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| Created: | Mar 11, 2026 at 3:37 p.m. (UTC) | |
| Last updated: | Mar 13, 2026 at 11:56 a.m. (UTC) | |
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Abstract
This resource provides the data, model, and model results underlying the modeling work presented in the Planning for an Uncertain Future section of the "Great Salt Lake Strike Team Data and Insights Summary" released by the Great Salt Lake Strike team, January 7, 2026. https://gardner.utah.edu/great-salt-lake-strike-team/, https://d36oiwf74r1rap.cloudfront.net/wp-content/uploads/2026/02/GSL-Jan2026-Final.pdf
1000 realizations of potential lake levels for the next 30 years were simulated for each of four scenarios. Results include the 1000 realizations and a statistical summary of these realizations for each of the four scenarios. Scenarios were developed by David Tarboton at Utah State University.
The scenarios are as follows:
- Baseline scenario assumes no additional inflows to Great Salt Lake. Inflows are randomly sampled from historical data between 2000 and 2025.
- Additional 250 KAF/year inflow scenario considers an additional 250 thousand acre-feet (KAF) of inflow each year to the lake from water conservation or other sources.
- Additional 375 KAF/year inflow scenario considers an additional 375 thousand acre-feet (KAF) of inflow each year to the lake from water conservation or other sources.
- Additional 800 KAF/year inflow scenario considers an additional 800 thousand acre-feet (KAF) of inflow each year to the lake from water conservation or other sources.
To capture hydrologic variability, the model performs 1,000 simulations for each scenario by randomly selecting historical data (annual inflow, precipitation, and evaporation) from historical values between 2000 and 2025. The past 26 years were selected to represent the contemporary period with elevated temperatures and decreased inflow to GSL. Projections start in 2025 with the lake at a level of 4191 ft and extend to 2055. The additional inflow scenarios were produced by adding the corresponding value to historical inflow data.
The values chosen represent approximately 10% conservation (250 KAF/yr), 15% conservation (375 KAF/yr) and a conservation or additional inflow value calculated to have the mean lake elevation across the 1000 simulations achieve a level of 4,198 feet by 2055 (800 KAF/yr). These are total basinwide additional inflow amounts without considering the source of the conservation required for them to be achieved.
The model output data in this resource include the mean, median, minimum, maximum, 5th percentile, 95th percentile, 25th percentile, and 75th percentile values for each simulation as well as the simulations themselves. Each single 30 year simulation is referred to as a realization. The mean and median are measures of central tendency. The percentile values characterize the probability distribution representing the variability across the 1000 realizations. Given that we used 1000 realizations, both the minimum and maximum values represent extreme situations with a probability of occurrence of 1/1,000, or a 30 year period that might be expected to occur statistically only once in 1,000 thirty year periods, or once in 30,000 years.
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Content
README.md
This resource provides the data, model, and model results underlying the modeling work presented in the Planning for an Uncertain Future section of the "Great Salt Lake Strike Team Data and Insights Summary" released by the Great Salt Lake Strike team, January 7, 2026.
David Tarboton, Utah Water Research Laboratory, Utah State University
Updated 3/11/26
1000 realization of potential lake levels for the next 30 years were simulated for each of four scenarios. Results include the 1000 realizations and a statistical summary of these realizations for each of the four scenarios.
Files and descriptions:
Results
Baseline scenario assumes historical inflows resampled from 2000 to 2025 to Great Salt Lake.
- Simfigdata_2000_to_2025.csv - This holds the mean, median, quantiles, minimum and maximum lake levels of the 1000 realizations
- simrealizations_2000_2025.csv - a 1000 x 30 matrix. Each row contains the 30 lake level values that represent a lake level realization. There are 1000 rows, for the 1000 simulations.
Additional 250 thousand acre-feet (KAF) of inflow each year to the lake. 250 KAF added to historical inflows resampled from 2000 to 2025 to Great Salt Lake
- Simfigdata_2000_to_2025_plus_250.csv - This holds the mean, median, quantiles, minimum and maximum lake levels of the 1000 realizations for the additional 250 thousand acre-feet (KAF) of inflow each year to the lake scenario.
- simrealizations_2000_2025_plus_250.csv - a 1000 x 30 matrix. Each row contains the 30 lake level values that represent a lake level realization. There are 1000 rows, for the 1000 simulations.
Additional 375 thousand acre-feet (KAF) of inflow each year to the lake. 375 KAF added to historical inflows resampled from 2000 to 2025 to Great Salt Lake
- Simfigdata_2000_to_2025_plus_375.csv – This holds the mean, median, quantiles, minimum and maximum lake levels of the 1000 realizations for the additional 375 thousand acre-feet (KAF) of inflow each year to the lake scenario.
- simrealizations_2000_2025_plus_375.csv - a 1000 x 30 matrix. Each row contains the 30 lake level values that represent a lake level realization. There are 1000 rows, for the 1000 simulations.
