Wednesday, November 18, 2009

Figuring Water Flow - The Easy Way

Figuring Water Flow - The Easy Way

I am working on the irrigation part of setting up my new garden
scheme and would like to ask a question about figuring the exact
water flow. How would be the best way to figure what was actually
getting to the beds. My water system gives a gallon every 10 seconds
through the end of a water hose, but this will not be the actual
amount given through the PVC pipe in the bed since there would need to
be excess capacity to the PVC in order for it to remain pressurized
its full length and deliver a uniform amount. Any thoughts will be
helpful. Maybe it doesn’t matter but in order to use 2/3rds of a gallon of
water per S.F. per week I would need to know more closely the rate of
application it would seem. Thanks


Let's not complicate things. Take a ruler and measure the depth of the water.
When you measure 1", that's enough water.

To apply 1" of water to a 30'-long soil-bed requires approximately 2 1/2 cubic
feet, or 18 gallons of water. This assumes your planting area is 12" wide.
This is figured by multiplying width by length by depth, or 1' X 30' X 1/12'.

For me the simplest way to determine the amount of time necessary to water a
soil bed is to turn on the water, look at your watch, when you have 1" of water
in the bed look at your watch again, and subtract the first time from the second
(or use a stop watch). Or you could do the following:

If you're watering with a hose:
1) place the end of the hose near the head of the bed,
2) place it in a 5 gallon bucket,
3) turn on the water,
4) simultaneously look at your watch,
5) look at your watch when the bucket is full.
6) subtract the beginning time from the ending time,
7) this is the time for five gallons,
8) divide by 5 to get the time for one gallon,
9) multiply by the number of gallons needed to water the bed.

If you are using a PVC pipe system your first step is simply to remove the pipe
and place a bucket next to your ball valve.

Man, that's complicated. I just water them. But I guess if someone is going to
automate completely they should know how long it takes for each bed, so they can
water when they are away from home. That's a trick though, since the water
pressure to the end of the last bed may be different than that going to the
first bed. Life's tough, isn't it!

Jim Kennard