A physically constrained accounting framework for how water moves through—and sustains—the Great Salt Lake system
Purpose
The Great Salt Lake Water Ledger applies the Great Salt Lake Accounting Methodology to publicly available data to construct a basin-scale, physically constrained account of climate inputs, human depletions, terminal inflows, lake precipitation, evaporation, mineral depletions, and observed storage change. By reconciling these components under consistent definitions, system boundaries, assumptions, and control volumes, the ledger allows baseline, long-term rolling, and recent lake conditions to be compared within the same reproducible accounting structure.
The ledger is an accounting reconstruction, not a predictive hydrologic simulation or operational planning model. It organizes measured, estimated, and derived basin-scale relationships within one physical system so that changes in climate, human use, water delivery, and lake response can be evaluated without shifting definitions or reporting boundaries.
The reconstruction begins with the combined Bear, Weber, and Jordan Basin Plans and the 1961–1990 period, when the system appears to have operated near long-term equilibrium at approximately 4,200 feet in the South Arm. That baseline supplies the reference structure for the tables that follow. The same accounting framework is then carried forward into the 1996–2025 rolling period and the 2021–2025 shock period, allowing changes in system behavior to remain visible rather than being absorbed into changing assumptions.
Within that structure, the ledger follows water through a physical sequence that is often described in separate parts but rarely reconciled as a whole:
Precipitation → Natural Evapotranspiration → Basin Yield → Depletions → Net Inflow → Lake Balance
Each term represents a major hydrologic or accounting component within the defined basin-scale control volume. Basin precipitation and natural evapotranspiration define the climate-controlled production of water. Basin yield represents the portion of that water that becomes available to the managed system. Human depletions reduce that supply before it reaches the lake. The remaining flow—measured near the terminus and scaled consistently with basin plan assumptions—becomes the inflow that sustains the lake.
At the lake, the accounting resolves into a simple physical balance: inflow plus direct precipitation must equal evaporation, mineral depletions, and any change in storage. Lake evaporation is solved as the residual reconciliation term required for the accounting framework to remain consistent with observed lake storage behavior. In that sense, the observed lake response provides one of the strongest integrative constraints within the accounting framework.
Across all tables, the structure is held constant. Where data improves or definitions evolve, those changes affect how flows are attributed among categories, but not the total volume of water moving through the system. The accounting is considered reconciled when independent measurements and derived terms—gages, climate estimates, depletions, and observed lake response—align within a consistent control volume and assumption set.
This approach is intentionally conservative in structure and transparent in method. It preserves comparability with basin plan assumptions while making explicit where simplifications are carried forward—such as the treatment of wetland and reservoir terms or the scaling of gaged inflows to represent total terminal supply. These choices are documented so that future updates can refine attribution without altering the underlying physical balance.
The result is a ledger intended to be transparent, internally consistent, and methodologically traceable rather than a perfect representation of every individual hydrologic process. It provides a common framework within which different climate regimes, management actions, and policy questions can be evaluated against the same physical system.
Great Salt Lake Basin Water Ledger
The table below presents the Great Salt Lake Basin Water Ledger under baseline (1961–1990) conditions, constructed from the combined Bear (Utah only), Weber, and Jordan Basin Plans. It presents the system under an approximate long-term equilibrium configuration where long-term inflows, depletions, and lake processes reconcile to a stable South Arm elevation of approximately 4,200 feet. Each term represents a major component of the basin water balance, organized into climate-controlled processes, human management, and terminal lake processes. Volumes are expressed in thousand acre-feet per year (kaf/year) and reflect the planning framework used by the State, carried forward here using consistent definitions so that the system can be evaluated as a single, closed accounting.
