Insights from the Hill Air Force Base Resiliency Study

Easton Hopkins, PE

Steve Jones, PE

APA UT Fall Conference

September 9, 2026

HAFB – Water Resilience Study

HAFB – Water Resilience Study

https://sentinellandscapes.org/landscapes/great-salt-lake/#resources

Study to review water resilience in the region surrounding HAFB.

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Develop “water budget”

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Review:

1. Existing and future demands & DEPLETION (M&I, ag, environment (GSL))
2. Reliable Water supply for groundwater and surface water (infrastructure, water rights, physical water supply)

HAFB – Water Resilience Study

OBJECTIVE

The goal of the study is to increase the resilience of HAFB and provide a reliable water supply to support operations, safeguard the riparian buffer, and ensure long-term sustainability.

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This can be done by bolstering the resilience of the regional water supply and helping the surrounding environment

Phase 1:

Initial Assessment

Phase 2:

Implementation Strategy

WAIT…

There’s more that happened before this study — let’s rewind.

WHERE WE'RE HEADED TODAY

1

Mt. Nebo Groundwater Program

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Why does a supply-first approach matter — and how do we work together?

2

M&I Conservation Opportunities

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How do we bend the demand curve?

3

HAFB Water Resilience Study

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A case study looking at both

MAIN MESSAGE

We need to work together to optimize our supply and demand

SUPPLY

Fixed

DEMAND

Can be altered

ONE FINITE SUPPLY, THREE COMPETING DEMANDS

FIXED SUPPLY

M&I

Agriculture

Environment (GSL)

Municipal & Industrial

Growth could add demand; conservation and smart land use planning bend the curve

Agriculture

Large water user — one of the biggest partner in stretching supply

Environment — Great Salt Lake

Receives what is left; shortfalls show up here first

The box cannot grow — more for one demand means less for another

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*boxes not to scale*

ALIGNING DEVELOPMENT EXPECTATIONS WITH WATER REALITY

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• Transportation infrastructure often drives growth and influences long-term planning decisions.

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• Transportation-based population estimates typically do not account for water supply constraints

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• Population projections from water resource studies show a realistic estimate of a city’s growth capacity based on water supply

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• Aligning city planning and development with water availability is critical to supporting future growth responsibly

CASE STUDY: EAGLE MOUNTAIN CITY

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Existing Population:

75,000

Transportation Master Plan

2060 Population Projection from UDOT:

152,500

• Transportation and other infrastructure may enable growth, but water availability determines if the demand can be sustained

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• Amending these projections is critical in determining a successful “water budget” and to avoid planning for development that exceeds the supply

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Usage Period

SECTION 01

Groundwater Management

Mt. Nebo Water Agency

• Coalition of water users in Southern Utah County to better manage water supplies.
• Interlocal agreement for sustaining groundwater supply impacted by future growth.
• Members of MNWA are largest users of groundwater in the area and hold majority of groundwater rights.

https://www.sciencedirect.com/science/article/pii/S0048969724006946

Danger

Zone

Empty

Full

Historic High

Healthy Operation

GROUNDWATER LEVEL GAUGE

• State Engineer stepping in
• Danger of Subsidence

Underused aquifer/increased evaporation

Path Forward

Data Collection

• Collect data from member agencies
• Identify large users and gather their data

Model Development

• Update model with new data
• Model existing and future groundwater trends

Options Development

• Review management alternatives for short- and long-term goals

Technical Committee

• Meet annually before spring to review options
• Develop plan and agreements

Board Approval

• Review plan and vote for approval

GROUNDWATER PLAN COLLABORATION

River Commissioner

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SHORT AND LONG-TERM BENEFITS

Outputs of the Groundwater Management Program

1

Understand the aquifer condition and develop best management practices

2

Local water users collaborate in and own the program

3

Measure and monitor to make informed decisions

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Updated annual groundwater management plan

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A foundation for long-term surface, groundwater, and import water optimization for all users

Conclusions

Plan Around Available Supply

Build growth, land use, and development decisions around the water that is actually there. Supply is fixed.

Collaborate Regionally

Work with neighboring water users to optimize and stretch a limited, shared supply together.

SECTION 02

M&I Water Conservation Opportunities

Legislative Brief

~14 Pages

Appendix

~ 100+ pages

Two Pager

Links

Report

Fact Sheet

Recommendation

1

Develop water budgets based on water supply, demand, and depletion

2

Set an individual conservation goal

3

Utilize water conservation tools

DELIVERED THROUGH

Water policies

Water conservation programs

Historical Trends - Total Depletion

4%�INDOOR DEPLETION

AVERAGE: 2019–2023

INDOOR DEMAND

~280,000 ac-ft

OUTDOOR DEMAND

~415,000 ac-ft

INDOOR DEPLETION

~14,000 ac-ft

OUTDOOR DEPLETION

~333,000 ac-ft

Roughly 5% of indoor demand is depleted, compared with about 80% of outdoor demand.

