California Drought Monitor

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FGUS75 KREV 082049
ESFREV

ESFREV
NVZ001>037-CAZ070>073-180000-

WATER SUPPLY OUTLOOK
NATIONAL WEATHER SERVICE RENO NV
1153 AM PDT TUE FEB 8 2011

...WATER SUPPLY AND SPRING FLOOD POTENTIAL OUTLOOK FOR NEVADA AND
EASTERN CALIFORNIA AS OF FEBRUARY 8 2011...

ISSUED JOINTLY BY THE NATIONAL WEATHER SERVICE AND NATURAL
RESOURCES CONSERVATION SERVICE...

1/WATER SUPPLY OUTLOOK...SUMMARY...
JANUARY WAS EXCEPTIONALLY DRY.  THIS CAUSED A PRECIPITOUS DECREASE
IN SNOWPACK THROUGHOUT NEVADA AND EASTERN CALIFORNIA. IN EARLY
JANUARY...SNOWPACK WAS NEAR RECORD BREAKING VALUES...NEARLY DOUBLE
AVERAGE IN MANY CASES.  BY EARLY FEBRUARY SNOWPACK HAD DECREASED TO
VALUES THAT ARE SOMEWHAT ABOVE AVERAGE.  FORTUNATELY...THE WET FALL
AND EXTRAORDINARILY SNOWY MONTH OF DECEMBER PROVIDED ENOUGH OF A
CUSHION TO OFFSET THE DRY JANUARY.  THE DRY PATTERN THAT STARTED
AFTER THE NEW YEAR HAS CONTINUED INTO FEBRUARY.  ANOTHER COUPLE
WEEKS OF THIS DRY PATTERN AND MOST OF THE REGION WILL BE BACK TO
AVERAGE SNOWPACK CONDITIONS.

THERE IS HOPE THAT THIS DRY PERIOD IS SIMPLY A PROLONGED PAUSE IN
THE MIDDLE OF WHAT IS TYPICALLY THE SNOWIEST TIME OF THE YEAR AND
NOT A MAJOR GAME CHANGE FOR OUR SPRING RUNOFF.  IT NOW APPEARS THAT
STORMIER CONDITIONS MAY DEVELOP FOR A TIME AFTER ABOUT FEBRUARY
15TH.

GIVEN THE WET CONDITIONS LEADING UP TO THE NEW YEAR AND ALSO
THE CURRENT SNOWPACK VALUES...STREAMFLOW FORECASTS REMAIN ABOVE
AVERAGE FOR MOST OF THE REGION.  IMPROVEMENTS IN RESERVOIR STORAGE
IN MANY BASINS COUPLED WITH THIS PROJECTED ABOVE AVERAGE RUNOFF
SHOULD LEAD TO FEW WATER SHORTAGES THIS UPCOMING SUMMER.  THE NEXT
COUPLE OF MONTHS WILL BRING OUR WATER SUPPLY PICTURE INTO SHARPER
FOCUS.

2/SPRING FLOOD POTENTIAL OUTLOOK...SUMMARY
SPRING FLOOD POTENTIAL IN NEVADA AND EASTERN CALIFORNIA DEPENDS ON
SEVERAL FACTORS...INCLUDING SNOWPACK...SOIL MOISTURE...RESERVOIR
STORAGE...AIR TEMPERATURES DURING MELT AND HOW MUCH RAIN THERE IS
DURING THE MELT PERIOD.

THIS EARLY IN THE SEASON...IT IS STILL DIFFICULT TO DETERMINE MANY
OF THESE FACTORS.  SO...THE SPRING SNOWMELT FLOOD POTENTIAL IS BEING
CLASSIFIED AS AVERAGE...OR EQUAL CHANCES OF IT BEING ABOVE OR BELOW
AVERAGE...IN NEVADA AND EASTERN CALIFORNIA AS OF FEBRUARY 8.

FOLLOWING ARE THE REASONS FOR THIS CLASSIFICATION OF SPRING SNOWMELT
FLOOD POTENTIAL...

SNOWPACK HAS DWINDLED FROM NEAR DOUBLE AVERAGE ON MANY BASINS TO 110
TO 125 PERCENT OF AVERAGE OVER THE PAST MONTH.  IF THE SNOWPACK
CONTINUES TO DECREASE...THERE WILL PROBABLY BE FEW SPRING FLOODING
PROBLEMS.  BUT...IF THERE ARE MORE MAJOR SNOWSTORMS OVER THE NEXT
TWO MONTHS...AND SNOWPACK INCREASES SIGNIFICANTLY...THERE COULD BE
FLOOD PROBLEMS...DEPENDING ON HOW THE SNOW MELTS.

SOIL MOISTURE IN AREAS WITH SNOWPACK IS HIGH DUE TO A VERY WET
FALL.  HOWEVER...IN AREAS WITHOUT SNOWPACK...SOILS HAVE BEEN ABLE TO
DRY OUT DUE TO PROLONGED DRY AND MILDER THAN AVERAGE CONDITIONS.  IF
THERE ARE SIGNIFICANT STORMS OVER THE NEXT TWO MONTHS AND SOILS ARE
AGAIN WET DURING SPRING RUNOFF...THERE COULD BE HIGHER THAN NORMAL
SPRING FLOOD POTENTIAL.  HOWEVER...IF IT REMAINS DRY...POTENTIAL FOR
FLOODING WILL BE LOWER.

