How many gallons of water is needed to water a lawn that is 5000 sq ft

I understand it depends on many parameters. But I thought I ask anyway.
We have a lawn that is around 5000 sq ft with st. augustine grass in Austin, TX.

What is typical watering schedule of this lawn will need in gallons per month?

I believe I am adding around 5000-6000 gallons per month in a summer month (June/July months).
What I am wondering is it too much, too less or what.


If you had zero precipitation during the month (just calculating the extreme case), and wanted to give your grass an inch of water a week, let’s round and say you give it 4 inches of water a month.
5000 sq ft * 1/3 ft = 1666.66 cuft = 12,468 gallons of water.

A quick search for average rainfall in Austin gives around 4 inches in June, and close to 2 inches for both July and August.
This would give you 0 additional watering required in June, and around 6,234 gallons during July and August.


@Videoguy, a quick formula to ballpark the gallons of irrigation water needed per day (excluding rainfall) is:
((Eto x PF x SF x 0.62 ) / IE) – multiply this value by the number of days in the month.

ETo = Reference ET
PF = plant factor
SF = area to be irrigated in square feet
0.62 = constant value used for conversion.
IE = Irrigation efficiency.

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