Comprehensive reporting for better planning
When it comes to reporting water use, there isn’t a national standard for what is included and what is not, which makes meaningful comparisons difficult. Some cities and states only report certain types of water use and/or apply a credit for water that is returned to the system. Utah includes all potable, secondary and reuse by all users (residential, commercial, institutional, and industrial) in its gallons per capita per day (GPCD). This all-inclusive accounting method means Utah’s numbers look higher than other cities or states that don’t include all water use in their calculations.
Some cities only report single-family residential potable water use and exclude multi-family residential use, commercial, institutional, industrial, secondary and/or recycled water. The resulting GPCD of a city that reports only single-family residential use is significantly less (around 80 GPCD) than Utah’s average GPCD of 223 (according to the 2019 M&I report) that includes all potable, secondary, and reuse water by all users. If you look at just metered residential use for Salt Lake City – the water use number reported by some municipalities – the GPCD is 96.
Population calculation method impacts the numbers
GPCD is calculated by dividing water use by the population, then dividing by the number of days in a year. Because GPCD is impacted by population, how a city or state calculates population also affects water reporting. Some calculate population by applying the average person per household to all residential units rather than using the Census Bureau population estimates. Utah uses the Census Bureau’s estimated permanent resident population, adjusted to water provider service area boundaries.
Many of Utah’s counties, including Washington, Rich, Grand, Kane and Summit, have a high number of second homes and are popular tourist destinations. However, seasonal residents and visitors are not included in the Census Bureau population, so this water use is added to the permanent population’s use, which yields a higher GPCD than for those states and cities that use the average person per household calculation method.
Tracking use is essential for planning
Tracking water use is an essential part of the state’s water planning. These numbers are also used to help set goals and demonstrate accountability. Comparing Utah’s water use to another city or state isn’t an “apples to apples” comparison because of different water accounting practices. The different methods aren’t good or bad – just different – but it’s important to understand how they impact the results. It’s more meaningful to compare current numbers against past performance and ensure the state is seeing improved conservation and efficiency.
Open Water Data website
Visit the Open Water Data website for access to a wealth of data including the latest water use numbers, interactive apps, maps and data visualizations. The site provides access to water data produced and maintained by the division that is useful for planning purposes.
The website features three primary data categories: Municipal & Industrial Water Use, Water-Related Land Use, and Water Budget. A wide variety of data can be explored and downloaded in many useful formats. Many are summarized by state, county, basin or water supplier boundaries. A gallery of online maps as well as resources from outside entities is also available.
Additional Background
Water Resources White Paper on M&I Water Use – A document with descriptions of M&I water use and population.
Developments in Agricultural and M&I Data – Assistant director Todd Stonely’s presentation to the Board of Water Resources on December 3, 2020, and learn more about agricultural and M&I data.
Audit Methodology Change – 2015 marks a significant methodology and data frequency review milestone. This fact sheet outlines the changes.
For more information, please contact Rachel Shilton at 801-538-7271 or email rachelshilton@utah.gov.