HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE PORTLAND OR
1110 AM PDT TUE APR 11 2006
...OREGON WATER SUPPLY AND SPRING FLOOD POTENTIAL OUTLOOK AS OF
APRIL 11TH 2006...
THE OUTLOOK FOR THE SPRING AND SUMMER CALLS FOR ABOVE-NORMAL WATER
SUPPLY IN MOST OREGON RIVER BASINS...EXCEPT FOR NEAR-NORMAL WATER
SUPPLY IN NORTHWEST OREGON...BASED ON CURRENT CONDITIONS AND
EXPECTED PRECIPITATION AND TEMPERATURES THROUGH THE REMAINDER OF THE
WINTER AND SPRING. THE SPRING FLOOD POTENTIAL IS MODERATE FOR
SEVERAL RIVERS IN CENTRAL AND EASTERN OREGON DUE TO THE ABOVE-NORMAL
SNOWPACK...WITH SOME FLOODING IN EASTERN OREGON HAVING ALREADY
OCCURRED THIS SPRING DUE TO SNOWMELT AND RAINFALL. REFER TO THE LAST
SECTION OF THIS PRODUCT FOR SPRING SNOWMELT PEAK FORECASTS.
MARCH PRECIPITATION WAS NEAR TO ABOVE NORMAL IN NORTHEAST OREGON...
NEAR NORMAL IN NORTHWEST OREGON...AND BELOW NORMAL IN SOUTHERN
OREGON. SEASONAL PRECIPITATION REMAINS ABOVE NORMAL IN ALL BASINS.
SNOWPACK IS MUCH ABOVE NORMAL IN THE SOUTHERN OREGON CASCADES AND
OCHOCO MOUNTAINS AND NEAR NORMAL IN THE NORTHERN OREGON CASCADES AND
BLUE MOUNTAINS. NOAA'S OUTLOOK FOR THE REST OF THE SPRING LEANS
TOWARD ABOVE-NORMAL TEMPERATURES AND INDICATES EQUAL CHANCES OF
NORMAL...ABOVE-NORMAL...OR BELOW-NORMAL PRECIPITATION. FOR THE
SUMMER...THE OUTLOOK IS FOR AN ENHANCED PROBABILITY OF BELOW-NORMAL
PRECIPITATION AND ABOVE-NORMAL TEMPERATURES. FOR MORE INFORMATION...
VISIT THE CLIMATE PREDICTION CENTER WEB PAGE AT...
http://www.cpc.ncep.noaa.gov/
THE NEXT UPDATE TO THIS OUTLOOK WILL BE ISSUED BY MAY 11TH.
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...SNOWPACK ACROSS OREGON...
MOUNTAIN SNOWPACK AS OF APRIL 1ST WAS ABOVE NORMAL IN ALL OREGON
BASINS...RANGING FROM 112 TO 164 PERCENT OF NORMAL. THIS TIME LAST
YEAR...SNOWPACK WAS ONLY 25 TO 75 PERCENT OF NORMAL. MOST SNOTEL
SITES ABOVE 5000 FEET HAVE CONTINUED TO ACCUMULATE SNOW INTO EARLY
APRIL. THE TABLE BELOW SHOWS THE SNOWPACK PERCENT OF NORMAL AS OF
APRIL 1ST AND THE CHANGE FROM MARCH 1ST.
LOCATION PCT OF NORMAL CHANGE
...CENTRAL AND EASTERN OREGON...
KLAMATH BASIN 164 +20
LAKE COUNTY/GOOSE LAKE BASINS 143 +19
HARNEY COUNTY BASINS 137 +18
OWYHEE AND MALHEUR BASINS 154 +27
GRANDE RONDE...POWDER...BURNT AND IMNAHA 119 +7
UMATILLA...WALLA WALLA...WILLOW...ROCK... 112 +5
AND LOWER JOHN DAY BASINS
UPPER JOHN DAY BASIN 146 +16
UPPER DESCHUTES AND CROOKED BASINS 149 +11
LOWER DESCHUTES AND HOOD BASINS 126 +10
...WESTERN OREGON...
SANDY BASIN 128 +13
WILLAMETTE BASIN 123 +16
ROGUE AND UMPQUA BASINS 162 +39
===================================================================
...PRECIPITATION ACROSS OREGON...
MARCH PRECIPITATION WAS GENERALLY NEAR NORMAL ACROSS OREGON...WITH
SOME ABOVE-NORMAL AMOUNTS IN EAST-CENTRAL OREGON AND BELOW-NORMAL
AMOUNTS IN SOUTHERN OREGON. SEASONAL PRECIPITATION REMAINS ABOVE
NORMAL IN ALL BASINS...RANGING FROM 108 TO 155 PERCENT OF NORMAL.
