Executive Update: Hydrologic Conditions in California

Executive Update

Hydrologic Conditions in California (05/01/2015)

Northern Sierra Precipitation Accumulation (1)
Rainfall & Snow Water Content (in inches)
 
Water Year Amount to Date (since Oct. 1, 2014): 34.03      
Average to Date: 45.50      
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) 68 %  

(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 0.50                   3                   2                  
Central Sierra 0.80                   4                   3                  
Southern Sierra 0.10                   1                   1                  
Statewide 0.50                   3                   2                  

(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 April (in 1000 AF)766       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

(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 04/30/2015 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 1,184   2,020   59   2,448   48   ---      
Shasta Lake Sacramento 2,662   3,924   68   4,552   58   -1,890      
Lake Oroville Feather 1,782   2,877   62   3,538   50   -1,677      
New Bullards Bar Res Yuba 586   767   76   970   60   -310      
Folsom Lake American 576   729   79   977   59   -227      
New Melones Res Stanislaus 491   1,505   33   2,400   20   -1,735      
Don Pedro Res Tuolumne 843   1,487   57   2,030   42   -875      
Lake McClure Merced 104   607   17   1,032   10   -746      
Millerton Lake San Joaquin 192   366   53   520   37   -328      
Pine Flat Res Kings 211   613   34   1,000   21   -789      
Isabella Kern 45   231   19   568   8   -316      
San Luis Res (Offstream) 1,273   1,822   70   2,041   62   ---      

(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 05/01/2015

Station
Oct 1 to Date
2014 - 2015
%
Average
Season to Date
2013 - 2014
%
Average
% Average
Oct 1 - Sep 30
Mount Shasta31.958211.693073
Eureka29.858116.304474
Redding22.177115.975164
South Lake Tahoe9.645611.856947
Sacramento Executive Airport15.30888.925283
Santa Rosa (Sonoma Co AP)22.246513.684061
San Francisco17.347711.925373
Stockton10.57806.995375
Yosemite14.294115.874638
Monterey14.21938.215488
Paso Robles8.13674.914064
Fresno5.85554.874651
Bakersfield4.61762.373971
Death Valley1.05561.005344
Los Angeles7.46525.744050
Riverside4.23361.871634
Palm Springs2.07450.922036
San Diego6.53664.904963
Comments
As of April 30, statewide hydrologic conditions were as follows: precipitation, 70 percent of average to date; runoff, 55 percent of average to date; snow water content, 2 percent of average to date (1 percent of the April 1 average); and reservoir storage, 65 percent of average for the date. Sacramento River Region unimpaired runoff, for Water Year 2015, observed through April 30, 2015 was about 7.5 million acre-feet (MAF), which is about 56 percent of average. In comparison to Water Year 2014, the observed Sacramento River Region unimpaired runoff through April 30, 2014 was about 5.5 MAF, or about 41 percent of average. On April 30, the Northern Sierra 8-Station Precipitation Index Water Year total was 34.0 inches, which is about 75 percent of the seasonal average to date and 68 percent of an average water year (50.0 inches). During April, the total precipitation for the 8-Stations was 2.3 inches, or about 59 percent of average for the month. Last year on April 30, the Water Year 2014 seasonal total for the 8-Stations was 28.1 inches, or about 62 percent of average. On April 30, the San Joaquin 5-Station Precipitation Index Water Year total was 16.0 inches, which is about 43 percent of the seasonal average to date and 39 percent of an average water year (40.8 inches). During April, the total precipitation for the 5-Stations was 2.3 inches, or about 64 percent of average for the month. Last year on April 30, the Water Year 2014 seasonal total for the 5-Stations was 18.2 inches, or about 49 percent of average. The latest National Weather Service Climate Prediction Center (CPC) long-range, 1-month precipitation outlook for May 2015, issued April 30, 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 Friday, June 12, 2015, for conditions on June 1, unless there are significant hydrologic changes.


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