Most water used indoors returns to Great Salt Lake, while most water used outside is depleted.

The Great Evaporator: Outdoor Water Use

50% total water �use depleted�through �evaporation

Existing Ratio

M&I Water Use Breakdown

40% �indoor

60% �outdoor

75% �indoor

25% �outdoor

15% total water �use depleted�through �evaporation

Future Predicted Ratio

The Great Evaporator: Outdoor Water Use

M&I diversion will increase but depletion needs to stay the same (or less).

Can only be achieved through depletion focused land use planning

Water Budget

A water budget balances water sources against water use within a basin — a fundamental input to water planning.

SOURCES

Surface Water

Diverted from streams and reservoirs

Groundwater

Pumped from the aquifer

DEMANDS

Municipal & Industrial

Diverted and depleted by cities

Agricultural

Diverted and depleted by irrigation

A balanced water budget must be maintained to support M&I and agriculture, especially as both sectors see ongoing shifts in land use, demand, and market dynamics.

Water Budgets

Region-specific depletion budgets would account for the constraints that different regions experience with water supply and demand

A maximum allowed depletion and minimum return flow should be balanced between M&I and agriculture

Existing

Future

Recommendations

Conclusions

We must work together to reduce depletion and preserve a limited water supply

Outdoor water demand

HIGH DEMAND

HIGH DEPLETION

Several strategies exist to reduce demand

Programs

Focused on reducing existing demands

Policies

Focused on reducing future demands

SECTION 03

HAFB Water Resilience Study

STUDY AREA

MASS BALANCE: SUPPLY & DEMAND

MASS BALANCE: SUPPLY & DEMAND

MASS BALANCE: SUPPLY & DEMAND

Runoff

MASS BALANCE: SUPPLY & DEMAND

700,000 ac-ft deficit

* GSL strike team report

Runoff

MASS BALANCE: SUPPLY & DEMAND

Great Salt Lake Basin

Weber Delta Region

MASS BALANCE: SUPPLY & DEMAND

2

5,000,000 ac-ft

precipitation runoff

700,000 ac-ft

depletion deficit

Great Salt Lake Basin

Weber Delta Basin

75,000 ac-ft

precipitation runoff

??? ac-ft

depletion deficit

10,500 ac-ft

depletion deficit

Weber Delta Deficit =

Water Supply

Groundwater

Average Recharge: 104,927 ac-ft/yr

Safe Yield: 52,464 ac-ft/yr

Average Well Discharge: 46,853 ac-ft/yr

• Well Discharge:
• Added in new wells (post-1984) to the model, then used DWR data to update 1985-2025 well discharge data in the model
• Annual Recharge:
• Values for bedrock recharge stayed consistent throughout entire model (calculated within well package)
• Infiltration through precipitation was calculated using precipitation data (1985-2025) divided over the primary/secondary recharge areas

WELLS

• Model grid cell coordinates (IJK) correlated with Division of Water Rights well locations (1984 – 2025)

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Wells built 1985 - 2025

Wells built prior to 1985

Surface Water

SURFACE WATER

Preliminary estimates for runoff derived from study: HB 429 Great Salt Lake Stormwater Study by Hansen, Allen & Luce and Utah Division of Water Resources

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https://water.utah.gov/wp-content/uploads/2024/02/GSL-Stormwater-Study-Report.pdf

SURFACE WATER

Drinking water sources accounts for mostly municipal purchases from WBWCD, alongside some municipal sources

PRELIMINARY FINDINGS: SURFACE WATER

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From PRISM datasets

Mean: 20.7 inches

PRELIMINARY FINDINGS: SURFACE WATER

PRELIMINARY FINDINGS: SURFACE WATER

Days

PRELIMINARY FINDINGS: SURFACE WATER

Days

PRELIMINARY FINDINGS: SURFACE WATER

267,000 ac-ft ≈ 268,000 ac-ft

Demand is usually equal to annual surface water supply.

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Total Outdoor Use (M&I + Ag) ≈ Surface Water Supply

Any additional diversions would negatively impact the existing ecosystem

Water Rights Analysis

WATER RIGHTS ANALYSIS

Groundwater: 228,000 ± 29,200 ac-ft

• Cutoff: 1915 - 1920

Surface Water: 3.42 million ± 0.584 million ac-ft

• Some large water right holders (> 1 million ac-ft)
• 1.56 million ± 0.197 million ac-ft

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Process:

1. Pull point of diversion shapefile from DWRi
2. Set to study area of the study
3. Remove duplicates, update based on change application
4. Estimate volume by median ac-ft/cfs
5. Update city information through quick review

WATER RIGHTS ANALYSIS

WATER RIGHTS ANALYSIS

Cumulative groundwater rights by year

Next Steps: Phase 2 Discussion

NEXT STEPS

Potential Options

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1. Water Conservation
2. Groundwater Recharge
3. Groundwater Management Program
4. Agricultural Optimization
5. Phragmites Removal
6. Storm Drain Optimization
7. Education

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NEXT STEPS

Water Conservation

Groundwater Recharge

Groundwater Management Program

Agricultural Optimization

Phragmites Removal

*Invasive species

Storm Drain Optimization

Education

Resilient

Water Supply

NEXT STEPS

Potential options, ranked by unit cost

1

Agricultural Optimization

$310 / ac-ft

2

Water Conservation

$1,250 / ac-ft

3

Phragmites Removal

$2,350 / ac-ft

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Groundwater Recharge

$4,810 / ac-ft

Cost estimates pending

Groundwater Management Program

Storm Drain Optimization

Outreach

Questions?

