In particular, orchards spread through much of California's central valley. These are perennial plants (trees or vines), living decades in some cases.
If you've mortgaged the farm to plant acres of fruit or nut trees, you're not going to let them die in a drought. You'll fight hard for any running water you can get your hands on, and then you'll dig wells and suck as much water out of the ground as your trees need.
Groundwater has been (uncharacteristically!) unregulated in California, so aggressive ranchers or farmers can draw down the water table, threatening their neighbors' wells and causing a 'tragedy of the commons' situation and a race to drill. Sucking all that water out of the ground has all sorts of environmental concerns - as a result, California just passed laws to become the last western state to regulate groundwater usage.
Who has the bigger lobby group?
"Nature provides about 200 million acre-feet of precipitation to California in average years. Of this total, 65% is lost through evaporation and transpiration by trees and other plants. The remaining 35% stays in the state’s system as runoff. More than 30% of this runoff flows out to the Pacific Ocean or other salt sinks. The rest is used by agricultural, urban, and environmental purposes.
About 75% of the annual precipitation falls north of Sacramento, while more than 75% of the demand for water is south of the capital city. Most of the rain and snowfall occurs between October and April, while demand is highest during the hot and dry summer months" 
While evaporation is part of the natural process, I question how much is self-inflicted by transporting / storing large volumes of water where evaporation will occur at high rates.
Further, while residential may only use around 10% of the roughly 49 million square feet allocated for human use, we really should consider the evaporation costs incurred from transporting part of the base 200 million square feet down south.
I have been unable to find a reliable source that measures the evaporation from the 16 aqueducts , let alone the 100s of reservoirs . Please share if you have one.
 - http://www.acwa.com/content/california-water-series/californ...
 - http://en.wikipedia.org/wiki/List_of_aqueducts
 - http://en.wikipedia.org/wiki/List_of_dams_and_reservoirs_in_...
Thus they'll plant extra plants to provide shade for the ground and reduce evaporation.
It is sad though to click on the other tab "When Snows Fall" and see the central valley referred to as an "inhabited desert". We continually try to give the impression that we turned the Central Valley from desert into farmland, when the opposite is the case: we turned what was a winter wetlands into a desert.
True, it's not Mojave or the Sahara, but it's pretty hot and dry. Savanna a la Africa is not a bad comparison.
The Ottawa River is a major river, Ottawa is the only major user of its water, and doesn't really make a dent in the flow, especially since we put our wastewater back into the Ottawa (after treatment, mostly).
They had no concern about water security, but they did have a concern about fires. There were a couple of cases where dry lawns made it easier for fires to jump from one property to another, so they sent out the notice.
Maybe it was a water delivery limit as opposed to a water source limit.
Although i do remember the river would get so low you could walk quite far out to the middle and Champlain rapids were more like a shallow stream
If we switch to desalination, it will cost about $0.12/Barrel to generate water. Distribution will, of course, dwarf that cost, but production of water is cheap. We just use ridiculous amounts of it, and it's energy expensive to distribute it if you can't take advantage of gravity.
There are 326,000 gallons in an acre-foot. So, Most Farms can't pay much more than 2000/326000, = $0.006/Gallon.
$0.75/cubic meter = .75 / 264 = $0.002/Gallon.
It's within range - but, once again, it's not the cost of generation, but the cost of distribution that gets expensive. The Sierra Nevada has the advantage of all that potential energy from its altitude.
http://www.kcet.org/news/rewire/science/in-talk-of-solar-des... - Saltwater reclamation from the ocean in Carlsbad using Reverse Osmosis will cost about $2000/acre foot.
EDIT: For runoff water from farms, there is a cheaper solution http://www.sfgate.com/science/article/California-drought-Sol...
"His solar desalination plant produces water that costs about a quarter of what more conventionally desalinated water costs: $450 an acre-foot versus $2,000 an acre-foot."
Of course, the elephant in the room is always - what do you do with the components you've removed from the runoff water. They are pretty toxic.
A hectare is 10000 square meters. A centimeter is 0.01 meters. Thus, if 1 centimeter of rain falls on a 1 hectare field, then that's simply 100 cubic meters of water.
