Johnny Walker asks, ‘How much water does a golf course use for irrigation?’

By: Jeffrey D. Brauer

Water demand is a factor of climate, turf acreage, evapotranspiration (ET), turf type, and agronomic and soil characteristics.

A parcel of 120 turf acres allows comfortable play and isn't burdensome to mow. One hundred and sixty acres is only necessary within housing developments requiring wall-to-wall irrigation. Courses in desert regions and those participating in the Audubon Cooperative Sanctuary System program are limited to 90 acres of intensively irrigated turf. With desert and un-irrigated rough, 90 acres is feasible, but with woods or prairie causing lost golf balls, it is less practical.

ET (a single measure of turf water loss from evaporation and plant transpiration) also determines water need. ET rates are different for different turfs, but yield surprisingly similar results across most of the country, typically averaging about 0.125 – 0.25 inches daily in Northern climates, and average 0.15 – 0.3 in the South during growing months, or 1.0-1.5 inches weekly and maximum demand reaches 1.75 – 2.0 inches weekly.

Most irrigation systems provide for slightly above-average demand, accepting some risk in droughts, since turf can survive without full replacement of ET. Cost increases dramatically beyond most budgets if designed for the worst possible drought, and water may not be available anyway.

We calculate average and maximum water demand for the golf course, using average ET and rainfall to calculate Average Demand, and Maximum Demand assuming ET at historical levels, and no summer rainfall. A sample calculation for the Midwest is in the table below.

Column D shows months requiring supplemental irrigation with underlines.

Column F shows average weekly demands, likely having these characteristics:

With typical spacing of 70-80 feet, this course will require 1,300-1,500 sprinklers to cover the 130 acres of turf (about 11 heads per acre, plus specialty heads).

We anticipate minimal watering from March to May and November, and varying degrees of irrigation in other summer months. However, the irrigation system must be designed to meet peak, providing about 1.5 inches per week, corresponding to the average maximum demand in July.

Typical run time is about 8 hours (from 8 PM to 4PM, to allow early mowing) and a

Pumping capacity is at least 1,800 gallons per minute (GPM), which allows running 16 -18 irrigation stations (usually made up of two 40-55 GPM sprinklers) at a time to finish the schedule.

A computerized control system and weather station would calculate actual ET, and apply about 90 percent of that, since in Iowa, you can expect that it will rain soon enough to help you catch up.

Total water usage in Des Moines, Iowa, should be about 30 million to 35 million gallons in an average year, if the superintendent applies water only to the turf need.

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