Question:
How long does it take to provide the right amount of water when I irrigate?Answer:
Most garden areas, including the lawn, vegetable garden, and perennial garden, perform best when they receive an inch of water each week. When this is not supplied by rain, the gardener must do it using a hose, bucket, or sprinkler.
Determine How Much Water is Needed
It takes 0.623 gallons of water to supply 1 inch of water to 1 square foot of garden space.
To determine how many gallons of water are needed for your garden, multiply the area of your garden by 0.623. If you are watering a specific tree, shrub, or other plant, find the area of the root zone under the plant.
For example, a newly planted tree with a root zone area of 16 square feet would require ~10 gallons of water to deliver 1 inch of water to the root zone (16 sq ft × 0.623 gallons per sq ft = 9.97 gallons ≅ 10 gallons)
If watering by bucket or watering can, measure out this amount and apply it to the area slowly enough to prevent runoff.
Determine How Much Water is Supplied
Hose
When watering with a hose, you need to determine how much water it supplies next. Use the nozzle you plan to use while watering, and turn the hose on to the water pressure you plan to use while watering. In most cases, this is not all the way on, as a lot of water will run off if it is supplied too quickly.
Determine how many minutes and seconds it takes to fill a five-gallon bucket. Divide the bucket's capacity by the time to fill it to determine the gallons per minute.
For example, it takes 2 minutes and 26 seconds to fill a five-gallon bucket, so the hose delivers 2.1 gallons per minute
(5 gallons ÷ 2.43 minutes = 2.1 gallons per minute; remember, 26 seconds is 0.43 minutes; 25 ÷ 60 = 0.43).
Soaker Hose
For a soaker hose, the flow rate is provided on the package in gallons per hour (GPH). If the hose provides a flow rate per foot (GPH per foot), multiply that by the hose length to determine how many gallons of water it delivers. To get gallons per minute, divide the GPH by 60. While the flow rate will vary with water pressure, this calculation is typically close enough for home garden watering.
Determine the Watering Time Needed
Using the amount of water needed and the flow rate, you can calculate how long to run the hose to get the required amount of water. Take the number of gallons needed divided by the gallons per minute to get the number of minutes needed to water.
For example, the watering time needed for a newly planted tree with
- 16 square feet of area
- requiring 9.97 gallons of water
- provided using a hose that delivers 2.1 gallons per minute
would be 4 and 42 seconds
(9.97 gallons ÷ 2.1 gallons per minute = 4.7 minutes or 4 minutes and 42 seconds; remember, 0.7 minutes is 42 seconds; 60 × 0.7 = 42).
Watering Using a Sprinkler
Watering using a sprinkler or soaker hose is more straightforward. To calculate the time needed to deliver an inch of water, start by setting up the sprinkler to cover the area you wish to irrigate.
Then set up several shallow, flat-sided containers in the spray. Turn the water on at the pressure you plan to use while watering and determine how long it takes to fill them to one-half inch. Multiply the number by 2 to get the time needed to deliver 1 inch of water to the irrigated area.