

(3) For more information see Sacramento & San Joaquin Valley Water Year Type Index forecast: Latest | Previous
    (Issued monthly from December 1 through May 1)

Key Reservoir Storage As of 03/31/2015 midnight
Reservoir River Storage
(in 1000 AF)
Avg Storage
(in 1000 AF)
%
Average
Capacity
(in 1000 AF)
%
Capacity
Flood Control (4)
Encroachment
(in 1000 AF)
Trinity Lake Trinity 1,191   1,927   62   2,448   49   ---      
Shasta Lake Sacramento 2,689   3,691   73   4,552   59   -1,863      
Lake Oroville Feather 1,794   2,696   67   3,538   51   -1,369      
New Bullards Bar Res Yuba 602   701   86   970   62   -194      
Folsom Lake American 572   628   91   977   58   -129      
New Melones Res Stanislaus 553   1,510   37   2,400   23   -1,485      
Don Pedro Res Tuolumne 893   1,483   60   2,030   44   -797      
Lake McClure Merced 93   565   16   1,032   9   -643      
Millerton Lake San Joaquin 205   366   56   520   39   -316      
Pine Flat Res Kings 185   564   33   1,000   18   -726      
Isabella Kern 46   201   23   568   8   -315      
San Luis Res (Offstream) 1,354   1,846   73   2,041   66   ---      

(4) Temporary encroachment into seasonally reserved flood storage space; requirements can vary considerably on a daily basis due to numerous variables: rainfall amounts, anticipated snowmelt, time of year, soil moisture, etc.

Daily Precipitation (in inches) for Selected Stations as of 04/01/2015

Station
Oct 1 to Date
2014 - 2015
%
Average
Season to Date
2013 - 2014
%
Average
% Average
Oct 1 - Sep 30
Mount Shasta30.588610.863070
Eureka27.298214.934568
Redding20.997315.735561
South Lake Tahoe8.295110.876741
Sacramento Executive Airport13.45837.054473
Santa Rosa (Sonoma Co AP)20.846512.944057
San Francisco16.047610.204868
Stockton9.45786.165167
Yosemite11.393613.124230
Monterey13.32947.045083
Paso Robles7.70674.313860
Fresno4.60474.014140
Bakersfield4.53811.813270
Death Valley1.05600.895144
Los Angeles7.33555.394049
Riverside3.85361.511431
Palm Springs2.07460.871936
San Diego6.51714.374863
Comments
As of March 31, statewide hydrologic conditions were as follows: precipitation, 75 percent of average to date; runoff, 60 percent of average to date; snow water content, 5 percent of average to date (5 percent of the April 1 average); and reservoir storage, 70 percent of average for the date. Sacramento River Region unimpaired runoff, for Water Year 2015, observed through March 31, 2015 was about 6.9 million acre-feet (MAF), which is about 63 percent of average. In comparison to Water Year 2014, the observed Sacramento River Region unimpaired runoff through March 31, 2014 was about 4.3 MAF, or about 39 percent of average. On March 31, the Northern Sierra 8-Station Precipitation Index Water Year total was 31.7 inches, which is about 76 percent of the seasonal average to date and 63 percent of an average water year (50.0 inches). During March, the total precipitation for the 8-Stations was 1.0 inch, or about 14 percent of average for the month. Last year on March 31, the Water Year 2014 seasonal total for the 8-Stations was 25.4 inches, or about 61 percent of average. On March 31, the San Joaquin 5-Station Precipitation Index Water Year total was 13.7 inches, which is about 41 percent of the seasonal average to date and 34 percent of an average water year (40.8 inches). During March, the total precipitation for the 5-Stations was 0.4 inches, or about 7 percent of average for the month. Last year on March 31, the Water Year 2014 seasonal total for the 5-Stations was 15.0 inches, or about 45 percent of average. The latest National Weather Service Climate Prediction Center (CPC) long-range, 1-month precipitation outlook for April 2015, issued March 31, 2015, suggests equal chances of wet or dry conditions for all of California. Updates to the Executive Summary will generally be issued approximately weekly, biweekly, or monthly (depending on conditions) through the wet months of winter and spring. Beginning about June 1, this product is updated monthly through the dry seasons of summer and fall. The next update of this product will be issued about Wednesday, May 13, 2015, for conditions on May 1, unless there are significant hydrologic changes.


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