Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

Most of us have become familiar with the Air Quality Index, or AQI. We see it in weather apps, on air-quality websites, and in forecasts warning us when pollution may make it better to limit time outdoors. The familiar green, yellow, orange, and red categories provide a simple answer to an important question: How is the air today? But what actually goes into that number?

In this issue of Salt & Sky Brief, we take a closer look at the AQI, including where it comes from, how it is calculated, and how to interpret it. We’ll also look at what the AQI doesn’t tell us, and why Utah’s growing dust problem may expose an important blind spot in the way current air-quality conditions are communicated.

In 60 seconds

• The Air Quality Index (AQI) turns air pollution measurements into a simple scale designed to communicate potential health risks. It is based on several of the pollutants regulated under the Clean Air Act, including ozone and particulate matter (PM₂.₅ and PM₁₀).

• AQI values range from 0 to 500, with higher numbers indicating greater potential health concern. Each pollutant is assigned its own AQI value based on its measured concentration, and the pollutant with the highest value generally determines the overall AQI reported for a location.

• An AQI above 100 does not necessarily mean that an air-quality standard has been violated. Compliance with the National Ambient Air Quality Standards (NAAQS) depends on pollutant-specific averaging periods, statistical calculations, and, in many cases, multiple years of measurements.

• In Utah, ozone and PM₂.₅ have historically driven most poor-air-quality days, but dust is making PM₁₀ increasingly important. If PM₁₀ is not included in the DAQ current-conditions AQI display, a significant dust event could degrade air quality while the reported AQI remains low.

• AQI is useful, but it isn’t a complete picture of the air we breathe or an exact dividing line between “healthy” and “unhealthy.” It doesn’t account for every pollutant, and health responses vary with individual susceptibility, exposure, and activity.

Where Does the AQI Come From?

The AQI has its roots in the Clean Air Act, which requires the U.S. Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS) for pollutants that are widespread in outdoor air and can harm human health or the environment. EPA has established standards for six of these criteria air pollutants: ozone (O₃), particulate matter (PM), carbon monoxide (CO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and lead (Pb).

Note: EPA sets NAAQS for six criteria pollutants, but the AQI is calculated for only five. Lead is not included because the AQI is designed to communicate short-term, day-to-day air-quality conditions, whereas the current lead standard is based on a rolling three-month average. Lead is typically measured by collecting particles on filters and analyzing them in a laboratory, so results are not generally available in real time.

The NAAQS are not arbitrary thresholds. EPA periodically reviews a large body of scientific evidence (including epidemiological studies, controlled human-exposure studies, toxicology, and atmospheric science) to determine pollutant concentrations and exposure periods associated with adverse health and environmental effects. The resulting standards specify both a concentration and an averaging period. For example, the current ozone standard is based on an 8-hour average, while particulate-matter standards include both short-term and longer-term measures.

The AQI takes this regulatory framework and turns it into a public-health communication tool. Instead of asking people to interpret concentrations reported in different units (e.g., parts per billion for ozone or micrograms per cubic meter for particulate matter) the AQI converts pollutant concentrations onto a common scale. That allows a complicated set of air-quality measurements to be communicated with a single, familiar number and color.

Turning Pollution into an Index

Air pollutants are measured in different units and have different health effects, so their concentrations cannot be compared directly. The AQI solves this problem by converting the measured concentration of each pollutant to a common 0–500 scale using pollutant-specific breakpoints established by EPA (See Method Note at the end of this issue for details). An AQI of 0–50 is considered Good, 51–100 Moderate, and values above 100 indicate increasing levels of health concern.

Each pollutant is assigned its own AQI value, and the highest of those values becomes the AQI reported for that reporting area. That number identifies the pollutant driving the day’s AQI category. It does not combine concentrations or health effects across pollutants.

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Utah’s AQI Has Historically Been a Two-Pollutant Story

As we discussed in Issue 2, concentrations of many of the pollutants that once plagued northern Utah have declined substantially over the past several decades. For roughly the last 20 years, our most persistent air-quality challenges (and therefore our highest AQI values) have largely been dominated by two pollutants: PM₂.₅ during winter inversions and ozone during the summer. As a result, the way many of us think about Utah’s air quality has become relatively simple: winter means PM₂.₅ and summer means ozone.

But dust is complicating that picture. Dust from exposed Great Salt Lake playa, local quarries and mining operations, construction sites, disturbed soils, and other local and regional sources can substantially increase concentrations of coarse particulate matter, or PM₁₀, even when ozone and PM₂.₅ remain relatively low (Figure 1). This creates a potential blind spot in how we communicate current air quality. Utah DAQ’s current-conditions website focuses on ozone and PM₂.₅, meaning that during some dust events the displayed air quality may appear good even when elevated PM₁₀ indicates otherwise. As discussed in Issue 1, the expanding Utah Dust Observation and Research Network (UDORN) should greatly improve our ability to observe when and where dust is moving across northern Utah. Those measurements may also provide an opportunity to improve how dust-related air quality is characterized and communicated to the public.

Figure 1. Pollutant-specific AQI values during the December 17, 2025 dust event at the Salt Lake City–1480 North 800 West monitor. Ozone and PM₂.₅ remained below AQI 100, but PM₁₀ reached AQI 125 and therefore determined the overall AQI during the dust event.

What the AQI Doesn’t Tell You

For all its usefulness, the AQI has important limitations. First, an AQI above 100 does not necessarily mean that a NAAQS violation has occurred. The AQI is designed to communicate current or recent pollution levels and their potential health significance, while compliance with federal air-quality standards is determined using pollutant-specific averaging periods and statistical forms, often using multiple years of data. A single day with elevated ozone, for example, does not by itself constitute a violation of the ozone standard.

Second, the AQI is not a measure of everything in the air. It provides information about specific criteria pollutants but tells us little about volatile organic compounds, hazardous air pollutants, ammonia, ultrafine particles, or the chemical composition of particulate matter. This distinction can be especially important for dust: two locations could have the same PM₁₀ concentration (and therefore the same PM₁₀ AQI) while the particles themselves have very different chemical compositions and potentially different health implications.

Finally, the AQI categories should not be interpreted as sharp boundaries between “healthy” and “unhealthy” air. An AQI of 99 is not biologically safe while an AQI of 101 suddenly becomes harmful. Health risks change along a continuum, and individual responses vary with age, health, activity, exposure, and susceptibility. The AQI colors are useful communication thresholds, not biological switches.

The Takeaway

The AQI is a remarkably useful shorthand for communicating air quality, but shorthand is exactly what it is. It translates concentrations of several important pollutants into a simple number and color that can help us understand when the air may pose a greater health concern. But it is not a comprehensive measure of everything in the air, an AQI above 100 is not synonymous with a regulatory violation, and its categories are not sharp boundaries between healthy and unhealthy air. In Utah, there is an additional challenge: for decades, our AQI story has largely been about winter PM₂.₅ and summer ozone. As dust becomes a more prominent concern, PM₁₀ needs to be part of how we think about, and communicate, current air quality. Ultimately, the AQI is only as complete as the pollutants we measure and report.

Method Note:

Figure 2. How EPA converts a PM₁₀ concentration into an Air Quality Index (AQI) value. EPA uses pollutant-specific concentration breakpoints and linear interpolation within each breakpoint range; it does not calculate AQI as a percentage of the 150 µg/m³ 24-hour PM₁₀ standard. For the December 17, 2025 dust event, a 24-hour PM₁₀ concentration of 203 µg/m³ falls within the 155–254 µg/m³ breakpoint range and corresponds to AQI 125. The steeper lower portion of the curve results from EPA’s selected AQI breakpoints, which translate health-based air-quality information into public-facing categories. It should not be interpreted as a direct, quantitative biological dose-response curve.

If you have questions or comments, feel free to reply directly to this email.

Sources & Further reading

U.S. Environmental Protection Agency. Technical Assistance Document for the Reporting of Daily Air Quality — the Air Quality Index (AQI). 2024. - https://document.airnow.gov/technical-assistance-document-for-the-reporting-of-daily-air-quailty.pdf

U.S. Environmental Protection Agency. National Ambient Air Quality Standards (NAAQS) Table. - https://www.epa.gov/criteria-air-pollutants/naaqs-table

Utah Division of Air Quality. Salt Lake County Current Conditions. - https://air.utah.gov/currentconditions.php

U.S. Environmental Protection Agency. AirData: Outdoor Air Quality Data. - https://www.epa.gov/outdoor-air-quality-data

AirNow. AQI Calculator: Concentration. - https://www.airnow.gov/aqi/aqi-calculator-concentration/

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Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

The last issue asked where water is depleted before it can reach Great Salt Lake. This issue turns to the next question.

If Utah saves water, how does that water actually reach the lake?

That question matters because conservation and delivery are not the same thing. Water can be conserved upstream, but if it is reused, diverted, evaporated, or never physically makes it downstream, Great Salt Lake may not benefit.

For the lake, the practical test is simple: conserved water has to become measurable, protected inflow.

In 60 seconds

• Conserving water is necessary, but it is not the same as delivering water to Great Salt Lake.

• Saved water can be reused, diverted by others, lost along the way, or arrive at a time when it does not reliably reach the lake.

• Water shepherding means tracking conserved water through rivers, canals, reservoirs, and diversions so it remains protected for Great Salt Lake.

• Utah has made important investments in measurement infrastructure, including stream and canal metering, because water cannot be managed well if it cannot be measured.

• Recent legal changes also matter. Water dedicated to Great Salt Lake can now be recognized as a beneficial use, creating a pathway for conserved water to be protected for the lake.

• The takeaway: conservation becomes recovery only when saved water is measured, protected, timed well, and delivered downstream.