The nice thing about this is that you can easily compare quantities from different contexts. A cubic meter is a cubic meter, whether the water came from a pipe or from the sky.
But what does it mean to have an acre-foot of piped water? Nobody specifies pipe cross-sections in acres. Or a barrel of rain falling on a 1-acre field. How many inches is that equivalent to?
It's not just water. Look at HVAC. In the US, natural gas is billed in therms, and electricity is billed in kilowatt-hours. In metric countries, both electricity and natural gas are specified in kilowatt-hours.
And why not? Energy is energy. If you have a heat pump with gas backup, then you could use gas and electricity interchangeably to heat your house. If you've got a residential cogen system, like they have in Japan, then you could buy either gas or electricity to run your television.
It's funny you use that example, because kWh are silly, unnecessarily convoluted units themselves :-) the "proper" unit for this dimension is the joule, and 1 kWh = 3.6 MJ (1000 J/s ∙ 1 hr ∙ 3600 s / hr ∙ 1 MJ / 1e6 J).
There actually is, however, some value in having different units for methane vs electricity, since you have to run methane through a suboptimal furnace to harness its energy. Granted, modern gas-powered furnaces are usually more than 90% efficient, but there's still some loss. And since each customer has a different furnace with a different eta, it's usually not useful to directly compare natural gas tariffs vs electricity tariffs even if you do have a cogen unit.
Well, heat pumps transfer more than 1 kWh of heat transfer for every kWh of electricity. You have to account for the performance factor anyway, whether you're using natural gas or electricity.
The point is that, once you've divided by COP or AFUE, you get price per effective kWh, which you can then compare directly. As opposed to getting a price per therm, which you must apply a conversion factor to.
With cogen, you get both electricity and heating out of the unit. If it's all in kilowatt-hours, then you simply add them up and compare to the kWh of the incoming natural gas to get efficiency. But how does a therm of electricity translate to volts and amps?
As for the kilowatt-hour, I think the reason we don't use megajoules is that metric time never took hold. If we had metric hours, minutes, and seconds, then the kilowatt-hour would be as awkward as the hectare-centimeter.
But really -- read the comments and check out the number of times these units are mentioned and converted:
- "200 million acre-feet of precipitation to California in average years"
- "No doubt when water hits $100/barrel..."
- "1 Barrel = 42 Gallons. It costs $0.75/cubic meter (264 Gallons)"
- "There are 326,000 gallons in an acre-foot. So, Most Farms can't pay much more than 2000/326000, = $0.006/Gallon."
- "$0.75/cubic meter = .75 / 264 = $0.002/Gallon."
- "In 2011, the average californian used about 326 gallons/day of water"
If you are going to have a conversation about how urban residents compete with farmers for water, it helps to have a common unit. People don't drink water in acre-feet and farmers don't consume gallons or cubic feet or whatever of water. But if the conversation were in liters or cubic meters, at least you'd have a fighting chance of talking the same units.
Take this from the comments: "For example, Crystal Springs, a 70k cubic meter reservoir in San Mateo, is entirely for urban use. There is no agriculture competition for it. Every gallon we conserve there, is another gallon conserved for city use."
First, it is not 70 000 cubic meters. It's 70 000 000 cubic meters or 70 000 000 000 liters. 
What would that look like? Well, we have 7e7 cubic meters to divide up into three dimensions. It would be a lake like 700 meters across by 10 meters deep by 10 000 meters long (10 km).
Those Californians who consume 326 gallons (1200 liters) per day? One of them could use that reservoir in about 60 000 000 days. Or if you had a million of them, they'd take two months.
Four acre-inches would be like  one hectare by 10 cm deep -- 10 000 square meters by 0.1 meters, so 1000 cubic meters or 1 000 000 liters. So you can irrigate 70 000 hectares with that much water at that depth per area of land.
I am saying the math is way simpler and you can pretty much do it in your head. And you can visualize it. So: common unit across multiple uses, easily scaled up, easily visualized.