Accounting-boundary note: The baseline value of 2,400 kaf/year is the basin plans’ rounded design-condition estimate of total inflow at the lake-delivery boundary. It should not be compared directly with the observed 1964–1990 average of 2,317 kaf/year at the four Zone 1 terminal gages. The 2,400 kaf figure represents a planning estimate at the lake boundary after below-gage routing, groundwater and return-flow additions, wetland processes, and other Zone 2 effects; the 2,317 kaf figure is an observed average at the upstream Zone 1 measurement boundary. The corresponding basin-plan design values are 1,979 kaf/year at the four Zone 1 gages and 2,400 kaf/year at the lake-delivery boundary, producing the 0.8246 terminal-gage scaling relationship used by this framework.
This baseline ledger establishes the reference structure for all subsequent analysis. The system is considered reconciled because basin yield, depletions, and lake processes are represented within a consistent basin-scale control volume.
Several terms are worth noting. Basin yield represents the net water produced by climate after natural evapotranspiration. Depletions reflect consumptive uses that reduce flow before it reaches the lake. In the baseline ledger, Net Inflow to Lake is stated at the lake-delivery boundary using the basin plans’ rounded design-condition estimate. In the reconstructed annual ledgers, inflow begins with measurements at the four Zone 1 terminal gages and is divided by the 0.8246 basin-plan relationship to estimate total delivery to the lake. This adjustment represents the net effect of below-gage routing, groundwater and return-flow additions, wetlands, terminal bays, and other Zone 2 processes between the terminal gages and the open lake. At the lake, evaporation is represented as the residual reconciliation term required to maintain consistency with observed lake conditions.
Some categories—particularly wetland and reservoir depletions—function as reconciliation terms within the basin plans, capturing below-gage processes and storage-related losses. Holding these terms consistent preserves comparability across periods, even as their internal composition may evolve with improved data.
The result is not a perfect representation of each component, but a basin-scale accounting system in which total flows are constrained and methodologically traceable.
How The Ledger Should Be Interpreted
This ledger should be interpreted as a structured accounting of how water moves through the basin, not as a direct measurement of each individual component.
Each term reflects a combination of measured data, planning assumptions, and derived quantities. Basin precipitation and lake precipitation are based on observed climate records scaled to the basin and lake surface area. Some terms also aggregate processes that are not independently resolved within the ledger, including portions of shallow groundwater interaction, unmanaged landscape evapotranspiration, and below-gage routing effects inherited from basin-plan accounting structures. Natural evapotranspiration is taken from basin plan estimates in the baseline and reconstructed as a residual reconciliation term within the same control volume. Basin yield is not directly measured as a single quantity; it is the net result of precipitation and evapotranspiration and represents the water made available to the managed system.
Net inflow to the lake is anchored to four Zone 1 terminal gage measurements and adjusted using a basin-plan-consistent terminal inflow scaling relationship intended to approximate total delivery to the lake system. This includes surface flow and implicitly captures groundwater and ungaged contributions within the control volume. The use of a consistent terminal inflow adjustment relationship allows the ledger to remain comparable to the planning framework, even where direct measurement is incomplete.
At the lake, the accounting simplifies. Inflow, direct precipitation, evaporation, and mineral depletions must reconcile to the observed change in lake storage. Because lake elevation and volume are well measured, evaporation is solved as the residual required to close the system. This makes evaporation and total inflow become strongly constrained by observed lake storage behavior within the accounting framework.
Differences between this accounting and a lake-surface mass balance are expected. These arise from below-gage additions such as return flows and effluent, groundwater exchange, timing effects, and differences in how the system boundary is defined. These differences affect how water is attributed among categories, but they generally affect attribution within the accounting framework more than the reconstructed long-term total inflow volume.
As data improves, the primary effect will be to refine attribution within the ledger—how much water is assigned to groundwater, wetlands, or specific depletion categories—rather than to materially change the total system balance. The accounting is therefore designed to be stable in total, while allowing components to evolve as measurement and understanding improve.
The key point is that the lake responds to total inflow, not to how that inflow is categorized. The purpose of the ledger is to ensure that total inflow is consistently defined, traceable, and reconcilable across different datasets and time periods.
