How Utah counts water use per person, and why a city's number can't be lined up against another's
The state's gallons-per-capita-per-day figure counts every drop a provider delivers and divides by the people it serves. Here is what goes in, what does not, and why the state itself says the numbers aren't comparable with other measures.
When a Utah city or water district says its residents use a certain number of gallons a day, the figure usually comes from one state formula. Knowing what is in it makes the number easier to read, and easier to distrust when someone sets it beside a number from somewhere else.
The formula
The Division of Water Resources calls the measure gallons per capita per day, or GPCD. It takes all the water a provider delivers to customers in a year, divides by the number of full-time residents in the provider's service area, then divides by the days in the year. [1]
The people count comes from the Census Bureau's estimate of permanent residents inside the provider's service boundary. The division says it does not estimate population by multiplying homes by an average household size. A district that serves part of a city, or several cities, is measured against its own boundary, not a city line. [1]
What counts as water use
The measure includes both drinking-quality (potable) and non-potable water, and it counts reuse and secondary water. It covers all customers: homes, businesses, institutions and industry. [1]
That has a plain consequence. A city with large commercial users, schools or irrigation systems, or with many seasonal visitors who are not counted as residents, can post a higher figure than its households alone would suggest. The number describes a provider's whole system, not what a typical family uses.
Why the figures don't line up
The division is blunt about comparison: there is no national standard for measuring water use, GPCD can be calculated many ways, and Utah's method counts all delivered water, so its figures look higher than those in regions that count differently. Differences in what is called "use" or "population" can change results substantially. [1]
It also draws a line between GPCD and consumptive use, the water that is actually used up rather than returned. The page says the two figures "are not comparable." Four districts, covering Utah, Salt Lake, Washington, Weber and Davis counties, are assigned to report consumptive use annually for the state's largest counties, those with 175,000 or more people. [1]
What it is used for
The state's regional conservation goals use 2015 water use as the baseline, and state-funded system improvements are measured against it. GPCD is also the yardstick for progress toward the 2030 county and regional goals. Current figures are posted on the state's Open Water Data site. [1]
When you read a local claim, check four things: the year, which provider's boundary it covers, whether it is GPCD or consumptive use, and who the comparison is against.
This guide describes what the Division of Water Resources' page says about its method. The page carries no revision date; we checked it on Oct. 27, 2026. It gives no current figures, so none are quoted here.
Sources
Background explainer by The Utah Ledger. AI-assisted reporting, checked against the sources above.