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WATER SUPPLY OUTLOOK  
NATIONAL WEATHER SERVICE PORTLAND OR  
300 PM PST TUESDAY MAY 10 2022  
   
..OREGON WATER SUPPLY SUMMARY AS OF MAY 10TH 2022
 
 
THE WATER SUPPLY FORECAST FOR THE SPRING AND SUMMER OF 2022 IS BELOW  
AVERAGE FOR SOUTHWEST, CENTRAL, AND EASTERN OREGON. FORECASTS FOR  
NORTHWEST, WEST-CENTRAL, AND NORTHEAST OREGON ARE NEAR OR ABOVE  
AVERAGE. MOST OF THE AREAS PROJECTED TO BE BELOW AVERAGE ARE ALREADY  
STRESSED DUE TO DROUGHT CONDITIONS FOR MUCH OF THE PAST 2 YEARS.  
 
PRECIPITATION SO FAR THIS WATER YEAR (OCTOBER 1, 2021 TO PRESENT) IS  
BELOW AVERAGE FOR MOST OF OREGON, EXCEPT NEAR TO ABOVE AVERAGE FOR  
NORTHWEST OREGON AND THE MOUNTAINS OF NORTHEAST OREGON. SEASONAL  
PRECIPITATION IS PARTICULARLY LOW RELATIVE TO AVERAGE FOR CENTRAL  
AND SOUTHEAST OREGON. MOUNTAIN SNOWPACK WAS MOSTLY UNCHANGED FROM  
MID JANUARY THROUGH MARCH, BUT SNOWPACK INCREASED IN THE CASCADES  
AND BLUE MOUNTAINS IN APRIL. AS OF EARLY MAY, MANY LOWER ELEVATON  
SNOW-MONITORING STATIONS HAVE COMPLETELY MELTED OUT, BUT MANY HIGHER  
ELEVATION STATIONS HAVE CONTINUED TO ACCUMULATE SNOW AND REMAIN NEAR  
OR ABOVE AVERAGE.  
 
DESPITE THE RECENT WET CONDITIONS, SEASONAL DEFICITS REMAIN FOR LONG-  
TERM PRECIPITATION, SNOWPACK, SOIL MOISTURE, AND RESERVOIR STORAGE,  
ESPECIALLY FOR THE SOUTHERN HALF OF OREGON. THE FOLLOWING COUNTIES  
ALREADY HAVE RECEIVED DROUGHT DECLARATIONS FROM THE GOVERNOR'S  
OFFICE: CROOK, DESCHUTES, GILLIAM, GRANT, HARNEY, JACKSON,  
JEFFERSON, KLAMATH, LAKE, MALHEUR AND MORROW. ADDITIONAL COUNTIES  
ARE LIKELY TO REQUEST DROUGHT DECLARATIONS THIS SPRING.  
 
REFER TO THE SECTIONS BELOW AND LINKS PROVIDED FOR DETAILS REGARDING  
SNOWPACK, PRECIPITATION, SEASONAL CLIMATE OUTLOOKS, RESERVOIRS,  
STREAMFLOW, AND WATER SUPPLY FORECASTS.  
 
THE NEXT UPDATE TO THIS OUTLOOK WILL BE ISSUED BY JUNE 10, 2022.  
 
   
..PRECIPITATION AND TEMPERATURES ACROSS OREGON
 
 
PRECIPITATION FOR THE 2022 WATER YEAR THUS FAR (OCT 1, 2021 THROUGH  
MAY 9, 2022) RANGES FROM 60 TO 105 PERCENT OF AVERAGE IN OREGON. THE  
SOUTHERN TWO-THIRDS OF THE STATE ARE WELL-BELOW AVERAGE, ALTHOUGH  
APRIL PRECIPITATION BOOSTED SEASONAL TOTALS BY 5 TO 10 PERCENT OF  
AVERAGE. THE LOWEST TOTALS RELATIVE TO AVERAGE HAVE BEEN IN CENTRAL  
AND SOUTHEAST OREGON, AREAS THAT HAVE ALSO BEEN BELOW AVERAGE FOR  
MUCH OF THE PAST TWO YEARS. THE HIGHEST TOTALS, 100 TO 120 PERCENT,  
HAVE BEEN IN THE FAR-NORTHERN CASCADES, THE NORTHERN BLUE MOUNTAINS,  
AND THE WALLOWA MOUNTAINS IN FAR-NORTHEAST OREGON.  
 
