938
FGUS75 KREV 072249
ESFREV
TTAA00 KRNO DDHHMM
NVZ001>037-CAZ070>073-200000-
HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE RENO NV
345 PM PDT WED MAY 7 2008
...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...
MUCH OF NEVADA AND THE EASTERN SIERRA ENDED THE SNOW YEAR ON
A VERY DRY NOTE. MARCH AND APRIL 2008 WAS ONE OF THE DRIEST
MARCH-APRIL PERIODS IN THE LAST 100 YEARS IN WESTERN NEVADA AND THE
EASTERN SIERRA. WHILE NORTHEAST NEVADA MANAGED TO END THE SEASON
WITH AVERAGE TO ABOVE AVERAGE CONDITIONS...STREAMFLOW IS EXPECTED TO
REMAIN LOW THIS SPRING AND SUMMER ACROSS MOST OF THE REGION. THE
EXCEPTIONS WILL BE THE NORTHEAST CORNER OF NEVADA...THE EAST SIDE OF
THE RUBY MOUNTAINS AND THE LOWER COLORADO RIVER BASIN. WHILE OUR
AREA IS IN MUCH BETTER SHAPE THAN LAST YEAR...A SECOND DRY SEASON IS
NOT WHAT WE NEEDED. AFTER TAPPING INTO RESERVOIRS LAST SUMMER...
MANY BASINS CURRENTLY HAVE LOW RESERVOIR STORAGE AS WE COME INTO THE
PEAK WATER USE PERIOD OF THE YEAR. MEETING ALL WATER DEMANDS WILL
BE MUCH HARDER TO DO THIS YEAR THAN LAST YEAR FOR MANY AREAS. THE
MUCH NEEDED MIRACLE MARCH OR AWESOME APRIL FAILED TO MATERIALIZE...
SO WE ARE BACK TO STRUGGLING THROUGH ONE MORE DRY SUMMER.
SUMMARY...SPRING FLOOD POTENTIAL...
MUCH OF EXTREME NORTHEASTERN AND EASTERN NEVADA...INCLUDING THE
SNAKE...OWYHEE...CLOVER AND FRANKLIN RIVER BASINS...HAVE AVERAGE
SPRING SNOWMELT FLOOD POTENTIAL CONDITIONS DUE TO NEAR TO ABOVE
NORMAL MAY 1ST SNOWPACK AND NEAR NORMAL PRECIPITATION FOR THE
SEASON. THE REMAINDER OF NEVADA AND THE EASTERN SIERRA HAS BELOW
AVERAGE SPRING SNOWMELT FLOOD POTENTIAL CONDITIONS DUE TO BELOW
NORMAL SNOWPACK...PRECIPITATION...DRY SOILS AND LOW RESERVOIRS.
2/ SNOWPACK...
MAY 1 SNOWPACK CONDITIONS FOR NEVADA AND THE EASTERN SIERRA WERE
WELL BELOW AVERAGE IN THE SIERRA NEVADA BASINS AND AVERAGE TO ABOVE
AVERAGE FOR MOST OF THE REST OF NEVADA. THE BOTTOM FELL OUT OF
WESTERN NEVADA AND EASTERN SIERRA SNOWPACK IN APRIL...WHILE CENTRAL
AND NORTHERN NEVADA HAVE MANAGED TO MAINTAIN THEIR SNOWPACKS INTO
EARLY MAY. THE CLOVER VALLEY AND FRANKLIN RIVER BASIN HAD THE
HIGHEST VALUE AT 144 PERCENT OF AVERAGE...WHILE BOTH THE LAKE TAHOE
AND CARSON RIVER BASINS HAD THE LOWEST VALUES AT 56 PERCENT OF
AVERAGE EACH.