RESERVOIR STORAGE AS OF EARLY FEBRUARY...ALL BASINS...WITH THE
EXCEPTION OF THE WALKER...HAVE PLENTY OF RESERVOIR STORAGE REMAINING.
IF RESERVOIRS CONTINUE TO HAVE ABUNDANT STORAGE CAPACITY...CHANCES
FOR SPRING FLOODING WOULD DECREASE.  HOWEVER...IF RESERVOIRS WITHOUT
DEDICATED FLOOD CONTROL SPACE ARE ALLOWED TO FILL BEFORE MOST OF THE
SNOW HAS MELTED...THIS WOULD INCREASE CHANCES FOR SPRING FLOODING.

AIR TEMPERATURES DURING MELT...UNKNOWN AT THIS TIME.  IF
TEMPERATURES REMAIN RELATIVELY COOL DURING THE MELT PERIOD...MELT
WOULD BE SLOW AND OCCUR OVER A LONG PERIOD.  THIS WOULD DECREASE
FLOOD POTENTIAL.  IF MELT OCCURS VERY QUICKLY DUE TO A SUDDEN
WARMUP...THIS WOULD INCREASE FLOOD POTENTIAL.

RAINFALL DURING MELT...UNKNOWN AT THIS TIME.  HEAVY RAIN ON SNOW
COULD RESULT IN MAJOR FLOODING ANYTIME FROM NOW THROUGH LATE
SPRING.  HOWEVER...LITTLE OR NO RAIN DURING THE MELT PERIOD
TYPICALLY RESULTS IN ONLY MINOR TO POSSIBLY MODERATE
FLOODING...DEPENDING ON THE AMOUNT OF SNOWPACK.

3/SNOWPACK AS OF FEBRUARY 1...
FEBRUARY 1 SNOWPACK CONDITIONS FOR NEVADA AND EASTERN CALIFORNIA
REMAINED AT RESPECTABLE LEVELS...BUT DECLINED DRASTICALLY FROM THEIR
JANUARY 1 READINGS...DROPPING BY AS MUCH AS 100 PERCENTAGE POINTS
FOR SOME BASINS DURING THE MONTH.  THE HIGHEST SNOWPACK VALUE WAS IN
EASTERN NEVADA AT 151 PERCENT OF AVERAGE...WHILE THE OWYHEE RIVER
BASIN WAS LOWEST AT 96 PERCENT.

                              LAST YEAR           THIS YEAR
BASIN                    PERCENT OF AVERAGE   PERCENT OF AVERAGE
LAKE TAHOE ....................  99 ................ 136
TRUCKEE RIVER .................  99 ................ 124
CARSON RIVER .................. 108 ................ 124
WALKER RIVER .................. 104 ................ 138
NORTHERN GREAT ................  92 ................ 113
UPPER HUMBOLDT RIVER ..........  74 ................ 117
LOWER HUMBOLDT RIVER ..........  73 ................ 116
CLOVER VALLEY & FRANKLIN RIVER   71 ................ 103
SNAKE RIVER ...................  64 ................ 120
OWYHEE RIVER ..................  89 ................  96
EASTERN NEVADA ................ 116 ................ 151

3/PRECIPITATION AS OF FEBRUARY 1...
PRECIPITATION FOR NEVADA AND EASTERN CALIFORNIA WAS A BUST IN
JANUARY... ESPECIALLY IN SOUTHERN NEVADA.  2011 WATER YEAR
PRECIPITATION...WHICH BEGAN OCTOBER 1...CONTINUES TO RUN WELL ABOVE
AVERAGE FOR THE ENTIRE REGION DUE TO THE VERY WET CONDITIONS LEADING
UP TO THE NEW YEAR.  JANUARY PRECIPITATION WAS HIGHEST IN THE SNAKE
RIVER BASIN AT 71 PERCENT OF AVERAGE AND THE LOWEST IN THE LOWER
COLORADO RIVER BASIN AT JUST 2 PERCENT.  AS OF FEBRUARY 1...WATER
YEAR PRECIPITATION WAS HIGHEST IN THE LOWER COLORADO RIVER BASIN AT
208 PERCENT OF AVERAGE AND THE LOWEST IN THE OWYHEE RIVER BASIN AT
134 PERCENT.
   JANUARY 2011       2011 WATER YEAR
BASIN                         PERCENT OF AVERAGE   PERCENT OF AVERAGE
LAKE TAHOE .........................  22 ................ 155
TRUCKEE RIVER ......................  15 ................ 148
CARSON RIVER .......................  24 ................ 145
WALKER RIVER .......................  29 ................ 163
NORTHERN GREAT .....................  39 ................ 141
UPPER HUMBOLDT RIVER ...............  35 ................ 159
LOWER HUMBOLDT RIVER ...............  34 ................ 146
CLOVER VALLEY AND FRANKLIN RIVER ...  50 ................ 155
SNAKE RIVER ........................  71 ................ 141
OWYHEE RIVER .......................  49 ................ 134
EASTERN NEVADA .....................  21 ................ 200
LOWER COLORADO RIVER ...............   2 ................ 208