Conservation is not the same as lake inflow

It is easy to describe Great Salt Lake recovery as a conservation problem. That is true, but incomplete.

Conservation creates the opportunity for more water to reach the lake. It does not guarantee that the water will get there.

A city may reduce outdoor water use. A farmer may temporarily reduce irrigation. A canal company may improve operations. A reservoir manager may release stored water. Each action can make water available. But unless that water is measured, protected, and moved downstream at the right time, it may not increase lake inflow (Figure 1).

Figure 1. From saved water to lake water.
Conservation becomes lake recovery only when saved water is measured, legally protected, timed for reliable delivery, and shepherded downstream to Great Salt Lake. Without those steps, conserved water can be reused, diverted, lost to evaporation, or delivered at a time when it provides little or uncertain benefit to the lake.

What water shepherding means

Water shepherding is the process of protecting conserved water as it moves downstream.

The idea sounds simple. If water is saved in one place, it must remain in the system long enough for it to reach Great Salt Lake.

In practice, that is difficult.

The Great Salt Lake watershed is not a single pipe. It is a complex network of rivers, canals, reservoirs, irrigation and municipal systems, groundwater interactions, return flows, and diversions. Water moving through this network is also governed by an extensive system of water rights. As a result, water saved in one part of the watershed may need to pass numerous points of potential diversion before it reaches the lake.

That is why shepherding has both a physical and a legal meaning.

Physically, the water has to remain in a stream, canal, reservoir release, or river system long enough to move downstream. Legally, it has to be recognized and protected so that it is not simply available for another use before it reaches the lake.

Water shepherding is the bridge between conservation and lake recovery.

It asks a basic question: can Utah track a conserved acre-foot from the place it was saved to the place it is needed?

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Measurement is the foundation

Before water can be shepherded, it has to be measured.

That is why investments in stream gauges, canal measurement, diversion meters, and water accounting systems matter. They are not just technical upgrades. They are the infrastructure that makes water conservation meaningful for Great Salt Lake.

If a farmer, city, or water district reduces use, the state needs a way to estimate how much water was actually saved. It also needs to know where that water enters the system, how it moves downstream, whether it passes other diversions, and whether it ultimately contributes to lake inflow.

Without measurement, water savings can remain abstract.

With measurement, conservation can become part of a water budget that can be tracked, verified, and protected.

Utah has made substantial investments in better measurement across the Great Salt Lake watershed, including tributary streams and canals (Figure 2). That work is essential because many parts of the water system were built for delivery to farms, cities, and industry, not for tracking conserved water all the way to a terminal lake.

Better data will not solve the lake’s water imbalance by itself. But without better data, it is difficult to know whether conservation is changing the lake’s water balance at all.

Figure 2. How stream gauges turn water levels into flow measurements.
A stream gauge continuously records river stage, or water height, using a fixed staff gauge and sensor. Hydrologists periodically measure actual streamflow at different water levels and use those measurements to develop a rating curve, which converts stage into estimated discharge. This process allows managers to track how much water is moving through the river over time and evaluate whether conserved water is likely to reach downstream destinations such as Great Salt Lake.

The law now allows water to be dedicated to the lake

Measurement is necessary, but measurement alone is not enough.

Saved water also has to be legally protected.

This is where recent changes in Utah water law are important. For much of western water history, a “beneficial use” of water usually meant diverting water for farms, cities, industry, or other direct human uses. Leaving water instream or allowing it to reach a terminal lake was not always treated the same way.

That created a problem for Great Salt Lake.

If water users conserved water but had no secure way to dedicate that water to the lake, the saved water could be vulnerable to reuse, diversion, or loss of water-right protection. Conservation might reduce use at one location without increasing inflow to the lake.

In 2022, Utah passed H.B. 33, the Instream Water Flow Amendments, which changed that legal foundation. The bill, which was sponsored by Rep. Joel Ferry and Sen. Scott Sandall, allowed approved water-right changes to provide water for instream flows or for use on sovereign lands. Because Great Salt Lake is sovereign land, this created a pathway for water to be legally dedicated to the lake rather than treated simply as unused water.

That is a major shift.

It means water can be intentionally conserved and protected for Great Salt Lake as a recognized beneficial use. It also gives water users, state agencies, and conservation partners more tools to lease, dedicate, or manage water for lake benefit.

This does not solve every problem. Legal recognition does not automatically move water downstream. The water still has to be measured, administered, protected past other diversions, and shepherded through a complicated system.

But it changes the foundation. Great Salt Lake can now be treated not only as the place where leftover water ends up, but as a legally recognized destination for conserved water.

Timing and location matter

Even when water is conserved and legally protected, timing matters.

The same acre-foot of water can have different lake benefits depending on when and where it enters the system.

Water released or conserved during the irrigation season may face more competing demands, higher evaporation losses, and greater uncertainty as it moves downstream. In some parts of the watershed, summer flows may be low enough that water does not reliably travel all the way to Great Salt Lake.

The Bear River is a good example. Putting water into the Bear River in August may not produce the same lake benefit as releasing or protecting that water later in the year, especially during periods when low flows, diversions, and channel conditions make delivery to the lake less reliable.

Fall and winter can be different. Cooler temperatures reduce evaporation losses. Irrigation demand is lower. Rivers may have a better chance of carrying protected water downstream. In some cases, timing conserved water for fall or winter delivery may increase the likelihood that it reaches the lake.

Location matters too.

Water conserved closer to the lake may be easier to protect and deliver. Water conserved farther upstream may have to pass more diversions, reservoirs, canals, seepage zones, and administrative boundaries. That does not mean upstream conservation is unimportant. It means upstream conservation requires careful accounting and coordination.

For Great Salt Lake, an acre-foot is not just an acre-foot. Its value to the lake depends on whether it is conserved, protected, timed well, and delivered.

Figure 3. Timing changes delivery risk.
The timing of conserved water deliveries can strongly influence whether water reaches downstream destinations. Summer deliveries may face higher irrigation demand, greater evaporation losses, and lower reliability in some tributaries. Fall and winter deliveries often occur during periods of lower demand and reduced evaporation, creating potentially better windows for moving conserved water toward Great Salt Lake.

Conserved water has to be protected from reuse

One of the hardest parts of Great Salt Lake recovery is that saved water can disappear into the system.

That does not necessarily mean it is physically lost. It may be put to another use.

A city may reduce per-capita water use, but population growth can absorb the savings. A farm may reduce diversion, but if the conserved water is not protected, it may be diverted downstream. A water efficiency project may reduce the amount of water applied, but if it mainly reduces return flows rather than consumptive use, the lake benefit may be smaller than expected.

This is why conservation programs need to be designed around lake benefit, not only water-use reduction.

The key questions are practical.

• How much depletion was actually reduced?

• Where did the saved water enter the system?

• Was it legally dedicated to Great Salt Lake?

• Could it be tracked past downstream diversions?

• Did it arrive at a time when delivery to the lake was reliable?

Those questions can feel technical, but they are central to whether conservation changes the lake’s future.

Conservation creates the opportunity. Protection determines whether the lake receives the water.

This is why partnerships matter

Water shepherding is not only a technical challenge. It is also a trust challenge.

Farmers, cities, water districts, canal companies, industries, state agencies, and conservation groups all have roles in the Great Salt Lake watershed. Many of them also have different incentives, obligations, and risks.

For water users, participation requires confidence that conserved water will be measured fairly, compensated appropriately, and administered consistently. For the lake, participation has to produce real reductions in depletion and measurable inflow. For the public, programs have to be transparent enough to show that investments are changing the water balance.

That is why partnerships matter.

Water shepherding will not work if it is only a slogan or a legal category. It has to become a set of practical agreements that people trust enough to use.

The technical challenge is measurement. The legal challenge is protection. The human challenge is trust.

Great Salt Lake recovery will require all three.

The takeaway

Issue 8 showed where water is depleted before it can reach Great Salt Lake. This issue shows why conservation is only the first step: saved water must be measured, protected, timed well, and delivered downstream if it is to become real lake inflow. That requires meters, stream gauges, accounting tools, water-right changes, delivery agreements, timing decisions, and partnerships across the watershed.

If you have questions or comments, feel free to reply directly to this email.

Sources & Further reading

Null, Sarah, and Bethany Neilson. Water Shepherding: Delivering Saved Water to Great Salt Lake. Utah State University, Institute for Land, Water and Air, 2023. – https://www.usu.edu/ilwa/reports/2023/water/2a-water-shepherding-salt-lake

Utah Office of the Great Salt Lake Commissioner. Great Salt Lake Strategic Plan. 2024. – https://greatsaltlake.utah.gov/great-salt-lake-strategic-plan-2

Great Salt Lake Strike Team / Kem C. Gardner Policy Institute. Water Distribution and Shepherding. Great Salt Lake Policy Summary, 2024. – https://gardner.utah.edu/wp-content/uploads/2024/01/GSL-Insights-Summary-Jan2024.pdf

Utah Division of Water Rights. Great Salt Lake Distribution Management Plan. 2025. – https://waterrights.utah.gov/GSLDMP/final_GSL_distribution_management_plan_2025101.pdf

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Independent publication notice

Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

The last issue asked how much water it might take to stabilize Great Salt Lake. This issue turns to the next question: how is water currently depleted across the watershed?

That question matters because not all “water use” has the same effect on the lake. Some water taken from rivers returns to the system. Some is consumed by crops, lawns, evaporation, or other processes before it can flow downstream.

For Great Salt Lake, the key accounting question is not just how much water is diverted. It is how much is depleted before it reaches the lake.

In 60 seconds

• Great Salt Lake recovery depends on understanding the watershed water budget, especially where water is consumed or otherwise removed before it can reach the lake (i.e., depleted).

