hairmetal4ever(Z7 MD), if you look closely to the lawns of Las Vegas off the tourist strip, you see they are plastic. That has been an industry in Las Vegas. No more cutting grass :-)

I don't know about Boise or Denver, but some plants depend more on underground supplies of water. Take Date Palms for example, one too many movies set in North Africa, has convinced people that those palms are like cacti and grow in sand. Not true, they are tapping into subterranean supplies of water. You mentioned the West, I imagine that western flora depend a lot on the run off of melting mountain snows in the spring. Of course, we see some of this in the East but I imagine, there is no comparison. Besides, most places in the East are wet enough. Eastern precip is also very evenly divided over the entire year..., (until you get down to about South Florida with a summer maximum and a winter minimum). Eastern gardeners complain about their mini droughts while the climate still supports over 40 inches of rain. My average is closer to 50 inches and a few years ago it was 80 inches. Forget the threshold precipitation for 'forests'..., thinking it's under 30 in the U.S. ( but remember, the warmer the climate, the more rainfall you need due to higher evaporation/transpiration rates!) Yours is an interesting question, because you get to see that it's complicated. There are also areas out in California (in Redwood country), that absolutely depend on FOG for their moisture (not RAIN).

I don't know about Boise but, yes, most trees you see in the suburban areas of Denver are definitely irrigated. If a street tree is planted, it will be watered until its roots can reach into someone's yard that is watered. (Years ago I actually had a huge argument with a friend from college who moved out there, about the questionable long term suitability of these practices in the western USA.) When you head toward the foothills past Boulder, you start to see the naturally occurring trees, but they are all drought tolerant conifers. Some washes or gullies have deciduous trees, though, that survive on the extra ground water in those areas. It is helpful that it is a summer peak of rainfall.

In this photo, it's easy to see where the natural tree line starts above Boulder.

https://en.wikipedia.org/wiki/Boulder,_Colorado#/media/File:The_Flatirons_in_autumn..JPG

Hair, I was in Denver a couple years back. Sure there is more precipitation and less evaporation than in the deserts of Phoenix and Vegas but they do not have enough water. The newspapers there are full of stories about the east/west water rights battles. Also, on here I have read in at least parts of Colorado there are rules regarding storing rainfall off your roof.

For the purposes of working with our environment and keeping nlthe national overhead low I wish Uncle Sam would step in and force some rezoning regulations down people's throats. If broke historically Republican governored hippy California isn't fit to grow crops in or maintain 50 million people so be it.

There, I was bipartisan.

Tornado, you might find this interesting: http://ecowatch.com/2015/04/21/california-drought-colorado-river/

I've actually been thinking about this and googling for the past 15 minutes...I really ought not to spend time of this, given I have other things to do. It will never fly in California, but I had a crazy moment of thinking "WWCD". NO, not what would California do, we already know too little too late - what would China do! We just don't think big enough in this country! What about damming the ENTIRE Central Valley! Sure you might have to relocate some rare California Delta Snail to another area...as well as the entire city of Sacramento, but think of the benefits. All that rain that is lost in the wet years by flowing out to the ocean could be saved! You'd have the biggest artificial lake in the world, and agriculture could continue along its shores. Which generally happens now anyhow with certain crops, they typically grow things like oranges on the ridges anyhow, because they avoid inversion freezes that way. It would take a few years to fill of course, during which time we'd all have to buy our broccoli grown elsewhere. Lake Volta in Africa is 3200 sq. miles and is the largest reservoir in the world; the Central Valley's land area is listed as 22,000 sq. miles but of course you probably wouldn't make the lake nearly that big. Surely if they could dam 3200 sq. miles in Africa decades ago, we could manage 16,000?

Generally in Texas, we are able to grow drought-tolerant trees in areas with 24-36" of rainfall if you plan to water your trees for first 2-3 yrs til they establish. This is even if one doesn't water the yard. Further west species such as Arizona Cypress, certain Junipers, Pinyon Pine, and Afghan Pine seem to do well in areas with less than 24" of rainfall. Some areas with 15" rainfall are also much higher in elevation which helps some. I have seen trees (Pinyon Pine and Arizona Cypress) at Big Bend National Park grow all the way down to 4,900' elevation following a ridge which yielded some shade from sun and a dry creek bed which may have had water in it once or twice a year for a few hours. This is in an area often described as high desert but that I refer to as the back side of hell.

I remember seeing Salt Lake City, Utah, from the air. A green patch on the desert.

Hairmetal,

Yes, we water. Otherwise we'd have nothing much but prairie grass, tumbleweeds, yucca, cacti, Juniperus scopulorum, Pinus edulis, riparian ash, willow and elm and the later 3 would be found mostly along stream and river banks. A big chunk of the population here are transplants from other places and think those plants are ugly. Since that's the population that's buying houses, they put in lawns and trees that would never survive here without irrigation.

I have mostly natives, but have put in a few beds with non-natives that can take drought and alkaline clay soil and I water to get them established, then as needed when it's dry. I also have about 15 roses that don't require nearly as much care as you'd think.

It's catching up with us. There's a lot of discussion around here on water storage and reducing water usage as we've come through some tremendous drought years. The last 2 years have been different with above normal rainfall and flooding.

Barb

I forgot to add that if you have a well, you are permitted to have 2 rain barrels to catch roof runoff and they recently passed a bill to allow homeowners to collect rain water as well. It would never be enough to sustain the average suburban lot, though.

David, I lauged then thought man I hope he was kidding lol.

Where I am the state and cities issue welfare bonds for the benefit of people looking to sell farmland and their partners looking to buy and develop it. These bonds are public money used to build levees for them to raise their property values artificially. This would be necessary if we were some small island nation looking to reclaim land. Instead we have tons of open land along I 70, I 55 and I 44 etc that does not flood so while it may not benefit St Peters to build there it does not stick future generations with the trouble of maintaining higher and higher levees.

Hair, I could not imagine you use "lush" to describe US West. I see you are in Maryland.

It does annoy me that people move West to escape humidity and clouds, as well as snow if it's AZ or CA, but then expect their yards to look exactly like they did back East, only without the horrible inconvenience of having it rain, and not always be sunny and 77 degrees. Can you detect the snark?

I don't know....I've hung out in places like Denver, Vegas, and so on. They never seemed like anything but awfully dry places to me, obvious irrigated exceptions noted. I think all the people heading west to escape the "awful eastern weather" will get their just rewards at some point. Or, their offspring will. But the developers, the local govt. officials with their hands in the money pot....they'll have made their bundle and moved on to new areas to exploit.

+oM