Watering the Vegetable Garden

by Doug
(in the garden)

One of the biggest questions that seems to pop up with watering the vegetable garden is how to measure the amount of water we’re putting onto the garden. I’ve taken the liberty of rounding numbers out whenever possible. This is gardening - not rocket science.

Overhead sprinklers are easy. Simply put a wide pot of some kind under the sprinkler. Measure how long it takes the sprinkler to put one-inch (3 cm) of water in the pan. Let’s say it takes 20 minutes to do this.

We want to add 1 and a half inches so we have to run this for 30 minutes to get that amount of water. If we want to add 1 and a half inches a week - we’re going to run our sprinklers for 15 minutes one day and 15 minutes the next day.

The important thing is that you have to test your own system! Water pressure and sprinkler patterns are different and what my system produces isn’t going to be applicable to yours. But that’s how you do it.


Now drip systems are just as easy but a bit more math.

Take your entire length of drip hose (one of the units) say it’s 50 feet long. Put it all in a 5 gallon bucket. Turn on the hose and see how long it takes to fill up the bucket. That length of time is the amount of time it takes to apply 5 gallons to the garden - let’s say it takes 20 minutes to do this.

Now....

Your drip system is going to apply water between 2 and 3 feet wide (depending on your hose and the soil. Lay a hose on the ground and let it run for an hour. See how far the water spreads. Let’s say it spreads 3-feet. And that it’s 50 feet long (as above). That means the hose has a coverage area of 3x50 = 150 square feet. If we put one inch water onto the garden, we now have to do the following math.

150 square feet = 144x150 (144=number of square inches in a square foot) =21,600 square inches.

Apply one inch of water and we have 21,600 cubic inches. Divide by 231 (231 cubic inches to a U.S. gallon) and we have 93 U.S. gallons of water. (5 U.S. gallons = 4 Imperial gallons)

If it took 20 minutes to produce 5 gallons, its going to take 93/5 =18 times 20 minutes or 360 minutes. So 6 hours of watering will put on 1-inch of water.

Again, if your drip system is faster or slower or your soil allows water distribution in a different width, your numbers are going to be different.

Drip will always be slower and take longer than you think. :-)

But that’s how you figure it out.