HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE RENO NV
335 PM PDT TUE APRIL 8 2006
...WATER SUPPLY AND SPRING FLOOD POTENTIAL OUTLOOK FOR NEVADA AND THE
EASTERN SIERRA NEVADA...
ISSUED JOINTLY BY THE NATIONAL WEATHER SERVICE AND NATURAL RESOURCES
CONSERVATION SERVICE...
1/ SUMMARY...WATER SUPPLY...
MARCH PRECIPITATION WAS DISAPPOINTING IN MUCH OF NEVADA AND THE
EASTERN SIERRA. MANY AREAS RECEIVED A QUARTER OR LESS OF NORMAL
MARCH PRECIPITATION. THE SIERRA NEVADA...EASTERN NEVADA AND
SOUTHERN NEVADA WERE ON THE LOSING END OF THE DRY SPELL. THOUGH
SOMEWHAT WETTER...CENTRAL AND NORTHEAST NEVADA STILL RECEIVED WELL
BELOW AVERAGE PRECIPITATION AMOUNTS FOR THE MONTH. TAKE OUT SOME
MELT OF THE EXISTING SNOWPACK AND MANY BASINS DROPPED BELOW AVERAGE
AS OF APRIL 1...THOUGH THE HUMBOLDT SYSTEM AND NORTHEAST NEVADA
MAINTAINED ABOVE AVERAGE READINGS. THE SIERRA NEVADA BASINS ALL HAD
BELOW AVERAGE SNOWPACK...ALTHOUGH THE WALKER BASIN AT 96 PERCENT OF
AVERAGE WAS CLOSE. THIS HAS RESULTED IN AVERAGE TO BELOW AVERAGE
FORECASTS FOR WESTERN NEVADA AND THE EASTERN SIERRA AND AVERAGE TO
ABOVE AVERAGE FORECASTS FOR THE REMAINDER OF NEVADA. WHILE WATER
SUPPLY THIS YEAR IS NOTHING TO GET TERRIBLY EXCITED ABOUT...MEETING
THE WATER NEEDS OF OUR STATE SHOULD BE EASIER TO DO THIS YEAR THAN
IT WAS LAST YEAR.
SUMMARY...SPRING FLOOD POTENTIAL...
MOST OF THE NORTHERN TWO THIRDS OF NEVADA AND THE EASTERN SIERRA HAS
HAD AVERAGE TO BELOW AVERAGE PRECIPITATION AND SNOWPACK...ALONG WITH
DRY SOILS AND BELOW AVERAGE RESERVOIR STORAGE CONDITIONS. SO...
FLOOD POTENTIAL FROM SPRING SNOWMELT IS NEAR TO BELOW AVERAGE FOR
THIS AREA. FLOOD POTENTIAL IS BELOW AVERAGE FOR THE SOUTHERN
THIRD OF NEVADA.
2/ SNOWPACK...
APRIL 1 SNOWPACK IN NEVADA AND THE EASTERN SIERRA WAS QUITE
VARIABLE. A FAIRLY DRY MARCH AND SOME EARLY MELT OF THE EXISTING
SNOWPACK CAUSED SNOWPACK VALUES TO DROP QUITE A BIT SINCE MARCH 1.
THE LOWER HUMBOLDT RIVER BASIN HAD THE HIGHEST VALUE AT 120 PERCENT
OF AVERAGE...WHILE THE LOWER COLORADO RIVER BASIN WAS LOWEST AT 81
PERCENT.
PERCENT OF AVERAGE SNOWPACK
BASIN APR 1 2007 APR 1 2008
LAKE TAHOE............................ 43 ................ 89
TRUCKEE RIVER ........................ 50 ................ 86
CARSON RIVER ......................... 37 ................ 82
WALKER RIVER ......................... 41 ................ 96
NORTHERN GREAT ....................... 47 ................ 102
UPPER HUMBOLDT RIVER ................. 51 ................ 105
LOWER HUMBOLDT RIVER ................. 38 ................ 120
CLOVER VALLEY & FRANKLIN RIVER ....... 44 ................ 110
SNAKE RIVER .......................... 49 ................ 108
OWYHEE RIVER ......................... 39 ................ 115
EASTERN NEVADA ....................... 52 ................ 98
LOWER COLORADO RIVER................. 19 ................ 81
3/ PRECIPITATION...
