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Fluxmuster t1_j5p92ss wrote

I'm a civil engineer in CA working mostly in stormwater retention facility design. When building a new development or redeveloping in most areas of California, you have to prove that it is infeasible to infiltrate the full volume of the 85th percentile storm on site before you can consider any other methods of stormwater treatment. Onsite storm water infiltration is already a huge thing in California.


CrankyStinkman t1_j5pmqc9 wrote

China figured it out 1500 years ago with their monsoon flooding. Fuck tons of canals.


MrMissus t1_j5pyqn9 wrote

I'm pretty sure Chinese cities have catastrophic flooding happen to them all the time because of a significant lack of infrastructure.


CrankyStinkman t1_j5q7peo wrote

Yeah, I don’t think that those canals were maintained and expanded across multiple regime changes.


tankerdudeucsc t1_j5q9cfo wrote

Well the most famous one was the dam that they built. 3 gorges dam that helped with the Yangtze River problems.

So maybe not 1500 years but they do build infrastructure faster than the US.


CrankyStinkman t1_j5qbmdl wrote

The canals were built during the Warring States period, somewhat ironically the footprint of the canal system overlaps with the 3 gorges dam.

The Chinese have been with flooding for a long time, many historians believe that dealing with flooding was the key driver that led to the development of centralized governmental bodies in ancient China.


Locha6 t1_j5swfqw wrote

Didn’t they also have over 250,000 deaths when many, many dams collapsed like dominos?


[deleted] t1_j5sxosr wrote



Words_Are_Hrad t1_j5t5aqa wrote

>250k people or dams 1500 years ago

China's population during the warring states period ~2500 years ago was ~40 million. And the oldest dams in the world date back ~5000 years ago. Hard to imagine China not having dams 1500 years ago.


moldyfishfinger t1_j5rrvis wrote

Can you explain what you mean?


Words_Are_Hrad t1_j5t5q7b wrote

Water infiltration is the process of the ground absorbing water and it flowing down into the water table underground. You have to prove that your site can't reasonably absorb the water before you are allowed to divert it elsewhere.


ChiseledTwinkie t1_j5sme97 wrote

Why can't we pump the water back into the ground? Like a reverse well. We could create temporary rainy season reservoirs and pump the water back into the ground near farmlands


Justanothebloke t1_j5sw3q1 wrote

It is feisable. It is called ASR. Aquifer storage and recovery. The concept is to drill and case the bore to a specific depth in the bedrock that aligns with a fracture. Those fractures hold enormous amounts of water as they go for kilometres. Clean the captured water and pump it down the hole and recover it at a later date when needed.


Fluxmuster t1_j5vgpdo wrote

This is done in a lot of places. Especially places with deep sandy soil. Orange county California has a pretty extensive ground water recharge program. They actually inject partially treated water in a line along the coast to prevent salt water intrusion into the water tables as they pull from the aquifers, lowering freshwater tables.


trappingsofignorance t1_j5wn822 wrote

Seawater intrusion is a major issue all along the coast. Once your aquifer goes salty you pretty much need to find a new aquifer.

Also implicated in the Delta which is part of why keeping a certain amount of water flowing into San Pablo Bay is a big deal


inc0ncise t1_j5stfgd wrote

That exists in the oil fields actually. They are called water injection wells! Wonder if it’s viable for what you suggested.


informativebitching t1_j5tmrk8 wrote

What is the 85th percentile equal to for recurrence interval? What makes it infeasible? Subsurface conditions only or combination of the site being hemmed in and subsurface conditions? Ever discover a new fault while investigating the subsurface?


Fluxmuster t1_j5vfjd9 wrote

Usually infeasibility is proven based on the underlying soil's conductivity . We have to do infiltration tests as part of the geotechnical investigation for the site prior to design. If the volume of water from the 85th percentile storm can't be infiltrated within a 36 hour period it's infeasible. There are other criteria like nearby utilities, steep slope, contaminated soil etc that can preclude infiltration as well. 85th percentile is based off long term (80 years) local rain gauge data. Never encountered a new fault being discovered, but most geotech investigations don't go deep enough for that.


informativebitching t1_j5vnqt9 wrote

Fun. I’m a civil but never had the pleasure of working on storm water or subsurface anything


l397flake t1_j5s2dh6 wrote

How about building reservoirs like other modern countries do it. POS state


Words_Are_Hrad t1_j5t5xu4 wrote

Lmao California has the most extensive network of water works in the entire nation by a massive margin. Go read some books...


sjb204 t1_j5tr498 wrote

I can’t tell if you read the article. The current drought, more so the larger environmental changes, are exceeded their reservoir system.

The reservoir system also just has a ton of bleed ( I know Tahoe supplies Nevada, not California, but the evaporation rates are kind of crazy. More efficient water usage just makes sense…?


l397flake t1_j60169g wrote

In 2014 we approved a 7.5 BILLION bond to build reservoirs in Cal. Maybe someone can tell me how many have been built since then