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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 the right amount of water? |
5” rain
gauge with 1” watering gauge for measuring irrigation
sprinkler output.
What
is a rain gauge?
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 products.
- Wastes valuable water and impacts water supplies.
- Encourages shallow root zones and increases plant
susceptibility to disease.
- Wastes
time and money – it costs money to irrigate.
A
rain gauge measures 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. Irrigation should only
be used to make up the difference, and it should not be
set to an automatic schedule.
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Where
to place a rain gauge:
Rain gauges should be placed in an open area away from trees,
buildings, and other structures, as this may cause an inaccurate
reading.
A general guideline to follow is placing
the rain gauge twice as far away from the height of an
object such as a tree. 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.
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Using
a rain gauge:
After installing a rain gauge, you will need to check
it once each day
and record the amount of precipitation collected. If you
do not
check
your rain gauge at about the same time each day, evaporation
could occur and result in an inaccurate reading. Be
sure to take the reading at eye level
to
avoid error and to empty the rain gauge
after checking it. Add
the daily precipitation measurements at the
end of each week to obtain a weekly precipitation
amount. If the total weekly precipitation 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 refer to the
Water Wisely factsheet. Back
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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 the water collected
in the 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”.
Back
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more information about water conservation:
View our Water Wisely fact sheet
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