MARCH WAS GENERALLY DRY IN NEVADA AND THE EASTERN SIERRA. IT WAS
ESPECIALLY DRY IN THE SIERRA NEVADA...EASTERN NEVADA AND SOUTHERN
NEVADA. MARCH PRECIPITATION WAS HIGHEST IN THE SNAKE RIVER BASIN AT
87 PERCENT OF AVERAGE AND LOWEST IN THE LOWER COLORADO RIVER BASIN
AT 12 PERCENT. WATER YEAR PRECIPITATION (SINCE OCTOBER 1 2007) WAS
HIGHEST IN THE CLOVER VALLEY AND FRANKLIN RIVER BASIN AT 111 PERCENT
OF AVERAGE AND LOWEST IN THE LOWER COLORADO RIVER BASIN AT 73 PERCENT.
PERCENT OF AVERAGE PRECIPITATION
BASIN MARCH 2008 2008 WATER YEAR
THRU APR 1 2008
UPPER PIT RIVER .................. 30 ................ 78
UPPER FEATHER RIVER .............. 24 ................ 69
LAKE TAHOE ....................... 27 ................ 80
TRUCKEE RIVER .................... 28 ................ 83
CARSON RIVER ..................... 23 ................ 73
WALKER RIVER ..................... 22 ................ 98
NORTHERN GREAT ................... 69 ................ 97
UPPER HUMBOLDT RIVER ............. 71 ................ 103
LOWER HUMBOLDT RIVER ............. 59 ................ 99
CLOVER VALLEY AND FRANKLIN RIVER . 74 ................ 111
SNAKE RIVER ...................... 87 ................ 105
OWYHEE RIVER ..................... 75 ................ 100
EASTERN NEVADA ................... 22 ................ 79
LOWER COLORADO RIVER ............. 12 ................ 73
4/ RESERVOIRS...
END OF MARCH RESERVOIR STORAGE IN NEVADA AND THE EASTERN SIERRA WAS
GENERALLY POOR. ONLY THE TRUCKEE RIVER BASIN WAS NEAR AVERAGE.
RESERVOIR STORAGE WAS HIGHEST IN THE TRUCKEE RIVER BASIN AT 94
PERCENT OF AVERAGE...WHILE THE WALKER RIVER BASIN WAS LOWEST AT 50
PERCENT.
BASIN PERCENT OF PERCENT OF
RESERVOIR CAPACITY AVERAGE STORAGE
AS OF APRIL 1 2008
MIDDLE FORK FEATHER RIVER...... 57 ................ 75
LAKE TAHOE .................... 35 ................ 66
TRUCKEE RIVER ................. 56 ................ 94
CARSON RIVER .................. 41 ................ 55
WALKER RIVER .................. 34 ................ 50
LOWER HUMBOLDT RIVER .......... 33 ................ 58
OWYHEE RIVER .................. 43 ................ 67
LOWER COLORADO RIVER .......... 52 ................ 61
5/ STREAMFLOW...
STREAMFLOW FORECASTS FOR NEVADA AND THE EASTERN SIERRA ARE EXPECTED
TO VARY FROM BELOW TO ABOVE AVERAGE. STREAMFLOW FORECASTS ARE
HIGHEST FOR THE LOWER COLORADO RIVER BASIN AT 120 PERCENT OF AVERAGE
AND LOWEST FOR THE CARSON RIVER BASIN AT 75 PERCENT.
NOTE...FORECASTS BELOW ARE FOR THE MOST PROBABLE OUTCOME...THE BEST
ESTIMATE THAT CAN BE PRODUCED GIVEN CURRENT CONDITIONS. SO...THERE
IS A 50 PERCENT CHANCE THAT ACTUAL STREAMFLOW VOLUME WILL BE LESS
THAN THESE FORECAST VALUES ...AND A 50 PERCENT CHANCE THAT THEY WILL
EXCEED THEM. FORECASTS ARE BASED ON THE OUTCOME OF SIMILAR PAST
SITUATIONS.
PERCENT OF AVERAGE FLOW
MOST PROBABLE FORECAST
BASIN /50 PERCENT CHANCE OF EXCEEDANCE/
PIT RIVER ......................................... 86
FEATHER RIVER ..................................... 76
LAKE TAHOE ........................................ 78
TRUCKEE RIVER ..................................... 80
CARSON RIVER ...................................... 75
WALKER RIVER ...................................... 88
NORTHERN GREAT .................................... 109
UPPER HUMBOLDT RIVER .............................. 101
LOWER HUMBOLDT RIVER .............................. 103
CLOVER VALLEY AND FRANKLIN RIVER .................. 116
SNAKE RIVER ....................................... 98
OWYHEE RIVER ...................................... 105
EASTERN NEVADA .................................... 110
LOWER COLORADO RIVER .............................. 120
6/ SPRING FLOOD POTENTIAL OUTLOOK...
