Shasta Dam water releases explained

CITY OF SHASTA LAKE, Calif. - Water rights are always a touchy subject in the Northstate. That is especially so this year with the historic drought.

And that's leading some to question about the job the Bureau of Reclamation is doing to keep enough water in the Sacramento Valley for farmers and residents. 

The truth is that Shasta Dam releases almost five times the amount of water during the summer as during the winter.  Over the past five years, Shasta Dam has released around 11,000 cubic feet per second of water starting in late June and extending through September.

In late October and early November the outflow is cut back to between 3,000 and 3,500 cubic feet per second.

But almost all of that water is put to use.  Most of the water released in the summer months goes to agricultural use for farmers in the Central Valley.  The greater demand for water warrants the greater outflows during the hottest months.

The water is also used in cities and towns in the Central Valley, in industries that line the river and to help preserve the ecology of Northern California. 

The river also helps preserve farmland in the Sacramento Delta.  The push of fresh water is used to keep the ocean from flooding the low-lying farms between Sacramento and San Francisco.  If the river wasn't flowing the ocean water is liable to flood farmlands, allowing salt to penetrate into the soil and destroying the farms for Sacramento Delta farmers.

The other key point is that the releases are all required by law.  Shasta Dam must release a minimum amount of water to be available for the farms, municipalities and unique environmental areas in the Sacramento Valley.

The lake's water is also released during the summer in order to make room for more rain during the winter.  Every year the Bureau of Reclamation must prepare for an average rainfall for Northern California.  That means the dam itself can expect about 60 inches of rain, easily enough to fill the reservoir.

Climate models are nowhere near accurate enough to accurately forecast one month in the future, let alone six months.  The Climate Prediction Center is fairly inaccurate even with general trends three months out so there is virtually no way to know how wet or dry a season will be months away.

This year marks the third year in a row with below average rainfall.  To this point Shasta Dam has received only 9.16 inches of rain, or 22 percent of normal rainfall for this time of year. 

Officials say that the longer the dry weather last the greater the strain becomes both on farmers trying to grow crops and on the reservoirs providing water to the valley's agriculture.

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