Basin Plan Source Ledgers
The tables below present the Bear (Utah only), Weber, and Jordan Basin Plan ledgers in a consistent format. These are the source accounting structures used to construct the Great Salt Lake baseline ledger. Each basin plan organizes climate inputs, available supply, depletions, and net outflow to the lake within its own defined control volume. The values shown here are not newly derived; they are restated from the basin plans with consistent units and structure so that they can be combined and compared directly.
Bear River
Weber River
Jordan River
Taken together, these three basin ledgers form the basis for the combined Great Salt Lake Basin accounting. Differences in how each plan defines system boundaries, treatment of imports and exports, and representation of wetland and reservoir terms are preserved rather than normalized. This is intentional. The purpose of this section is not to reinterpret the basin plans, but to present them transparently in a comparable format so that the combined system can be reconciled in the baseline ledger.
Regime Context
The figure below summarizes three distinct operating periods of the Great Salt Lake system: the 1961–1990 baseline, the 1991–2020 modern period, and the 2021–2025 recent period. For each, it shows the average South Arm elevation and corresponding lake volume. These are not model outputs; they are observed conditions grouped into periods that are commonly used in water planning. The purpose of the figure is to establish context for how the system has behaved under different climate and management conditions before introducing the 30-year rolling and recent (shock) ledgers that follow.
The baseline period (1961–1990) represents an approximate long-term equilibrium condition, with average elevations near 4,200 feet. The 1996–2025 rolling period reflects a lower average elevation of 4,195.9 ft—a 3.7-foot decline from the baseline—consistent with the structural inflow deficit documented in the rolling ledger that follows. The 2021–2025 period shows a further step down, with substantially lower elevations and reduced lake volume over a short interval.
These periods are presented to illustrate that the system has not changed continuously or linearly. Instead, it has moved between operating ranges that reflect the combined effect of climate variability and managed depletions. The figure also highlights an important distinction for the analysis that follows: commonly used planning periods (such as 1991–2020) do not necessarily align with the current operating condition of the lake. A 30-year rolling window, anchored in the most recent data, provides a more current representation of the system’s average behavior, while shorter periods capture recent conditions that may not persist.
The sections that follow build on this context. The 30-year rolling ledger represents the current average operating condition of the system using the same accounting structure as the baseline. The recent (shock) ledger isolates short-term conditions to show how the system behaves under more extreme inputs. Net balance values are rounded regime-scale estimates derived from observed storage change between operating conditions. They should be interpreted as comparative regime imbalances, not as exact annualized storage change within each period. A comparison across these regimes allows changes in inflow, precipitation, evaporation, and storage to be evaluated within a consistent framework.
1996-2025 30-Year Rolling Ledger
The table below presents the Great Salt Lake Basin Water Ledger using a 30-year rolling period (1996–2025). This ledger retains the same accounting structure as the baseline but updates climate inputs and observed system response to reflect current conditions. The regime graphic above uses the traditional 1991–2020 planning period. This ledger uses a current 30-year rolling period (1996–2025) to better represent present operating conditions. A rolling period aligns the ledger with the climate regime the system is actually experiencing rather than a fixed historical reference period.
All terms are defined consistently with the baseline ledger so that differences can be attributed to changes in inputs rather than changes in methodology. Basin precipitation is adjusted from the baseline using the change in the observed KSLC precipitation index, while Basin Yield is reconstructed independently from terminal inflow and the other ledger terms. Natural ET is then calculated as the residual between Basin Precipitation and Basin Yield.
The 30-year rolling ledger represents a system operating below the baseline equilibrium condition. Net inflow to the lake declines relative to the baseline, while lake precipitation and evaporation adjust to a lower average South Arm elevation of approximately 4,196 feet. The negative terminal system balance reflects the corresponding long-term decline in average lake storage.
That storage change is calculated by comparing the average lake-elevation regimes for 1961–1990 and 1996–2025. Applying those average elevations to all four Casey-Root bathymetric compartments—South Arm, North Arm, Bear River Bay, and Farmington Bay—produces estimated total storage of approximately 14.772 MAF for the baseline regime and 11.612 MAF for the rolling regime. The difference is approximately 3.159 MAF. Expressed over the 30-year planning horizon, this equals approximately −105 kaf/year, conventionally rounded to the −100 kaf/year terminal system balance shown in the ledger. It is a regime-scale measure of the system’s long-term storage ride-down, not a claim that lake storage declined by precisely that amount in every year.
