Agriculture takes the biggest swallow of Utah’s water, but more water will be needed for the 2.8 million new residents that Utah expects by 2065, according to a Utah Foundation report.
The Utah Foundation released a research report in August that covered Utah’s water supply and future demand and how the state finances water development.
Titled “High and Dry: Water Supply Management, and Funding in Utah,” the report claims that as one of the driest states, water has helped mold Utah’s growth patterns.
Sustaining the state’s projected growth rate of 1.3% per year puts a focus on ensuring that future residents will have enough water, according to the report.
Like the state, Tooele County also anticipates growth with concerns about water, according to the county’s general plan.
“With the improving economy and increasing growth pressures, the need to address development and growth is imminent, as it places constraints on limited resources in Tooele Valley, especially water,” states the county’s 2016 update to the general plan.
The general plan’s population projections show Tooele County’s population growing from 67,782 in 2015 to 127,340 in 2040. The majority of that growth is expected to be in Tooele Valley. The valley’s population is expected to grow by 53,835 new residents, accounting for 90% of the total growth projected for the county by 2040.
Long-term average precipitation drops 61.5 million acre-feet of water on the state each year, according to the foundation report.
An acre-foot is the amount of water it takes to cover one acre of ground with one foot of water, which is 325,851 gallons or roughly one half the volume of an Olympic-size swimming pool.
Out of the 61.5 million acre-feet of precipitation annually, 53.8 million acre-feet, or 88% of the total precipitation, stays in what the report calls the “natural system” and is consumed through evapotranspiration — largely evaporation from plants.
A net of about 0.4 million acre-feet, or 0.6% of Utah’s precipitation, ends up in other states. That leaves 7.3 million acre-feet of water to enter the state’s ground and surface water supply system.
Of that 7.3 million acre-feet of water, 3 million acre-feet evaporates from the Great Salt Lake annually. Another 1 million acre-feet evaporates annually from other streams and lakes in Utah.
At the end there is 3.3 million acre-feet, or 5.4% of the total precipitation, left for use by municipal, private and industrial use.
Some used water is passed on for future reuse. For example, water running down a sink drain or down a shower drain ends up back in the water system and is used again.
While there is 3.3 million acre-feet of available water annually in Utah, 2.6 million acre-feet of that water is consumed to the point that it no longer stays in the water system, according to the foundation report.
However, Utah water users divert, or remove from the ground or streams for use, 5.2 million acre-feet of water annually, because they reuse some of the 2.6 million acre-feet of consumed water before it is finally depleted from further use.
The largest part of the 5.2 million acre-feet of diverted water, around 4.2 million acre-feet are used in agriculture. That’s 81% of the 5.2 million acre-feet.
Of the remaining 0.95 million acre-feet, 0.72 million acre-feet, or 14% of the 5.2 million acre-feet, are used by public community water systems, 0.22 million acre-feet are used by public non-community water systems, and 0.02 million acre-feet are used by domestic wells.
Out of the 0.72 million acre-feet used by municipal water systems, 0.178 million acre-feet are used for residential indoor use, and 0.331 million acre-feet are used for residential outdoor use, according to the foundation report.
The balance of the public community water system use, 0.208 million acre-feet, is used for industrial, commercial and institutional use.
At 0.178 million acre-feet of water for indoor residential use, 0.29% of the original 61.5 million acre-feet of annual precipitation ends up used indoors for residential purposes.
Tooele County’s water use follows a similar pattern, but with a higher percentage of water used by agriculture.
A total of 89% of the freshwater used in Tooele County in 2015 was used for irrigation and livestock, 10% was used for residential use, and 1% for commercial and industrial, according to data from the United States Geological Survey.
In 2015, the per capita use of water from public supplies in Tooele County was 257 gallons per person per day.
With 53,835 new people expected in Tooele Valley by 2040, at the rate of 257 gallons/person/day, water providers in the county will need to develop the capacity to deliver an additional 16.13 million gallons per day. In 2015 the public water supply was 13.8 million gallons per day.
Some of that water could come from converting agricultural water to residential water, if irrigated land is converted to residential use. In 2015 irrigation use in Tooele County averaged 83.2 million gallons per day, according to the USGS.
Some of the water could come from existing unused groundwater. In October 2018 an engineer with the Utah Division of Water Rights estimated that around 48,600 acre-feet of Tooele Valley’s estimated annual 67,000 acre-feet of recharge water, or water flowing annually into the valley, was currently being used.
The August report from the Utah Foundation is one of four reports the foundation plans on water and water development. The next three reports will focus on methods of financing water development.
According to the August report, the next three reports will “dive deeper into how using property taxes and water rates to fund water development and delivery can affect key priorities, including conservation, fairness, fiscal health, transparency and representation.”
The Utah Foundation is a non-profit organization. Its mission is “to produce objective, thorough and well-reasoned research and analysis that promotes the effective use of public resources, a thriving economy, a well-prepared workforce and a high quality of life for Utahns.”