One of the problems California faces in drought conditions is that the majority of the rain we get just runs off into the ocean. So, I had an idea…
What if we turned the LA River into a series of catchment panels. The river is nothing but cement (see Terminator 2, Grease, Buckaroo Banzai, etc.) So, every mile of the river, starting in the San Gabriel Valley, we tear up a hundred yards of cement and dig a 10 foot deep pit. Maybe auger down to bedrock in a pattern. Then fill the pit with gravel or some other percolation medium. Do that every mile or so to the Pacific. That way at least some of the otherwise wasted water enters the groundwater system around the city.
This is too simple a solution to be practical. What am I missing here?
I’ll grant you the labor cost. But what lien/easement issues? The river is property of the cities it passes through. No eminent domain involved. Hell, it’s only because it’s cement that it isn’t under Federal control.
Someone double check my math here. 100 yards, 40 feet wide, 10 feet deep is 2.7 million gallons. 200 of these, if they held the water instead of letting it run into the ground, would hold a 1 day supply (542 million gallons).
I don’t think there’s 200 miles between the San Gabriel Valley and the ocean. This seems like a drop in the bucket (pin intended).
Eta: I missed the part about the gravel so the math may math differently depending on how permeable the soil is.
I didn’t mean to solve the problem, just ameliorate it a little bit. The engineering is simple. So is the implementation. Which means @Munch is probably right - lawsuits would tie it up for a century, just because people are assholes.
What you are missing is the rate water will percolate into the (bedrock) aquifer.
It’s low. Very low.
Sometime movement of water through an aquifer is measured in metres/yards per decade.
The vast magority of the water in your retention pits will evapourate rather than percolate.
What you will create is a series of stagnant ponds and a whole lot of algae … might even get a sand swamp or quick sand.
I do apologize for adding to the assholeness of the world by raining on your hypothetical. I know you were looking for more practical obstacles. (But yeah - those lawsuits are gonna sting.)
The Santa Ana river in Orange County has a lot of recharge basins built into its channelization. Has had since the river was channelized in the 1960s.
It’s not about creating an integral series of tanks to hold runoff.
It’s about letting the water get below the impervious layer of concrete and asphalt that covers almost the entire county so it can soak into the natural aquifer below. The capacity down in the aquifer is vast. The problem is the aquifer’s acceptance rate per unit of surface area is low.
We’re doing it in New Mexico, and the groundwater levels in Albuquerque are rising slowly after years of depletion. They use injection wells rather than just drilling holes for the water to percolate through, though.
My hydrologist skills aren’t sufficient to analyse and query, much less rebut … and if it’s working 'tis good.
However, I am unsure of how artesian water resources that took tens of thousands of years to accumulate and were depleted by over extraction for decades (and this rate of extraction I assume largely continues) can be reversed in a mere handful of years.
I’d also want to see more information on changes in salinity through introducing surface water directly into the aquifer.
I’m a bit leery of it myself. Albuquerque used to run exclusively on well water (the line in the 70’s was, “there’s a limitless aquifer” and even back then, as a child, I knew that was BS), but once its level had decreased dramatically, the powers that be started taking water from the San Juan/Chama rivers. The injection wells were added after a long period of study and debate. The river water is treated before injection, so they aren’t just pumping it in straight from the river.
There’s no doubt that enacting water conservation measures much earlier in order to avoid depleting the aquifer works have been a better solution. As it is, this seems better than nothing.
Any real reason they couldn’t do something like this in Los Angeles? Seems like it’s good and deep (120 feet below ground), and could just be used as a straight-up reservoir if designed correctly. Lots of city parks along the river that would be candidates too.
There is an LA River Project that’s been working to make at least some parts of it more like a river. If you search with the words LA river restoration, you’ll find many videos.
I haven’t dug too deeply into the subject, so I don’t know if they’re breaking the concrete. But if they’re not, they’re bringing in rocks, gravel, trees, and other plants to build up riverbed on top of it.