I am sending this just after the power was restored.

HEATWAVE!  When the temperature hovers around 100 degrees F you need to check moisture in the ground.  A lot of fruit will start splitting after a spell of hot weather if the moisture in the soil drops too low.  Tomatoes, navel oranges, pomegranates, some cultivars of figs, and some late ripening grapes are quite vulnerable.  Try to keep the soil constantly moist to at least 1 foot deep (in the locations where you normally irrigate).  This means you should be able to push a metal rod or stake at least 1 foot deep by hand into good garden soil.  (If you have highly compacted soil near a slope, or rocky soil the stake won't penetrate.) 

With daily highs near 100 degrees the amount of water used by plants increases dramatically.  No one could give you an exact amount except for weather stations that have an evaporation pan since evaporation rate depends upon several factors including temperature, humidity and air movement.  Don't be surprised, however, if you must water twice every day to maintain soil moisture.  (Remember that most local soils only absorb about 4-5 minutes of sprinkler irrigation at a time.  The excess runs off.) 

Another way to look at it is gallons per tree per day.  A mature citrus tree (about 15' tall) can evaporate over 50 gallons of water per day at 100 degrees.  Don't forget that a large mature tree nearby can steal a hundred gallons per day. 

Yes, I do know many gardeners that claim that they have a productive old tree that they never water.  Old trees can have very long roots.  These trees cannot adapt to low water conditions; they are simply using a neighbors' irrigation water. 

 

One problem many homeowners face is trying to grow a young plant within a garden of mature plants. 

 

With each crop a farmers only has to be concerned with the water needs of one type of plant.  All the plants of the crop are of similar age and have similar water use.

If a homeowner starts growing a young trees in a garden surrounded by mature trees, the homeowner cannot simply apply what the young tree is using, unless the water needs of all the surrounding trees are also met. 

A twenty-year old tree can have roots 100 feet long.  The mature plants in a garden can belong to one network of roots that shares water to any plant within the network. 

Until a young tree becomes part of the existing network, it will require extra water (and fertilizer) to thrive.  If the other trees of the network can thrive on drier conditions, the new tree will always need extra water on a frequent basis. 

Was the true value of a farmer's plow the fact that it severed the roots of nearby trees and shrubs?  Note that roots of all plants generally exist within 12-18" of the soil surface, therefore a plow severs most competing roots.  Does this mean that the true value of digging a large hole when installing a plants is the destruction of competing roots?

I remember a homeowner, who lived in a forest, telling me that they could plant and grow anything as long as it was watered three times per day, every day.