Sunday, July 22, 2012

The Deal with the Delta (California’s big ole’ watering hole)

 By Matthew Green  
About two-thirds of Californians drink, bathe, brush their teeth, and flush their toilets with water that comes from the Sacramento-San Joaquin Delta. That’s roughly 25 million people who get at least some portion of their hydration from one big triangular watering hole.
But ask most folks what the Delta is, and you’re guaranteed to get a lot of blank stares. Onerecent poll found that about 4 out 5 people in California had pretty much no ideas what the Delta is.
It’s pretty easy to take for granted that water just magically pours out of the tap when you turn your faucet on. But chances are, that H20 has gone through a serious journey to reach you.
See, one of the things that’s kind of funky about California (among the many), is that the majority of the population lives in the southern part of the state, but most of the available freshwater supply is in the northern half. So, to hydrate the millions of people living and farming in the state’s drier regions, California has had to, ahem, tap the crap out of its available resources, pumping water hundreds of miles over large mountains to reach the populations that rely on it.

So what is the Delta?

Credit: USGS
Just south of Sacramento on the western edge of the Central Valley is where California’s two major rivers meetup – the San Joaquin from the south and the Sacramento from the north. Between them, they drain almost half of California’s freshwater supply, collecting and concentrating rainfall and snow-melt from the Sierra Nevada and funneling it towards the San Francisco Bay.
And this makes the Delta: a 700-square-mile inland estuary at the confluence of these two great rivers, where freshwater from the mountains mixes with saltwater from the Pacific.
Think of it as California’s big drain.

How it used to be …

Courtesy of Bay Nature Magazine; artist: Laura Cunningham
Before we started messing with it, the Delta was a vast brackish marsh filled with wetland plants (tules) and winding tidal channels. Much of it was submerged; all the freshwater from mountain snow melt mixed with saltwater from the ocean. In fact, when Spanish explorers first viewed the Delta from the top of Mt. Diablo in the late 1700’s, they thought they had discovered an inland sea. The area teemed with birds and game animals, including elk, antelope, and grizzly bears. It’s only human inhabitants – small settlements of Miwok Indians – fished and hunted there only during summer months on small areas of dry land.

And how it is now …

As you may have guessed, things are a bit different now. Over the last 150 years, we’ve dramatically and irreversibly changed the environment and landscape of the Delta, an epic effort to meet the steep demands of California’s increasingly crowded, thirsty population. Today’s Delta is dotted with more than a 1,000 miles of earthen walls – called levees. Much of the area has been “reclaimed” for agricultural use – land that’s been drained and cordoned off by the levees. Huge pumps now deliver millions of gallons of freshwater to cities throughout the lower half of the state and farms in the arid San Joaquin Valley to the south.

A fragile system

In 2004, a breach in the Upper Jones Tract Levee flooded the surrounding farmlands and residential areas. The probable culprit: a rodent - possibly a beaver. (source: CA Department of Water Resources)
But the transformation has greatly upset the fragile environmental balance of the region, threatening many of the fish and plant species living there who can’t survive without steady streams of freshwater. The debate over how much water should be diverted from the Delta has long been a hot button political issue, instigating ongoing battles between northern and southern cities. It’s also pitted environmentalists against heavy water users, like farmers, who demand large consistent deliveries.
The modern development of the Delta has also created an equally fragile water delivery system that millions of Californians depend on. Most of the levees are old and crumbling. If hit by a big enough earthquake, many would likely be destroyed. And because much of the reclaimed land in the region is below sea level (because ongoing land subsidence), the area would be flooded, along with the nearly 400,000 people who live there.
Source: CA Dept. of Water Resources
Perhaps even more catastrophic: because the levees separate freshwater from saltwater, if they collapse, the waters mix, leaving much of the state high and dry without a major freshwater source.
Pretty serious business.
State leaders have been arguing for years about how to deal with this threat. One pricey proposal – build a multibillion dollar peripheral canal around the Delta -  may eventually go before voters in 2014.

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