Several structural features remain unchanged. Basin yield continues to represent climate-driven water production, while depletions reduce available supply before delivery to the lake. Net inflow remains anchored to near-terminal gage measurements and is scaled consistently with basin-plan assumptions. At the lake, evaporation is solved as the residual required to reconcile inflow, precipitation, mineral depletions, and the regime-scale change in storage.
What differs from the baseline is not the accounting structure, but the inputs and outcomes. Lower effective inflows and reduced precipitation at the lake surface result in a system that no longer maintains the previous operating elevation under average conditions. The lake consequently declines in storage toward a lower operating range, where its reduced surface area and evaporation bring average outflows back into balance with average inflows.
This ledger should be interpreted as the average condition of the system over the current 30-year regime, not as a transient or short-term anomaly. It reflects the combined effects of climate variability and managed depletions over a full planning horizon. Because the accounting structure is held constant, the difference between this table and the baseline ledger directly measures how the system has shifted using physically consistent and comparable terms.
2021-2025 Shock Regime Ledger
The table below presents the Great Salt Lake Basin Water Ledger for the recent period (2021–2025). It uses the same accounting structure as the baseline and 30-year ledgers but reflects short-term conditions observed over a five-year interval. This period is shown separately because it captures a concentrated sequence of low inflow and reduced precipitation that is not fully represented in a 30-year average. The purpose of this ledger is to isolate recent conditions within a consistent framework, not to define a new long-term equilibrium.
The recent ledger shows a larger short-term storage deficit than the 30-year ledger, with lower net inflow and reduced lake precipitation contributing to a rapid decline toward an average South Arm elevation of approximately 4,192 feet. Net inflow remains anchored to near-terminal gage measurements, while lake evaporation is solved as the residual required to reconcile observed conditions.
The approximately −200 kaf/year terminal system balance is derived from the observed five-year endpoint change in lake storage. From the beginning of WY2021 to the beginning of WY2026, the South Arm declined from approximately 4,192.5 to 4,191.1 feet. Applying the observed North Arm elevations and all four Casey-Root bathymetric compartments, total storage declined from approximately 9.327 MAF to 8.487 MAF—a reduction of approximately 0.840 MAF. Divided over five years, the decline is approximately −168 kaf/year, conventionally rounded to −200 kaf/year in the ledger.
This is a short-term endpoint drawdown rate, not a fully adjusted equilibrium condition and not necessarily representative of long-term conditions. It differs from the 30-year rolling calculation, which compares average storage between two long-term elevation regimes. The shock ledger is included to show how the system behaved during a concentrated sequence of low-inflow and low-precipitation years; its balance should not be projected forward as a long-term annual deficit.
Ledger Comparison Across Regimes
The table below presents the baseline (1961–1990), 30-year rolling (1996–2025), and recent (2021–2025) ledgers side by side using a consistent accounting structure. Each column reflects a different operating condition of the same physical system. Because definitions and methods are held constant, differences across columns represent changes in climate inputs and system response, not changes in accounting. The comparison allows the magnitude and location of those changes to be evaluated directly.
Across the three regimes, the structure of the system remains stable while the inputs and outcomes shift. Available supply declines from the baseline through the 30-year and recent periods, reflecting reduced effective basin yield. Basin precipitation is adjusted from the baseline using the change in the observed KSLC precipitation index, while Basin Yield is reconstructed independently from terminal inflow and the other ledger terms. Natural ET is then calculated as the residual between Basin Precipitation and Basin Yield.
