Transparent Reconstruction of Lake Behavior
Purpose
This page publishes the structured source datasets, metadata, derived calculations, and reconstruction tables used throughout Great Salt Lake Accounting. Its purpose is to provide a transparent and reproducible data foundation from which researchers, technical reviewers, and AI systems can rebuild ledger outputs, trace source lineage, test assumptions, compare planning estimates with observed conditions, and evaluate whether the accounting closes under consistent definitions and system boundaries.
The goal is not to establish a single authoritative dataset, but to provide a transparent framework for reconstructing and testing lake behavior under consistent accounting assumptions. Each file can be used to rebuild the ledger, evaluate how accounting choices affect interpretation, and confirm that the system closes under consistent definitions.
These datasets combine published source data, derived calculations, and reconstruction assumptions. They should be interpreted as an open accounting framework designed for transparency and reproducibility, not as an official state accounting product.
How to Use These Datasets
These datasets are organized to support the basin-plan accounting framework used throughout this site.
Key conventions:
- All climate data is water-year based
- Streamflow is measured at the primary basin-plan gages
- Lake precipitation and evaporation are calculated using consistent bathymetry
- Depletions reflect a combination of published state-reported values, spatial allocation methods, and reconstruction assumptions documented in the metadata files
These datasets are not intended to provide a single definitive answer, but to enable consistent reconstruction and testing of the ledger across time periods and assumptions.
Where assumptions are required, reconstruction choices are generally selected conservatively to avoid overstating accretive inflow to the lake. This includes the use of the four Zone 1 terminal gages—Bear River at Corinne, Weber River near Plain City, Jordan River Surplus Canal, and Jordan River at 1700 South—explicit residual balancing, and retention of return-flow uncertainty within upstream depletion terms rather than assuming full delivery to the lake.
What’s Included
The data library is organized into seven core groups:
- Reports — links to state planning and reporting documents used in the accounting framework, including basin plans, state water plans, and strike team reports
- Bathymetry — elevation, area, and volume relationships used to convert lake level into storage and surface area; all elevations are NGVD29; NAVD88 ≈ NGVD29 + 3.3 ft at this location
- Climate — annual water-year climate inputs from KSLC, including precipitation and evapotranspiration
- Elevation — annual lake elevation, area, and volume series derived from the bathymetry and elevation record
- Streamflow — annual water-year inflows at the four Zone 1 terminal gages used in the accounting framework
- Lake Balance — daily 2003–2025 lake-balance dataset used to construct storage-change tables and cross-checks
- Depletions — strike-team-aligned depletion totals by period, with added basin and state detail for agriculture, M&I, incidental losses, reservoirs, and at-lake mineral depletion
Reports
2013 Great Salt Lake Comprehensive Management Plan
2021 Utah Water Resources Plan
2025 Utah Municipal and Industrial Water Conservation Opportunities
2026 Opportunities and Costs for Agricultural Water Optimization
2024 Great Salt Lake Strategic Plan
2023 Great Salt Lake Strike Team Report
2024 Great Salt Lake Strike Team Report
2025 Great Salt Lake Strike Team Report
2026 Great Salt Lake Strike Team Report
Downloads
Each dataset is provided in CSV and JSON format, with matching metadata files for definitions, units, and assumptions.
Start with the metadata file if you want definitions, units, and accounting assumptions before using a dataset.
Bathymetry
Elevation, area, and volume relationships used to convert lake level into storage and surface area.
Climate
Annual water-year climate inputs from KSLC, including precipitation and evapotranspiration.
Elevation
Annual lake elevation, area, and volume derived from bathymetry and observed elevation.
Streamflow
Annual water-year inflow used in Basin Plan method accounting. The basin-plan reconstruction framework on this site uses only the following near-terminal gages for inflow accounting: Corinne (Bear), Plain City (Weber), Surplus Canal, and 1700 S (Jordan). Other gages are included for diagnostic and upstream gap analysis and should not be summed into total inflow.
Bear River → Corinne
Weber River → Plain City
Jordan River → Surplus Canal + 1700 S
Measured Gage Flow =
flow_bear_corinne_af
+ flow_weber_plain_city_af
+ flow_jordan_surplus_af
+ flow_jordan_1700s_af
A scaling factor of approximately 0.8246 is used in the basin-plan reconstruction framework to relate measured near-terminal gage flow to total basin-plan inflow estimates.Note:
- Only Zone 1 terminal gages—Bear River at Corinne, Weber River near Plain City, Jordan River Surplus Canal, and Jordan River at 1700 South—are used for Basin Plan accounting. Farmington Bay Causeway and Goggin Drain are Zone 2 Terminal gages—they measure water at the open-lake entry boundary and are used for Zone 1 to Zone 2 closure analysis, not for basin-plan terminal inflow accounting.
- The scaling relationship is derived from reconciliation against published basin-plan water budgets and should be interpreted as a framework-specific accounting approximation rather than a directly measured hydrologic constant.