• A diversion is not the same as a depletion. Some diverted water returns to the river system.

• Recent estimates put average annual human water depletions in the Great Salt Lake watershed at about 2.387 million acre-feet per year. Agriculture is the largest category, followed by municipal and industrial use.

• Municipal water use is smaller than agriculture, but it still matters. Residential depletion has trended upward, and nearly all residential depletion now comes from outdoor use, including lawns, landscaping, and irrigation.

• Conservation matters most for the lake when it reduces real depletions. The next challenge is making sure saved water is protected and delivered downstream.

Diversions are not the same as depletions

Water discussions often use the word “use” as if it means one thing. But in a watershed, water can be diverted, consumed, returned, reused, or delivered downstream.

A diversion is water taken out of a river, stream, canal, reservoir, or groundwater system for human use. It may be used on farms, in homes, by cities, or by industry.

But not all diverted water is lost to the lake (Figure 1).

Some diverted water returns to the system. On farms, some water may seep into the ground and return later as groundwater recharge or return flow. In cities, much indoor water goes through wastewater treatment and returns to rivers. These return flows may still be available downstream.

A depletion is different. It is the portion of water that is consumed, evaporated, transpired by plants, incorporated into products, or otherwise removed from the system before it can reach Great Salt Lake.

This distinction matters because reducing diversions does not always produce the same amount of new water for the lake. If conserved water would have returned to the river anyway, the lake benefit may be smaller than the diversion reduction suggests.

For Great Salt Lake, the key measure is depletion. The lake responds to water that reaches it, not simply to water that was used or conserved upstream.

Figure 1. Diversions, depletions, and return flows.
Water diverted from a river can follow different paths. Some is depleted through evaporation, plant use, or outdoor water use. Some may return to the system later as groundwater recharge, runoff, or treated wastewater return flow. Great Salt Lake benefits from water that is not depleted and can continue downstream.

The watershed-scale water budget

Recent water-budget estimates put average annual human water depletions in the Great Salt Lake watershed at about 2.387 million acre-feet per year for 2020–2024 (Figure 2).

That total helps put the lake’s recovery challenge in perspective.

In the last issue, modeling suggested that adding 250,000 acre-feet per year would reduce the probability of the worst outcomes, but would not restore the lake to a healthy long-term range. Something closer to 800,000 acre-feet per year was the scale associated with long-term stabilization.

Compared with current depletions, 800,000 acre-feet per year is roughly one-third of recent total annual human depletions in the watershed. That does not mean every water use could or should be cut by one-third. Nor does it mean every conserved acre-foot would automatically reach the lake. But it does show the scale of the challenge.

The depletion picture is also concentrated. Agriculture is the largest category, averaging about 1.551 million acre-feet per year from 2020–2024, or about 65% of total human depletion. Municipal and industrial use is second, at about 640,000 acre-feet per year, or about 27%.

Lake mineral extraction is smaller, averaging about 136,000 acre-feet per year, or about 6%. Recent voluntary agreements with some mineral operators show how industrial depletions can also be limited or adjusted when lake levels are low. Other categories, including agricultural incidental losses and reservoir evaporation, make up the remaining share.

The water budget does not make the solution simple. But it does make the scale clear: any serious discussion of Great Salt Lake recovery has to account for the largest depletion categories.

Figure 2. Great Salt Lake watershed depletions by category.
From 2020–2024, average annual human water depletions in the Great Salt Lake watershed were about 2.387 million acre-feet per year. Agriculture and municipal/industrial use accounted for about 92% of those depletions. “Other” includes agricultural incidental losses and reservoir evaporation.

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Agriculture is the largest category

Agriculture is the largest water depletion category in the Great Salt Lake watershed. That makes it central to any serious discussion of lake recovery.

But agricultural water use should not be understood only as a number in a water budget. Irrigated agriculture supports rural communities, local economies, open space, food and forage production, and landscapes that are part of northern Utah’s identity. Agricultural lands can also provide habitat, groundwater recharge, and other ecosystem services.

It is also important to distinguish agricultural diversions from agricultural depletions. Much more water is diverted for irrigation than is ultimately depleted. Some diverted water returns to the system through seepage, runoff, groundwater recharge, or return flows. That is why reducing diversions alone does not always produce the same amount of new water for Great Salt Lake.

Because agriculture is the largest depletion category, solutions for Great Salt Lake will have to include agricultural partnerships that maintain rural lifestyles and economies while reducing consumptive use where possible.

That means agricultural conservation needs to be measured, compensated, and designed so that saved water is not simply used elsewhere. It also raises the next question: what legal and administrative tools are needed to shepherd conserved water downstream to Great Salt Lake?

The goal is to reduce real depletions in ways that work for agricultural communities and deliver measurable water to the lake.

Municipal water is smaller, but growth matters

Municipal and industrial use is smaller than agriculture, but it still matters.

One reason is growth. Residential depletion has generally trended upward over time, even as many communities have worked to reduce per-capita use (Figure 3). That is the basic urban water tension: each person may use less water, but a growing population can keep total demand from falling.

That makes indoor and outdoor conservation both important, but for different reasons.

Indoor conservation helps reduce per-capita water use and can help communities accommodate population growth without continually increasing total municipal demand. Outdoor conservation matters because outdoor irrigation is more likely to become depletion. Water applied to lawns, parks, ornamental landscapes, and other outdoor areas is often consumed through evaporation and plant use.

For reducing depletion, the bigger municipal lever is outdoor water. In 2024, GSL Strike Team data show that outdoor use accounted for nearly all residential depletion. That makes landscaping and outdoor irrigation one of the clearest municipal-side opportunities for reducing depletion.

Municipal conservation alone cannot stabilize Great Salt Lake. But cities still matter because outdoor water demand is directly connected to how northern Utah grows.

If new development locks in high outdoor water demand, municipal depletion will be harder to reduce. If landscaping standards, turf conversion, pricing, and development patterns reduce outdoor demand, cities can lower their water footprint even as population grows.

Figure 3. Municipal water, growth pressure, and outdoor use.
Residential depletion has generally trended upward over time, reflecting the pressure of population growth. At the same time, 2024 data show that nearly all residential depletion comes from outdoor use. This makes landscaping and outdoor irrigation central to the municipal side of Great Salt Lake conservation.

The takeaway

Great Salt Lake recovery is often described as a conservation problem. That is true, but incomplete.

The lake responds to delivered water.

Northern Utah uses water in many ways, but the depletion picture is more concentrated. Agriculture is the largest category. Municipal and industrial use is second. Together, they account for most recent human water depletions in the Great Salt Lake watershed.

That does not make the solution simple. Different sectors provide different benefits, face different constraints, and create different opportunities for conservation.

But it does clarify the policy test. Conservation has to change the lake’s water balance, not just upstream accounting.

That leads to the next question. If Utah saves water, how does that water actually reach Great Salt Lake?

If you have questions or comments, feel free to reply directly to this email.

Sources & Further reading

Great Salt Lake Strike Team, Data Insights and Summary (2026) - https://greatsaltlake.utah.gov/strike-team/

Utah Division of Water Resources. Great Salt Lake Water Budget. 2025. - https://dwre-utahdnr.opendata.arcgis.com/pages/water-budget

Great Salt Lake Strike Team / Utah State University. Great Salt Lake future lake-level scenario modeling results. HydroShare, 2026. - https://www.hydroshare.org/resource/885979f4acdd412ab3cf09799eab7ead/

Utah Division of Water Rights. Great Salt Lake Distribution Management Plan. 2025 – https://waterrights.utah.gov/GSLDMP/

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Independent publication notice

Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

This issue continues the Great Salt Lake series by asking a deceptively simple question: how much additional water would it actually take to stabilize the lake?

The answer is not “one wet winter.” Great Salt Lake will always rise and fall with snowpack, precipitation, runoff, temperature, and evaporation. The more useful question is whether Utah can shift the lake’s long-term range upward, so that dry years start from a safer place and wet years help rebuild the system rather than merely slow its decline. In this issue, stabilization does not mean holding the lake at one elevation; it means raising the lake’s long-term range enough to avoid chronic serious adverse effects.

Recent modeling from the Great Salt Lake Strike Team puts numbers on that question by comparing a baseline future with scenarios in which additional water reaches the lake year after year. The results are clear: 250,000 acre-feet per year would reduce risk, but roughly 800,000 acre-feet per year is the scale that begins to move the lake back toward a healthy long-term range.

In 60 seconds

• Great Salt Lake does not need a one-time rescue. It needs sustained additional inflows over many years.

• In the baseline scenario, average riverine inflow to the lake is about 1.665 million acre-feet per year. The modeled long-term mean lake level is about 4,191.1 feet, within the “serious adverse effects” range.

• Adding 250,000 acre-feet per year improves the outcome. It raises the modeled long-term mean lake level to about 4,193.7–4,193.8 feet and reduces the probability of serious adverse effects from 61% to 28%.

• But 250,000 acre-feet per year is a risk-reduction scenario, not a recovery scenario. The lake still spends most of its modeled future below the healthy range.

• Adding 800,000 acre-feet per year changes the picture. The modeled long-term mean lake level rises to about 4,198 feet, within the healthy lake elevation range.

• The hard part is not knowing whether more water would help. The hard part is delivering enough protected water to the lake, year after year, to change the lake’s long-term trajectory.

Stabilization is not the same as a temporary rebound

Great Salt Lake has always fluctuated. That is part of how terminal lakes work. In wet periods, more runoff reaches the lake. In dry periods, inflows decline and evaporation can draw the lake down. Temperature matters too, because evaporation increases as conditions become hotter and drier.