Depletions remain relatively constant, which means a larger share of available supply is consumed before reaching the lake. As a result, net inflow declines from approximately 2,400 kaf/year in the baseline to 1,900 kaf/year in the 30-year period and 1,600 kaf/year in the recent period. The shock period net balance of -200 kaf/year reflects observed storage change over 2021–2025 and should be interpreted as a short-term stress indicator, not a steady-state loss rate. The same period shows the lake operating approximately 3 MAF below its prior 30-year average storage condition, with partial recovery in 2023 and 2024 confirming the system's self-correcting behavior through evaporation reduction at lower elevations.
At the lake, precipitation decreases with reduced surface area, while evaporation adjusts as the lake declines in elevation. Because evaporation is solved as the residual required to reconcile observed conditions, it reflects both the physical response of the lake and the cumulative effect of upstream changes. The net balance term captures the resulting change in storage: near zero in the baseline, negative in the 30-year period, and more strongly negative in the recent period.
The comparison shows that the system responds through storage and evaporation adjustment rather than through indefinite continuation of short-term loss rates. Lower inflows do not result in linear disappearance of the lake, but in a transition to lower storage and reduced evaporation until a new operating range is reached. The magnitude of that adjustment—and the time required for it to occur—depends on the persistence of the underlying conditions.
This section is intended to make those relationships explicit. By holding the accounting framework constant, it isolates the variables that matter: inflow, precipitation, evaporation, and storage. Changes in attribution among categories may evolve as data improves, but the total balance—and the lake’s response to it—remains constrained by the same physical system.
Why the Lake Doesn’t Vanish
The table below illustrates how the lake responds to different inflow conditions using the same accounting framework applied in the preceding ledgers. Each row represents a steady-state condition at a given elevation, where inflow, lake precipitation, and evaporation approximate a stable long-term operating condition. The purpose of this table is not to describe a transition path, but to show how the system rebalances at lower elevations as surface area—and therefore evaporation—declines.
The table shows that lower inflows do not lead to continuous or unbounded decline. Instead, as the lake falls, its surface area decreases, which reduces both lake precipitation and evaporation. Because evaporation is the dominant outflow term, this reduction is sufficient to bring the system back into balance at a lower elevation. Each row represents a condition in which inflow plus precipitation equals evaporation and mineral depletions, resulting in no further change in storage.
This relationship explains why the lake does not “vanish” under reduced inflow conditions. The lake system responds dynamically to declining inflow through reductions in surface area and evaporation. Lower inflow produces lower storage, which in turn reduces evaporation until a new balance is reached. The result is a step-down in operating level rather than a linear continuation of loss.
It is important to distinguish between rates and steady-state conditions. The imbalances observed in the 30-year and recent ledgers represent the rate at which the lake moves between operating levels, not the conditions at which it stabilizes. Once the lake has adjusted to a lower elevation, the accounting framework again approaches reconciliation under average long-term conditions at that level.
This table is intended to make that distinction explicit. It shows the equilibrium conditions associated with different inflow levels, using consistent definitions and the same physical constraints that govern the full ledger.
Interpreting a 4,198 ft Target
This framework uses 4,198 ft as its primary reference target because it is identified in the Great Salt Lake Elevation Matrix and adopted in the Great Salt Lake Strategic Plan as the state’s management benchmark. The state has also identified 4,195 ft as an acceptable near-term threshold. Independent conservation organizations including the 4200 Project advocate for a higher target of 4,200 ft, consistent with the lake's historical baseline operating elevation documented in the basin plans. This framework does not take a position on which target is correct—that is a policy question. What the accounting shows is that each one-foot increment of target elevation increases the required inflow by approximately 100–150 kaf/year under current climate conditions, as shown in the FAQ 11 climate sensitivity table. The gap-to-close framework on this page can be applied to any target elevation using the structure provided.
A target elevation such as 4,198 feet is best understood as a long-term operating average, not a fixed minimum or guaranteed floor. The Great Salt Lake responds to both sustained inflow and year-to-year climate variability. Even when inflows are sufficient to maintain a given average condition, the lake will continue to fluctuate around that level as precipitation, evaporation, and timing vary across years.