AS OF EARLY APRIL...SNOWPACK AND PRECIPITATION FOR THE SEASON TO
DATE RANGED FROM SOMEWHAT ABOVE TO SOMEWHAT BELOW AVERAGE THROUGHOUT
MOST OF NEVADA AND THE EASTERN SIERRA. RESERVOIR STORAGE REMAINED
BELOW AVERAGE. SOILS BENEATH SNOWPACK WERE RELATIVELY DRY IN MOST
AREAS DUE TO THE DRIER THAN NORMAL FALL...SO A SIGNIFICANT PORTION
OF SPRING SNOWMELT WILL GO INTO WETTING SOILS BEFORE RUNOFF BEGINS.
THE APRIL 1ST 2008 U.S. DROUGHT MONITOR PLACED MOST OF NEVADA AND
THE EASTERN SIERRA IN THE ABNORMALLY DRY TO MODERATE DROUGHT
CATEGORY. HOWEVER...PORTIONS OF NORTHWEST AND CENTRAL NEVADA
REMAINED IN SEVERE DROUGHT.
CONSEQUENTLY...FLOOD POTENTIAL FROM SPRING SNOWMELT IS NEAR TO BELOW
AVERAGE FOR THE NORTHERN TWO-THIRDS OF NEVADA AND THE EASTERN SIERRA
AT THIS TIME. FLOOD POTENTIAL IS BELOW AVERAGE FOR THE SOUTHERN
THIRD OF NEVADA.
UNDER NORMAL SNOWMELT CONDITIONS...RUNOFF SHOULD BE EASILY
CONTROLLED...ESPECIALLY ON THE TAHOE AND TRUCKEE BASINS AND OTHERS
WHICH HAVE PLENTY OF FLOOD CONTROL STORAGE AVAILABLE IN RESERVOIRS.
HOWEVER...HEAVY RAINFALL OR SEVERAL DAYS OF WELL ABOVE AVERAGE
TEMPERATURES DURING THE MELT SEASON COULD RESULT IN LOCALIZED
FLOODING ANYWHERE IN THE REGION UNTIL THE SNOWMELT SEASON ENDS.
MAXIMUM SPRING SNOWMELT ON RIVERS AND STREAMS IN NEVADA AND THE
EASTERN SIERRA TYPICALLY OCCURS IN MAY OR EARLY JUNE. ALTHOUGH
SPRING SNOWMELT FLOODING ON MAINSTEM RIVERS USUALLY ONLY OCCURS
DURING THE SPRING MONTHS IN NEVADA AND THE EASTERN SIERRA...
URBAN...SMALL STREAM AND FLASH FLOODING IS A POSSIBILITY DURING
HEAVY RAIN ANY TIME OF YEAR.
7/ LONG RANGE WEATHER OUTLOOK FOR NEVADA AND THE EASTERN
SIERRA...FOR APRIL...PRECIPITATION IS EXPECTED TO BE NEAR AVERAGE
NORTH OF A LINE FROM MONO LAKE CA TO PIOCHE NV...AND BELOW AVERAGE
SOUTH OF THIS LINE TEMPERATURES ARE EXPECTED TO BE NEAR AVERAGE FOR
THE ENTIRE AREA IN APRIL.
THE LONG RANGE OUTLOOK FOR THE MONTHS OF MAY THROUGH JULY IS FOR
ABOVE NORMAL TEMPERATURES OVER THE ENTIRE REGION. PRECIPITATION IS
EXPECTED TO BE NEAR AVERAGE THROUGHOUT THE AREA...EXCEPT IN THE
EXTREME NORTH...WHICH IS EXPECTED TO BE BELOW AVERAGE.
8/ FOR MORE DETAILED WATER SUPPLY AND STREAMFLOW FORECAST
INFORMATION FOR THE EASTERN SIERRA AND NEVADA...PLEASE REFER TO THE
FOLLOWING WEB SITES...
NWS WESTERN WATER SUPPLY FORECASTS...
http://www.cbrfc.noaa.gov/westernwater/map.php?map=wsup
NWS CALIFORNIA NEVADA RIVER FORECAST CENTER...
http://www.cnrfc.noaa.gov/
NATURAL RESOURCES CONSERVATION SERVICE...
http://www.nv.nrcs.usda.gov/snow/
CALIFORNIA DEPT. OF WATER RESOURCES...
http://cdec.water.ca.gov/
NWS CLIMATE PREDICTION CENTER LONG RANGE OUTLOOK MAPS...
http://www.cpc.ncep.noaa.gov/products/forecasts/
U.S. DROUGHT MONITOR...
http://www.drought.unl.edu/dm/monitor.html