Stabilization does not mean holding the lake at one fixed elevation. A healthy lake will still have high years and low years.

The real goal is to shift the range of likely outcomes upward. If the lake starts from a higher elevation, dry years are less damaging. If it starts from a lower elevation, even normal variability can keep pushing the system into dangerous territory.

This is why the Strike Team modeling is useful. It does not simply ask where the lake might be in one particular year. It asks how the lake behaves over many possible futures, given natural meteorological variability and different levels of additional inflow.

That is the comparison at the center of this issue.

Scenario 1: Baseline — doing nothing leaves the lake in chronic risk

In the baseline scenario, no additional water is delivered to the lake beyond current assumptions. Average riverine inflow is about 1.665 million acre-feet per year.

Under that scenario, the modeled long-term mean lake level is about 4,191.1 feet. That is in the “serious adverse effects” range (Figure 1).

The most important result is not just the average elevation. It is the distribution of outcomes.

In the baseline scenario:

• 61% of long-term simulations fall in the serious adverse effects range.

• 27% fall in the adverse effects range.

• 10% fall in the transitionary range.

• Only 1% reach the healthy range.

In other words, doing nothing does not leave the lake low but safely stable. It leaves the lake with a high probability of remaining in the most damaging elevation range.

Figure 1. Baseline scenario. Without additional inflows, Great Salt Lake remains in the serious adverse effects range in most long-term simulations. The modeled mean lake level is about 4,191.1 feet, and only 1% of simulations reach the healthy range.

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Scenario 2: An additional 250,000 acre-feet per year helps — but does not solve the problem

The second scenario adds 250,000 acre-feet of water per year to the lake. Average inflow rises to about 1.915 million acre-feet per year.

That additional water makes a real difference. The modeled long-term mean lake level rises to about 4,193.7–4,193.8 feet, roughly 2.6 to 2.8 feet above the baseline. The likelihood of serious adverse effects falls from 61% to 28% (Figure 2).

That is meaningful. Reducing the probability of the worst outcomes by more than half would be a major improvement.

But it is not recovery.

With an additional 250,000 acre-feet per year:

• 7% of simulations reach the healthy range.
• 26% fall in the transitionary range.
• 40% remain in the adverse effects range.
• 28% remain in the serious adverse effects range.

This is the distinction Utah needs to keep clear. An additional 250,000 acre-feet per year would reduce risk. It would buy time. It would make the future less dangerous than the baseline. But in most simulations, the lake would still remain below the elevation range considered ecologically healthy.

That does not make 250,000 acre-feet unimportant. It means it should be understood as partial progress, not the endpoint.

Figure 2. Additional 250 KAF/year scenario. Adding 250,000 acre-feet per year improves lake outcomes and reduces the probability of serious adverse effects, but the modeled long-term mean lake level remains below the healthy range.

Scenario 3: An additional 800,000 acre-feet per year is the recovery-scale scenario

The third scenario adds 800,000 acre-feet of water per year to the lake. Average inflow rises to about 2.465 million acre-feet per year.

This is the scenario that changes the lake’s long-term condition.

With an additional 800,000 acre-feet per year, the modeled long-term mean lake level rises to about 4,198 feet. That reaches the lower end of the healthy lake elevation range. The probability of remaining in the serious adverse effects range falls to 0% (Figure 3).

With an additional 800,000 acre-feet per year:

• 47% of simulations reach the healthy range.
• 44% fall in the transitionary range.
• 9% remain in the adverse effects range.
• 0% remain in the serious adverse effects range.

The modeling also suggests that by the 2034 Winter Olympic Games, the mean simulation reaches about 4,196.9 feet. That is near the upper end of the transitionary zone and about 1.1 feet below the healthy range.

That timing matters. Even under this more ambitious scenario, the lake is not modeled to recover immediately. The result depends on assumptions about future inflows, evaporation, and meteorological variability. But it provides an important benchmark.

If the goal is simply to reduce the worst risks, then 250,000 acre-feet per year matters. If the goal is to move Great Salt Lake back toward a healthy long-term elevation, the modeling suggests the scale of action is closer to 800,000 acre-feet per year.

Figure 3. Additional 800 KAF/year scenario. Adding 800,000 acre-feet per year shifts the lake’s modeled long-term elevation range upward. The mean lake level reaches about 4,198 feet, and the probability of serious adverse effects falls to zero in the simulations.

The scale of the challenge

Eight hundred thousand acre-feet per year is easier to understand when compared with current water depletions in the Great Salt Lake watershed.

Recent estimates put total average annual depletions at roughly 2.3 million acre-feet per year. These depletions include agricultural use, municipal and industrial use, reservoir evaporation, agricultural incidental losses, and lake mineral extraction.

Across recent five-year periods, total annual depletions have generally ranged from about 2.15 million to 2.48 million acre-feet per year. The 2020–2024 estimate is about 2.387 million acre-feet per year.

Agriculture is the largest depletion category, usually accounting for about 1.4 to 1.6 million acre-feet per year. Municipal and industrial depletions are smaller, generally around 0.5 to 0.7 million acre-feet per year. Reservoir evaporation, agricultural incidental losses, and lake mineral extraction also matter, but they are smaller pieces of the total.

This puts the 800,000 acre-foot target in perspective.

An additional 800,000 acre-feet per year is roughly one-third of total annual depletions in the watershed. It is also roughly half of recent agricultural depletions.

That does not mean every water use could or should be cut by one-third. Nor does it mean that all conserved water would automatically reach the lake. Some water savings reduce diversions without reducing consumptive use. Some conserved water may be reused. Some water needs legal protection to ensure it actually stays in the river system and reaches Great Salt Lake.

But the comparison makes one thing clear: stabilizing the lake is not a marginal adjustment. It is a watershed-scale challenge.

Conservation is necessary, but delivery matters

The lake does not respond to intentions alone. It responds to water.

That means the central policy challenge is not just to conserve water. It is to convert conserved water into measurable, protected, sustained inflows to Great Salt Lake.

This distinction matters because not every conservation action has the same effect. Reducing outdoor municipal use can reduce consumptive use, though the total volume is limited by the size of the municipal sector. Agricultural changes can produce larger water savings, but only if they reduce consumptive use and the saved water is not simply used elsewhere. Infrastructure improvements can reduce diversions, but in some cases they may also reduce return flows that would have otherwise reentered the system.

This is why “water saved” and “water delivered to the lake” are not always the same thing.

For Great Salt Lake, success should be measured by the second category.

The relevant question is not only how much water Utah can conserve on paper. It is how much additional water reaches the lake in practice.

What would success look like?

The modeling suggests a simple but demanding answer.

Success would mean shifting Great Salt Lake’s long-term elevation range upward. It would mean fewer years in the serious adverse effects range. It would mean more years in the transitionary and healthy ranges. It would mean that wet years help rebuild the lake rather than merely slow its decline.

In other words, success should be measured not just by one year’s lake level, but by whether the lake’s long-term risk profile is changing.

A useful accountability framework would track several indicators:

• annual inflow to Great Salt Lake;
• conserved water legally protected for delivery to the lake;
• lake elevation;
• lake salinity;
• exposed lakebed acreage;
• frequency of years in the healthy, transitionary, adverse, and serious adverse effects ranges.

This matters because a single wet year can create the appearance of recovery. But a lake can rise temporarily without being stabilized.

A stabilized lake requires sustained inflows across wet years, average years, and dry years.

The takeaway

The encouraging part of the modeling is that Great Salt Lake still responds strongly to additional water. The discouraging part is the scale.

Adding 250,000 acre-feet per year would help. It would reduce the probability of the most serious outcomes and raise the lake’s long-term mean elevation. But it would not restore the lake to a healthy long-term range.

Adding 800,000 acre-feet per year is different. In the Strike Team modeling, that is the scenario that moves the long-term mean lake level to about 4,198 feet and reduces the probability of serious adverse elevation outcomes to zero in the long-term simulations.

That does not make 800,000 acre-feet a magic number. But it does clarify the scale of the problem.

Great Salt Lake can be stabilized. But not through symbolism, not through one wet winter, and not through small changes that are celebrated before they reach the lake.

The lake needs sustained water. The policy test is whether Utah can deliver enough of it, for long enough, to change the lake’s future.

If you have questions or comments, feel free to reply directly to this email.

Sources & Further reading

Great Salt Lake Strike Team, Data Insights and Summary (2026) - https://greatsaltlake.utah.gov/strike-team/

Dr. David Tarboton, Utah State University. Great Salt Lake future lake-level scenario modeling results. Hydroshare, 2026 – https://www.hydroshare.org/resource/885979f4acdd412ab3cf09799eab7ead/) This dataset provides the model results underlying the Great Salt Lake Strike Team’s “Planning for an Uncertain Future” section, including the baseline, +250 KAF/year, +375 KAF/year, and +800 KAF/year scenarios.

Utah Division of Water Rights. Great Salt Lake Distribution Management Plan. 2025 – https://waterrights.utah.gov/GSLDMP/

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Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

This issue focuses on Great Salt Lake as a water-balance problem. The lake has always risen and fallen with wet and dry periods, but its recent decline differs from past fluctuations. Since the record-high levels of the late 1980s, the lake’s long-term trend has been downward because inflows reaching the lake have generally been too low to balance evaporation.

In 60 seconds

• Great Salt Lake is a terminal basin lake: water flows in through rivers, groundwater, and precipitation, but it has no outlet to the ocean. Water leaves mainly through evaporation.

• Since the late 1980s, Great Salt Lake’s long-term water balance has averaged a net deficit of roughly 500,000 acre-feet per year, reflecting a persistent imbalance between inflow and evaporation.