To illustrate this, the table below applies the observed 1996–2025 climate sequence and evaluates how the lake would behave if annual inflow were held at approximately 2,200 kaf/year—consistent with maintaining a 4,198-foot average under prevailing conditions.
This result reflects the physical behavior of the system rather than any specific management action. A 4,198-foot target does not imply that the lake will remain at or above that elevation at all times. Instead, it defines a condition under which the lake, on average, stabilizes near that level over time. In practice, natural variability will continue to produce multi-foot fluctuations around the mean, even under steady inflow conditions.
Understanding this distinction is important for interpreting policy targets and evaluating outcomes. It clarifies that short-term declines below a target elevation do not necessarily indicate system failure, just as temporary increases above it do not imply long-term recovery. The lake responds to cumulative conditions over time, not to individual years in isolation.
Gap-to-Close Framework
The gap-to-close framework separates two distinct components of the problem. The first is the steady-state gap between current inflows and the inflow required to maintain a target lake elevation under prevailing climate conditions. The second is the refill gap created by starting below that target elevation. Together, these define the total additional inflow required, expressed as an annualized volume over a specified planning horizon.
This framework is derived directly from the lake balance. Required inflow is calculated as lake evaporation plus mineral depletions, less direct precipitation on the lake surface, at the target elevation. The steady-state gap is the difference between that required inflow and current observed inflow. The refill gap is the change in lake volume required to reach the target elevation, divided by the selected time horizon. Both components are expressed in consistent units so they can be combined into a single annual requirement.
Gap-to-close values represent long-run average requirements under defined conditions. They are not forecasts and should be interpreted alongside scenario-based climate variability.
30-year Rolling Gap to Close
The table below presents the gap to close using a 30-year planning horizon. This aligns with standard water planning practice and reflects the time required for climate variability and system response to average out. The steady-state flow gap is based on the difference between current 30-year inflows and the inflow required to maintain approximately 4,198 feet. The refill gap distributes the required increase in lake storage over the same 30-year period.
Under a 30-year horizon, the refill gap is relatively small compared to the steady-state flow gap. This reflects the fact that most of the required change is not the one-time recovery of storage, but the ongoing difference between current inflows and the inflow required to sustain the target elevation. Once the lake reaches the target level, only the steady-state gap remains. The table therefore distinguishes between a temporary requirement associated with recovery and a persistent requirement associated with maintaining the system at a higher operating level.
Olympics Gap to Close
The table below presents the same framework using a shorter planning horizon, corresponding to a target of reaching approximately 4,198 feet by 2034. The steady-state flow gap remains unchanged, as it is defined by climate and lake physics at the target elevation. The difference in this table is the refill gap, which must be achieved over a much shorter period.
With a shorter time horizon, the refill gap becomes the dominant component of the total requirement. The steady-state gap does not change, but the annualized volume required to raise lake storage increases significantly. This illustrates that the total gap to close is not a fixed quantity; it depends on both the target elevation and the timeframe in which that target is pursued.
Across both tables, the underlying structure is the same. The lake balance defines the steady-state requirement, and the difference between current and target storage defines the refill requirement. The framework makes explicit that these are separate components that respond to different factors: one to climate and system physics, the other to timing.
All gap-to-close values are derived using consistent bathymetry, precipitation, and evaporation relationships, and are expressed in terms of additional inflow required at the lake. As with the ledger, improved data will refine the attribution of flows within the system, but will not materially change the total inflow required to achieve a given elevation over a defined period.
Gap-to-close and climate uncertainty
The gap-to-close values shown above are accounting averages. They are designed to identify the sustained inflow required to maintain or reach a defined lake condition under a stated period of record.
They are not stochastic forecasts. The Strike Team’s simulation work remains the appropriate reference for evaluating the range of possible future climate outcomes around those averages. The ledger provides the accounting frame; scenario modeling describes the uncertainty around that frame.
