Q. With all the beautiful rain that we had recently, what
should we do regarding future watering? Has it been enough water to just stop watering
until after the first of the year?
A. Rains come in all forms. This one was rather unique in
that it came down over a nice, long period of time giving it a chance to soak
into our landscapes instead of running off the surface and into the streets.
Landscapes
are supposed to be contoured to force rain off landscapes and into the streets.
Once water enters the streets they act as “storm sewers” and help remove water from
properties. If landscapes are not contoured correctly it is feared that water
might accumulate on the landscape and flood homes causing damage.
For
gardeners who are interested in “harvesting” water on their property, this rule
may seem to be counterproductive but it is meant for the “general good”. There
are ways to store water and improve the effectiveness of rainfall such as dry
stream beds and pools but you must be careful when doing this. I will post some
ideas on my blog as examples.
As a general
rule we consider about 40% of our rainfall to be what we call “effective”. This
means that 40% of the rain, four tenths to every inch, actually gets into the
soil where it is stored rather than running into the streets. This rain event however
was more “effective” than most.
Another
problem was that the rain was not evenly spread throughout the valley. This
makes it hard to make a general statement about how long to turn off irrigation
systems throughout the valley. For shallow rooted plants like flowers and turfgrass
they will still need a couple of irrigations the rest of this year. Deeper
rooted plants, such as trees and large shrubs, can probably get by.
Unless
you know your rainfall amount, I would count this rainfall as a single
irrigation event, skip one irrigation and then continue irrigations unless we
get more rain. The savings will still be significant.
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