 Not because an acre is the same size as a hectare but because you'd have proportionately fewer hectares than acres.
(I'll admit to having to have Soulver up just to have this conversation - Metric system would make it way, way easier.)
Maybe when wikipedia says that the reservoir is 57,910 acre-feet you have a sense of what that would look like, but I have absolutely no intuition on that, even though I know that an acre is 43 560 square feet and that there are 640 acres to a square mile.
57,910 acre feet would actually be more "intuitive" to me than 70,000 cubic meters (though much harder for me to do calculations and almost impossible to do unit shifting).
57,910 acre feet is roughly 100' deep of water on a section of land. I can "visualize" what that reservoir would would like.
Or, for more practical/relevant to irrigation purposes, it's 100 sections of land, 1' deep.
But yes, I'm still going to argue for the metric system. I promise.
- Development of a robust water entitlement exchange
- Decoupling a water right from the land to create a more tradable asset
- Regulation change to allow for water leases
- A shift away from growing 'thirsty' crops in drought-prone regions
- Decentralization of water treatment plants to reduce distribution costs
- Increased use of grey and recycled water in the home
- Pricing changes based on its use within high water use industries
- Increased use of GM crops designed to require less water
- State-sponsored overseas farming specifically for US import of thirsty crops
- Less water exporting occurring. I.e. selling thirsty crops to China
And I'm sure, much, much more.
I don't know that this is something the US has done but the motivators noted above still stand.
Instead of giant agricultural fields that are open to evaporation, hydroponic or aquaponics inside of greenhouses could vastly reduce water usage.
Instead of huge farms or corporations producing food tens or hundreds of miles away from where it is eaten, community/neighborhood or even household food production could be an alternative. This would be more efficient and save on energy and other costs needed for transporting and retailing food.
These things will probably become more economically viable and popular as solar becomes a consumer-level reality. As in, people are buying solar kits at Walmart or Home Depot regularly. The prices are almost already there.
Pretty sure that a lot of this is related to network effects and trends. The neighborhood urban hydroponic farming thing becomes more economically viable as it becomes more popular, simply because more people are cooperating (via the market) in order to make that more convenient.
Of course, there is a limit to how much food we can produce locally. Right now, even if we converted every Target into an urban farm, and every home and apartment used advanced technology to pull in solar energy efficiently and dedicated a full 1/3 of its space to hydroponic or aquaponic produce, we might only be able to supply a fraction of our food needs that way. What fraction that would be, 10%, 20% or 50%, not sure.
But I feel like that more local production is going to be more efficient and robust in the end, and more and more popular as we start to distribute production technologies more evenly.
When I think of local food production personally I am envisioning taking advantage of the latest in technology in order to create the most efficient and self-sufficient process possible. For now that means things like hydroponics and aquaponics. In the future that could be more sophisticated biotechnology or nanotechnology of some sort.
Its sort of a localization and distribution mindset.
One basic idea is that if food is produced far away, as it is often produced hundred or thousands of miles away, some energy must be expended to transport it. So if a tomato grows hydroponically in the corner of the room, the distance it needs to travel to my mouth in order for me to eat it may be say 10 feet. If it grows in the ground 500 miles away, it would need to travel 500 miles (plus 10 feet). Certainly the energy required to move a tomato 500 miles is greater than zero. Add that up for everything you eat, and there is a fair amount of inefficiency.
Another idea is that producing food or other needs locally means less dependence on more centralized control and distribution systems, which means more security for individuals and families. Its sort of like extending the idea of solar panels and 3d printing. If we can get our own energy from the sun, and print out our own products, why do we have to go to the store to buy food that was grown 400 or 4000 miles away?
The problem in California isn't lack of water for individual use (for the most part, there are a few small communities that are having to truck in water), it's the impact on Agriculture, which is hugely important to the economy of California, and our general food security.
If you were wondering why there aren't more water restrictions for individuals, (Like leaning on people hard to take shorter shower, or use low-flush toilets, or ultra-low-flush toilets) - here's why: Changes to individual use will only have a small impact on our water use - 80% is used for agriculture. Individual restricting use by 20% will only have a 4% impact on overall water use.