Thank you

Steve Jones | 801-718-8217 | steve@halengineers.com

Easton Hopkins | 801-664-0901 | ehopkins@halengineers.com

WATER CONSERVATION

Unit Savings

(ac-ft / irrigated acre)

Cost

($ / ac-ft)

0

1.7

$0

$7,500

WATER CONSERVATION

WATER CONSERVATION

Secondary metering is required at the state level (much of this area already has it)

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Tiered based rates will now have to be adopted. Savings will range from 0 to 20%.

Existing outdoor demand: ~110,000 ac-ft

Possible total reduction: 22,000 ac-ft

Existing average use per irrigated acre: ~4.0 ac-ft/irr-ac

Could be: 3.2 ac-ft/irr-ac

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GROUNDWATER RECHARGE

Northern Utah County Aquifer Council

Managed Aquifer Recharge (MAR) Study

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• Study found a potential increase to groundwater recharge by 15%-17% (depends on soil types and if they are like Utah valley)
• Capital cost range: $477 - $9,139 per AF

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GROUNDWATER RECHARGE

Existing Groundwater Recharge: 105,000 ac-ft

Existing Groundwater Safe Yield: 52,500 ac-ft (1/2 of recharge)

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Potential Increase in Recharge (15%): 15,750 ac-ft

Potential Increase in Safe Yield (15%): 7,850 ac-ft

* Could fill the gap

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PRELIMINARY ESTIMATED COST: $7,500,000 to $144,000,000

Average: $75,750,000

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GROUNDWATER MANAGEMENT PROGRAM

Framework from Mt. Nebo Water Agency Groundwater Management Program

Quick glance indicates that a lot of systems are looking to develop more groundwater supply

AGRICULTURAL OPTIMIZATION

https://water.utah.gov/wp-content/uploads/2026/05/GSL-BIP_AgWaterOptimizationReport_FINAL_2026-04-21.pdf

AGRICULTURAL OPTIMIZATION

Best options and preliminary cost to save 30,000 ac-ft

Irrigation System Upgrades

Convert inefficient systems to more efficient irrigation

~$133 – $508 per ac-ft saved

$4.0M – $15.25M

Switch Crop Type

Shift from alfalfa to corn / winter wheat

~$275 – $425 per ac-ft saved

$8.25M – $12.75M

PHRAGMITES REMOVAL

Unit savings: 2.07 ac-ft/acre

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Cost: $610-$4,050 per ac-ft

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STORM DRAIN OPTIMIZATION

Derive numbers from this study: https://water.utah.gov/wp-content/uploads/2024/02/GSL-Stormwater-Study-Report.pdf

STORM DRAIN OPTIMIZATION

Baseline Values

Assume 11,000 acres of ag develops

*LID helps with water quality concerns, while traditional SD does not

CONCLUSION

There is not enough water to support significantly more drinking water demand (maybe all demand)

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Demand matches supply, and both are far below what is available through water rights

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DEMAND��*RESULTS ARE PRELIMINARY, MAY CHANGE WITH FURTHER ANALYSIS*

DEMANDS

110,000 ac-ft

32,000 ac-ft

M&I

Ag

160,000 ac-ft

M&I: Indoor Demand

M&I: Outdoor Demand

Ag

Indoor Estimate: Based on end use meter data (sewer flows)

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Outdoor Estimate: Based on remaining drinking water not used indoor & remaining secondary water not used for agriculture

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Agriculture Estimate: Based on NDVI analysis

DEMANDS

M&I: Indoor Demand

M&I: Outdoor Demand

Ag

Total Water Demand

Drinking Water and Secondary Water Systems

Drinking Water

Secondary Water

M&I DEMANDS – SEWER FLOWS

NDVI

M&I

Ag

Area: 27,500 acres

Demand: 107,000 ac-ft

4.02 ac-ft/irr-ac

Area: 46,200 acres

Demand: 160,000 ac-ft

3.47 ac-ft/irr-ac

NDVI

M&I

NDVI

Ag

AG DEMANDS

Process:

1. Collect crop type and irrigation method from WRLU dataset (DWRe).
2. Obtain net irrigation requirements (ET) by crop type from USU Appendix I.
3. Apply irrigation efficiency factors (USU)
4. Quantify demand
5. Compare against irrigation company information reported information

Total: 160,000 ac-ft