• The Great Salt Lake Strike Team estimates that climate warming accounts for about 8–11% of the recent decline, drought and natural variability account for about 15–23%, and natural and human consumptive water use account for about 67–73%.

• Water depletion has shifted the lake’s baseline downward. Under current conditions, Great Salt Lake requires roughly 130% of normal snowpack just to maintain its level in a given year.

• The takeaway: Great Salt Lake is not shrinking solely because of drought or climate change. Long-term upstream water consumption has substantially reduced the inflows reaching the lake.

A lake built on balance

Great Salt Lake is the lowest point in a large closed watershed. Snow falls in the mountains, melts into streams, recharges groundwater, and eventually flows toward the lake through the Bear, Weber, and Jordan River systems. Once water reaches the lake, it has no outlet to the sea. It leaves mainly through evaporation.

That is why Great Salt Lake is salty. Water enters the lake, water evaporates, and dissolved salts are left behind.

It is also why the lake’s elevation is controlled by a relatively simple water balance. If inflow from rivers, groundwater, and precipitation exceeds evaporation and other losses, the lake rises. If inflow is less than evaporation and other losses, the lake falls.

On seasonal timescales, the lake typically rises during spring snowmelt and declines during the warmer months. On longer timescales, it responds to wet and dry periods. Wet decades tend to raise the lake. Dry decades tend to lower it.

That long-term variability is natural. However, since the late 1980s, the lake’s average level has shifted substantially downward as inflows have increasingly failed to keep pace with evaporation.

What changed after the late 1980s?

Great Salt Lake reached record-high levels in 1986–1987 after a series of unusually wet years. Since then, the lake has followed a long-term downward trend, reaching a historic low in 2022 (Figure 1).

Figure 1. Great Salt Lake elevation over the last 125 years shows substantial seasonal and decadal variability. However, since the late 1980s, the lake’s long-term trend has shifted downward, with water levels reaching a historic low in 2022. [Source: Great Salt Lake Strike Team, Data Insights and Summary, 2026].

A useful way to describe that decline is in water volume. Since the late 1980s, Great Salt Lake has experienced an average net water loss on the order of 500,000 acre-feet per year. The exact number depends on whether the comparison uses peak volume, annual average elevation, end-of-year elevation, or a smoothed trend. But the approximate scale is clear: the lake has experienced a large, sustained net loss of water.

This is the key point: evaporation is not a new process at Great Salt Lake. Terminal lakes always lose water through evaporation. The lake’s decline reflects a long-term imbalance in which inflows reaching the lake have generally been insufficient to offset evaporative losses.

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Climate change: raising the difficulty level

Climate change matters because warmer temperatures increase evaporation and can reduce the fraction of snowpack that ultimately becomes streamflow. A warmer watershed generally requires more precipitation to produce the same amount of runoff. Weather station data across northern Utah show that average temperatures have risen by roughly 1.5°F since the mid-1980s. Climate models project an additional 3–5°F of warming by 2050 depending on future greenhouse gas emissions (Figure 2).

Figure 2. Climate model projections for northern Utah show continued warming under all greenhouse gas emission scenarios. Warmer temperatures increase evaporative losses and are expected to raise water demand across the watershed. Under the medium, medium-high, and high emissions scenarios, the projected average temperatures late this century exceed the warmest historical average temperatures observed between 1979 and 2014. [Source: Great Salt Lake Strike Team, Data Insights and Summary, 2026]

The Great Salt Lake Strike Team estimates that climate warming over the last 40 years (i.e., 1.5°F) explains about 8–11% of the lake’s recent record-low elevation. That is significant, but it is not the dominant cause.

The best way to think about climate change is that it raises the difficulty level for maintaining lake levels. A warmer climate increases evaporative losses and reduces runoff efficiency, meaning the watershed generally needs more precipitation to deliver the same amount of water to the lake. Climate change is therefore an important contributing factor, especially in the future, but it does not by itself explain the magnitude of the lake’s long-term decline.

Drought: the stress test

Drought also matters. Dry years reduce snowpack, reduce runoff, increase demand for stored water, and leave less water available to reach the lake. The ongoing multi-decade western drought has intensified stress on Great Salt Lake.

The Great Salt Lake Strike Team estimates that drought and natural variability explain about 15–23% of the lake’s recent decline.

But drought alone does not explain the long-term pattern. Great Salt Lake has always experienced dry periods. In a balanced terminal lake system, water levels typically fall during drought and recover during wetter periods. The problem today is that wet years no longer refill the lake as effectively as they once did.

Drought temporarily reduces supply. Water depletion changes the baseline.

Water depletion: the dominant cause

The largest factor is consumptive water use upstream.

The Great Salt Lake Strike Team estimates that natural and human consumptive water use explains about 67–73% of the lake’s recent decline. This includes water consumed by crops, cities, lawns, industries, reservoirs, wetlands, and other landscape processes before it reaches the lake.

This does not mean every upstream use is wasteful. Agriculture, cities, industries, wetlands, and communities all depend on water. But for the lake, the cumulative effect is the same: water that is consumed upstream does not reach the terminal basin.

The scale is large. More than 2 million acre-feet of water per year are consumed or otherwise depleted from the tributary systems before reaching Great Salt Lake (Figure 3). The Bear River alone supplies roughly half of the lake’s inflow, making depletion in that system especially important.

Figure 3. Estimated historical and measured contemporary water depletions from tributary systems feeding Great Salt Lake. Contemporary depletion levels remain substantially higher than those estimated during the late 19th century. [Sources: Wurtsbaugh et al. (2017); Utah Division of Water Resources (2024)]

Dr. Wayne Wurtsbaugh (Utah State University) and colleagues estimated that consumptive water use has lowered Great Salt Lake by about 11 feet and reduced its volume by nearly half relative to conditions without upstream depletion. Their analysis found that climate variability can obscure the role of diversions in the short term, but that long-term changes in the lake’s water balance are strongly associated with consumptive use.

The 130% snowpack problem

One of the clearest ways to understand the imbalance is the snowpack threshold.

In a balanced system, average snowpack would roughly maintain the lake over time. Some years would be below normal and the lake would fall. Some years would be above normal and the lake would rise. Over time, those ups and downs would fluctuate around a relatively stable range.

That is not the system Great Salt Lake has now.

Because upstream water depletion has substantially reduced inflows, Great Salt Lake now requires roughly 130% of normal snowpack just to avoid a net annual loss of water. In other words, an average year is no longer enough to hold the lake steady.

That is a strong indication that the system is no longer in balance.

A lake that requires an unusually wet year merely to maintain its level is no longer in long-term equilibrium. Under current conditions, the system operates with a persistent water deficit.

Why this is more than natural fluctuation

Great Salt Lake has always fluctuated. That history of variability can make the current decline appear cyclical at first glance. But the water-balance evidence points to something different.

Natural variability moves the lake up and down. Consumptive water use shifts the whole system downward.

That means a wet year can still raise the lake. Recent wet winters have shown that the lake can respond quickly when more water reaches it. But temporary recovery during wet years does not necessarily mean the underlying imbalance has been resolved. If upstream depletions remain too large, the lake will continue to require unusually wet conditions just to hold steady.

A stable Great Salt Lake should rise in wet years, fall in dry years, and persist through average years. Current conditions no longer consistently produce that pattern.

The take-home message

Great Salt Lake is shrinking because its long-term water balance is no longer in equilibrium.

Climate change increases evaporation and makes the challenge harder. Drought reduces inflow and accelerates decline during dry periods. But the dominant long-term factor is water depletion within the watershed’s rivers and groundwater systems that feed the lake.

The lake’s decline is therefore not just a story about weather. It is a story about a terminal basin receiving too little water to balance its losses.

Great Salt Lake is no longer in balance because upstream consumptive use substantially reduces the water reaching the lake.

If you have questions or comments, feel free to reply directly to this email.

Sources & Further reading

Great Salt Lake Strike Team, Data Insights and Summary (2026) - https://greatsaltlake.utah.gov/strike-team/

Wurtsbaugh, Wayne A., Craig Miller, Sarah E. Null, R. Justin DeRose, Peter Wilcock, Maura Hahnenberger, Frank Howe, and Johnnie Moore. “Decline of the World’s Saline Lakes.” Nature Geoscience 10, no. 11 (2017): 816–821. https://doi.org/10.1038/ngeo3052

Utah Division of Water Resources & U.S. Bureau of Reclamation, Work Plan for the Great Salt Lake Basin Integrated Plan (2024) - https://water.utah.gov/wp-content/uploads/2023/11/GSLBIP-Work-Plan-FINAL-4-8-24.pdf

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Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

If Utah’s electricity system is under pressure, the next question is not simply how much power to build—but what kind.

This issue is the third in a three-part series on electricity in Utah. The last issue examined why the system is under strain. This one turns to what comes next: what kinds of resources Utah could add, and what role each would actually play.

In 60 seconds

• Not all electricity does the same job. Some resources provide steady output, some vary with conditions, and some can respond when demand changes.

• Utah has strong solar potential and significant geothermal resources, while wind is often developed in neighboring states and delivered through the regional grid.

• Fossil-fuel generation and battery storage can help balance the system, but they serve different functions and operate on different timescales.

• Each option comes with tradeoffs in cost, timing, reliability, and how easily it can be connected to the grid.

The central question is not simply what Utah can build, but what each option can realistically contribute to a reliable and affordable system.

From pressure to options

If the last issue was about why Utah’s electricity system is under pressure, this one is about what comes next.

That question is often framed too simply: what should Utah build to meet rising demand?

In practice, the challenge is more complicated. Different resources solve different problems, and they do not contribute equally at all times. A resource that works well in one context may be far less useful in another.

Understanding those differences is the starting point for evaluating Utah’s options.

