Los Angeles has seen more precipitation in the last week than in the last year and a half. As a result, we've also seen welcome snow on the local slopes, not so welcome floods and mudslides, and lots of reminders that this doesn't mean the drought is over, yet. One outcome that hasn't been discussed much, so far, is the impact of this huge first flush of water through LA on water quality at our local beaches. Not only do they look like trash dumps right now, but fecal bacteria counts in the water will likely be far above state bathing water standards for days to come.
In 1997, the California legislature passed AB 411, a law that requires weekly water quality monitoring at public beaches during the recreation season from April 1 through October 31. The law also requires public agencies to close beaches after sewage spills, and for public health officials to warn swimmers and surfers to stay out of the water for 72 hours after a rain. This warning became known as the three-day rule. It was based on the best professional judgment of public health professionals. And it is supposed to provide time for the concentration of fecal bacteria in the water to be reduced by dilution and the disinfectant properties of sunlight and saltwater.
Last year, seven UCLA senior environmental science students worked with Heal the Bay to complete a study on the accuracy of the three-day rule. They analyzed seven years of beach water quality monitoring data from the 32 most monitored beaches in California, all in LA and Orange County. After analyzing 87,000 data points for enterococcus fecal indicator bacteria, they came to several conclusions.
Most importantly, the three-day rule isn't adequate for protecting the health of swimmers and surfers at beaches affected by storm drains, creeks and rivers, and piers-- including such popular surf breaks as Malibu Surfrider Beach, Topanga, and Doheny Beach in Dana Point. On average, it took more than five days after a rain for fecal bacterial counts at these beaches to return to minimal public health standards. And it took even longer--10 days or more--for average enterococcus counts to return to minimal water quality standards for bathing at enclosed beaches such as Cabrillo Beach and Mothers Beach in Marina Del Rey.
The good news is the three-day rule is more than adequate for open ocean beaches with no nearby sources of pollution. And the vast majority of California beaches are open ocean beaches.
The results of this study will be released today. Our first major storm of the year is now over. But a storm-driven swell is still pounding Southern California beaches with surf in the four-to-seven-foot range. Big surf means that a lot more surfers--like the one above at Dockweiler State Beach this morning--will brave polluted waters in the days to come. But surfers beware: at some of Southern California's most popular breaks, you might want to wait until Friday before paddling out, unless you are willing to weather a nasty stomach bug in exchange for good waves.
"Men often sit with their dishes upside down while it is raining money," the Los Angeles Herald observed in 1905. "After the shower is past they wonder why they did not get any."
The article was about a gold rush in Nevada, but the observation could apply equally well to our own attitude to the rain that fell on LA in the last week. "Now the shower of wealth is falling in Goldfield," the Herald reported, "and the dishes that are face up are filling for everybody that is wise enough to have them ready. Many people's plates are always right side up."
Unfortunately, most of our dishes are upside down, according to Hadley Arnold of the Arid Lands Institute at Woodbury University. With the rain drumming down outside her office this weekend, Arnold put pencil to paper to try to figure out what we're missing. She made some very broad stroke, conservative estimates. Roughly 65 percent of the city of Los Angeles is covered with impermeable surfaces, roads, highways, houses, and other buildings, she calculated. Only 35 percent of our landscape stands ready to absorb the windfall of a good rain.
The city of Los Angeles covers roughly 500 square miles. That's 320,000 acres. In the average year, about 12 inches of rain falls in LA. Actually it's about 14 inches, but Arnold was being conservative, and 12 inches is a convenient rough number to use because it equals a foot. And a foot of rain on one acre of land equals an acre-foot, the common measurement for water. So around 320,000 acre-feet of water falls on LA in an average year in the form of rain, and 65 percent, or 208,000 acre-feet runs off impermeable surfaces to the ocean. Now one-acre foot of water is enough to meet the needs of about six people for a year. So in an average year, this runoff would be enough for 1,272,000 people or one-third of the city's population.
Now, let's say that three inches of rain fell on LA this weekend (in most areas it was more, in a few it was less). In the last week, then, we got about one-quarter of our average annual rainfall--enough to supply 8 percent of the city's annual water if we were able to capture it and store it in groundwater aquifers--that is, if we didn't have our dishes upside down while it is raining money.
And how much money are we letting get flushed down the drain as a result? Oh, about $176 million a year based on the Metropolitan Water District's average wholesale price for water, which is around $850 per acre foot.
While she was sketching this out, Arnold decided to look at this picture one other way. That 208,000 acre-feet of water that runs off to the ocean? We have to get it somewhere else. And that's equivalent to about 5 percent of the water that the Met gets from the Colorado River. It takes energy to get that water to LA--about 2,000 kilowatt-hours per acre foot, actually. Using our current energy mix of gas and coal, moving an acre foot of water from the river to LA contributes about 3,000 pounds of carbon dioxide equivalent to the atmosphere--which adds up to a total of 318,000 tons of carbon dioxide equivalent for all the water we import from the Colorado to make up for the water that runs off when it rains here. If we were able to capture that rainwater, and not use that energy, it would be roughly equivalent to taking 80,000 cars off our roads each year.
Now, if only it were as easy as turning a single bowl face up. It's not, of course. Many dishes will need to be turned right side up to catch the rain in LA. And pencil sharpeners will come out when such calculations are done to justify each and every investment to capture more water locally--as they should, Arnold says. But there's nothing like a good hard rain to remind us what is getting away when our dishes are turned upside down.
Photos: Wave of infections? Surf's up, but in all likelihood so are fecal bacteria counts at LA beaches after recent rains. Still, surfers braved the water off Dockweiler State Beach on Monday morning. Newspaper clip from the Los Angeles Herald, January 1, 1905. Thanks to Mary Adams Urashima aka Surf City Writer for the clip.