The Water Swap

[forestofglory]

I'm going to explain how part of California's water system works. This is part of the larger context of my thesis which looks at the history of Shasta Dam in the 1930's and 40's. The system I'm going to tell you about made significant changes and is still the backbone of the state's water supply today.

I'll be explaining how it worked in 1952 after the completion of the Central Valley Project, but before the constriction of the State Water Project. The system still works the same way, but more dams and canals have been added, making it a bit more complex.

There are several things that it useful to understand about California before one begins to try and understand the state's water system.

First a quick lesion in geography: Two rivers flow through California's great Central Valley, the Sacramento in the north and the San Joaquin in the south. In roughly the middle of the valley, between the cities of Sacramento and Stockton, the Sacramento and San Joaquin Rivers meet and flow through a complex delta into the San Francisco Bay.

Next is important to understand the seasonal nature of precipitation in California. The state has what is know as Mediterranean climate, with rainy winters and dry summers. Finally you should know that the state is much wetter in the north than it is the the south. Both of these are problems for irrigated agriculture. Which takes place all through the Central Valley and grows crops through out the year.

The Central Valley Project which began construction in 1937 aimed to store winter rain fall and spring snow melt for summer use, and also to move water form the north of the state to the south.

Here is a map that might help to glance at as you read this explanation.

Lets start at Friant Dam on the headwaters of the San Joaquin river, this dam impounds the water coming out of the Serra Nevada mountains into the river. This water is sent south in the Friant-Kern Canal which ends near Bakersfield. The water is uses primarily for irrigation.

The water taken at Friant is enough to seriously deplete and in many years even de-water the San Joaquin. So to replace the water in the river water is pumped through the Delta, down the Delta-Mendota canal to the Mendota Pool. This water is used to refill the San Joaquin.

The water pumped from the delta comes form further north: Shasta Dam which sit near the head waters of the Sacramento River. Shasta is really important part of the system because it provides most of the water to make the whole thing work.

So there you have it California's strange "Water Swap" were water is sent form north to south.

Comments

[jack]

Thank you! It's fascinating to actually read about. I hadn't realised how much control there had to be over the water.

PS. Congrats on the thesis draft, yay!

PPS. I got your postcard to the new house, thank you! It's really cheering to get nice post to my permanent address.

[davidgillon]

There's a couple of similar systems in the UK. The Kielder Transfer System with water daisy-chained through reservoirs and tunnels from Kielder Water on the Tyne south to the Wear and the Tees; and the system that supplies Liverpool from Wales which was deeply controversial when built - to the point that Liverpool issued a letter of apology 40 years later. In both those cases the driving factor was industrial water use, though, not agricultural.

[forestofglory]

Oh I didn't know that. Thanks for telling me.

[davidgillon]

My dad was a civil engineer before retiring, so it's the kind of thing that I grew up hearing about ;)

[liv]

Cool, thank you so much for explaining this interesting stuff so clearly.

[forestofglory]

Yay! I'm glad you found it both clear and interesting.

[nicki]

and yet despite all the control over where to move the water to, there's often relatively little control over the actual usage of that water.

*frowny face at Ag industry and So Cal*

[forestofglory]

Yes, there definitely should be more conservation, especially in Ag which uses 80% of the water in the state.

[kaberett]

Huh! Interesting, thank you for the write-up :-)