The three roles every grid needs

A reliable electricity system depends on resources that do different jobs (Figure 1).

Some provide steady output over long periods and help anchor the system. Others produce electricity only when conditions allow, such as when the sun is shining or the wind is blowing. Still others can respond when demand rises or when other resources fall short.

These roles are often described as firm, variable, and dispatchable or flexible. The labels matter less than the underlying point: no single category is enough on its own.

Utah’s electricity future is therefore better understood as a portfolio problem—not a technology contest.

Figure 1. Not all electricity does the same job. Electricity resources play different roles in a power system. Firm resources provide steady output over long periods and help anchor reliability (e.g., geothermal, nuclear). Variable resources depend on time and conditions (e.g., solar, wind). Flexible resources can respond when demand changes or other resources fall short (e.g., fossil-fuel generation, battery storage). A reliable system depends on all three roles—not just one technology.

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What each option could contribute

Solar can add large amounts of energy and is well suited to Utah’s resource conditions. Its output, however, depends on time of day and weather, which means it does not by itself address periods when demand remains high after sunset.

Geothermal provides the potential for steadier, around-the-clock output and is one of Utah’s more distinctive in-state firm-resource options. Its limitations are that projects can be site-specific, capital-intensive, and slower to develop.

Wind can also contribute energy, but its role in Utah is closely tied to the broader western grid. In many cases, wind resources are stronger in neighboring states, meaning their contribution depends on transmission and regional integration as much as in-state development.

Fossil-fuel generation and battery storage provide flexibility, though in different ways. Fossil-fuel plants can adjust output to match changing system conditions, but they introduce fuel costs and other long-term tradeoffs. Battery storage can respond quickly and shift energy over shorter periods, but its effectiveness depends on duration and cost at scale.

Nuclear can provide firm output over long periods and could play a role in future system planning. Its constraints include long development timelines, high upfront costs, and uncertainty around deployment.

The practical takeaway is that each option solves a different part of the problem—and none solves it on its own. Utah is unlikely to meet future electricity needs with a single resource type because the problem itself has more than one dimension.

Cost is part of the tradeoff

Cost matters, but it is not a single number.

Some resources can produce low-cost energy under the right conditions. Others may appear more expensive on paper but provide reliability or flexibility that those comparisons do not capture. A resource that is inexpensive when it operates may still require additional investment in storage, backup generation, or transmission to be useful when the system needs it most.

That is why simple cost comparisons can be misleading. The value of a resource depends not only on how cheaply it can generate electricity, but on when it produces power and how it fits into the broader system.

The cheapest megawatt is not always the most useful megawatt.

The real constraint: time and transmission

The question is not only what can be built, but how quickly and where.

New generation takes time to permit, finance, and construct. Transmission often takes even longer. Without sufficient transmission capacity, even generation that exists—or could be built—may not be able to deliver power where it is needed.

This matters in Utah because the state is part of a larger western grid. Regional interconnection allows power to move across state lines, but it also means Utah depends on transmission availability and conditions beyond its borders. During periods of high demand, that flexibility may be limited.

This is why discussions about energy resources can be misleading. A technology may look promising in isolation, but still face practical limits if it cannot be deployed in time or connected where it would matter most.

The take-home message

Utah’s electricity future is unlikely to be defined by a single breakthrough or a single winning technology. Different resources solve different problems. Some add energy when conditions are right. Some provide steady output over time. Others help the system respond when demand changes or supply falls short.

A reliable grid needs all of those functions. That is why the real challenge is not choosing a winner—it is assembling a portfolio that can perform under a wide range of conditions.

Across this series, a clearer picture has emerged of how Utah’s electricity system actually works and where the real constraints lie. Utah’s electricity system is under growing pressure, demand is becoming harder to plan, and the available options all come with tradeoffs. The path forward is not about finding a perfect solution. It is about making a set of imperfect choices that, taken together, are reliable enough, flexible enough, and affordable enough.

What this means in practice is that the debate over Utah’s electricity future is often framed too narrowly. The question is not which technology to build. It is how to combine different resources in a way that works—not just in theory, but in time, at scale, and under real-world constraints.

The central question is no longer whether Utah needs more power. It is whether the state can build the right mix of resources—fast enough, and in the right places—to meet demand as it evolves.

Utah’s electricity challenge is not choosing the right technology—it is building the right system.

If you have questions or comments, feel free to reply directly to this email.

Further reading

NREL (National Renewable Energy Laboratory):

• Solar Energy Potential - https://www.nlr.gov/gis/solar-resource-maps

• Geothermal Energy Potential - https://www.nlr.gov/gis/geothermal

Global Wind Atlas: https://globalwindatlas.info/en/

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Independent publication notice

Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs.

Utah’s electricity system is entering a more demanding phase, as multiple sources of demand and a changing supply mix place new pressure on a system built for a different era.

This issue is the second in a three-part series on electricity in Utah. Building on the previous installment, it examines where those pressures are coming from—and why they are becoming harder to manage in practice.

In 60 seconds

• Utah’s electricity system is facing new pressures after decades of relative stability.

• Demand is rising from multiple directions, including population growth, electrification, industrial expansion, and large new loads such as data centers.

• Utah’s population is projected to grow from about 3.6 million to 5.6 million by 2065, adding steady long-term demand.

• Large individual facilities can require 50 to more than 100 megawatts at a single site, meaning new demand does not always arrive gradually.

• The supply mix is shifting toward a more varied set of resources.

• The central challenge is not just how much electricity Utah will need, but whether the state can maintain reliable and affordable power as the system becomes more complex.

A system built for a different moment

For decades, Utah’s electricity system followed a relatively simple pattern: dependable fossil-fuel generation, modest load growth, and electricity prices that remained low by national standards.

That foundation still matters. But it was built for a world in which demand generally rose in step with population and economic activity, very large new loads were relatively rare, and the generation mix was dominated by resources that could run continuously or be dispatched when needed.

Today, that picture is changing. Demand is growing in new ways, the supply mix is evolving, and the system is increasingly shaped by conditions beyond the state’s borders. The result is not a single challenge, but a system under pressure from multiple directions at once.

Many pressures, one system

Utah’s electricity system is now shaped by several overlapping forces. Population growth remains part of the story. The Kem C. Gardner Policy Institute projects Utah’s population will rise from nearly 3.6 million residents today to about 5.6 million by 2065—an increase of roughly 2 million people over the next four decades.

But population is no longer the whole story (Figure 1). Electrification is expanding electricity use into vehicles and buildings. Industrial activity is increasing energy needs across sectors. And large concentrated loads—especially data centers—can add significant demand at a single location. At the same time, the broader supply mix is changing, and transmission constraints across the West are becoming more visible.

No single factor explains the challenge. It is the combination that is reshaping how the system must operate.

Figure 1. Multiple forces are putting Utah’s electricity system under pressure simultaneously. Population growth remains part of the story, but electrification, industrial expansion, large concentrated loads, changing generation resources, and regional transmission constraints are all adding complexity to a system built for a different era.

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Demand doesn’t arrive smoothly

It is easy to assume that electricity demand grows gradually. In reality, it often does not.

A new subdivision typically adds demand over time as homes are built and occupied. But large individual loads can arrive in discrete steps. Data centers, for example, can require roughly 50 to more than 100 megawatts at a single site—enough to create a planning challenge almost immediately.

That distinction matters because the planning problem is shaped not just by how much demand is growing, but by when it appears. Utilities and regulators must manage both steady background growth and sudden step changes that can alter planning timelines very quickly.

Figure 2 captures a point that is often missed in public discussions: electricity demand does not always grow smoothly, and timing can matter as much as total volume.

Figure 2. New electricity demand does not always arrive gradually. Traditional growth from population and development tends to build over time, while large individual loads can appear in discrete increments. Together, these patterns create both immediate and sustained planning challenges.

Why is this becoming harder

Planning for electricity is not just about adding more generation. The system must be able to meet demand at the times it is most stressed, and that depends on when electricity is needed, not just how much is used over the course of a year.

That challenge is becoming more complicated as the supply mix becomes more varied. Some resources provide steady output, some depend on time and conditions, and some can respond when needed. Reliability therefore depends less on any one resource than on how different resources work together.

Utah policymakers have already signaled the scale of the issue. Operation Gigawatt, launched in 2024, reflects a growing recognition that demand is rising, the system is changing, and additional infrastructure will be needed.

If new resources and transmission do not keep pace, the likely result is a tighter system—one with higher costs, greater dependence on imports during stressed periods, and less room for error.

Utah’s electricity system is not in crisis. But it is entering a more demanding phase.

What’s next

If the challenge is clear, the next question is harder. Utah does not simply need more electricity. It needs resources that can do different jobs at different times—some that provide steady output, some that can respond when demand changes, and some that can add large amounts of energy when conditions are right.

That is where the debate becomes more complicated. The question is not just what Utah can build, but what each option can realistically contribute to a reliable system, how quickly it can be deployed, and what tradeoffs come with it.

In the next issue, we turn to Utah’s main options—and the role each could play.

If you have questions or comments, feel free to reply directly to this email.

Sources & further reading

Sources referenced in this issue:

Kem C. Gardner Policy Institute (University of Utah)
• Utah population projections: https://gardner.utah.edu/demographics/population-estimates/

State of Utah / Governor’s Office
• Operation Gigawatt: https://energy.utah.gov/homepage/about-us/operation-gigawatt/

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Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly note on Utah science and the public decisions it informs. This issue is the first in a three-part series on electricity in Utah. Before asking how the system might change, it helps to understand what exists today.

