HYDROLOGIC OUTLOOK NATIONAL WEATHER SERVICE SACRAMENTO CA 1200 AM PDT WED APR 12 2006
...SUBSTANTIAL RAINFALL AND SNOW PACK ACCUMULATION DURING MARCH RESULTS IN ELEVATION OF THE SPRING FLOOD POTENTIAL TO ABOVE AVERAGE IN THE SAN JOAQUIN BASIN...
MARCH TURNED OUT TO BE WET FOR MOST OF CALIFORNIA WHERE MORE OR LESS CONTINUOUS PERIODS OF RAINFALL PERSISTED DURING THE ENTIRE MONTH. SIGNIFICANT RAINFALL HAS CONTINUED INTO EARLY APRIL. THE GREATEST AREA OF CONCERN ARE THE WATERSHEDS OF THE SAN JOAQUIN RIVER DRAINAGE...ESPECIALLY THE MAINSTEM SAN JOAQUIN RIVER...WHERE SUBSTANTIAL INCREASES TO THE MOUNTAIN SNOW PACK COMBINED WITH INCREASED RUNOFF FROM THE MARCH AND EARLY APRIL RAINS IS EXPECTED TO IMPACT THE RIVER AND LEVEE SYSTEMS IN THE REGION. THE SPRING FLOOD POTENTIAL OUTLOOK WILL REMAIN HIGH FOR THE NEXT SEVERAL WEEKS IN THIS REGION.
UPPER KLAMATH LAKE BASIN: SNOW PACK CONDITIONS CONTINUE TO IMPROVE IN THE UPPER KLAMATH BASIN. THE WATER CONTENT OF THE SNOWPACK IS AT 165 PERCENT AS OPPOSED TO 45 PERCENT AT THIS TIME LAST YEAR. UNIMPAIRED RUNOFF IS ABOUT 106 PERCENT OF THE SEASONAL AVERAGE. THE BASIN RECEIVED ABOUT 95 PERCENT OF THE MONTHLY AVERAGE PRECIPITATION IN MARCH AND THE SEASONAL AVERAGE STANDS AT ABOUT 125 PERCENT. STORAGE AT UPPER KLAMATH LAKE IS 97 PERCENT OF THE AVERAGE-TO-DATE. THE APRIL THROUGH SEPTEMBER RUNOFF FORECAST FOR THE UPPER KLAMATH LAKE INFLOW AS OF APRIL 1ST IS MUCH ABOVE AVERAGE AT 159 PERCENT. THE SPRING FLOOD OUTLOOK FOR THE UPPER KLAMATH LAKE BASIN REMAINS AVERAGE DUE TO THE ABOVE AVERAGE SNOWPACK AND THE WET ANTECEDENT CONDITIONS IN THE BASIN. FLOODING COULD OCCUR DURING WARM STORM EVENTS WITH HIGH MELT LEVELS DURING THE PEAK SNOWMELT SEASON.
NORTH COASTAL DRAINAGE: TRUE TO MANY OTHER AREAS IN CALIFORNIA...THE NORTH COAST RECEIVED MUCH ABOVE AVERAGE PRECIPITATION DURING MARCH. HOWEVER...THE RIVER SYSTEM WAS NOT SERIOUSLY IMPACTED BY THE ADDITIONAL RUNOFF AS IT WAS DURING THE NEW YEARS STORMS. THE SEASONAL TOTAL PRECIPITATION REMAINS ABOVE AVERAGE FOR THE SMITH...EEL...RUSSIAN AND NAPA BASINS. THE TRINITY RIVER BASIN HAS RECEIVED ABOUT 145 PERCENT OF THE SEASONAL PRECIPITATION TO DATE...THE LOWER KLAMATH RIVER BASIN ABOUT 170 PERCENT. SNOWPACKS STAND AT ABOUT 175 PERCENT OF THE APRIL 1ST AVERAGE IN THE TRINITY BASIN. THE APRIL THROUGH JULY RUNOFF FORECAST FOR THE TRINITY RIVER INFLOW IS 157 PERCENT...AN INCREASE OF 44 PERCENT FROM LAST MONTH. IT IS EXPECTED THAT THE RIVER AND RESERVOIR SYSTEM SHOULD BE ABLE TO HANDLE ANY PERIODS OF SUBSTANTIAL PRECIPITATION DURING THE COMING MONTHS. THE SPRING FLOOD POTENTIAL FOR THE NORTH COASTAL BASINS IS AVERAGE.
