Executive Update: Hydrologic Conditions in California

Executive Update

Hydrologic Conditions in California (08/01/2015)

Northern Sierra Precipitation Accumulation (1)
Rainfall & Snow Water Content (in inches)
 
Water Year Amount to Date (since Oct. 1, 2014): 36.73      
Average to Date: 48.80      
Percent of Average to Date: 75 %  
Average for the Water Year (Oct. 1 through Sep. 30) 50.00      
Percent of Average for the Water Year (Oct. 1 through Sep. 30) 73 %  

(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 ---                   --- (3)                   ---                  
Central Sierra ---                   --- (3)                   ---                  
Southern Sierra ---                   --- (3)                   ---                  
Statewide ---                   --- (3)                   ---                  

(2) April 1 is the date of normal maximum accumulation for the season.
(3) 'Percent Average to Date' is not calculated this early in the WY when the historical average is small.

Forecast of Regional Water Supply Indices (5)
Index Value Year Type
8 River Index for July (in 1000 AF)364       n/a
Sacramento Valley Water Year Type Index (40-30-30) @ 50%4.0       Critical
Sacramento Valley Water Year Type Index (40-30-30) @ 90%3.8       Critical
San Joaquin Valley Water Year Type Index (60-20-20) @ 50%0.7       Critical
San Joaquin Valley Water Year Type Index (60-20-20) @ 75%0.7       Critical

(4) 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 07/31/2015 midnight
Reservoir River Storage
(in 1000 AF)
Avg Storage
(in 1000 AF)
%
Average
Capacity
(in 1000 AF)
%
Capacity
Flood Control (6)
Encroachment
(in 1000 AF)
Trinity Lake Trinity 825   1,954   42   2,448   34   ---      
Shasta Lake Sacramento 1,990   3,234   62   4,552   44   -2,562      
Lake Oroville Feather 1,162   2,579   45   3,538   33   -2,376      
New Bullards Bar Res Yuba 462   750   62   930   50   -504      
Folsom Lake American 286   691   41   977   29   -691      
New Melones Res Stanislaus 344   1,467   23   2,400   14   -2,076      
Don Pedro Res Tuolumne 694   1,548   45   2,030   34   -1,336      
Lake McClure Merced 110   627   17   1,025   11   -915      
Millerton Lake San Joaquin 179   327   55   520   34   -342      
Pine Flat Res Kings 156   509   31   1,000   16   -844      
Isabella Kern 33   274   12   568   6   -328      
San Luis Res (Offstream) 523   996   52   2,041   26   ---      

(5) 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 08/01/2015

Station
Oct 1 to Date
2014 - 2015
%
Average
Season to Date
2013 - 2014
%
Average
% Average
Oct 1 - Sep 30
Mount Shasta35.098212.232980
Eureka30.097617.254475
Redding23.126816.214867
South Lake Tahoe13.817213.667168
Sacramento Executive Airport15.43858.934983
Santa Rosa (Sonoma Co AP)22.326213.703862
San Francisco17.647512.045175
Stockton10.67787.005176
Yosemite18.405016.734548
Monterey14.57928.335290
Paso Robles8.40674.913966
Fresno6.50574.924357
Bakersfield5.29832.413882
Death Valley1.05521.025044
Los Angeles8.67595.743958
Riverside5.81481.871547
Palm Springs2.50501.192444
San Diego10.02994.904897
Comments
As of July 31, statewide hydrologic conditions were as follows: precipitation, 75 percent of average to date; runoff, 45 percent of average to date; and reservoir storage, 55 percent of average for the date. Sacramento River Region unimpaired runoff, for Water Year 2015, observed through July 31, 2015 was about 8.7 million acre-feet (MAF), which is about 50 percent of average. In comparison to Water Year 2014, the observed Sacramento River Region unimpaired runoff through July 31, 2014 was about 6.9 MAF, or about 39 percent of average. On July 31, the Northern Sierra 8-Station Precipitation Index Water Year total was 36.7 inches, which is about 75 percent of the seasonal average to date and 73 percent of an average water year (50.0 inches). During July, the total precipitation for the 8-Stations was 0.7 inches, or about 350 percent of average for the month. Last year on July 31, the Water Year 2014 seasonal total for the 8-Stations was 29.1 inches, or about 60 percent of average. On July 31, the San Joaquin 5-Station Precipitation Index Water Year total was 18.8 inches, which is about 47 percent of the seasonal average to date and 46 percent of an average water year (40.8 inches). During July, the total precipitation for the 5-Stations was 1.1 inches, or about 367 percent of average for the month. Last year on July 31, the Water Year 2014 seasonal total for the 5-Stations was 19.6 inches, or about 49 percent of average. The latest National Weather Service Climate Prediction Center (CPC) long-range, 1-month precipitation outlook for August 2015, issued July 31, 2015, suggests equal chances of wet or dry conditions for most of California, except for the southeastern portion of the State where above average precipitation is suggested. 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 Monday, September 14, 2015, for conditions on September 1, unless there are significant hydrologic changes.


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