In 60 seconds

• Electricity is only one part of Utah’s broader energy economy—but it’s the part now under the most pressure

• In 2023, electricity accounted for 17.1% of Utah’s end-use energy consumption (excluding losses)

• Coal remains Utah’s largest source of electricity, though natural gas and solar have grown rapidly

• Most Utahns receive electricity from Rocky Mountain Power, the state’s only rate-regulated public electric utility

• Utah’s system is still dominated by firm generation, but the mix is beginning to shift

These are the basics—but they’re not the whole story.

Electricity in context

This is an electricity story, not a full “energy” story. Utah still uses much more petroleum and natural gas overall than electricity. According to the U.S. Energy Information Administration (EIA), the federal agency that tracks national and state energy data, Utah’s end-use energy consumption in 2023 was 49.0% petroleum, 31.5% natural gas, and 17.1% electricity (Figure 1).

That matters because many public debates blur these together. Electricity is only one piece of Utah’s energy economy—but it is the part increasingly expected to carry more of the load.

Figure 1. Utah end-use energy consumption by source (2023).
Petroleum and natural gas account for most of Utah’s end-use energy consumption, while electricity makes up a smaller share that is expected to grow as vehicles, buildings, and some industrial processes electrify. Note: The coal and renewables categories shown here represent direct non-electric end uses, not fuels used to generate electricity. Coal burned in power plants is counted under electricity, while the renewables category reflects non-electric renewable uses such as biofuels. Source: U.S. Energy Information Administration (EIA), State Energy Data System (SEDS), Utah, Table CT3, “Total end-use sector energy consumption estimates, selected years, 1960–2023, Utah.”

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Why this matters now

Electricity has become a more prominent public issue in Utah, but the conversation often jumps straight to future demand without first explaining the system Utah already has. Before asking how much more electricity the state may need, it helps to understand what exists today and why it has worked as well as it has. That baseline starts with a simple but often overlooked question: who actually provides electricity in Utah?

Who provides electricity in Utah

Most Utahns get power from Rocky Mountain Power. Utah’s Office of Consumer Services describes Rocky Mountain Power as the state’s only rate-regulated public electric utility. The rest of the state is served by a patchwork of municipal utilities and rural electric cooperatives, which operate under different governance and regulatory structures.

Who serves customers is only part of the story, however. To understand why Utah’s electricity has historically been relatively affordable and why current debates are becoming more complicated, it also helps to look at what the state actually generates.

What Utah generates today

Utah’s electric system is still anchored by thermal generation (Figure 2). In 2024, Utah generated about 45% of its electricity from coal and about 33% from natural gas. Solar contributed about 15%, while hydroelectric and wind each supplied a little over 2%, geothermal about 1%, and other renewables less than 1%. Utah had no in-state nuclear generation in 2024, and petroleum played almost no role.

Figure 2. Net electricity generation in Utah by energy source, 1960–2023 (gigawatt-hours). Coal dominated Utah’s electricity generation for decades, but its share has declined in recent years as natural gas, solar, and other sources have grown. Note: One gigawatt-hour equals one million kilowatt-hours. Source: Utah Geological Survey, Utah Energy & Mineral Statistics, Chapter 5: Electricity, Table 5.11a, “Net Generation of Electricity in Utah by Energy Source, 1960–2025.”

Those shifts in the generation mix matter because different resources do different jobs on the grid. A system that relies heavily on coal, gas, hydro, or solar is not just changing fuels; it is changing the operational roles those resources can play.

Utah’s grid is also part of a broader western transmission network, allowing electricity to flow across state lines. That means Utah’s system cannot be understood in isolation: the state both imports and exports electricity depending on time of day and system conditions. With that context in mind, it becomes easier to understand why terms like baseload, dispatchable, and variable matter.

Baseload, dispatchable, and variable — what those terms actually mean

These terms are often used loosely, but they describe different jobs on the grid. EIA defines baseload as the minimum amount of electric power required over a given period, and a baseload plant as one that runs more or less continuously to serve that minimum demand. In Utah, coal has historically filled much of that role.

Dispatchable generation refers to resources operators can ramp up or down when needed; natural gas and hydropower often fit here. Variable generation refers to resources whose output depends largely on weather or daylight, like solar and wind.

Utah’s current mix is still weighted toward resources that are generally firm or dispatchable, but solar is now large enough that the distinctions matter much more than they used to—especially during certain hours of the day.

Electricity demand changes throughout the day. Different resources meet different parts of that curve (Figure 3).

Figure 3. How baseload, dispatchable, and variable generation work together over a typical day. Baseload resources run steadily to meet minimum demand, variable resources such as solar fluctuate with natural conditions, and dispatchable resources adjust output to fill the gap between available generation and changing electricity demand.

Bottom line: These aren’t competing categories—they serve different roles on the grid. As solar grows, the importance of flexible, dispatchable resources increases.

The price story

Why those distinctions matter becomes even clearer when cost enters the picture. Utah’s electricity has long been discussed not only in terms of reliability, but also in terms of price—and by national standards, it has historically been inexpensive.

Utah Geological Survey data show that the state’s all-sector average retail electricity price rose from 4.84 cents per kilowatt-hour in 2000 to 9.97 cents in 2024. Residential prices rose from 6.29 cents to 12.22 cents over the same period.

But after adjusting for inflation, the increase is much smaller—real residential electricity prices have been relatively stable since 2000 following decades of decline.

Even after recent increases, Utah remained low-cost relative to the national average in 2024: 9.97 cents per kilowatt-hour across all sectors in Utah versus 12.94 cents nationally, and 12.22 cents residential in Utah versus 16.48 cents nationally.

The big takeaway

Those cost advantages did not happen by accident. They grew out of the same legacy system described above: abundant fossil resources, long-lived infrastructure, and a regional utility structure that helped keep electricity relatively affordable. But that legacy no longer guarantees that the future will look like the past.

The key question now isn’t how the system worked in the past—but whether it can adapt to what comes next.

What’s next

This is part one of a three-part series on electricity in Utah. The first step is understanding the system Utah has today. The next installment examines why that system is coming under increasing pressure—from population growth, electrification, industrial demand, and shifting load patterns. The final installment asks what Utah can realistically build, and how fast, to meet those pressures.

If you have questions or comments, feel free to reply directly to this email.

Sources & further reading

Sources referenced in this issue:

U.S. Energy Information Administration (EIA) - Utah energy overview

• Utah Electricity Profile — https://www.eia.gov/states/ut/overview

• Detailed Utah Electricity Data — https://www.eia.gov/electricity/data.php

• Figure 1 Data — https://www.eia.gov/state/seds/data.php?incfile=/state/seds/sep_use/tx/use_tx_UT.html&sid=UT

Utah Geological Survey (Figure 2 Data) — https://geology.utah.gov/energy-minerals/info/energy-mineral-statistics/#toggle-id-5

Utah Office of Consumer Services — https://commerce.utah.gov/ocs/learn-about-your-service-provider/electric-utilities/

Rocky Mountain Power (PacifiCorp) — 2024 program and customer data

• https://www.rockymountainpower.net/about.html

• https://www.rockymountainpower.net/about/regulation.html

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Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly, one-page note on Utah science and the public decisions it informs.

This issue examines a question many Utahns ask: Has air quality in northern Utah been getting worse over the past few decades?

The short answer is more nuanced than most people expect. Because there’s a lot to unpack in the data, this issue runs slightly longer than usual.

In 60 seconds

• What’s the perception problem? When I speak publicly about air quality, I often ask: “How many of you think Utah’s air quality is getting worse?” Typically, about two-thirds of the room raises their hands.

• What the long-term record shows: For most regulated criteria pollutants, Utah’s air quality has improved substantially over the past several decades, particularly for particulate pollution and several combustion-related pollutants.

• What’s the catch? Ozone is now the primary challenge. Under the current 8-hour federal ozone standard, the Northern Wasatch Front remains in nonattainment.

Figure 1. Historical Clean Air Act attainment and nonattainment classifications for the seven federal criteria air pollutants in Salt Lake County. Source: EPA Green Book.

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Why this matters now

If we don’t recognize what has improved—and why—it becomes harder to sustain the programs that worked and harder to focus attention on the pollutant that still needs the most progress.

So the question this issue tackles is straightforward:

Are air-quality trends in northern Utah getting better over time, or worse?

For policymakers, regulators, businesses investing in emissions controls, and residents being asked to change behavior, trend direction matters. It shapes whether the story becomes “nothing works” or “progress is real—and there’s still work to do.”

A quick primer: “criteria pollutants” and federal standards

Under the Clean Air Act, the U.S. Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for common pollutants that are widespread and clearly linked to human health and environmental harm.

These “criteria pollutants” include:

• Particulate matter (PM₂.₅ and PM₁₀)

• Ozone (O₃)

• Nitrogen dioxide (NO₂)

• Sulfur dioxide (SO₂)

• Carbon monoxide (CO)

• Lead (Pb)

The key point: NAAQS are health-based thresholds. They are designed to protect public health—with an added margin of safety—and public welfare, including visibility, ecosystems, and materials.

A note on AQI: The Air Quality Index (AQI) is a public communication tool that helps people make day-to-day decisions about outdoor activity. But long-term regulatory progress is measured against NAAQS compliance and multi-year trends, not whether a particular day felt smoky or hazy.

What “nonattainment” actually means (in plain language)

If monitoring shows that an area violates a National Ambient Air Quality Standard (NAAQS), the EPA can designate it “nonattainment.”

That designation isn’t just symbolic. It can trigger:

• A formal classification (based on severity) and a deadline to reach attainment

• A required State Implementation Plan (SIP) detailing emissions inventories, control measures, and a pathway to meet the standard

• Stricter permitting requirements for some new or expanding industrial sources

• Potential sanctions—including transportation-related consequences—if required plans aren’t submitted or approved

In other words, nonattainment is a regulatory fork in the road. It requires a more structured—and enforceable—strategy to reduce emissions and bring the area back into compliance.