With that said, there is a lot of room for California to transition to a "Desert Water Existance"
In 2011, the average californian used about 326 gallons/day of water. With water restriction, that can, with a little bit of expense, and changes in landscaping (no green lawns), be brought down to 150 gallons/day, and with a bit more expense (typically around the toilet), be brought down to 100 gallons/day with some lifestyle changes (typically shorter showers).
On the flip side, California almonds use 1.1 trillion gallons of water each year. That one crop uses enough water to support a population of about 30 million people @ 100 gallons a day.
For individual water use, though - a lot of the California population is right beside the ocean. Desalination costs about $0.75/cubic meter (264 gallons) based on recent Singapore Desalination plant deployments. If we didn't want a lifestyle change, then 329 gallons / day * 30 days / 264 gallons * 0.75 = about $28 to generate the water needed to maintain our lavish California lifestyle (add some more for distribution, which is reasonable for coastal cities without distance or elevation for pumping.
This only works for individuals though - Agriculture needs cheap water to be sustainable, and much of the farmland is too far away from the coast (or too high), too make for economical distribution.
I am gobsmacked - this is a phenomenal amount of water. This is an order of magnitude more than we use here in Melbourne. 326 gallons = 1230 litres, whereas we use ~ 230 litres per person on average. I'm genuinely puzzled by how you use so much water every day.
Previously at the end of a 10-year drought and very low reserves, the government target was 155 litres/day, which was easily done - our household was using about 65-75 litres/day/person, while still doing laundry, daily showering, and keeping a garden. And while we were water-conscious, we weren't particularly strict about it.
I just can't fathom how so many people are using so much water on average every day. Even your tightest suggestion (100 gallons) is double what we're using now in non-drought mode.
I just pulled up my monthly bill to confirm--my current bill reflects 33 days of service, and is for 3900 gallons. I live in Austin, TX in a single-family home that typically has 3-4 adults in it (me, my roommate, and an Airbnb that's booked out almost every day with 1-2 additional adults.) That 3900 gallon usage, or 118 gal/day, is for all of us combined. So it's quite doable in the US!
I think the biggest contributing factors are:
1) We don't water the lawn. Ever.
2) I've installed all extremely energy-efficient appliances, including new toilets, a washer and a dishwasher that use very little energy.
3) We don't take baths--only showers.
I never feel like I'm scrimping when it comes to water. In fact, if anything, I think we do way more laundry/dishes than the typical household thanks to having an Airbnb and wanting to keep everything clean for our guests.
My conclusion: Americans are going to have to give up on their green lawns, and prioritize energy efficiency in appliances, to get to this level. But it's really doable here in the US.
Things like toilets/showers/washing machines are the major indoor elements for high water consumption, California is starting to adopt all of the technologies that Australia has pioneered for decades - things like low flush toilets, low volume showers, low flow faucets, etc... But it will take time (and money) to update the infrastructure.
Also, much of the water use comes from outdoor use - a lot of green lawns in California that are going to have to go away. Also, leaks are a major components.
In order to get to 100 Gallons/day, people are going to have to give up their lawns. And stop filling their swimming pools.
There is zero chance, outside of a major disaster like an earthquake, that Californians would ever use "65-75 liters/day/person" - that's 17 gallons/day/person. You'd see broad deployments of solar powered desalination plants first.
And our consumption is not so modest because we'd be short of water; clean water is the one natural resource we have in abundance here. A drought in the sense of California (or even Britain) is just completely unknown thing here.
By the way, the consumption of water is higher in blocks of flats than it is in detached houses. This is because in detached houses each family or household pays for their own water, but in condominium houses the bill is typically shared among all the flats and the paid out in the maintenance fee.
This applies often even to hot water, so there have been cases where a single old man tells his neighbours that he lets hot water run through the sink just so that he gets even with the family with three small children in the neighbouring flat.
That said, it's pretty obscene to drive through the central valley and see people growing rice for acres and acres. In the desert.
