Water doesn't just sit in those upper few inches of soil. It either percolates deeper or is transpired by plants.

Now, of course one big issue is that light rainfalls tend to be caught by the above-ground vegetated surfaces (leaves) and so much less actually reaches the soil. Rainfall of less than 0.10 inch isn't considered "wetting".

whaas,
You have my compassion. We got dried out in summer 2011, and the sub-soil has never been recharged. We have been wetter for the last 6 weeks or so, but not nearly enough to recharge the subsoil. Even when there's be a couple inches of rain, no water is standing 2 hours later. And the soil is very dry 4-5 days later, as the surface soil is dried from below. A pond I drive by on the way home from work has about 4" of water in it, It has been like that for a couple months. I've been driving by is since 1989, and have never seen it anywhere near as low as it is now. Another nearby has dried up completely repeatedly over the last two years, and I never saw it dry up completely before last year. Been lots of tree death the last two years, and it will continue for years to come, even if rains return.

Translation, we feel your pain.

Arktrees

We're doing a stream renovation down deep in a wooded ravine. One aspect involves bringing in or re-using existing clay to form the banks of the new streambed. Now keeping in mind this is at the bottom of the streambed...the clay is too dry to compact properly to get the necessary stability. Contractor is having to water and mix before each lift. Crazy stuff.

+oM

Whass, I've noticed that too, been flabbergasted..never saw anything like it..I too wonder if/how the subsoil will ever recharge (me, who is dealing with the bog over overammended over the rock hard unbelievable dry impermeable clay underneath..I just wonder how much money people are going to be willing to spend to ...do whatever...lots of people around here seem to have some major trees chopped down, and just using ..rocks, or mulch, or grass.
amy

>Now, of course one big issue is that light rainfalls tend to be caught by the above-ground vegetated surfaces (leaves) and so much less actually reaches the soilAnd yet the forest drips loudly even where there has only been a heavy fog. Some places have what are called fog deserts, where the vegetation is pretty much living off of the moisture it collects from coastal fogs, as it hardly ever rains in these areas.

bboy, there's several issues with your understanding of what I said.

1) A light rainfall is generally completely from above, and not wetting all plant surfaces from the top down immediately like fog condensation does. Thus, as it drips down the light rain-produced moisture fades away as it keeps hitting dry surfaces, while fog drip is hitting wet surfaces and building.

2) Most places living off fog drip get fog all the time and thus never have a chance to dry out between heavy rains. This is much different from a place that has dried out and then experiences a bit of fog. Its a lot easier to keep a place moist if its always foggy, than it is to moisten it back up after just a little fog.

There shouldn't be any tree casualties (due to lack of water) if people would get out their hose and use it! It isn't that difficult. Yes, it can be a pain and time consuming if you have a lot of trees, but when you plant something you've made a commitment to do right by it.

ilovemytrees,

You realize, of course, that during times of severe drought there are often water restrictions, yes?

The other issue is being able to supply enough water to mature trees. We could be talking about areas as large as 8,000 sq. ft.

I didn't really get the fog comment either. After most 1/8" or less waterfalls the moisture lies on the leaves and evaporates. I can't tell you how many times the mulch remained dry under the canopies of my mature lindens.

For the last 2 years my water bills have been atrocious. My neighbors do not water at all, thus the roots are coming to my yard. I can not dig a hole anywhere without digging up roots.
To water my trees, I turn the hose to a very small stream, lay it under a tree and let it run all night.
In my block alone, 4 trees have been taken out this year and 2 more need it. If you fly over the city you can see dead trees everywhere.

Houston had a really bad drought last year. Several million trees died, primarily pines and magnolias, but a lot of oaks, too. About 6 pines on my block are dead (that's 100% of the pines on my block). A lot of houses that lost trees are rent houses, and believe me, most renters don't give a fig about the landscaping. I told the renter next door to me that he needed to water or the trees would die and he blew me off. Now there are 2 dead pines in his yard, and supposedly he's buying the house, but doesn't have enough money to get the dead trees cut down. I hope they don't fall anytime soon. It takes a LOT of water to keep a pine alive, since they have a really deep tap root. Also, people on limited incomes (like me) can't afford a huge water bill. I was saving water from my a/c just to keep my roses and other plants alive.

These trees weren't just in peoples' yards, but were on city rights-of-way, city parks, and large natural parks that don't have any water unless it rains. The 200 acre arboretum, which is mostly forest, has thousands of dead trees and looks terrible now. Plus, we had water restrictions. And the city quit watering trees on their property to conserve water. Plus, water lines broke all over the city because concrete and asphalt buckled, and a lot of water was lost that way, too. Crews had to come from other cities to help repair the leaks.

It isn't as easy as just dragging the water hose around.