APRIL PRECIPITATION WAS ABOVE AVERAGE FOR MOST OF WESTERN, NORTH-  
CENTRAL AND NORTHEAST OREGON. MEANWHILE FOR CENTRAL AND SOUTHEAST  
OREGON, PRECIPITATION WAS BELOW NORMAL, WITH MONTHLY TOTALS  
GENERALLY LESS THAN AN INCH. APRIL TEMPERATURES WERE 2 TO 6 DEGREES  
ABOVE AVERAGE STATEWIDE, AN ABRUPT CHANGE AFTER MUCH-ABOVE AVERAGE  
TEMPERATURES IN MARCH.  
 
DETAILS ON PRECIPITATION AND TEMPERATURES:  
 
NOAA NATIONAL WEATHER SERVICE - NORTHWEST RIVER FORECAST CENTER  
WWW.NWRFC.NOAA.GOV/WATER_SUPPLY/WY_SUMMARY/WY_SUMMARY.PHP  
 
NOAA NWS - CALIFORNIA-NEVADA RIVER FORECAST CENTER (KLAMATH BASIN)  
WWW.CNRFC.NOAA.GOV/WATER_RESOURCES_UPDATE.PHP  
 
   
..SNOWPACK ACROSS OREGON
 
 
AS OF EARLY MAY, MOUNTAIN SNOWPACK IS ABOVE AVERAGE FOR THE NORTHERN  
AND CENTRAL CASCADES AND THE BLUE AND WALLOWA MOUNTAINS IN NORTHEAST  
OREGON, INCLUDING 195 PERCENT OF AVERAGE FOR THE HOOD-SANDY-LOWER  
DESCHUTES AREA. SNOWPACK FOR ALL OF SOUTHERN OREGON IS NEAR TO BELOW  
AVERAGE. ASSESSING SNOWPACK IN TERMS OF PERCENT OF AVERAGE IS TRICKY  
IN MAY, SINCE SNOWPACK IN AT LOWER AND MID ELEVATIONS IS TYPICALLY  
MELTING OUT. HOWEVER, WITH COOL TEMPERATURES AND AMPLE PRECIPITATION  
IN APRIL, MID AND HIGH ELEVATIONS IN THE CASCADES, SISKIYOUS, BLUE,  
AND WALLOWA MOUNTAIN RANGES ALL SAW SNOWPACK INCREASE IN RECENT  
WEEKS. HOWEVER, THE OVERALL SEASONAL SNOWPACK WAS BELOW AVERAGE FOR  
ALL BUT THE FAR-NORTHERN CASCADES, THE WALLOWAS, AND NORTHERN  
PORTIONS OF THE BLUES, DUE TO A LACK OF SNOW ACCUMULATION FROM MID  
JANUARY THROUGH MARCH.  
 
ADDITIONAL SNOWPACK INFORMATION:  
 
NOAA NATIONAL WEATHER SERVICE - NORTHWEST RIVER FORECAST CENTER  
WWW.NWRFC.NOAA.GOV/SNOW/  
 
USDA NATURAL RESOURCES CONSERVATION SERVICE  
WWW.NRCS.USDA.GOV/WPS/PORTAL/NRCS/MAIN/OR/SNOW/  
 
   
..PRECIPITATION AND TEMPERATURE OUTLOOK
 
 
THE CLIMATE PREDICTION CENTER PRODUCES MONTHLY AND SEASONAL  
OUTLOOKS, IN WHICH THERE IS A WEIGHING OF THE ODDS OF NEAR NORMAL,  
ABOVE NORMAL, OR BELOW NORMAL TEMPERATURES AND PRECIPITATION.  
 
THE MAY OUTLOOK SHOWS A SLIGHTLY-ENHANCED LIKELIHOOD OF BELOW-  
AVERAGE TEMPERATURES STATEWIDE BUT ESPECIALLY FOR THE NORTHERN HALF  
OF THE STATE. FOR PRECIPITATION, THE OUTLOOK LEANS SLIGHTLY ABOVE-  
AVERAGE FOR NORTHERN OREGON AND SLIGHTLY BELOW-AVERAGE FOR SOUTHERN  
OREGON.  
 
THE OUTLOOK FOR JUNE THROUGH AUGUST INDICATES AN ENHANCED  
PROBABILITY OF BELOW-AVERAGE PRECIPITATION FOR ALL OF OREGON. FOR  
TEMPERATURES, THERE IS AN ENHANCED PROBABILITY OF ABOVE-AVERAGE  
TEMPERATURES FOR ALL BUT COASTAL PORTIONS OF OREGON.  
 
VISIT WWW.CPC.NCEP.NOAA.GOV FOR MORE ABOUT SEASONAL OUTLOOKS.  
   
