<tt><small>UPDATE</small>: see added great links & info from culhwtch's comment. edited into the foot of this diary, by permission.</tt>
How much stormwater could be captured?
Southern California has the most potential for collecting stormwater — as much as 1.9 million acre feet a year, depending on rainfall, according to the Pacific Institute. Even though the region has little precipitation, it has vast amounts of pavement and other surfaces that create runoff….
The above heads the stormwater section of CalMatters.org’s <big><big>How Can California Boost its Water Supply.</big></big>And the link there (from Pacific Institute.org) goes to a very thorough 48-pg-pdf report.
Editorial comment: despite pavement and storm-drain systems in situ making Los Angeles in particular —largest city in California, 2nd largest in the US— an obvious target, single-solution over-focus is a known cause of failure historically and globally on a vast range of social and climate change issues. Even wars —and political campaigns— can’t be won by a single type of ammunition. Diversity and scope are our greatest strengths — true of human communities meeting shared problems, and true of solutions themselves.
Back to the CalMatters article, other sections give status-and-potential reports for ■ recycling ■ ocean water and brackish water desalination (the later reportedly more energy-efficient, among other positives) ■ transforming California agriculture (said to currently use 80% of developed state water not counting direct rainfall) ■ luxury waste (lawns, turf, car-washing including daily on car-lots, etc) ■ pipe/aquaduct/canal loss to leaks and evaporation ■ reservoir strategy improvement ■ aquifer recharge ■ climate change control ■ water rights reform/environmental justice ■ cloud-seeding (including Nevada, Wyoming, Montana, Colorado and Australia) ■ evaporative recapture by hydropanels being pioneered “ around the world in places that lack clean water, including a Navajo reservation in Arizona, Australia, India and Kenya … and by actor Robert Downey’s eco-friendly house in Malibu ■ and pop-fic notions vs logistics.
More from the stormwater recapture section:
The rainwater and spillover from sprinklers that flows off roads, yards and rooftops — much of it eventually emptying into waterways or the ocean — could help boost California’s water supply. The state's urban areas shed 770,000 to 3.9 million acre feet of runoff a year that could be captured, according to the Pacific Institute. That’s enough to supply between 2.7 and 13.7 million households for a year.
[Currently, the] Fresno Metropolitan Flood Control District [in Central California] captures runoff across 400 square miles in Fresno County. The water is used to fill more than 150 ponds, where it trickles through the soil to refill groundwater stores. In bone-dry 2021, storm flows accounted for almost all of the district’s groundwater recharge. [And] Santa Monica has been a leader in treating urban runoff [with] plans to upgrade a recycling facility built near its famous pier more than 20 years ago. The plan is to treat the collected runoff and stormwater so it’s clean enough to be injected directly into Santa Monica’s groundwater basin.
Strategies for using stormwater also include installing permeable pavement in yards and communities and building basins that let it drain into the soil instead of flowing into storm drains or streets.
But barriers remain to capturing more of the flows. These include high costs and a lack of funding, concerns about impacts to water quality, and lengthy planning and approval processes.
Read more at the top biglink.
from culhwtch:
- This is a recent paper about identifying some buried gravel river channels in the California central valley, which could be leveraged to fast recharge the aquifer with floodwaters. If the proper infrastructure is built over the old river beds. Also places of high concern to keep from pollution, as it is a quick link down into the aquifer.
https://phys.org/news/2022-11-air-scientists-fast-paths-recharging.html
- They’re using aerial surveys to identify these buried channels. Using some huge hexagonal booms suspended from helicopters, to measure the ground transient electromagnetic, magnetic, and radiometric properties. Essentially getting tomography down to about 1000 feet subsurface. Hopefully identifying valuable minerals while they’re at it… https://skytem.com/geophysical-surveys/
- Unfortunately, much of the aquifer has already collapsed, so the capacity is much less than previously available (or perhaps the original capacity was overestimated, and what is has collapsed to is more realistic).
https://www.newscientist.com/article/2343617-california-has-lost-more-groundwater-than-held-in-all-its-reservoirs/
- As mentioned in this diary, urban runoff is a potentially barely tapped resource. This paper says California could shrink water use in cities by 30% or more just using water more efficiently. There are many initiatives on this, and this is something that could be done systematically and globally, though with tailoring to the local conditions of each city. https://phys.org/news/2022-04-california-cities.html
- I think ice stupas could be a useful water storage for high mountainous regions. Particularly placed on shaded slopes. Or perhaps shaded by solar panels used to power the pumps... Small artificial glaciers, taking advantage of the phase change. https://www.sciencenews.org/article/ice-stupa-tower-india-drinking-water-irrigation
- Dealing with eutrophic standing water would improve surface water quality and reduce filtration, fish kills. And I’m pretty sure reduce surface evaporation since the water would be cooler with better mixing and not mats of absorbing algae. Here is an interesting concept where they were originally thinking maybe make a water battery. Instead they supercharged microbial aerobic respiration by completing the circuit, similar to filamentous cable bacteria, but on a scale of tens of meters instead of centimeters. It lets the microbial community capture phosphorous and store it in the sediment much more efficiently than in anoxic conditions. Sink one stainless steel grid in the sediment, float another grid near the surface, connect them with wire, let sit, and your nasty green water will get better much faster than just reducing fertilizer runoff. The phosphorous enriched sediment should actually make good fertilizer itself. Turning it into a resource instead of a water treatment cost.
https://phys.org/news/2021-07-method-oxygenating-lakes-results.html
(summary) https://www.sciencedirect.com/science/article/abs/pii/S0043135421003067?via%3Dihub (main article, paywalled unfortunately, but at least shows a better drawing of the system)
Finally, I’ve seen a lot out there on fog capture, and other air capture of water. I think this needs to be done carefully to avoid legionella contaminating drinking water. Same with trying to capture the drips from an air conditioner. It can be done, but it needs to be done correctly or people will get sick.