Wikipedia tells me this about Tuolumne:
"The river's water has been a source of contention for many years. About 15% of the total flow is diverted to San Francisco from Hetch Hetchy Reservoir, which floods an eponymous valley in the Sierra Nevada once compared to Yosemite Valley for its natural beauty. Further downstream, about one-half of the river flow is diverted at La Grange Dam to irrigate farmland in the Central Valley."
It looks to me like there is agriculture competition for San Francisco's water.
But it's not very informative to say that there's competition for the river, because there's obviously competition for water somewhere, since it all comes from the same places. My point is that the water rights are secured for most of the major cities in California, and we're not in the position that if we cut back our domestic usage, the farmers will use it all up. We're conserving so that we don't drain our reservoirs.
Given that in this case, the "River" feeds into the "Reservoir" - the two water bodies can be viewed as the same entity for purposes of water sourcing. Given that only 15% of the Tuolumne is needed for the Reservoir, and 50%+ is required for Agriculture, the major drain on the Tuolumne is not San Francisco residents, but Agriculture. San Francisco may have rights to the Tuolumne, but I don't know whether they are Sr. to the Central Valleys, or, what happens if San Francisco has to turn off the water downstream in order to keep Hetch Hetchy full.
But - I do see your point, it's not the case that all water comes from the same place - there's lots of reservoirs that can't be used for Agriculture in the Central valley. For example, Crystal Springs, a 70k cubic meter reservoir in San Mateo, is entirely for urban use. There is no agriculture competition for it. Every gallon we conserve there, is another gallon conserved for city use.
But - it's important to realize, Cities and Agriculture are in competition for the Sierra Nevada water. And every gallon that goes to the farms, is one less gallon that goes to the residents. As the cities conserver more, and more, reducing showers to 5 minutes, and switching to Ultra-Low-Flush .5 gallon flow Toilets, that water is going to become more valuable to city residents, than it will be to agriculture.
I'm not suggesting we don't cut back residential usage - I'm a huge fan of conservation (and an even bigger fan of efficiency) - but, I am saying that we could go to emergency rationing of 50 gallons/day (down from 329 gallons currently), and agriculture could still use up all the Sierra Nevada water. The inverse isn't true - if Agricultural use somehow cut its water use by the same percentage, it would be difficult for residential use to consume the existing supplies.
I first heard the word, "fungible" from Dick Cheney of all people. It was in the context of Canada selling Oil through its ports to the Chinese instead of building a pipeline down to the United States, and his was response was, "That's fine. Oil is fungible." - I.E. Canada Selling Oil to the Chinese would be just as beneficial to the United States, as Canada Selling Oil to the United States, because the oil that we sold to the Chinese, would free up oil from other sellers, which would then go to the United States. All that mattered was that oil was produced and placed on the "Global" Market.
Water, on the other hand, is expensive to distribute compared to its generation, so water from Crystal Springs Reservoir, all 70,000,000 m^3 of it, really only has value for residential use. There is no agriculture competition for it.
In the case of the Sierra Nevada - I think we both concur that water is useful for both residential or agricultural use.
Every single farmer can argue the same way ("I only use a tiny fraction of what the state as a whole uses, so it won't help" or "almond farming only uses 10% (I'm making up this number), so it won't help if we, almond farmers, economize on water use")
Everybody can find a group they are in that will have a small impact.
Last year California became the first state to require re-fitting all existing structures with low-flow systems: http://www.huffingtonpost.com/2013/08/23/low-flow-toilets-re...
There is a pretty major water crisis in the western states, particularly California, but very little in the way of "electric grid failures."
I once met a retired government employee in the desert in Utah, and we talked a bit about water and droughts before he said, "things would have to get really, really, REALLY bad before you couldn't get tap water on demand anymore, even in a desert like this." Listening to his experience I realized that he had the benefit of some experience that I didn't. Not that it makes a draught feel any better. And the wildfires that make your city smell like a campground for days at a time don't help either. :-)
Please let me know if you find it useful!
edit: or maybe it's my browser, but I didn't check
it did look pretty decent once I did that. It took me a while to realize the page was broken in the first place though