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Utah planners shown two methods to build required water budgets
Summary
A Utah Division of Water Resources presentation described two data-driven methods — a billing- and provider-coordination approach and an ERU/duty-value approach — that counties and most cities can use to prepare water use and preservation elements required by state law.
A presenter from the Utah Division of Water Resources outlined two methods planners can use to develop a water budget required by state law, describing steps to assess growth, reliable supply and current and future demand.
The presenter said the requirement stems from "SB 1 10 and 76," and that a water budget "is a comprehensive planning tool used to assess and project the hydrologic costs and demands associated with land use." The presentation described a provider-coordination method that uses water billing and provider data and a second method that uses equivalent residential units (ERUs) and irrigation duty values to estimate demand.
The presentation framed the water budget as a comparison between reliable supply and total current and projected demand. The presenter said planners should first "understand how your city or county is growing" and determine projected changes in population and land use. Reliable supply was defined as "the amount of water that can be counted on year after year even when faced with shifting conditions like seasonal changes or extended periods of drought," and the presenter distinguished that reliable supply is not the same as total water rights.
For the provider-coordination method, the presenter recommended that planners work with public works and water providers to obtain annual water-usage data that providers report to the Division of Water Rights, noting that data are "publicly available on its website categorized by residential, commercial, industrial, institutional, and other uses." As an example of how providers' data can be used, the presenter said Tremonton’s total actual water available in 2021 "was around 4,000 acre-feet" in the slide shown.
The presenter advised selecting roughly five sample properties per zoning type (single-family, duplex, multifamily, commercial, institutional) and using billing records or provider data to calculate average annual consumption for each land-use category to establish a baseline.
The ERU method was presented as an alternative that the state engineer uses to standardize peak-day sizing. The presenter said the state engineer's ERU sizing requirement for residential indoor use is 800 gallons per day (GPD). Using ERU ratios tied to a single-family home (ERU=1), the presenter gave example ratios: a townhome 0.75, apartments 0.3–0.8, and office space 0.05–0.1 per 1,000 square feet, and explained how to multiply ERU ratios by unit counts or building square footage and then by 800 GPD to estimate peak-day indoor demand.
Both methods, the presenter said, require including secondary (irrigation) water where applicable by using state engineer irrigation appropriations and duty values. The presentation directed planners to a duty-value map and to the Division of Water Resources' staff: "If you are struggling to determine green space for diverse land use types, please reach out to our green space analyst, Jack Heinsman, at the Division of Water Resources. He can determine these values for you." The presenter emphasized combining current demand from water-rights data with projected demand from new development to compare against reliable supply.
The presentation recommended that water providers and irrigation companies review municipal and county water budgets to verify assumptions and assess whether reliable supply will meet projected demand. The presenter closed by inviting planners to contact citycountyplanning@utah.gov or the Division of Water Resources for assistance.