THE TABLE BELOW SHOWS PRECIPITATION TOTALS IN TERMS OF PERCENT OF
NORMAL FOR MARCH AND FOR THE 2006 WATER YEAR THROUGH MARCH...ALONG
WITH THE CHANGE IN SEASONAL PERCENT OF NORMAL FROM THE PREVIOUS
MONTH.
BASIN PERCENT OF AVG FOR MAR OCT-MAR CHANGE
...CENTRAL AND EASTERN OREGON...
KLAMATH (OREGON ONLY) 76 151 -14
LAKE COUNTY/GOOSE LAKE 70 139 -14
HARNEY/MALHEUR BASIN 84 149 -15
OWYHEE/MALHEUR 110 143 -7
GRANDE RONDE/BURNT 86 108 -4
UMATILLA/LOWER JOHN DAY 118 125 -1
UPPER JOHN DAY 121 137 -4
UPPER DESCHUTES/CROOKED 107 155 -8
HOOD/LOWER DESCHUTES 81 119 -5
...WESTERN OREGON...
WILLAMETTE VALLEY 81 115 -6
ROGUE/UMPQUA 112 150 -7
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...MAJOR IRRIGATION RESERVOIRS...
AT THE CLOSE OF MARCH...2,322,000 ACRE-FEET OF WATER WAS STORED
IN 27 MAJOR IRRIGATION RESERVOIRS IN OREGON. THE CURRENT STORAGE
REPRESENTS 93 PERCENT OF AVERAGE...AND IS 71 PERCENT OF THEIR
HOLDING CAPACITY. THE CURRENT STORAGE IS 140 PERCENT OF STORAGE FOR
THIS SAME TIME LAST YEAR. RESERVOIR DATA IS PROVIDED COURTESY OF THE
NATURAL RESOURCES CONSERVATION SERVICE AND THE CORPS OF ENGINEERS.
==================================================================
...CURRENT AND FORECAST STREAMFLOW...
OBSERVED STREAMFLOW IN FEBRUARY WAS ABOVE NORMAL ACROSS MOST OF THE
STATE WITH SOME MINOR FLOODING IN SOME EASTERN AND SOUTHERN OREGON
BASINS DUE TO RAINFALL AND SOME SNOWMELT. IN NORTHWEST OREGON...
STREAMFLOW WAS NEAR TO A LITTLE BELOW NORMAL.
FORECAST STREAMFLOW VOLUMES FOR THE SPRING AND SUMMER REMAIN AT OR
ABOVE NORMAL FOR ALL OREGON BASINS. THE FORECAST FOR THE COLUMBIA
RIVER AT THE DALLES IS 100% OF AVERAGE AND REFLECTS CONDITIONS
ACROSS THE COLUMBIA BASIN. FORECASTS FOR BASINS IN SOUTHEAST AND
SOUTH-CENTRAL OREGON WERE INCREASED SIGNIFICANTLY DUE TO CONTINUED
ABOVE-NORMAL SNOW ACCUMULATION THROUGH THE END OF MARCH.
THE FOLLOWING TABLE SUMMARIZES THE FORECASTS FOR SELECTED
RIVERS...UPDATED APRIL 7TH. THESE FORECASTS ARE BASED ON OBSERVED
PRECIPITATION AND SNOWPACK AND ASSUME NORMAL PRECIPITATION FOR THE
REMAINDER OF THE FORECAST PERIOD.
W A T E R S U P P L Y F O R E C A S T S
...FORECAST AND AVERAGE ARE IN THOUSANDS OF ACRE-FEET...
...'%' IS PERCENT OF AVERAGE BASED ON 1971 - 2000 NORMALS...
...'CHANGE' IS THE PERCENT OF NORMAL CHANGE FROM THE APR 7TH FCST...