Additional 800 thousand acre-feet (KAF) of inflow each year to the lake. 800 KAF added to historical inflows resampled from 2000 to 2025 to Great Salt Lake
- Simfigdata_2000_to_2025_plus_800.csv – This holds the mean, median, quantiles, minimum and maximum lake levels of the 1000 realizations for the additional 800 thousand acre-feet (KAF) of inflow each year to the lake scenario.
- simrealizations_2000_2025_plus_800.csv - a 1000 x 30 matrix. Each row contains the 30 lake level values that represent a lake level realization. There are 1000 rows, for the 1000 simulations.
Note: 2000_to_2025 in the name of each of the files refers to the historical years of data used for random sampling in the Monte-Carlo simulations.
Description of variables in Simfigdata files:
- year - References simuilation water year end
- mean – Mean level across 1000 simulations for the associated water year end
- median - Median level across 1000 simulations for the associated water year end
- quant05 - 5th percentile level across 1000 simulations for the associated water year end
- quant25 - 25th percentile level across 1000 simulations for the associated water year end
- quant75 - 75th percentile level across 1000 simulations for the associated water year end
- quant95 - 95th percentile level across 1000 simulations for the associated water year end
- min - Minimum level across 1000 simulations for the associated water year end
- max - Maximum level across 1000 simulations for the associated water year end
AverageSensitivity.csv - This holds mean, median and quantiles for long term lake level ranges under sustained additional inflow.
UpdatedRequiredInflows.csv - This holds solutions for the steady inflows required to reach set target levels in a given time period.
ind_matrix.csv - This holds the resampling index matrix used for the random set of realizations. To reproduce these results exactly read in this matrix, rather than generate a new random set.
Code
RModelWork.R - This is the work script intended not to be run in its entirety, but stepped through blocks of lines at a time examining and saving results along the way.
GSLRmodel2.R - R code for annual GSL model to assess the sensitivity of GSL level to inflows.
GSLFunctions.R - R code for some utility functions.
Input files
GSLM_Bathymetry_noProposedPonds.csv - Bathymetry file used. This is from https://www.hydroshare.org/resource/89125e9a3af544eab2479b7a974100ba/
GSLLevelVolAnn.csv - Historical annual level and volume
GSLLevelVol.csv - Historical monthly level and volume
GSL_Prism_ppt_ann.csv - Historical lake precipitation from PRISM and Gridmet
annstreamflow.csv - Historical streamflow
DepletionPaperData. Folder with some data from https://doi.org/10.22541/essoar.170688956.67127321/v1 where area volume data was extended to higher levels and there are salinity records used
R workspace file
Workspace.RData - This holds the contents of the R workspace at the end of this analysis. To use it remove workspace from the name so it is just .RData and then open with R.
Citation
The Great Salt Lake Strike Team. (2026). Great Salt Lake Data and Insights Summary: A Synthesized Resource Document for the 2026 General Legislative Session. https://gardner.utah.edu/great-salt-lake-strike-team/, GSL-Jan2026-Final.pdf
Related Resources
Tarboton, D. (2017). Great Salt Lake Area Volume Data, HydroShare, http://www.hydroshare.org/resource/89125e9a3af544eab2479b7a974100ba
Tarboton, D. (2025). Collection of Great Salt Lake Data, HydroShare, http://www.hydroshare.org/resource/b6c4fcad40c64c4cb4dd7d4a25d0db6e
Tarboton, D., E. Albers, Great Salt Lake Strike Team (2025). Great Salt Lake Surface Elevation Monte-Carlo Simulation Results 2024, HydroShare, http://www.hydroshare.org/resource/ea98db4caa1141cdbae92606f79f6909
Related Resources
| This resource updates and replaces a previous version | Tarboton, D., E. Albers, Great Salt Lake Strike Team (2026). Great Salt Lake Surface Elevation Monte-Carlo Simulation Results 2024, HydroShare, http://www.hydroshare.org/resource/ea98db4caa1141cdbae92606f79f6909 |
| This resource is described by | The Great Salt Lake Strike Team. (2026). Great Salt Lake Data and Insights Summary: A Synthesized Resource Document for the 2026 General Legislative Session. https://gardner.utah.edu/great-salt-lake-strike-team/, https://d36oiwf74r1rap.cloudfront.net/wp-content/uploads/2026/02/GSL-Jan2026-Final.pdf |
| Title | Owners | Sharing Status | My Permission |
|---|---|---|---|
| Collection of Great Salt Lake Data | David Tarboton | Public & Shareable | Open Access |
Credits
Funding Agencies
This resource was created using funding from the following sources:
| Agency Name | Award Title | Award Number |
|---|---|---|
| Utah Water Research Laboratory | None | None |
How to Cite
This resource is shared under the Creative Commons Attribution CC BY.
http://creativecommons.org/licenses/by/4.0/
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