CA WATER COMMISSION: Hydrology and State Water Project operations update

“This year to date, we’ve been running at a record pace for the majority of the winter in terms of the amount of precipitation that we’ve seen in the Northern Sierra,” he said.
The average for the northern Sierra is 50” for the water year.
The January-February inflow was 4.4 MAF which is equal to the average annual inflow into Lake Oroville.
“If you recall, we’re well over 200% of average on precipitation and about 166% on snowpack, so what that tells us essentially is we’ve been seeing the volume of precip has been coming in a warmer form than would be average, so that’s why the snowpack is not keeping up with the volume in terms of precipitation.” He noted that the snowpack number is a little bit closer on the Central and Southern Sierra, and there is still a concern moving into the spring of being able to manage the snowmelt that’s going to occur on the San Joaquin basin.
“So the 50% exceedance would include all of the snowpack melt that’s occurred as of March 1st plus precipitation that would occur on average from that point forward.
“Those are all based on those inflows into those reservoirs and the Sacramento Valley.” “To date, we’re running 282% of average in terms of runoff,” he said.
“That also tells you that the storms have been warmer than average because we’re 200% of average on precipitation but we’re 282% in terms of runoff, so typically more of the precipitation would have fallen as snow than it did this year and would runoff later in the year.” With respect to where we were last year, last year there was about average precipitation but runoff was only 6.7 MAF versus the 22.1 MAF, so over three times more runoff so far this year than last year, Mr. Leahigh said.
For Delta outflows just since January 1st , 26 MAF of outflow went out the Golden Gate, so 26 Folsom Reservoirs just since January 1st of water that had to be passed through for flood control purposes in order to continue to hold that vacant storage for snowmelt and for any subsequent precipitation events that could occur from this point forward.” He said that reservoir storage on the San Joaquin system is very high right now, so they are working to create as much of a hole in the tributary reservoirs in order to absorb that snowpack when it does start to melt off a little bit later this spring.
We have some uncertainties with Lake Oroville, but in years like this, there are a lot of other flows that are coming into the Delta so that we’re much less reliant on storage from Lake Oroville in the very wet years, so we’re looking for opportunities to increase that allocation as we move forward in the spring.” To conclude, Mr. Leahigh showed a comparison of the this year’s drought monitor compared to last year at about the same time.
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