Melt­ing snow could af­fect wa­ter lev­els on the Mokelumne

Lodi News-Sentinel - - FRONT PAGE - By Oula Miq­bel NEWS-SEN­TINEL STAFF WRITER

The re­lent­less pro­ces­sion of rain this past win­ter, cou­pled with record-break­ing snow lev­els, has left the East Bay Mu­nic­i­pal Util­ity Dis­trict mon­i­tor­ing the Pardee and Ca­manche Dams around-the­clock.

Ac­cord­ing to the Cal­i­for­nia Depart­ment of Wa­ter Re­sources, this past win­ter has been recorded as the fourth wettest win­ter year on record for the re­gion, dat­ing back to the 1950s.

The DWR Phillips Sta­tion snow sur­vey of 2019 recorded 53.9 inches of snow depth and a snow wa­ter equiv­a­lent of 34.43 inches, which is 202 per­cent of av­er­age for this lo­ca­tion.

The Sierra snow­pack is one of Cal­i­for­nia’s most im­por­tant wa­ter sources, with its spring and sum­mer runoff feed­ing rivers and reser­voirs. Moun­tain snow­pack pro­vides about 30 per­cent of the yearly fresh wa­ter sup­ply for Cal­i­for­nia.

“We not only had a lot of pre­cip­i­ta­tion this win­ter, (but) colder tem­per­a­tures as well, which caused a dense snow­pack. Dense snow means there is a lot more wa­ter con­tent in the ice than when it’s pow­der,” EBMUD Man­ager of Wa­ter Op­er­a­tions David Briggs said.

Although the wa­ter source pro­vides wa­ter for the Cen­tral Val­ley through the Mokelumne River, it presents a se­ri­ous dan­ger for flood­ing in the re­gion.

“Pardee dam is cur­rently at 101 per­cent (ca­pac­ity) and Ca­manche is at 86 per­cent,” EBMUD Se­nior Pub­lic In­for­ma­tion Rep­re­sen­ta­tive An­drea Pook said. “Once Pardee fills, it spills over into Ca­manche, and we re­lease wa­ter into the Mokelumne.”

As the snow trick­les into nearby dams and streams, EBMUD cal­cu­lates the vol­ume of wa­ter be­ing re­leased from the Dams into the Mokelumne River based on fed­eral reg­u­la­tions as a mea­sure of flood con­trol.

The United States Army Corps of En­gi­neers is the fed­eral agency that per­mits the re­lease rate of wa­ter from the dams into the rivers, Briggs said.

“We main­tain wa­ter lev­els to con­firm they ad­here to com­ply with flood con­trol guidelines of 5000 (cu­bic feet per sec­ond),” he said.

One cu­bic foot of wa­ter weighs 62.5 pounds, and cu­bic feet per sec­ond, or cfs, is the mea­sure­ment used to de­ter­mine the amount of wa­ter pass­ing from any given point into a river within one sec­ond.

“We are cur­rently at 2,900 cfs (at Ca­manche). We still have a lot of room and time be­fore we get to 5000 cfs,” Briggs said.

As EBMUD re­leases wa­ter into the Mokelumne River, the impression that the river is ris­ing is only tem­po­rary.

Briggs ex­plained that through the month of June, EBMUD will re­lease more wa­ter from the dams, but once we reach July 1 the wa­ter lev­els will drop to nor­mal lev­els be­cause ice melt will slow down or stop com­pletely.

“As we go through th­ese mi­nor heat waves we will be re­leas­ing more, but that is com­mon this time of year un­less we are in a drought,” he said.

As wa­ter is re­leased, recre­ational ac­tiv­ity on Lake Ca­manche and the Mokelumne River is more risky, due to the faster wa­ter flow com­ing in.

“We warn about the peo­ple about the speed of the wa­ter more than any­thing. The tem­per­a­tures don’t drop as much (dur­ing the wa­ter re­lease), be­cause wa­ter at the bottom of the lake is brought to the top,” Joe Waid, an en­gi­neer with the Cle­ments Fire Depart­ment said.

The rapid wa­ter speeds have forced the clo­sure of Still­man Magee Park, which is home to recre­ational wa­ter ac­tiv­i­ties, in an ef­fort to pre­vent any drown­ing at the park.

The clo­sures are tem­po­rary, ac­cord­ing to Waid, but are ex­pected to open once wa­ter lev­els slow down.

ALLEN J. SCHABEN/LOS AN­GE­LES TIMES

A snow plow clears a road near High­way 395 near Mam­moth Lakes on Feb. 6.

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