STREAM AND STATION PERIOD FORECAST % AVERAGE CHANGE
COLUMBIA RIVER
THE DALLES JAN-JUL 107000.0 100 107300. 0
OWYHEE RIVER
OWYHEE RES INFLOW MAR-JUL 960.0 157 613. +38
MALHEUR RIVER
NEAR DREWSEY MAR-JUL 230.0 209 110. +65
N.F. MALHEUR RIVER
BEULAH RES INFLOW MAR-JUL 163.0 201 81. +65
BURNT RIVER
NEAR HEREFORD MAR-JUL 90.0 176 51. +43
POWDER RIVER
NEAR SUMPTER MAR-JUL 133.0 190 70. +70
IMNAHA RIVER
IMNAHA MAR-JUL 340.0 113 301. +7
GRANDE RONDE RIVER
LA GRANDE MAR-JUL 220.0 88 249. -6
TROY MAR-JUL 1680.0 106 1578. +3
UMATILLA RIVER
NEAR GIBBON APR-JUL 78.0 107 73. 0
PENDLETON APR-JUL 151.0 101 149. +1
S.F. WALLA WALLA RIVER
NEAR MILTON APR-JUL 59.0 111 53. +2
M.F. JOHN DAY RIVER
RITTER APR-JUL 153.0 124 123. +9
N.F. JOHN DAY RIVER
NEAR MONUMENT MAR-JUL 715.0 120 597. +9
JOHN DAY RIVER
SERVICE CREEK MAR-SEP 1340.0 116 865. -5
DESCHUTES RIVER
BENHAM FALLS APR-SEP 590.0 112 528. +2
CROOKED RIVER
PRINEVILLE RES INFLOW MAR-JUL 260.0 141 184. -11
OCHOCO CREEK
OCHOCO RES INFLOW MAR-JUL 50.0 139 35. 0
MCKENZIE RIVER
NEAR VIDA APR-SEP 1230.0 102 1300. -2
S. SANTIAM RIVER
WATERLOO APR-SEP 590.0 101 587. 0
N. SANTIAM RIVER
MEHAMA APR-SEP 810.0 97 834. -1
WILLAMETTE RIVER
SALEM APR-SEP 4850.0 101 4804. -2
CLACKAMAS RIVER
ESTACADA APR-SEP 880.0 118 748. +10
N. UMPQUA RIVER
LEMOLO LK INFLOW APR-SEP 185.0 123 151. +5
ROGUE RIVER
RAYGOLD APR-SEP 1160.0 130 889. +9
CHEWAUCAN RIVER
NEAR PAISLEY MAR-JUL 135.0 152 89. +12
SILVIES RIVER
NEAR BURNS APR-SEP 175.0 177 99. +30
WILLIAMSON RIVER
BELOW SPRAGUE APR-SEP 610.0 158 385. +19
SPRAGUE RIVER,
NEAR CHILOQUIN APR-SEP 390.0 170 230. +29
KLAMATH RIVER
UPPER LAKE INFLOW APR-SEP 820.0 159 515. +19
THESE FORECASTS ARE SELECTED FROM THOSE PREPARED BY: NATIONAL
WEATHER SERVICE, NATURAL RESOURCE CONSERVATION SERVICE, AND B.C.
HYDRO AND POWER AUTHORITY. FOR VARIOUS PROJECT INFLOWS, THE
FORECASTS HAVE BEEN COORDINATED WITH THE U.S. ARMY CORP OF ENGINEERS
AND THE U.S. BUREAU OF RECLAMATION. FOR FURTHER DETAILS VISIT...
http://www.nwrfc.noaa.gov/water_supply/water_supply.cgi
AND
http://www.cnrfc.noaa.gov/water_supply.php
==================================================================
...SPRING FLOOD POTENTIAL AND PEAK FLOW FORECASTS...
CONTINUED SPRING SNOWMELT FLOODING IS LIKELY FOR SEVERAL RIVERS IN
CENTRAL AND EASTERN OREGON DUE TO THE ABOVE-NORMAL SNOWPACK...
ESPECIALLY IN BASINS WHERE ADDITIONAL RAINFALL OCCURS. FLOODING OF
WESTERN OREGON RIVERS IN APRIL OR MAY WOULD ONLY BE CAUSED BY A
COMBINATION OF PROLONGED HEAVY RAIN AND SNOWMELT AND IS UNLIKELY.
THE TABLE BELOW SHOWS FORECAST PEAK STAGE AND FLOW FOR SEVERAL
RIVERS IN OREGON. FORECASTS INCLUDE THE MOST PROBABLE ('MID') AND
VALUES MINUS ('LOW') AND PLUS ('HIGH') ONE STANDARD DEVIATION. THESE
FORECASTS ARE PROVIDED BY THE NOAA/NWS NORTHWEST RIVER FORECAST
CENTER AND WERE UPDATED APRIL 8TH.
STAGE IN FEET FLOW IN KCFS
FLOOD ------------------- -------------------
STAGE LOW MID HIGH LOW MID HIGH
MALHEUR R NR VALE
9.5 6.3 8.3 10.3 1.6 2.6 3.6
IMNAHA R AT IMNAHA
5.5 4.7 5.5 6.4 2.5 3.8 5.1
GRANDE RONDE R AT LAGRANDE
10.0 6.5 8.1 9.6 2.4 4.4 6.4
GRANDE RONDE R AT TROY
10.0 7.8 8.4 9.0 10.6 13.2 15.8
UMATILLA R AT PENDLETON (FLOOD FLOW IS 6.6 KCFS)
5.7 6.1 6.4 2.2 3.0 3.7
JOHN DAY R AT SERVICE CREEK
11.5 9.5 10.5 11.5 11.7 14.7 17.7
WILLAMETTE R AT PORTLAND
18.0 8.5 11.5 14.5
BRYANT