SACRAMENTO DRAINAGE: THE SACRAMENTO DRAINAGE RECEIVED MUCH ABOVE AVERAGE PRECIPITATION DURING MARCH. SEASONAL AMOUNTS INCREASED SOMEWHAT OVER LAST MONTH AND NOW RANGE FROM 135 PERCENT FOR THE AMERICAN RIVER BASIN TO 150 PERCENT FOR THE FEATHER.
SNOWPACKS IN THE SACRAMENTO DRAINAGE VARY FROM 122 PERCENT OF THE APRIL 1ST AVERAGE FOR THE PIT RIVER BASIN...117 PERCENT FOR THE FEATHER...103 PERCENT FOR THE YUBA AND 114 PERCENT FOR THE AMERICAN RIVER BASIN...INCREASES OF ABOUT 45 TO 55 PERCENT FROM LAST MONTH.
REGION-WIDE RESERVOIR STORAGE IS ABOUT 112 PERCENT OF THE AVERAGE-TO-DATE. IT IS ANTICIPATED THAT RESERVOIRS SHOULD BE ABLE TO HANDLE RUNOFF FROM SNOWMELT THIS SPRING. SEASONAL RUNOFF TOTALS ARE MUCH ABOVE AVERAGE FOR THE MAJOR RIVERS IN THE SACRAMENTO DRAINAGE...AVERAGING ABOUT 153 PERCENT. THE I STREET GAGE IN SACRAMENTO HAS RECORDED STAGES ABOVE 20 FEET SINCE MARCH 1ST...SUBSTANTIALLY HIGH FOR THIS TIME OF YEAR. THE APRIL THROUGH JULY WATER SUPPLY RUNOFF PROJECTIONS RANGE FROM 130 PERCENT FOR THE PIT RIVER NEAR MONTGOMERY CREEK...142 PERCENT FOR THE SHASTA LAKE NEAR REDDING...131 PERCENT FOR THE OROVILLE RESERVOIR INFLOW...AND 141 PERCENT FOR THE FOLSOM RESERVOIR INFLOW. BECAUSE OF THE ABOVE AVERAGE CONDITION OF THE NORTHERN SIERRA SNOWPACK...THE SPRING FLOOD POTENTIAL OUTLOOK FOR THE SACRAMENTO RIVER DRAINAGE IS AVERAGE. IT IS ABOVE AVERAGE FOR THE SACRAMENTO-SAN JOAQUIN DELTA REGION AS RIVER STAGES SHOULD REMAIN HIGH FOR THE NEXT FEW WEEKS AS SUBSTANTIAL UPSTREAM RUNOFF ARRIVES FROM THE SACRAMENTO AND SAN JOAQUIN RIVER DRAINAGES.
CENTRAL COAST DRAINAGE: PORTIONS OF THE CENTRAL COAST RECEIVED MUCH ABOVE AVERAGE MONTHLY PRECIPITATION DURING MARCH...ESPECIALLY IN THE COASTAL DRAINAGES. SEASONAL TOTAL PRECIPITATION NOW STANDS FROM ABOUT 120 PERCENT OF AVERAGE FOR THE PAJARO RIVER DRAINAGE...AND ABOUT 100 PERCENT FOR THE SALINAS RIVER BASIN. THE SPRING FLOOD POTENTIAL IS AVERAGE FOR ALL BASINS IN THE CENTRAL COAST DRAINAGE.
