I had a lawn in my front yard. Emphasis on “had”. I took it out after realizing how much water it needed.
Grab a tape measure and measure your lawn. Start at one end and lay the tap measure down, if you run out of tape measure, stop in that spot, coil up the tape and start measuring again from that spot. Then add all the lengths together for that run. Then measure perpendicular from the run you just had so you end with a final Length x Width. Multiply the two numbers together to get your lawn area.
If you don’t have a tape measure, walk out the lawn area by using the length of your foot step either heel to toe or your normal walking pace. If your feet are 12″ long then each step toe to heel is a foot. Otherwise measure your pace, usually between 2-3 feet.
If you have a weird shaped lawn, measure at the widest point, and then at about an average width spot for the other dimension. It will give you a ballpark of about how big your lawn is.
You’ve got this.
I had 546 square feet of lawn in my front yard.
Lawn Area: 21 feet wide x 26 feet long = 546 square feet
Through searching online for “recommended watering for lawns“, I need to water my grass between 1″ – 2.5” of water a week. How much water is that?
1 foot X 1 foot X 1 foot = 1 cubic foot 7.48 gallons = 1 cubic foot Recommended Weekly Watering: 1 inch to 2.5 inches 546 square feet X (1 inch a week/12 inches depth of water) X 7.48 gallons = 340.34 gallons OR 546 square feet X (2.5 inches a week/12 inches depth of water) X 7.48 gallons = 850.85 gallons
1″ weekly watering is 340.34 gallons while 2.5″ weekly watering is 850.9 gallons.
Remember, this assumes 100% of the water coming out of your sprinklers goes into the ground. Here is the catch, if you water during the day when it is warm or windy, as much as 30% of the water will evaporate before hitting the ground. Turn on your sprinklers and watch the mist never hit the ground.
To calculate how much MORE water is needed, I continue using my numbers from above and get this:
340.34 gallons needed for 1 inch weekly watering 30% lost of evaporation (or 70% lands on the ground) Total Water Needed = Total Water Applied X 70% Simply Put: Total Water Needed / 70% = Total Water Applied 340.34 gallons / 70% = 485.71 gallons
For 1″ water a week, I’ll need 485.7 gallons of water.
850.85 gallons needed for 2.5 inches weekly watering 30% lost of evaporation (or 70% lands on the ground) Total Water Needed = Total Water Applied X 70% Simply Put: Total Water Needed / 70% = Total Water Applied 850.85 gallons / 70% = 1215.5 gallons
For 2.5″ water a week, I’ll need 1215.5 gallons!
To put this into perspective, with my 150 gallon tank, if I filled it all the way, I’d need to do 8 trips to the fill station a week to meet this demand. I’m sorry, but this is ridiculous. The lawn has got to go!
If you’d like to download this math in a Microsoft Excel format: http://1drv.ms/1zbpM3B Clicking the link will open in Microsoft Excel Online. Note: you are free to use as you please.