You can make a difference to the hurt being caused by climate chaos and the great extinction event in your town or your city! How? Reuse, repurpose, and recycle this information. You can push your local politicians to act. It will make a difference!
This is the letter for week 166 of a weekly climate strike that went on for 4 years in front of San Francisco City Hall, beginning early March 2019. For more context, see this story. For an annotated table of contents of the topics for all the strike letters, see this story. Meanwhile…
STRIKE FOR THE PLANET
For when San Francisco runs out of water
Reaction Guidelines for Water, pt. 3: Potable Water
This is a resource for when SF runs out of water. The goal is to have procedures you can pick up off the shelf and start putting in place when it’s too late to avoid disaster.
Glossary of terms used
aquifer — an underground layer of water-bearing permeable rock and unconsolidated materials
BCE — Before Common Era
blackwater — wastewater from toilets, primarily urine, feces, and toilet paper
CE — Common Era
gray water — domestic wastewater without fecal contamination, from sinks, showers, washing machines, etc.
groundwater — the roughly 30% of readily available freshwater in the world that is found in rock fractures and soil pore spaces under the earth’s surface
megadrought — a prolonged drought lasting two decades (20 years) or longer
potable water — water that is safe to drink
CA is in a megadrought
Based on past megadroughts in our region, and comparing the present drying rate to past drying rates, we are in year 22 of the worst megadrought in the west since at least 800 CE.1 Higher temperatures from climate change mean the west will continue to dry through the 21st century.2 Past California megadroughts that have been as dry as quickly as this one lasted over 200 years.3
How much potable water does SF need?
Water needed for survival
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1 gal/3.8 L per person per day (includes minimal washing and toileting)
0.3 gal/1 L per person per day (only sustainable for short periods)
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Current per person use in SF
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42.6 gal/161.3 L per day
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Current SF population
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~880,000 people
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Minimum amount of water needed per person for SF’s population
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880,000 gal/3,344,000 L per day (includes minimal washing and toileting)
264,000 gal/880,000 L per day (only sustainable for short periods)
(These numbers do not include pets, zoo animals, aquariums, or plants. Animal Care and Control estimates there are 150,000 dogs in SF.)
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SF’s current water use (2021)
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37,300,000 gal/141,000,000 L per day
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What are SF’s current water resources?
The Hetch Hetchy system, the West Side Basin, Lake Merced and other smaller lakes, Islias Creek and the buried creeks and lagoons of San Francisco, potential regional sharing, and any reused or recycled water.
How dependable are those resources?
Hetch Hetchy
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Provides ~80% of SF’s water. This water travels 167 miles by tunnel and aquaduct, through 7 counties (Tuolumne, Merced, Stanislaus, Alameda, San Mateo, Santa Clara, and San Francisco), down ~4,000 feet in elevation, and across 2 major and uncounted smaller faults. 3 of the counties it crosses are in Exceptional or Extreme Drought and facing mandatory water cuts, drying wells, a plummeting groundwater table, algae blooms, and the possibility of no water. When Tuolumne, Merced, and Stanislaus go dry, Hetch Hetchy water will not make it the 167 miles to San Francisco.
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West Side Basin
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This is a small basin, prone to saltwater intrusion. Pumping out more than is replenished by rain, runoff, or injection increases saltwater intrusion. Ocean level rise is already increasing saltwater intrusion into the basin. 10% of this basin’s supply is groundwater, so drought is already reducing the basin’s volume.
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creeks
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These are mostly underground, many were routed straight into the sewer system, some were co-opted by industry, and the few that remain somewhat functional are being greatly damaged by the megadrought.
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regional water sharing
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?? Everything depends on how localities react to scarcity and change.
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reused and recycled water
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This is entirely under San Francisco’s control. If we have these systems in place, we will have these sources.
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Which sources are we most likely to lose?
Hetch Hetchy. It might be held for a while at gunpoint, but ultimately this is too long a front to protect. Hetch Hetchy currently provides ~80% of SF’s water use. Removing Hetch Hetchy water leaves SF with 7,460,000 gallons, or almost 8.5 gal/32 L per person per day. This is above the minimum (listed in the first table above).
The West Side Basin. This basin is going to suffer from saltwater intrusion. How much water will be available is unknown.
How can SF immediately get more water?
Besides developing new water sources, such as rainwater and fog harvesting and mandatory gray water reuse, SF can save water by outlawing watering of grass, non-native plants or ecosystems, and mandating strict rationing. Tapping into other water resources, such as blackwater, requires forethought and planning.
It’s not quite Mad Max
But 8 gallons per person per day is awfully close. Reacting, instead of planning, only gets you so far.
FOOTNOTES
1. Chelsea Harvey. “Western ‘Megadrought’ Is the Worst in 1,200 Years”. Scientific American. 15 February 2022. https://www.scientificamerican.com/article/western-megadrought-is-the-worst-in-1-200-years/.
2. Jason Smerdon. “What historic megadroughts in the western US tell us about our climate future”. The Conversation. 16 February 2015. https://theconversation.com/what-historic-megadroughts-in-the-western-us-tell-us-about-our-climate-future-37615.
3. Paul Rogers. “California drought: Past dry periods have lasted more than 200 years, scientists say”. The Mercury News. 12 August 2016. https://www.mercurynews.com/2014/01/25/california-drought-past-dry-periods-have-lasted-more-than-200-years-scientists-say/.