USGS Visual Identifier

LakeVOC—A Deterministic Model to Estimate Volatile Organic Compound Concentrations in Reservoirs and Lakes

By David A. Bender, William E. Asher, John S. Zogorski

Open-File Report 03-212

National Water-Quality Assessment Program
National Synthesis on Volatile Organic Compounds


This report documents LakeVOC, a model to estimate volatile organic compound (VOC) concentrations in lakes and reservoirs. LakeVOC represents the lake or reservoir as a two-layer system and estimates VOC concentrations in both the epilimnion and hypolimnion. The air-water flux of a VOC is characterized in LakeVOC in terms of the two-film model of air-water exchange. LakeVOC solves the system of coupled differential equations for the VOC concentration in the epilimnion, the VOC concentration in the hypolimnion, the total mass of the VOC in the lake, the volume of the epilimnion, and the volume of the hypolimnion.

A series of nine simulations were conducted to verify LakeVOC representation of mixing, dilution, and gas exchange characteristics in a hypothetical lake, and two additional estimates of lake volume and MTBE concentrations were done in an actual reservoir under environmental conditions. These 11 simulations showed that LakeVOC correctly handled mixing, dilution, and gas exchange. The model also adequately estimated VOC concentrations within the epilimnion in an actual reservoir with daily input parameters. As the parameter-input time scale increased (from daily to weekly to monthly, for example), the differences between the measured-averaged concentrations and the model-estimated concentrations generally increased, especially for the hypolimnion. This may be because as the time scale is increased from daily to weekly to monthly, the averaging of model inputs may cause a loss of detail in the model estimates.




Purpose and Scope


Description and Theoretical Basis of LakeVOC Model

General Description

Air-Water Gas Transfer

Theoretical Formulation

Model Operation and Numerical Methods

User Instructions and Information Needs for LakeVOC Model

Using LakeVOC Model

Known Problems or Cautions in Using LakeVOC Model

Verification of LakeVOC Model

Simulations Using a Hypothetical Lake

Lake Mixing and Dilution Tests

Gas-Exchange Tests

Simulations Using an Actual Reservoir

Lake-Stratification and Lake-Volume Simulations

VOC Concentration Simulations

Daily Simulation

Weekly Simulation

Monthly Simulation




A. FORTRAN Code for LakeVOC Model

B. LakeVOC Model Input Parameter Files

C. LakeVOC Model Output Files

D. Example Physical/Chemical Properties for Selected Volatile Organic Compounds

This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.

The report can be downloaded in parts for a faster download time:
Body (PDF, 729KB)
Appendix A (PDF, 755KB)
Appendix B (PDF, 562KB)
Appendix C and D (PDF, 4.2MB)
The following are reference files for this report:
LakeVOC Executable File (EXE, 744KB) is executable version of the LakeVOC model and has been tested under all 32-bit versions of Microsoft Windows operating systems through Windows XP.
LakeVOC Example Input Parameter Files (WinZip, 9KB) for mixing, dilution, and gas exchange simulations.

Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Acrobat Reader 5.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.

Send questions or comments about this report to the author, D.A. Bender (605) 355-4560 ext. 248.

For more information about USGS activities in South Dakota, visit the USGS South Dakota District home page.

For more information about the USGS National Water-Quality Assessment Program, visit the NAWQA Program home page or more information about the USGS National Water-Quality Assessment Program Volatile Organic Compound National Syntheses, visit the VOC National Systhesis home page.

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