4/RESERVOIRS AS OF FEBRUARY 1...
RESERVOIR STORAGE IN NEVADA AND EASTERN CALIFORNIA HAS SEEN
SIGNIFICANT GAINS THIS YEAR.  RESERVOIR STORAGE WAS HIGHEST FOR THE
WALKER RIVER BASIN AT 162 PERCENT OF AVERAGE.  THE LOWER HUMBOLDT
RIVER BASIN WAS LOWEST AT 27 PERCENT.

BASIN                        PERCENT OF CAPACITY   PERCENT OF AVERAGE
LAKE TAHOE ........................  26 ................  53
TRUCKEE RIVER .....................  60 ................ 111
CARSON RIVER ......................  40 ................  67
WALKER RIVER ......................  81 ................ 162
LOWER HUMBOLDT RIVER ..............  13 ................  27
OWYHEE RIVER ......................  45 ................  82
LOWER COLORADO RIVER ..............  44 ................  53

5/STREAMFLOW FORECASTS...
APRIL TO JULY STREAMFLOW FOR NEVADA AND EASTERN CALIFORNIA IS
EXPECTED TO BE ABOVE AVERAGE.  STREAMFLOW FORECASTS ARE HIGHEST FOR
EASTERN NEVADA AT 162 PERCENT OF AVERAGE AND LOWEST FOR THE OWYHEE
RIVER BASIN AT 105 PERCENT OF AVERAGE.

                                 PERCENT OF AVERAGE STREAMFLOW
                                        APRIL TO JULY 2011
BASIN                             50 PERCENT CHANCE OF EXCEEDANCE
LAKE TAHOE ................................... 113
TRUCKEE RIVER ................................ 117
CARSON RIVER ................................. 135
WALKER RIVER ................................. 133
NORTHERN GREAT ............................... 124
UPPER HUMBOLDT RIVER ......................... 132
LOWER HUMBOLDT RIVER ......................... 125
CLOVER VALLEY AND FRANKLIN RIVER ............. 130
SNAKE RIVER .................................. 125
OWYHEE RIVER ................................. 105
EASTERN NEVADA ............................... 162
LOWER COLORADO RIVER ......................... 119

6/ LONG RANGE WEATHER OUTLOOK FOR NEVADA AND EASTERN CALIFORNIA...
FEBRUARY PRECIPITATION IS EXPECTED TO BE BELOW NORMAL SOUTH OF A
LINE FROM ABOUT DEATH VALLEY CA TO CALIENTE NV. IT IS EXPECTED TO BE
ABOVE NORMAL NORTH OF A LINE FROM ABOUT ALTURAS CA TO WELLS NV.
PRECIPITATION IS EXPECTED TO BE NEAR NORMAL IN THE REST OF THE
REGION.  FEBRUARY TEMPERATURES ARE EXPECTED TO BE BELOW NORMAL WEST
OF A LINE FROM ABOUT WELLS TO AUSTIN TO DEATH VALLEY...AND NEAR
NORMAL EAST OF THIS LINE.

THE LONG RANGE OUTLOOK FOR THE MONTHS OF MARCH THROUGH MAY IS FOR
BELOW NORMAL PRECIPITATION SOUTH OF A LINE FROM ABOUT BRIDGEPORT CA
TO ELY NV...WITH NEAR NORMAL PRECIPITATION EXPECTED NORTH OF THIS
LINE.  ABOVE NORMAL TEMPERATURES ARE EXPECTED IN SOUTHERN AND
EASTERN NEVADA...WHILE IN NORTHEAST CALIFORNIA AND EXTREME NORTHWEST
NEVADA TEMPERATURES ARE EXPECTED TO BE BELOW NORMAL. MOST OF CENTRAL
NEVADA IS EXPECTED TO HAVE NEAR NORMAL TEMPERATURES DURING THIS
PERIOD.

7/ FOR MORE DETAILED WATER SUPPLY AND STREAMFLOW FORECAST
INFORMATION FOR NEVADA AND EASTERN CALIFORNIA...PLEASE REFER TO THE
FOLLOWING WEB SITES /NOTE...ALL LETTERS IN WEB SITE ADDRESSES ARE
LOWER CASE/...

NWS CALIFORNIA NEVADA RIVER FORECAST CENTER...
HTTP://WWW.CNRFC.NOAA.GOV/

NATURAL RESOURCES CONSERVATION SERVICE...
HTTP://WWW.NV.NRCS.USDA.GOV/SNOW/INDEX.HTML

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 PORTAL...INCLUDING U.S. DROUGHT MONITOR...
HTTP://DROUGHT.GOV/

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