The USGS Toxic Substances Hydrology (Toxics) Program develops computer simulation and statistical models as an integral part of the Program's field investigations. The increased knowledge gained from the development and application of models greatly enhances the transfer value of research conducted at the Toxics Program’s research sites and can have a significant effect on decisions related to human and environmental exposure and remedial alternatives. Information on the types of simulation and statistical models used by the program is available. The information presented on this page cuts across lines drawn by individual investigations and projects so that information on the development of models can be presented in one place.

Investigations and Research Activities

• Surface Water Modeling
• Coupled Transport and Geochemical Processes Determining the Fate of Chemicals in Surface Waters
• One Dimensional Transport with Equilibrium Chemistry (OTEQ): A Reactive Transport Model for Streams and Rivers
• One Dimensional Transport with Inflow and Storage (OTIS): A Solute Transport Model for Streams and Rivers
• Precipitation - Runoff Modeling of Watershed Systems
• Load Estimator (LOADEST): A Program for Estimating Constituent Loads in Streams and Rivers
• USGS Surface-water quality and flow Modeling Interest Group (SMIG)
• Mining-Related Stream Transport Simulation Reader, A Reading List on Applications of OTEQ, OTIS, and Transient Storage for Metals, Cations, and Acidic Streams
• Ground Water Modeling
• Solute Transport Simulation in Ground-Water Systems
• Digital Modeling of Transport in the Saturated Zone
• Multiphase Flow, Transport, Reaction and Biodegradation
• Mathematical Simulation of Subsurface-Water Flow Using Uncertain and Incomplete Data
• Application of Stochastic Processes in Hydrogeology
• Reaction-Transport Modeling In Ground-Water Systems
• Kinetics and Thermodynamics of Chemical Evolution in Ground-Water Systems
• Mathematical Models for Simulating Flow and Transport in the Unsaturated Zone
• Unsaturated Zone Transport Models
• Unsaturated Zone Flow: Theory and Mathematical Models

Fact Sheets

• Improving ground-water flow model calibration with the advective-transport observation (ADV) package to MODFLOWP: USGS Fact Sheet FS-059-98.
• Linking selenium sources to ecosystems--San Francisco Bay-Delta model: USGS Fact Sheet 2004-3091.
• Modeling solute-transport and biodegradation with BIOMOC: USGS Fact Sheet 095-98.
• Nitrogen in the Mississippi Basin--Estimating sources and predicting flux to the Gulf of Mexico: USGS Fact Sheet 135-00.
• PHREEQCI--A graphical user interface to the geochemical model PHREEQC: USGS Fact Sheet 031-02.
• Simulating contaminant attenuation, double-porosity exchange, and water age in aquifers using MOC3D: USGS Fact Sheet 086-99.
• Simulating transport of volatile organic compounds in the unsaturated zone using the computer model R-UNSAT: USGS Fact Sheet FS-019-98.
• Using Geochemical and Statistical Tools to Identify Irrigated Areas that Might Contain High Selenium Concentrations in Surface Water: USGS Fact Sheet FS-O77-96.
• Using OTIS to model solute transport in streams and rivers: USGS Fact Sheet 138-99.

MOC3D simulation of MTBE at the Laurel Bay, SC, research site, based on field and lab data of Landmeyer and others (1998); MTBE in 1994 and 1998; 1998 color map shows simulated concentration ranging from 0 to 10,000 parts per billion (ppb); contours show 100, 1,000, and 10,000 ppb concentration levels.
(Click on Image for a Larger Version)

Headlines

• New Model Allows for More Accurate Simulation of Tritium Movement in the Unsaturated Zone
• New Version of NAS (Natural Attenuation Software) Available
• Decades Required for Natural Processes to Clean Wastewater-Contaminated Ground Water
• Biodynamic Model is Unraveling the Complexities of Metal Bioaccumulation from Contaminated Sediments
• A Tool for Predicting the Effect of Invasive Species on Aquatic Food Webs
• New Model Improves Understanding of the Transport of Carbon Isotopes in the Unsaturated-Zone
• Software Provides Estimates of How Long it Will Take for Remediation Efforts to Achieve Their Goals
• Tracer-Tests Steer Cleanup of Mined Watersheds

Bibliographies

• Computer Simulation Models (225 Publications)
• Model Applications (417 Publications)
• Statistical Models (38 Publications)
• All Publications on Models (598 Publications)

New Publications

Upcoming Publications

• Simulated response of water quality in public supply wells to land-use change: McMahon, P.B., Burow, K.R., Kauffman, L.J., Eberts, S.M., Bšhlke, J.K., and Gurdak, J.J., Water Resources Research, doi:10.1029/2007WR006731 (IN PRESS).

Newly Published

• Metals fate and transport modelling in streams and watersheds--State of the science and USEPA workshop review: Caruso, B.S., Cox, T.J., Runkel, R.L., Velleux, M.L., Bencala, K.E., Nordstrom, D.K., Julien, P.Y., Butler, B.A., Alpers, C.N., Marion, A., and Smith, K.S., 2008, Hydrologic Processes, v. 22, no. 19, p. 4011-4021, doi:10.1002/hyp.7114.
• Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region: Walvoord, M.A., Andraski, B.J., Krabbenhoft, D.P., and Striegl, R.G., 2008, Applied Geochemistry, v. 23, no. 3, p. 572-583, doi:10.1016/j.apgeochem.2007.12.014.
• Determination of dominant biogeochemical processes in a contaminated aquifer-wetland system using multivariate statistical analysis: Báez-Cazull, S.E., McGuire, J.T., Cozzarelli, I.M., and Voytek, M.A., 2008, Journal of Environmental Quality, v. 37, no. 1, p. 30-46, doi:10.2134/jeq2007.0169.
• Using biodynamic models to reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects: Buchwalter, D.B., Cain, D.J., Clements, W.H., and Luoma, S.N., 2008, Environmental Science and Technology, doi:10.1021/es703130e (Advanced Web release).