PERCENT OF AVERAGE SNOWPACK
BASIN MAY 1 2007 MAY 1 2008
LAKE TAHOE .......................... 15 ................ 56
TRUCKEE RIVER........................ 34 ................ 57
CARSON RIVER ........................ 18 ................ 56
WALKER RIVER ........................ 40 ................ 75
NORTHERN GREAT ...................... 20 ................ 93
UPPER HUMBOLDT RIVER ................ 21 ................ 102
LOWER HUMBOLDT RIVER ................ 37 ................ 92
CLOVER VALLEY & FRANKLIN RIVER ...... 0 ................ 144
SNAKE RIVER ......................... 70 ................ 114
OWYHEE RIVER ........................ 6 ................ 106
EASTERN NEVADA ...................... 55 ................ 59
3/ PRECIPITATION...
APRIL WAS VERY DRY IN NEVADA AND EASTERN CALIFORNIA. MARCH AND
APRIL 2008 WAS ONE OF THE DRIEST MARCH-APRIL PERIODS IN THE LAST 100
YEARS IN WESTERN NEVADA AND THE EASTERN SIERRA. THE EXCEPTION IN
APRIL WAS THE NORTHEAST CORNER OF NEVADA WHICH HAD AVERAGE
PRECIPITATION. THERE IS QUITE A PRECIPITATION DEFICIT ACROSS MUCH
OF THE REGION. MUCH OF SOUTHERN...WESTERN AND NORTHWESTERN NEVADA
ARE IN MODERATE TO SEVERE DROUGHT CATEGORIES...AS CLASSIFIED BY THE
U.S. DROUGHT MONITOR /ONLINE AT
HTTP://WWW.DROUGHT.UNL.EDU/DM/MONITOR.HTML/ APRIL PRECIPITATION
WAS HIGHEST IN THE OWYHEE RIVER BASIN AT 105 PERCENT OF AVERAGE AND
LOWEST IN THE LOWER COLORADO RIVER BASIN AT 0 PERCENT OF AVERAGE.
WATER YEAR PRECIPITATION THROUGH APRIL WAS HIGHEST IN THE CLOVER
VALLEY AND FRANKLIN RIVER BASIN AT 106 PERCENT OF AVERAGE AND LOWEST
IN THE LOWER COLORADO RIVER BASIN AT 51 PERCENT OF AVERAGE.
PERCENT OF AVERAGE PRECIPITATION
BASIN APRIL 2008 2008 WATER YEAR
THRU MAY 1 2008
UPPER PIT RIVER ................. 34 ................ 73
UPPER FEATHER RIVER ............. 9 ................ 70
LAKE TAHOE ...................... 15 ................ 75
TRUCKEE RIVER ................... 14 ................ 78
CARSON RIVER .................... 13 ................ 67
WALKER RIVER .................... 13 ................ 91
NORTHERN GREAT .................. 57 ................ 92
UPPER HUMBOLDT RIVER ............ 60 ................ 97
LOWER HUMBOLDT RIVER ............ 52 ................ 92
CLOVER VALLEY AND FRANKLIN RIVER . 77 ................ 106
SNAKE RIVER ...................... 95 ................ 103
OWYHEE RIVER .................... 105 ................ 100
EASTERN NEVADA .................. 14 ................ 68
LOWER COLORADO RIVER .............. 0 ................ 51
4/ RESERVOIRS...
RESERVOIR STORAGE IN NEVADA AND EASTERN CALIFORNIA WAS AVERAGE TO
WELL BELOW AVERAGE ON MAY 1ST. RESERVOIR STORAGE WAS THE HIGHEST IN
THE TRUCKEE RIVER BASIN AT 93 PERCENT OF AVERAGE...WHILE THE LOWER
HUMBOLDT RIVER BASIN WAS LOWEST AT 44 PERCENT OF AVERAGE.
