Seeing Green: Where Water Comes From

Opinion by Holly Moeller
Jan. 13, 2012, 12:28 a.m.

Seeing Green: Where Water Comes FromDuring the driest December in two decades, I snuck off for a long weekend in Yosemite National Park. When I booked the trip, I expected to visit a winter wonderland, photographing snowflakes pouring down the face of Half Dome and icicles dangling from every cabin. Instead, every single road was clear, and the only sign of winter was the frost edging Bridalveil Fall.


For my travel companion, a Yosemite rookie, the absence of snow proved a boon: We drove to every classic vista and hiked trails generally closed by that time of year. But if I was slightly disappointed by the lack of seasonal snowfall, I can only imagine the dismay of ski resorts across the American West.


The unseasonably dry weather has left Tahoe skiers scraping gravel, Colorado and Utah resorts facing slim snowpacks, and Yosemite itself still closed to snowsports. Snow-lovers with resources can still get their wintry kicks in parts of New Mexico and British Columbia, but in general, this year’s conditions are lamentable.


Worse, a bad ski season predicts a tough year for water-users (read: everyone) living in the American West.


Snowmelt from western mountain ranges form the headwaters of rivers harnessed to supply agricultural irrigation, drinking water, and hydroelectric power. During low-snowfall years, our frozen mountain reservoir is diminished, and drought looms.


Here on the Peninsula, 85 percent of our water comes the Hetch Hetchy Reservoir, perched within Yosemite National Park and filled by the dammed Tuolumne River. This water flows 167 miles down from the Sierras, across California’s Central Valley, underneath San Francisco Bay, to Peninsula reservoirs like Crystal Springs (the body of water visible from I-280 between San Francisco and Stanford).


The pipelines connecting the flooded Hetch Hetchy Valley to our dorm room taps were laid between 1914 and 1934, and cross three active faults. (The Crystal Springs Reservoir itself lies in the valley of the San Andreas Fault.) So it’s no surprise that the San Francisco Public Utilities Commission is currently in the midst of a decade-long, $4.6 billion project to reinforce and enhance the water transport system before the next “Big One” rattles a fault between here and the Sierras.


History predicts a severe earthquake along the Hayward Fault about once every 140 years, so we’re overdue for the next one. Geologists assign a 30-percent probability of a major earthquake within the next 30 years — a slippery number for a slippery fault. But in the (likely) event that this January remains dry, we may discover that the largest threat to our water security isn’t the shaky ground over which it flows. Perhaps we’ll see that the real threat is drought.


So far, we’ve gotten half the normal amount of precipitation, and the snowpack is 20 percent or less than normal for this time of year. It’s easy to see that California’s water supply is in trouble by glancing at your nearest reservoir. The bathtub ring — dirt and rock exposed along reservoir edges by falling water levels — of Lake Don Pedro (also filled by the Tuolumne River), which we passed on our drive home from Yosemite, must have been meters high. Even Crystal Springs here on the Peninsula is looking low. Across California — and across the world — we’re growing on borrowed water, outstripping the ability of our freshwater supply to replenish itself.


It’s a problem exacerbated by climate change. Not only will precipitation patterns change, potentially reducing the absolute amount of water that rains down on Californian watersheds, but warmer temperatures will mean less snow and more rain. Thus, rather than accumulating a large snowpack that melts in spring just in time to meet agricultural demand, we’ll have to find ways of capturing immediate runoff from winter storms by adding capacity to existing liquid reservoirs.


Scientists expect the Sierra Nevada snowpack to decline by 40 percent by 2050 and by up to 90 percent by 2100, assuming we keep up our current rates of fossil fuel use. Since it seems that, short of running out of those fuels, our carbon dioxide emissions are unlikely to slow, we’ll be dealing with significant dry-downs within our own lifetimes.


Time to start practicing.


One week after my visit to Yosemite, I found myself in another National Park: Death Valley. Water that flows into Death Valley doesn’t leave: The annual evaporation rate is 150 inches per year, and the valley floor is covered by salt deposits up to 5 feet deep. Our hotel room was plastered with warnings about heat and dehydration, and equipped with water conservation measures, like a rotating hourglass to time five-minute showers.


It’s amazing how quickly you learn to soap up (and how grateful you become for shorter haircuts) while watching sand trickle through the glass aperture. It was a lesson I took home with me: the perfect New Year’s Resolution shaped by two National Parks, one at elevation, the other (partly) below sea level, linked by water, or, rather, its absence.


Holly encourages you to try out the five-minute shower and to send water-saving tips, comments and critiques to hollyvm “at” stanford “dot” edu.

Holly is a Ph.D. student in Ecology and Evolution, with interests that range from marine microbes to trees and mushrooms to the future of human life on this swiftly tilting planet. She's been writing "Seeing Green" since 2007, and still hasn't run out of environmental issues to cover, so to stay sane she goes for long runs, communes with redwood trees and does yoga (badly).

Login or create an account

Apply to The Daily’s High School Winter Program

Deadline Extended!