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Rhode
Island
receives 40 to 50 inches of rain a year. However, during
the growing season, there can be periods of little
to no rain, causing plants to suffer from drought stress
and many of us to reach for the sprinkler. How do we know
we are applying enough water while not overwatering?
A rain
gauge is one of the most important tools in your home landscape.
With it you can properly manage lawn and
garden watering. Summer showers are often spotty and unpredictable.
The only way to know how much rain we’re getting is
to measure it using a rain gauge. While drought stress can
impact plants, over-watering creates many concerns such as:
· Increases
risk of pollution from yard and garden care chemicals
· Wastes valuable water and impacts water supplies
·
Encourages shallow root zones and increases plant’s
susceptibility to disease
·
Wastes time and money – it costs money to irrigate
Using the rain gauge, you measure rainfall and other precipitation
events, such as heavy dew and mist. Most lawns and gardens
need about one inch of water each week. By measuring and
recording rainfall, you will have an accurate account of
what nature has already supplied. You should water only to
make up the difference. As a result, you should not set your
watering on an automatic schedule.
Where to place your rain gauge:
Rain gauges should be placed in an open area away from trees,
buildings, and other structures, as they may cause the
rain gauge to get a false reading. Ideal areas to place
rain gauges are in open areas attached to posts or stuck
in the ground. A good general guideline to follow is placing
the rain gauge twice as far away from the height of an
object such as a tree.
The rain
gauge you may have just received contains a 5” rain
gauge and 1” watering gauge to measure irrigation sprinkler
output. To use the rain gauge
on the ground, place the 1” watering gauge in the ground
(part with the plastic spike), then place the 5” rain
gauge inside. If mounting on a post, the rain gauge can be
screwed on separately from the 1” watering gauge.
If you obtain your own rain gauge, depending on the type,
it may be made for mounting on a post with a screw, stuck
into the ground with a plastic or metal spike, or stand on
the ground with a special holder. Some holders are specially
designed to add decoration to the garden. Check with your
local garden supply or hardware store.
Using your rain gauge:
After you install your rain gauge you will need to check
it at about the same time once each day and record the
amount of precipitation collected. If you do not check
your rain gauge each day evaporation could distort your
reading. Make sure to take the reading at eye level to
avoid error. Be sure to empty the rain gauge each day after
your check it. Add your daily rain measurements at the
end of each week to obtain your weekly precipitation amount.
If the total weekly rainfall is less then one inch, the
difference can be supplied with irrigation. Before irrigating
check the weather forecast and for signs of drought stress
in your lawn or garden. For more information on proper
watering and identifying drought stress, refer to the Water
Wisely factsheet.
Measuring Sprinkler Output:
The 1” watering gauge can be used to collect water
from your sprinklers so you know how much water is being
applied. You can also use a bake pan or shallow can such
as a tuna can if you do not have an extra rain gauge or special
watering gauge. Place your watering gauge or can within the
wetted path or radius of the sprinkler just prior to watering.
Avoid placing at the extreme outer edge of your sprinkler’s
wetted path.
When watering is complete, read and record your
watering gauge. If using a pan or shallow can, take it
to a flat surface
and measure the depth of water with a measuring stick.
Here is an easy way to calculate sprinkler output:
· Run the sprinkler system for 30 minutes.
· Measure the amount of water collected in your watering gauge,
pan or shallow can.
· Multiply that depth by 2 to get the amount of water that
your sprinkler applies over a one hour period.
Adjust the flow rate and running time of the sprinkler to
apply the amount of water intended without causing runoff.
For example,
your sprinklers ran for 30 minutes and you collected ¾” of water. Multiplying ¾” by
2 equals 1.5 inches over a one hour period. You thought you
were applying ½” over 30 minutes, or 1” over
a one-hour period.
Next
time you irrigate, you can reduce the flow rate (gallons
per minute) as needed to result in ½” over 30
minutes or 1” over a one-hour period. You can figure
this out through trial and error. If the flow rate is set
and not contributing to runoff problems then simply reduce
the running time. For example, you could reduce the watering
time to 20 minutes and then measure again to see if you are
now at ½”.
For more information:
See our Water Wisely fact sheet
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