SAN JOAQUIN DRAINAGE: THE COPIOUS PRECIPITATION RECEIVED IN MARCH AND EARLY APRIL HAS DRAMATICALLY CHANGED THE FLOOD POTENTIAL OUTLOOK FOR THIS AREA. INSTANCES OF SEEPAGE AND BOILS NEAR LEVEES HAVE BEEN REPORTED ON PORTIONS OF THE MAINSTEM SAN JOAQUIN RIVER...AS FLOWS APPROACHED CHANNEL CAPACITY...PROMPTING THE ACTIVATION OF FLOOD FIGHT CREWS TO DEAL WITH THE SITUATION. NEARLY FULL RESERVOIRS ARE RELEASING WATER RECEIVED FROM THE MARCH STORMS TO MAKE ROOM FOR RUNOFF FROM ANTICIPATED SPRINGTIME SNOWMELT.
SNOWPACK CONDITIONS IN THE SAN JOAQUIN DRAINAGE CHANGED FROM BELOW AVERAGE LAST MONTH TO MUCH ABOVE AVERAGE THIS MONTH. SNOWPACKS RANGE FROM 128 PERCENT OF THE APRIL 1ST AVERAGE FOR THE STANISLAUS RIVER BASIN TO 143 PERCENT FOR THE UPPER SAN JOAQUIN...INCREASES FROM 45 TO 55 PERCENT OF THE APRIL 1ST AVERAGE OVER LAST MONTH WERE RECORDED.
SEASONAL PRECIPITATION RANGES FROM 110 PERCENT FOR THE UPPER SAN JOAQUIN BASIN TO 135 PERCENT FOR THE MOKELUMNE. STORAGE IN THE MAJOR RESERVOIRS VARIES FROM 117 PERCENT OF AVERAGE FOR NEW DON PEDRO RESERVOIR ON THE TUOLUMNE TO 143 PERCENT FOR THE STANISLAUS AT NEW MELONES.
SEASONAL RUNOFF AVERAGES ABOUT 140 PERCENT FOR ALL THE MAJOR TRIBUTARIES IN THE REGION. THE MAINSTEM SAN JOAQUIN RIVER IS EXPECTED TO FLOW AT HIGH LEVELS FOR THE NEXT SEVERAL WEEKS. THE APRIL THROUGH JULY WATER SUPPLY FORECAST CALLS FOR ABOVE TO MUCH ABOVE AVERAGE RUNOFF FOR THE MAJOR RIVER INFLOW FORECAST POINTS.
THERE IS A HIGH PROBABILITY OF SNOWMELT FLOODING IF TEMPERATURES RAPIDLY WARM TO ABOVE NORMAL LEVELS OVER THE NEXT FEW MONTHS. GIVEN THE COMBINATION OF WET ANTECENDENT SOIL CONDITIONS...MUCH ABOVE AVERAGE SNOWPACK...NEARLY FULL RESERVOIRS...AND EXPECTED LONG TERM FLOWS TO NEAR CHANNEL CAPACITY FOR SEVERAL OF THE MAJOR TRIBUTARIES OF THE SAN JOAQUIN RIVER...THE SPRING FLOOD POTENTIAL OUTLOOK FOR THE SAN JOAQUIN BASIN IS NOW ABOVE AVERAGE.