BASIN PERCENT OF PERCENT OF
RESERVOIR CAPACITY AVERAGE STORAGE
AS OF MAY 1 2008
MIDDLE FORK FEATHER RIVER...... 61 ................ 76
LAKE TAHOE ................... 34 ................ 63
TRUCKEE RIVER ................ 60 ................ 93
CARSON RIVER ................. 36 ................ 48
WALKER RIVER ................. 33 ................ 48
LOWER HUMBOLDT RIVER ......... 27 ................ 44
OWYHEE RIVER ................. 56 ................ 72
LOWER COLORADO RIVER ......... 50 ................ 60
5/ STREAMFLOW...
STREAMFLOW FORECASTS FOR NEVADA AND EASTERN CALIFORNIA ARE EXPECTED
TO RANGE FROM WELL BELOW AVERAGE FOR WESTERN NEVADA TO SLIGHTLY
ABOVE AVERAGE FOR NORTHEASTERN AND SOUTHERN NEVADA. STREAMFLOW
FORECASTS ARE HIGHEST FOR THE LOWER COLORADO RIVER BASIN AT
115 PERCENT OF AVERAGE. THE LOWEST EXPECTED FLOWS ARE IN THE
CARSON RIVER BASIN AT 51 PERCENT OF AVERAGE.
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 ......................................... 70
FEATHER RIVER ..................................... 60
LAKE TAHOE ........................................ 56
TRUCKEE RIVER ..................................... 67
CARSON RIVER ...................................... 51
WALKER RIVER ...................................... 78
NORTHERN GREAT .................................... 90
UPPER HUMBOLDT RIVER .............................. 77
LOWER HUMBOLDT RIVER .............................. 71
CLOVER VALLEY AND FRANKLIN RIVER .................. 104
SNAKE RIVER ....................................... 98
OWYHEE RIVER ...................................... 95
EASTERN NEVADA .................................... 97
LOWER COLORADO RIVER .............................. 115
6/ SPRING FLOOD POTENTIAL OUTLOOK...
MUCH OF EXTREME NORTHEASTERN AND EASTERN NEVADA...INCLUDING THE
SNAKE...OWYHEE...CLOVER AND FRANKLIN RIVER BASINS...HAVE AVERAGE
SPRING SNOWMELT FLOOD POTENTIAL CONDITIONS DUE TO NEAR TO ABOVE
NORMAL MAY 1ST SNOWPACK AND NEAR NORMAL PRECIPITATION FOR THE
SEASON. THE REMAINDER OF NEVADA AND THE EASTERN SIERRA HAS BELOW
AVERAGE SPRING SNOWMELT FLOOD POTENTIAL CONDITIONS DUE TO BELOW
NORMAL SNOWPACK...PRECIPITATION...DRY SOILS AND LOW RESERVOIRS.
7/ LONG RANGE WEATHER OUTLOOK FOR NEVADA AND THE EASTERN
SIERRA...FOR MAY...PRECIPITATION IS EXPECTED TO BE NEAR AVERAGE OVER
THE ENTIRE REGION...EXCEPT FOR EXTREME NORTHWEST NEVADA...WHICH IS
EXPECTED TO BE SOMEWHAT DRIER THAN AVERAGE. TEMPERATURES ARE
EXPECTED TO BE SLIGHTLY BELOW AVERAGE NORTH OF A LINE FROM
SUSANVILLE CA TO WELLS NV...AND NEAR AVERAGE SOUTH OF THIS LINE.
THE LONG RANGE OUTLOOK FOR THE MONTHS OF JUNE THROUGH AUGUST IS FOR
WELL ABOVE NORMAL TEMPERATURES OVER THE ENTIRE REGION. PRECIPITATION
IS EXPECTED TO BE BELOW AVERAGE NORTH OF A LINE FROM BISHOP CA TO
PIOCHE NV...AND NEAR AVERAGE SOUTH OF THIS LINE.
8/ FOR MORE DETAILED WATER SUPPLY AND STREAMFLOW FORECAST
INFORMATION FOR THE EASTERN SIERRA AND NEVADA...
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/
NNNN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page