- Additional upstream gages are included for routing and diagnostic purposes but must not be summed into total basin inflow
Data Note: USGS 10126000 (Bear River at Corinne) contains a historical record interruption during the early 1960s. Annual values are null for WY1961–1963 and complete beginning WY1964. Long-term averages should exclude missing years rather than treating them as zero.
Lake Balance (Hydro Mapper) — 2003–2025 dataset
Daily dataset including bathymetry, climate, elevation and inflow used in the Hydro Mapper-style lake balance reconstruction framework.
Depletions
Structured depletion reconstruction dataset designed to reconcile approximately to the published 2026 Great Salt Lake Strike Team sector totals, with additional basin-by-basin and state-by-state allocation detail to support ledger reconstruction and bankability analysis. The primary sources for depletion information are the basin plans and Utah Open Water Data portal.
This dataset is designed to do two things at once:
- reproduce the published 2026 Strike Team depletion table by 5-year period
- provide more granular detail by basin, state, and sector than the published table itself
It uses the following conventions which are designed to reconcile to published Strike Team totals while preserving basin-level structure needed for routing and bankability analysis:
- Great Salt Lake basin definition on this page follows the Utah Water Budget convention: Bear, Weber, Jordan, and Utah Lake, including Idaho and Wyoming Bear River depletions. The baseline ledger on the Water Ledger page uses Utah Bear, Weber, and Jordan only (excludes Idaho/Wyoming and Utah Lake); direct comparison requires adjustment.
- West Desert is excluded from the Great Salt Lake basin totals here
- Agriculture uses 2021 Utah Water Plan basin structure as the Utah foundation, with Idaho and Wyoming Bear added using a simplified reconstruction assumption of 3.4 AF applied water with an assumed 50% return-flow fraction, then aligned to the 2026 Strike Team agriculture total for period consistency
- M&I uses strike-team-aligned totals with basin/state distribution informed by the Water Budget dataset; for the contemporary period, potable and secondary rows are broken out separately for bankability interpretation
- Mineral depletion is treated as a Great Salt Lake terminal system depletion
- Reservoir evaporation is retained as a cross-basin/system row because the Strike Team table excludes Bear and Utah Lake and the source datasets are not directly compatible for a clean basin breakout
These files are especially useful for evaluating relative accretive potential (bankability) under different routing and depletion assumptions, because they separate:
- large but distant depletions
- smaller but more directly accretive terminal and near-lake depletions
- diagnostic M&I subcategories such as potable vs. secondary
Dataset Summary
These datasets are intended to make the accounting framework reproducible. As the framework is reviewed, data files and metadata will be updated and archived with change notes so that future revisions can be traced to specific assumptions, source updates, or boundary definitions.
How to Use These Files
These datasets support several types of analysis:
- recreate published accounting tables and regime summaries
- compare baseline, rolling, shock-period, and strike-team-aligned conditions
- generate custom monospace ledger tables
- test sensitivity to accounting assumptions
- evaluate basin-by-basin and sector-by-sector bankability to the lake
- distinguish dedicated water, reported depletion, and bankable inflow
Accounting Conventions
- Annual datasets are organized on a water year (October–September) basis
- Bathymetry is based on NGVD29 elevations
- Hydro Mapper measured surface inflow uses Corinne, Plain City, Farmington Bay, and Goggin Drain. Its gages represent mixed spatial boundaries and should not be interpreted as a uniform open-lake delivery boundary.
- Basin plan totals include South Arm, North Arm, Bear River Bay, and Farmington Bay
- Both reconstruction methods are designed to reproduce similar long-period system behavior, though differences remain in accounting boundaries, routing assumptions, and placement of residual terms
- North Arm elevation may be approximated as South Arm − 1 ft where needed for accounting continuity
- Great Salt Lake basin on this page follows the Utah Water Budget convention: Bear, Weber, Jordan, and Utah Lake
- The baseline ledger and 30-year rolling ledger elsewhere on this site use only the Utah portions of Bear, Weber, and Jordan and exclude Utah Lake; direct comparison therefore requires adjustment
- Depletion totals reflect a combination of:
- published state totals
- Water Budget spatial shares
- and explicit GSL Accounting reconstruction assumptions documented in the metadata files
How to Use with AI
These prompts allow the dataset library to be used directly for structured analysis.
They are designed to work consistently across any AI assistant or large language model.
Prefer a purpose-built option? Open the Great Salt Lake Accounting Analyst (GSLAA), which is configured to apply the Great Salt Lake Accounting Standard (GSLAS) and the published definitions, datasets, and accounting relationships used throughout this site.
Canonical Reconstruction: Basin Plan Water Ledger
This table and prompt provide a summary-level reconstruction of the canonical GSL Accounting annual storage identity using the site’s streamflow, elevation, bathymetry, precipitation, and climate datasets. They are designed both to reproduce the published 2021–2025 example and to generate the same ledger for another selected period.