TULARE LAKE DRAINAGE: SNOWPACK CONDITIONS IN THE TULARE LAKE DRAINAGE IMPROVED SIGNIFICANTLY OVER LAST MONTH. THE PACK NOW RANGES FROM 137 PERCENT OF THE APRIL 1ST AVERAGE FOR THE KINGS RIVER BASIN...131 PERCENT FOR THE KAWEAH RIVER BASIN...130 PERCENT FOR THE TULE...AND 127 PERCENT FOR THE KERN. MARCH PRECIPITATION WAS EXCELLENT...RANGING FROM 160 PERCENT FOR THE KAWEAH TO 235 PERCENT FOR THE TULE. SEASONAL PRECIPITATION RECEIVED VARIES FROM 105 PERCENT FOR THE KERN RIVER BASIN TO 110 PERCENT FOR THE KINGS AND KAWEAH. STORAGE IN THE MAJOR RESERVOIRS RANGES FROM 83 PERCENT FOR LAKE SUCCESS ON THE TULE RIVER TO 150 PERCENT FOR THE KAWEAH RESERVOIR AT TERMINUS. IT IS ANTICIPATED THAT RESERVOIRS SHOULD BE ABLE TO HANDLE RUNOFF FROM SNOWMELT THIS SPRING. SEASONAL RUNOFF VARIES FROM 78 PERCENT FOR THE TULE INFLOW TO SUCCESS TO 110 PERCENT FOR THE KINGS RIVER AT PINE FLAT. THE APRIL THROUGH JULY WATER SUPPLY FORECAST CALLS FOR MUCH ABOVE AVERAGE RUNOFF FOR ALL MAJOR RIVERS IN THIS BASIN. SOME SNOWMELT FLOODING COULD OCCUR IF TEMPERATURES RAPIDLY WARM TO ABOVE NORMAL LEVELS OVER THE NEXT FEW MONTHS. THE ABOVE AVERAGE CONDITION OF THE SNOWPACK AND WET SOIL CONDITIONS HAS ELEVATED THE SPRING FLOOD POTENTIAL OUTLOOK OF THE TULARE BASIN THIS MONTH. DUE TO POTENTIALLY HIGH FLOWS IN THE KINGS RIVER CHANNEL DURING THE SNOWMELT SEASON...THE SPRING FLOOD POTENTIAL FOR THE KINGS RIVER BASIN IS ABOVE AVERAGE. THE SPRING FLOOD POTENTIAL IS AVERAGE FOR THE KAWEAH...TULE...AND THE KERN RIVER BASINS.
SOUTH COAST DRAINAGE: PORTIONS OF THE SOUTH COAST DRAINAGE RECEIVED ABOVE AVERAGE PRECIPITATION DURING MARCH. HOWEVER...SEASONAL AVERAGES STILL REMAIN MUCH BELOW AVERAGE WITH LITTLE POSSIBILITY OF IMPROVEMENT OVER THE NEXT FEW MONTHS. DUE TO BELOW AVERAGE SEASONAL PRECIPITATION RECEIVED THUS FAR...THE SPRING FLOOD POTENTIAL IS BELOW AVERAGE FOR THE SOUTH COAST DRAINAGES AND MOUNTAINS.
SOUTHEASTERN CALIFORNIA DESERTS / EAST SLOPE SIERRA NEVADA IN INYO COUNTY: SEASONAL PRECIPITATION REMAINS ABOUT AVERAGE AND SNOWPACKS HAVE IMPROVED OVER LAST MONTH AND REMAIN ABOVE AVERAGE IN THIS REGION. THE FLOOD POTENTIAL IS EXPECTED TO BE AVERAGE FOR THE EAST SLOPE DRAINAGES OF THE SIERRA NEVADA MOUNTAINS IN INYO COUNTY.
SOUTHEASTERN CALIFORNIA DESERTS: EASTERN INYO COUNTY...DESERT AREAS OF SAN BERNARDINO COUNTY...EASTERN RIVERSIDE AND IMPERIAL COUNTIES: AREAS IN THE WESTERN PORTION OF THE REGION RECORDED NEAR TO ABOVE AVERAGE PRECIPITATION IN MARCH...HOWEVER...RAINFALL RECEIVED BY STATIONS ADJACENT TO THE COLORADO RIVER WAS MUCH BELOW AVERAGE. SEASONAL PRECIPITATION TOTALS STILL REMAINS BELOW AVERAGE TO MUCH BELOW AVERAGE. THE POTENTIAL FOR SPRINGTIME FLOODING IS PRIMARILY CAUSED BY PERIODS OF HEAVY RAINFALL INSTEAD OF SNOWMELT. HENCE...THE FLOOD POTENTIAL FOR THE DEATH VALLEY NATIONAL PARK...THE MOJAVE RIVER BASIN...EASTERN RIVERSIDE AND IMPERIAL COUNTIES IS BELOW AVERAGE THIS SPRING. STILL...LARGE AND SMALL STREAM FLOODING CAN STILL OCCUR AS THE RESULT OF PROLONGED HIGH INTENSITY RAINFALL THROUGHOUT THESE AREAS.