New Sea Level Study Calls Delta Tunnels Into Doubt

California homeowners will know the feeling. You shell out a huge amount of money for a place, and then suddenly you find yourself underwater -- owing more than the propertys worth.

But it isnt just that metaphorical fiscal water Jerry Browns California Water Fix project may find itself under. The at-least-$17-billion public works project, intended to divert Sacramento River water around the Delta to the giant pumps that send that water south to farms and cities, may well find its proposed tunnel intakes under three or four feet of seawater by the end of the century.

Thats according to a study published in late March in the journal Nature. The study suggested that the West Antarctic ice sheet, which is melting faster than anticipated, will likely cause a meter of sea level rise by the end of the 21st Century. When you add that to other factors causing sea levels to rise, that means Californias Bay and Delta may well see sea levels two meters higher in 2100 than they are now -- about six and a half feet of average sea level increase. And that may well push saltwater well past the planned intakes for the California Water Fixs tunnels.

At issue is a recent study by climate scientists Robert DeConto at the University of Massachusetts Amherst and David Pollard at Pennsylvania State University, published in the journal Nature in late March. The study, which examined the little-understood effect of melting surface ice on thinning continental ice sheets, suggested that Antarctic ice sheets could add enough water to Earths oceans to raise sea levels as much as a meter by 2100, with that rise in sea levels accelerating sharply thereafter.

That boost in sea level is in addition to all the other things causing our planetary ocean to rise: the increase in melting of the Greenland ice sheet, melting of mountain glaciers, and thermal expansion of ocean water chief among them. With the increase in Antarticas estimated contribution to sea level rise, the worlds oceans could well be 1.5-2 meters higher in 2100 than they are now, with that rise increasing at a faster pace in subsequent decades.

DeConto and Pollard suggest that by 2500, Antarcticas melting ice might well raise sea levels by 15 meters, or just under 50 feet. Add that to the seven meters of so a melted Greenland would likely contribute by then, and were looking at sea levels 22 meters higher - 72 or more feet - in the year 2500 than they are today.

Central Valley of the Future? | Photo: Dennis D., some rights reserved

That more distant forecast would mean a very different California. A giant inland sea would cover the Central Valley from Yuba City to Merced. Most low-lying cities in the Bay Area would be destroyed, as would much of Long Beach and Orange County, and the Sea of Cortez would extend beyond Interstate 10 near Indio. Millions of people now live in parts of California that would be inundated in sea water if sea levels rise 70 feet by 2500, and the waters would cover important transportation corridors as well.

But we dont need to wait 484 years for this newly projected sea level rise to have a devastating impact on California. That impact may become significant in just a few short decades. And an almost certain casualty of that rise is a project that ironically has pointed to sea level rise as one of the reasons for its existence.

Rising seas threaten the states existing system for getting fresh water from north to south. As it works now, huge pumps in the south Delta essentially suck water from the Sacramento River through a network of channels and sloughs in the interior of the Delta. When the water reaches the pumps, its siphoned into aqueducts for the Central Valley Project and the State Water Project, which send the water to farms and cities to the south.

The relevant problem here is that most of those sloughs and channels flow past levees that protect large islands whose surfaces are below sea level. Rising seas threaten to overtop those levees. When they do, or when either earthquakes or simple entropy causes the levees to fail even without rising seas, the resulting floods of those low-lying islands will pull brackish water into the Delta from San Francisco Bay, and that brackish water will likely contaminate the fresh water heading for the pumps.

The much-lauded and much-criticized project currently called California Water Fix by its partisans in government and the Bay Delta Conservation Plan by wonks with a historical memory, but generally called the Peripheral Tunnels by everyone else, is ostensibly intended to solve this problem. Three large intakes along the Sacramento River between Courtland and Clarksburg would shunt Sacramento River water into twin 30-mile tunnels, each of them 40 feet wide, that would be buried 150 feet below the surface of the Delta. The project, which the state estimates would cost $15 billion (though critics charge its cost over the next several decades could be four times that), will be capable of delivering almost five million acre-feet of the Sacramentos water to the pumps each year.

Critics have blasted the project as a way to ensure that water exports from the Delta will continue regardless of the actual amount of water in the Sacramento, to the detriment of species like the Delta smelt and the Sacramento River winter-run Chinook salmon. And this week, the group Public Employees for Environmental Responsibility charged that the state has spent millions of dollars in federal funds on the project that was supposed to go to improving habitat for the Bay Deltas beleaguered wild fish. A federal probe into those allegations is gearing up.

Artists rendition of the water intakes for the California Water Fix tunnels | Image: California Department of Water Resources

But the new Nature study on sea level rise due to surface melt from the Antarctic ice sheets calls the whole point of the

LINK:	https://www.kcet.org/redefine/new-sea-level-rise-study-calls-delta-tun...
	See more stories from kcet

Most recent headlines