How This Aligns with Statewide Water Accounting
The structure used in this ledger is consistent with how the State of Utah describes water at a high level. In How Utah Water Works (Utah Division of Water Resources, 2012), the state presents a simplified statewide accounting framework that traces water from precipitation through natural processes, into basin yield, and ultimately into consumptive use.
At a statewide scale, the system can be summarized as follows:
- ~61.5 MAF of precipitation
- ~53.8 MAF consumed by natural evapotranspiration
- ~7.7 MAF of basin yield (ground and surface water)
- ~7.3 MAF of available supply after interstate adjustments
- ~3.3 MAF available for consumptive use after lake and wetland losses
This framework establishes the same core relationships used throughout the Great Salt Lake ledger. Precipitation defines the total input to the system. Natural evapotranspiration reduces that input to basin yield. Adjustments for imports and exports define available supply. Depletions reduce that supply, and the remainder becomes outflow within each basin system or to terminal lakes.
The statewide summary is necessarily simplified, but the structure is consistent. The sections that follow apply this same accounting logic at finer spatial resolution, using basin-level data and consistent definitions to trace how water moves through the Great Salt Lake system.
That consistency is not just structural—it is numerical. The eleven Utah basin plans, when their basin yields are summed directly, produce approximately 8,480 kaf against the 7,700 kaf shown in the statewide graphic. The difference is methodological, not a discrepancy: the infographic derives yield from statewide average precipitation multiplied by total state area, while the basin plans measure tributary yield and include interstate inflows that the statewide estimate excludes. The 3.0 MAF Great Salt Lake evaporation figure aligns independently—the West Desert Basin Plan states explicitly that average annual evaporation from the Great Salt Lake equals average annual inflow, the same equilibrium condition the ledger uses. Two methods developed independently across more than a decade of basin planning converge on the same physical system. The basin-by-basin yield figures and sourcing notes underlying this sum are documented in the FAQ.
Statewide Water Ledger
The table below restates the statewide water system using the same accounting structure as the Great Salt Lake ledger, with values drawn from the State’s “How Utah Water Works” framework.
This is not a direct translation. It requires purposeful reconciliation across basin plans, statewide summaries, and boundary definitions to express climate production, human management, and terminal system response within a single, consistent framework. The result is a unified view that aligns how water is produced, allocated, and ultimately consumed across Utah.
In this form, the statewide system and the Great Salt Lake resolve to the same accounting structure: water produced by climate is depleted, transferred, or delivered to terminal systems where the balance closes. The lake is not a residual or downstream artifact—it is a central, defining component of that closure.
This is the key point. The lake’s scale and physical footprint make it integral to Utah’s water budget, not separate from it. When expressed consistently, statewide planning and basin plans already contain the lake—they simply do not always present it that way. This ledger makes that relationship explicit, reconcilable, and unavoidable.
Using This Framework
This ledger is designed to be applied directly to structured, repeatable analysis. The same accounting framework can be used across different time periods, provided that inputs are defined consistently.
Any time period within the observed record can be used to construct:
- a Baseline Ledger (fixed reference condition)
- a 30-Year Rolling Ledger (climate-adjusted condition)
- a Gap-to-Close Ledger (forward-looking requirement)
Each uses the same structure and accounting relationships. Only the inputs change.
The objective is not to simulate outcomes, but to reconstruct and reconcile the system using observed data and consistent definitions. When applied correctly, the ledger closes across independent measurements of inflow, precipitation, evaporation, and storage change.
How to Use with AI
This framework is designed to be used with AI tools to reconstruct water ledgers from defined inputs. The model should be constrained to the relationships and definitions established in this document. The goal is consistency and traceability, not substitution of alternative assumptions.
Provide the following inputs:
- Timeframe (e.g., 1996–2025)
- Basin scope (Bear (Utah only), Weber, Jordan)
- Dataset references (gage flows, precipitation proxy, bathymetry)
Then use structured prompts such as those below.
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.
Prompt: Build 30-Year Rolling Water Ledger
Prompt: Build 5-Year Shock Regime Ledger
Prompt: Build Gap-to-Close Table
© 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.