The claim in the OP is one often leveled by conservative politicians at California, but I didn’t put this in P&E because I am hoping to get a factual answer.
This claim seems to be based on on the ruling from rears ago that a certain amount of water needs to be allowed to flow into the Sacramento-San Joaquin Delta to protect the endangered delta smelt. The implication being that California would have more than enough water for human needs if it weren’t for those pesky environmental regulations requiring protections for those fish.
So, does that claim hold water (no pun intended*)? Is the amount of water required to be released actually significant enough to impact the state’s water supply? My understanding is that at least this time of year water needs to be released from reservoirs anyway in order to make room for the snow melt from the Sierras that we’ll be getting in a few months (yet I see posters on social media lamenting the fact that we’re “letting that water run into the ocean” when someone posts a picture of the dam with it’s floodgates open during the rainy season). I suppose, though, that protecting the smelt may require some more water be released during the dry summer months.
There’s also the allegation (not sure how true) that the water use allocation was established in California many many decades ago when populations were much smaller. Certain farmers and farming areas have high quotas and so have no incentive to reduce consumption with better water management - indeed, perversely the incentive is to use every bit of that allocation regardless, just in case they get future allocations reduced due to lack use use.
Not sure how true this is. Obviously water consumption and quotas are a touchy issue.
Well: you need water in a particular location. And the fact that there is plenty of water in Northern California doesn’t help your shortage of water in Southern California if there is insufficient methods to transport the water.
If it hadn’t been for William Mulholland, LA likely wouldn’t exist. He, along with two others, designed and engineered the 230 mile long Los Angeles Aqueduct from Owens Valley. It was an astonishing engineering feat for its time. Then, in the 60s, The 450 mi. California Aqueduct was built.
LA, as it is today, might not, but LA gets it’s water from other sources (Owens valley now only supplies about a third), and there was a town here before, Pop over 300000. But yeah, that aqueduct allowed LA to get a big growth spurt.
It is significant, altho only7% for the delta, but like 30% for all wild rivers- you do NOT want rivers drying up before they get to the ocean, very bad for the environment- salt water creeps back in instead.. But the main issue is that the rains dont fall all over CA.
Of the water that is NOT diverted, 80% goes to Agriculture, 10 to industry, 10% to homes, etc. I read that just the almond trees (they are very thirsty) use about as much as all residential use. So, it is NOT people watering their lawns.
The other issue is that CA naturally has wet/dry year cycles, and if the cycle goes wrong and you get 3 years of dry, a drought happens.
To put some numbers on it (and these are approximate because I’m not going to chase down the latest regulations and guidance to support fish and wildlife, but it will give you an idea of order of magnitude):
Looking specifically at the Sacramento-San Joaquin Delta, which seems to be the main flashpoint, it is generally recommended that flows be maintained at 6,000-12,000 cubic feet/second (cfs), or 5-10M acre-feet/year. Current regulations require the lower bound, but there are other factors including time of year, drought conditions, and managing salinity. There are newer recommendations that are based on a percentage of unimpaired flow (i.e., what the flow would be without dams or diversions), but I don’t know what that equates to.
If we take 5M acre-feet/year in terms of residential use, it’s enough to support 10-15 million households depending on conservation practices (and that number is likely higher now as conservation has improved). So if 100% of the Delta water was magically diverted to residences (emphasis on magically), it would be enough for CA. That ignores agriculture and industrial use and the impossibility of transporting the water.
And the fact that the Delta would salt up, ruining it for the fish and other creatures that live there, not to mention the crops grown there. Most of CAs rice production, plus alfalfa, wheat, and grapes. The Delta is a highly productive agricultural region, cultivating over 550,000 acres of crops. We’d lose all that.
It’s true that water rights were first negotiated long before the exponential growth of California and before Phoenix and Las Vegas and other western cities grew from small towns into metropolises. The states revisit the allocations regularly and always extremely contentiously. This year’s snowfall in the mountains has been exceptionally light until this weekend, which will provide some relief and maybe a return to the negotiations, but the region may literally be overgrown and should - heresy of heresies - start turning people away.
None of that has to do with Northern California. Colorado River water can’t be shipped north and the north’s water can’t be shipped south.
well thats what happens to all the short rivers at the north coast.
The north coast gets 40 to 100 inches a year, and so there is plenty of run off.
But theres no (big ) dams north of Mendicino and west of the Trinity dam.
But of course it is easier to supply water to a river area if the dam is upstream on the river, or uphill for canals and aquaducts, and all you have to do is dribble the water out when needed…..
run off from some urban area is not a good source of water. Especially when it butts up to the coast… the chance to dam it is very remote.. and the urban area is probably reasonably flat..
The land slides of the foot hills there at the coast, suggest these hills wouldnt work well as dam walls.
There are reasons the water isn’t able to be dammed … OP’s question is about the water being lost, not about water that is reasonably able to be dammed.
There are several spreading basins along the LA River before it empties into the ocean. This allows storm water to be captured to recharge the groundwater.
Fun fact (courtesy of the weather people on my local news channel): As of 2025 California was completely free of drought status in the entire state, which I believe is calculated by reservoir fill compared to capacity, and rainfall and snow pack and things like that. This is the first time in 25 years that this has been the case.
The northern Sierra snow pack was only at about 50% of normal, however; central Sierra at about 70% and southern Sierra at close to 100%. This was before various recent storms, so that may have improved.
I know this is not precisely the subject of the OP, but I think it’s a good thing to know in the discussion. Maybe water management is getting better, or maybe it’s all attributable to unreliable weather patterns.
It’s been a fairly normal winter rainy season so far. We get storm after storm for a few weeks. Then we go for a few weeks with no rain. After that we get another series of storms. It goes like this from about November to March.
The average snow pack is more than enough for one year. On the other hand, it’s never enough to cover three years of insufficient rain. No matter how much snow pack you get, it melts and runs off into the reservoirs, which may not have capacity to hold it all. Unless summers get cooler, so that less melts – but our climate does not seem to be moving in that direction.
The most cost-effective reservoir uses a dam across a canyon with a big river. Everything coming down the river gets caught behind the dam. Those places in California are all taken already. The newer ones are off-stream. They pump the water into them from a nearby river. How much to pump and when can be a difficult decision. With an on-stream reservoir, deciding how much room to leave for flood control can be another big decision. No one really knows how much water there will be until the rainy season is over.