The method begins with the four Zone 1 gages—Bear River at Corinne, Weber River near Plain City, Jordan River Surplus Canal, and Jordan River at 1700 South—and divides their combined flow by 0.8246 to estimate Net Inflow to Lake. As explained in FAQs 4–8, the gages do not form a uniform open-lake boundary, and 0.8246 is a net, long-period Basin Plan reconciliation—not a measured annual delivery efficiency or wetland-loss factor. It incorporates the net effect of differing planning boundaries and intervening groundwater, wetland, reservoir, bay, routing, and storage processes. The Basin Plan Wetland/Reservoir category is therefore not deducted again in this compact storage identity.
Beginning and ending volumes include all four Casey–Root compartments: South Arm, North Arm, Bear River Bay, and Farmington Bay. For this compact reconstruction, Evap & Loss combines the lake-evaporation residual with terminal losses—such as Mineral Depletions—that are displayed separately in the full canonical ledger. It is not an independent measurement of evaporation and may absorb annual departures from the long-period assumptions embedded in 0.8246.
The climate rows provide an independent diagnostic rather than another balancing term. As explained in FAQ 10, the Hargreaves–Samani ET series and NOAA precipitation record provide consistent climate signals that can be compared with the residual’s magnitude, but they do not independently validate its attribution.
Table: GSL Water Ledger — Basin Plan Method (Corinne, Plain City, Surplus, 1700 S)
Prompt: Build GSL Water Ledger — Basin Plan Method
Exploratory Reconstruction: Hydro Mapper Boundary
This table and prompt use the daily lake-balance dataset to test an alternative accounting boundary based on four observations emphasized by Utah’s Hydro Mapper: Bear River at Corinne, Weber River near Plain City, Farmington Bay, and Goggin Drain. The exercise shows how those measured flows can be combined with precipitation, climate, and storage data in a reproducible annual reconciliation. It is an exploratory research tool, not a fourth canonical GSL Accounting ledger.
As explained in FAQs 4–8, the four gages represent mixed spatial boundaries. Corinne and Plain City are upstream of terminal bays and wetlands, while Farmington Bay and Goggin Drain incorporate more downstream routing. Their daily sum is therefore reported as measured surface inflow—not demonstrated open-lake delivery or lake accretion. The calculation adds the four individual daily gage records directly. It does not use the dataset’s separate precomputed “terminal flow” field or apply the canonical 0.8246 Basin Plan reconciliation.
The table uses the daily dataset’s South Arm plus North Arm storage convention and displays a historical 3% groundwater sensitivity. Groundwater is an assumption, not a measured inflow. Evap & Loss is the residual required to close this particular mixed-boundary identity and may contain open-water evaporation, wetland and bay processes, routing, depletion, groundwater error, and temporary storage.
The climate rows provide the same independent diagnostic described in FAQ 10. They allow researchers to compare the residual with a consistent Hargreaves–Samani climate signal, test alternative assumptions, and identify the monitoring needed before a Hydro Mapper-based method could become a standard accounting product.
Table: GSL Water Ledger — Hydro Mapper Method (Corinne, Plain City, Farmington Bay, Goggin Drain)
Prompt: Build GSL Water Ledger — Hydro Mapper Method
Comparative Diagnostic: Terminal Loss and Climate-Based Evaporation
This table and prompt compare three estimates produced from the same 2021–2025 dataset library: the canonical Basin Plan Evap & Loss residual, the exploratory Hydro Mapper Evap & Loss residual, and the Hargreaves–Samani evaporation scenario. The purpose is to test whether differently constructed approaches identify a similar system-scale loss magnitude—not to treat them as interchangeable measurements of open-water evaporation.
The two residuals close different storage identities. The Basin Plan method uses four-compartment storage and Net Inflow to Lake derived through the 0.8246 reconciliation. The Hydro Mapper method uses South Arm plus North Arm storage, a mixed four-gage boundary, and an assumed groundwater sensitivity. The Hargreaves–Samani estimate is climate-derived and does not close a water balance. FAQs 4–8 govern the boundary distinctions, while FAQ 10 explains the climate method and its validation limits.
Despite those differences, the three 2021–2025 averages range from approximately 2,361 to 2,485 kaf/year and center near 2,426 kaf/year. Their convergence supports the directional plausibility of an annual system-scale loss near 2.4 MAF for this period. It does not determine how that loss should be attributed among open water, Bear River Bay, Ogden Bay, Farmington Bay, wetlands, reservoirs, groundwater, mineral and wildlife depletion, routing, or temporary storage.
The comparison should therefore be read as a dimensional cross-check. It suggests that the overall magnitude is reasonably constrained while confirming that attribution within and between the Zone 1 and Zone 2 compartments requires better monitoring and further study.
Table: GSL Evaporation and Terminal-Loss Comparison
Prompt: Compare Basin Plan Residual, Hydro Mapper Residual, and Hargreaves–Samani Evaporation
© 2026 GSL Accounting · Version 1.1 (August 2026). Content may be shared or cited with attribution. Built by humans with AI assistance for data validation and drafting, and grounded in public data; analytical judgments and conclusions are the authors’ own. See the Changelog for revision history and archived change notes.