Working with Hansen, Allen & Luce (HAL) for the Utah Division of Water Resources, LimnoTech helped address questions raised about the impact of stormwater management on flows to the Great Salt Lake.
Great Salt Lake, Utah. Image of rock, sand, and vegetation in the foreground and the lake in the background with cloudy skies in the horizon.

Location:
Great Salt Lake, Utah

Clients:
Utah Division of Water Resources and Utah Division of Water Quality

Partner:
Hansen, Allen & Luce (HAL)

Service Areas:

Our Expert:

Working with Hansen, Allen & Luce (HAL) for the Utah Division of Water Resources, LimnoTech helped address questions raised about the impact of stormwater management on flows to the Great Salt Lake. This study examines the potential impact of Low Impact Development (LID) practices on the water balance in one of Utah’s most critical ecosystems.

The Challenge

The Great Salt Lake (GSL) has faced historically low water levels, prompting urgent questions about how urban development affects its water budget. In response, the Utah Legislature passed HB429, mandated “…the completion of a wide-scale Great Salt Lake Watershed Integrated Water Assessment” (1). A key concern was whether post-construction stormwater permit requirements—specifically those involving LID—might reduce the volume of water reaching the lake.

The State of Utah needed a scientifically grounded evaluation of how LID practices that promote infiltration and evapotranspiration might impact both surface and groundwater flows to the lake. With increasing urbanization, understanding these dynamics is critical to balancing ecological health, water quality, and sustainable growth.

The Outcome

To address this challenge, Hansen, Allen & Luce (HAL) and LimnoTech developed a robust modeling framework that linked surface water and groundwater systems. The team simulated three scenarios: current baseline conditions, future development without LID, and future development with LID. These models quantified stormwater flows under each scenario, tracking both direct runoff and subsurface flows to the lake.

The findings revealed that while future development increases total runoff to the GSL, implementing LID significantly alters the flow pathways. LID reduces surface runoff but enhances groundwater recharge, ultimately still contributing to the lake through slower, subsurface routes. For example, per 100 acres of development, surface runoff to the lake was 71 acre-feet/year without LID, compared to 42 acre-feet/year with LID. These insights provide a nuanced understanding of how LID affects the lake’s water balance, providing a foundation for informed policy and planning decisions.

By delivering a methodology for evaluating LID impacts, the study equips Utah’s water managers with the tools to guide sustainable development while protecting the Great Salt Lake’s future.

(1) Hansen, Allen & Luce (HAL) and LimnoTech. 2023. HB 429 Great Salt Lake Stormwater Study. Prepared for the State of Utah Division of Water Resources. HAL Project No.: 420.03.100.

For more details on the Great Salt Lake Study, check out the links below:

• Final Report: HB 429 Great Salt Lake Stormwater Study
• Fact Sheet: Great Salt Lake Stormwater Study
• Website: Great Salt Lake Integrated Plan

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