UGS presents water-budget baseline for Shorelands Preserve, finds inflows ≈25,090 af/yr

Utah Geological Survey researchers presented new monitoring and water-budget results for the 4,400-acre Great Salt Lake Shorelands Preserve, finding average total inflows of about 25,090 acre-feet per year and total outflows of about 25,240 acre-feet per year.

The project, funded in part by the Great Salt Lake Tech Team, combined seven shallow groundwater monitoring wells, continuous stream gauges at Case Creek and the Freeport Drain, seasonal measurements of other inflows and OpenET evapotranspiration estimates. Lead presenter Claire Springberg said the team estimated groundwater inflow at roughly 1,500 acre-feet per year and surface inflows at about 15,900 acre-feet per year, with precipitation accounting for about 5,700 acre-feet per year.

“Our average total inflows for the preserve is 25,090 acre-feet per year,” Springberg said, summarizing the project’s annualized balance. She also reported evapotranspiration for the preserve at about 12,000 acre-feet per year, groundwater outflow near 400 acre-feet per year, and a surface-water outflow estimate of roughly 12,700 acre-feet per year under the team’s assumption that much outflow is consumed in phragmites-dominated fringe marshes.

Researchers emphasized methodological limits: channelized outflow is measurable, but much surface flow diffuses through phragmites beds and across fringing wetlands and is difficult to capture directly. Springberg said the team used an outflow-area approach combined with OpenET to estimate that diffuse loss and noted the water budget is still being refined, including formal uncertainty quantification and the planned addition of 2023 data to the final report.

In discussion, participants asked about measurement gaps for Holmes Creek and other overland flows; Springberg said access and repeated washout of monitoring equipment complicated some sites, and the team plans additional gain–loss assessments along stream reaches as resources permit. The study’s authors said managers may be able to use the project's baseline to inform short-term water moves (e.g., irrigation or diversion decisions) and to prioritize monitoring needs across Waterfowl Management Areas.

The UGS team also reported vegetation mapping and an NDVI time-series analysis that attribute most recent vegetation increases to Phragmites expansion, but showed local declines in areas with active treatment. Springberg said management actions were a primary explanatory variable behind vegetation patterns over the last decade and recommended monitoring be used to evaluate before-and-after treatment effects.

Next steps noted by presenters include finalizing the 2023 data, constraining component uncertainties in the written report, and sharing raw data where feasible to assist other managers.