..RESERVOIRS
 
 
STORAGE FOR MOST IRRIGATION RESERVOIRS ACROSS THE STATE IS MUCH  
BELOW AVERAGE, WITH MULTIPLE RESERVOIRS IN CENTRAL AND SOUTHWEST  
OREGON AT RECORD LOW LEVELS COMING INTO THIS WATER YEAR. THE  
COMBINATION OF LOW CARRY-OVER STORAGE FROM LAST WATER YEAR AND BELOW-  
AVERAGE PRECIPITATION AND SNOWPACK THIS WATER YEAR MEANS THAT  
RESERVOIR STORAGE IS UNLIKELY TO BE SUFFICIENT TO MEET ALL DEMANDS  
THIS SUMMER, ESPECIALLY FOR THE SOUTHERN HALF OF THE STATE. WHILE  
SOME RESERVOIRS HAVE REFILLED WITH RECENT PRECIPITATION AND  
SNOWMELT, MAJOR DEFICITS REMAIN AS OF EARLY MAY. CORPS OF ENGINEERS  
RESERVOIRS IN THE WILLAMETTE BASIN HAVE FILLED DUE TO AMPLE  
PRECIPITATION AND SNOWMELT IN MARCH AND APRIL, ALTHOUGH SOME  
RESERVOIRS HAVE BEEN KEPT PURPOSELY LOW FOR SPECIAL OPERATIONS.  
 
OWYHEE RESERVOIR, THE LARGEST IRRIGATION PROJECT IN THE STATE, HAS  
STORAGE OF ABOUT 326,000 ACRE-FEET, 46 PERCENT OF CAPACITY, AS OF  
EARLY MAY. THIS IS 61 PERCENT OF AVERAGE FOR THIS TIME OF YEAR.  
 
RESERVOIR DATA IS PROVIDED BY THE NATURAL RESOURCES CONSERVATION  
SERVICE, THE BUREAU OF RECLAMATION, AND THE US ARMY CORPS OF  
ENGINEERS.  
 
ADDITIONAL RESERVOIR INFORMATION:  
 
WWW.NWD-WC.USACE.ARMY.MIL/NWP/TEACUP/WILLAMETTE/  
WWW.USBR.GOV/PN/HYDROMET/SELECT.HTML WWW.WCC.NRCS.USDA.GOV/BASIN.HTML  
 
   
..OBSERVED STREAMFLOW
 
 
OBSERVED RUNOFF SO FAR THIS WATER YEAR HAS BEEN NEAR AVERAGE IN  
NORTHWEST OREGON AND BELOW AVERAGE FOR BASINS ELSEWHERE IN OREGON,  
NOTABLY MUCH-BELOW-AVERAGE IN SOUTHWEST, CENTRAL, AND EASTERN  
OREGON.  
 
RUNOFF IN APRIL WAS NEAR AVERAGE IN NORTHWEST AND WEST-CENTRAL  
OREGON AND BELOW AVERAGE FOR THE REST OF THE STATE.  
 
VISIT WATERWATCH.USGS.GOV FOR DETAILS ON OBSERVED STREAMFLOW. RUNOFF  
DATA IS AVAILABLE AT WWW.NWRFC.NOAA.GOV/NATURAL/INDEX.HTML AT WATER  
YEAR AND MONTHLY TIME SCALES FOR SEVERAL LOCATIONS IN OREGON.  
 
   
..WATER SUPPLY SEASONAL FORECASTS
 
 
WATER SUPPLY FORECASTS FOR APRIL-SEPTEMBER RUNOFF VOLUME VARY  
WIDELY, WITH SOME AREAS ABOVE AVERAGE AND SOME MUCH BELOW. FORECASTS  
ARE ABOVE AVERAGE FOR NORTHWEST, WEST-CENTRAL, AND FAR-NORTHEAST  
OREGON. FORECAST FOR SOUTHWEST, CENTRAL, AND SOUTHEAST OREGON ARE  
BELOW AVERAGE.  
 
THE FORECAST FOR THE COLUMBIA RIVER AT THE DALLES, WHICH IS A GOOD  
INDEX OF CONDITIONS ACROSS THE COLUMBIA BASIN, IS 97 PERCENT OF  
AVERAGE FOR APRIL-SEPTEMBER, NO CHANGE FROM A MONTH AGO.  
 
DETAILS ON BASIN-SCALE WATER SUPPLY FORECASTS:  
 
NOAA NATIONAL WEATHER SERVICE - NORTHWEST RIVER FORECAST CENTER  
WWW.NWRFC.NOAA.GOV/WS/  
 
USDA NATURAL RESOURCES CONSERVATION SERVICE  
WWW.WCC.NRCS.USDA.GOV/WSF/  
 

 
 
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