The long-term record: fewer pollutants in “nonattainment” over time

A few takeaways:

• In the 1980s and early 1990s, Salt Lake County was designated nonattainment for multiple criteria pollutants (see Figure 1). That history is easy to forget today, but it’s essential for understanding how much progress has occurred.

• Some standards didn’t even exist 40 years ago. The PM₁₀ standard was established in 1987, and the PM₂.₅ standard was added in 1997. As a result, earlier nonattainment designations don’t fully capture particulate pollution as we define and measure it today.

• Today, ozone under the current 8-hour federal standard is the primary active nonattainment issue tied directly to monitored concentrations along the Northern Wasatch Front.

One caveat worth noting: sulfur dioxide (SO₂) can still appear in nonattainment status because of SIP administrative history, even though monitored concentrations have not exceeded the applicable standard since 1981.

1) Particulate matter (PM₂.₅ and PM₁₀): down over the long term

Particulate pollution is Utah’s most visible air-quality issue—especially during winter cold-pool events (often referred to as inversions). The meteorology hasn’t changed, but our collective emissions have. At one long-term monitoring site in Salt Lake County (see Figure 2), annual average PM₁₀ and PM₂.₅ concentrations have declined by about 33% and 50%, respectively, over the past 30 years.

These long-term improvements are broadly consistent with:

• Cleaner vehicles and fuels

• Controls on industrial sources

• Reduced emissions from home heating, particularly fewer wood-burning stoves

• Improved emissions inventories and stronger State Implementation Plan (SIP) requirements following earlier nonattainment periods

PM₁₀ is also strongly influenced by episodic wind and dust events, which is one reason expanded monitoring—such as UDORN (discussed in Issue #1)—matters. Better measurement helps separate weather-driven spikes from long-term emissions-driven trends.

Figure 2. Annual average concentrations of PM₁₀ and PM₂.₅ measured at the Hawthorne Elementary monitoring site in Salt Lake City, 1997–2025. Source: EPA AirData.

2) Combustion-related pollutants (NO₂, CO, SO₂, Pb): large long-term declines

These pollutants represent one of the quiet success stories of U.S. air-quality policy, and Utah’s monitoring record reflects that same long-term trend. As shown in Figure 1, none of these pollutants has approached federal health standards in Salt Lake County for several decades.

Several technological and regulatory changes drove these declines:

• Vehicle technology improvements (catalytic converters, onboard diagnostics, tighter tailpipe standards)

• Cleaner fuels, particularly large reductions in fuel sulfur

• Industrial emission controls and permitting requirements

3) The hard part: ozone

Ozone is not emitted directly. It forms in the atmosphere when nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) react in sunlight. These reactions accelerate at higher temperatures, which is why peak ozone concentrations often coincide with the hottest days of summer.

Why ozone is tricky:

• It’s chemistry plus weather, not just emissions

• It operates on regional scales, with precursor emissions spread across large geographic areas

• Standards have evolved over time (from a 1-hour standard to an 8-hour standard that has been tightened further), so today’s nonattainment designations aren’t directly comparable to the regulatory landscape of the 1990s

Where we are now:

• The Northern Wasatch Front is designated nonattainment under the 2015 8-hour ozone standard (70 parts per billion, ppb)

• That designation drives the next generation of ozone planning, controls, and technology upgrades

Another important factor is regional transport. Ozone and its precursor pollutants can travel hundreds of miles, which means air-quality outcomes often depend on emissions reductions both within a state and upwind of it. Under the Clean Air Act’s “Good Neighbor” framework, states are expected to limit emissions that significantly contribute to nonattainment in downwind areas. In practice, that means reductions in upwind regions of the western U.S. can help Utah meet the ozone standard, just as emission reductions in Utah can help improve air quality in downwind states such as Colorado.

So why do so many people feel like the air is getting worse?

Several things can be true at the same time.

For one, we’re simply more aware of air quality than we used to be. Air-quality apps, automated alerts, and dense sensor networks now make pollution visible in real time. Years ago, many people only thought about air pollution during the worst inversion of the winter. Today, we see it every day.

At the same time, a handful of memorable events can shape public perception. Summers dominated by wildfire smoke, long stretches of winter inversions, or major dust storms can leave a lasting impression—even if they represent only a small portion of the long-term record.

Another factor is that the nature of Utah’s air-quality challenge has shifted. While wintertime particulate pollution still receives the most attention, the primary regulatory challenge today is often ozone, which forms in the summer. For many Utahns who associate air pollution mainly with winter inversions, that seasonal shift can make the problem feel new or worsening.

Finally, public awareness of the health impacts of air pollution has grown significantly. Organizations like Utah Physicians for a Healthy Environment, founded by Dr. Brian Moench, have spent years educating the public about the links between air pollution and human health. That outreach has helped many Utahns better understand—and pay closer attention to—the air they breathe.

What to watch next

Over the next few years, the most important trend questions won’t simply be “What was last week’s AQI?”

They’re bigger:

• Can ozone planning and controls deliver the same kind of durable progress Utah achieved for other pollutants?

• How much do wildfires and regional transport influence summertime ozone and particulate trends?

• As more of the Great Salt Lake’s playa becomes exposed, will we see measurable changes in the frequency, intensity, or composition of PM₁₀ dust events—and where?

These are measurement questions first—questions about monitoring networks, long-term datasets, and careful attribution.

Only after the trends are clearly understood do they become policy questions.

And the answers will shape Utah’s air-quality story for decades to come.

If you have questions or comments, feel free to reply directly to this email.

Sources & further reading

Sources referenced in this issue:

Utah DAQ PM2.5 Air Trend Plots — https://deq.utah.gov/air-quality/pm2-5-air-trend-plots

Utah DAQ PM10 overview — https://deq.utah.gov/air-quality/particulate-matter-10-pm10-overview

Utah DAQ Northern Wasatch Front Ozone Nonattainment Area —https://deq.utah.gov/air-quality/northern-wasatch-front-ozone

EPA National Ambient Air Quality Standards (NAAQS) table —https://www.epa.gov/criteria-air-pollutants/naaqs-table

EPA Green Book (nonattainment area status) — https://www.epa.gov/green-book

EPA AirData (download and visualize quality-assured monitoring data) — https://www.epa.gov/outdoor-air-quality-data

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Independent publication notice

Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

Welcome to Salt & Sky Brief — a bi-weekly, one-page note on Utah science and the public decisions it informs.

This first issue focuses on something practical: measuring dust better, especially along the Wasatch Front and around the Great Salt Lake.

In 60 seconds

• What is UDORN? A statewide network designed to track where dust comes from, what it contains (including metals), and what it may mean for public health.

• Why now? As Great Salt Lake water levels decline, new dust “hot spots” are being exposed. During some events, PM₁₀ levels along the Wasatch Front can approach the federal standard.

• What changes for the public? More consistent monitoring, clearer documentation of dust events, and better public-facing data tools — so decisions are based on measurements, not guesses.

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Why this matters now

Dust isn’t just a West Desert issue. When strong winds align with dry lakebed sediments, dust can move into population centers quickly.

The Great Salt Lake Strike Team’s 2026 summary notes that declining lake levels have exposed new dust hot spots. During dust events, PM₁₀ levels in Wasatch Front communities can occasionally approach the federal air-quality standard.

It also highlights an important point: dust from exposed lakebeds can contain metals and other elements, raising additional questions for sensitive populations.

To give a sense of scale: as the lake receded, Farmington Bay alone saw more than 120 square miles of exposed lakebed — including 21 square miles of known dust “hotspots.”

What UDORN is (in plain language)

UDORN stands for Utah Dust Observation and Research Network. Its goals are straightforward:

1. Identify dust sources (the Great Salt Lake is not the only one)

2. Measure dust composition, including heavy metals

3. Assess potential public-health risks during dust events

4. Share actionable information communities can use

A key point: not all dust that reaches the Wasatch Front originates from Great Salt Lake. UDORN is designed to distinguish sources across time, weather patterns, and geography.

How the network works

UDORN uses two types of stations:

Core stations
Long-term monitoring sites, often tied to existing regulatory infrastructure. These build multi-year records of dust frequency, intensity, and chemistry.

Satellite stations
Flexible, targeted monitors placed where specific questions matter most — and moved as needs change.

What they measure:

• Continuous PM₁₀ monitoring to capture the timing and intensity of dust events

• Filter-based PM₁₀ sampling so dust chemistry (including metals) can be analyzed

• Supporting tools such as basic meteorology and time-stamped imagery to verify and document dust events

UDORN is planned as a multi-year, dust-season effort, with public-facing data products updated regularly.

What to watch next

As the network expands, key questions include:

• How frequently do dust events exceed background levels?

• How often does dust chemistry vary by source region?

• Do patterns shift as lake levels change?

Those answers will shape future policy discussions.

If you have questions or comments, feel free to reply directly to this email.

Sources & further reading

Sources referenced in this issue:

• Great Salt Lake Strike Team — https://gardner.utah.edu/great-salt-lake-strike-team/

• Utah Division of Air Quality PM₁₀ overview — https://deq.utah.gov/air-quality/particulate-matter-10-pm10-overview

• EPA National Ambient Air Quality Standards — https://www.epa.gov/criteria-air-pollutants/naaqs-table

• Utah Dust Observation and Research Network (UDORN) overview — https://deq.utah.gov/air-quality/great-salt-lake-dust

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Independent publication notice

Salt & Sky Brief is an independent publication. The views expressed are solely those of the author and do not represent the University of Utah or any affiliated organization.

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