Model:OTEQ

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OTEQ

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Summary Contact Technical specs In/Output Process Testing Other Component info Also known as Model type Single Model part of larger framework Note on status model Date note status model Spatial dimensions 1D Spatial extent Watershed-Scale, Reach-Scale Model domain Hydrology, Terrestrial One-line model description One-Dimensional Transport with Equilibrium Chemistry (OTEQ): A Reactive Transport Model for Streams and Rivers Extended model description One-Dimensional Transport with Equilibrium Chemistry (OTEQ): A Reactive Transport Model for Streams and Rivers OTEQ is a mathematical simulation model used to characterize the fate and transport of waterborne solutes in streams and rivers. The model is formed by coupling a solute transport model with a chemical equilibrium submodel. The solute transport model is based on OTIS, a model that considers the physical processes of advection, dispersion, lateral inflow, and transient storage. The equilibrium submodel is based on MINTEQ, a model that considers the speciation and complexation of aqueous species, acid-base reactions, precipitation/dissolution, and sorption. Within OTEQ, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (waterborne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach. The model's ability to simulate pH, precipitation/dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between instream chemistry and hydrologic transport at the field scale. OTEQ is generally applicable to solutes which undergo reactions that are sufficiently fast relative to hydrologic processes ("Local Equilibrium"). Although the definition of "sufficiently fast" is highly solute and application dependent, many reactions involving inorganic solutes quickly reach a state of chemical equilibrium. Given a state of chemical equilibrium, inorganic solutes may be modeled using OTEQ's equilibrium approach. This equilibrium approach is facilitated through the use of an existing database that describes chemical equilibria for a wide range of inorganic solutes. In addition, solute reactions not included in the existing database may be added by defining the appropriate mass-action equations and the associated equilibrium constants. As such, OTEQ provides a general framework for the modeling of solutes under the assumption of chemical equilibrium. Despite this generality, most OTEQ applications to date have focused on the transport of metals in streams and small rivers. The OTEQ documentation is therefore focused on metal transport. Potential model users should note, however, that additional applications are possible. Keywords: biogeochemistry, water quality, Name Rob Runkel Type of contact Model developer Institute / Organization USGS Postal address 1 Postal address 2 Town / City Boulder Postal code 80303 State Colorado Country United States Email address runkel@usgs.gov Phone Fax Supported platforms Unix, Linux Other platform Programming language Fortran77 Other program language Code optimized Single Processor Multiple processors implemented Nr of distributed processors Nr of shared processors Start year development 1991 Does model development still take place? Yes If above answer is no, provide end year model development Code development status When did you indicate the 'code development status'? Model availability As code Source code availability (Or provide future intension) Through web repository Source web address http://water.usgs.gov/software/OTEQ/ Source csdms web address Program license type Other Program license type other http://water.usgs.gov/software/help/notice/ Memory requirements Typical run time Describe input parameters see user documentation Input format ASCII Other input format Describe output parameters Solute concentrations as a function of space and time Output format ASCII Other output format Pre-processing software needed? Yes Describe pre-processing software All I/O is done with flat ASCII files; The 'MINTEQ Input file' is created using the Proteq utility; remaining input files may be created using a text editor Post-processing software needed? Yes Describe post-processing software All I/O is done with flat ASCII files; Output files are first processed by a utility (posteq) -- resultant files can then be plotted with the user's own software. Visualization software needed? No If above answer is yes Other visualization software Describe processes represented by the model Physical transport: Advection, Dispersion, Inflow, Transient Storage, and Settling. Chemistry: Precipitation/Dissolution, Sorption/Desorption, Oxidation/Reduction, aqueous complexation, and acid-base reactions Describe key physical parameters and equations Partial differential equations describing mass transport (Advection-Dispersion-Reaction equations) and algebraic equations describing chemical equilibria are coupled using the Sequential Iteration Approach Describe length scale and resolution constraints Describe time scale and resolution constraints Describe any numerical limitations and issues see numerical aspects described in Section 4 of the documentation Describe available calibration data sets see user documentation; also see applications at http://water.usgs.gov/software/OTEQ/apps/ Upload calibration data sets if available: Describe available test data sets see user documentation; also see applications at http://water.usgs.gov/software/OTEQ/apps/ Upload test data sets if available: Describe ideal data for testing Do you have current or future plans for collaborating with other researchers? Is there a manual available? Yes Upload manual if available: Media:TM6ChB6.pdf Model website if any http://water.usgs.gov/software/OTEQ/ Model forum / discussion board Comments This part will be filled out by CSDMS staff OpenMI compliant No but possible BMI compliant No but possible WMT component No but possible PyMT component Is this a data component Can be coupled with:

Model info Authors Rob Runkel Source code Go to external source code site Model citations Nr. of publications: 2 Total citations: 138 h-index: 2 m-quotient: 0.07 QR-code Link to this page Other models by author LOADEST OTEQ OTIS

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Nr. of publications:	2
Total citations:	138
h-index:	2
m-quotient:	0.07

Featured publication(s)	Year	Model described	Type of Reference	Citations
Runkel, Robert L.; Bencala, Kenneth E.; Broshears, Robert E.; Chapra, Steven C.; 1996. Reactive Solute Transport in Streams: 1. Development of an Equilibrium-Based Model. Water Resources Research, 32, 409–418. 10.1029/95WR03106 (View/edit entry)	1996	OTEQ	Model overview	80
Runkel, Robert L.; McKnight, Diane M.; Bencala, Kenneth E.; Chapra, Steven C.; 1996. Reactive Solute Transport in Streams: 2. Simulation of a p H Modification Experiment. Water Resources Research, 32, 419–430. 10.1029/95WR03107 (View/edit entry)	1996	OTEQ	Model overview	58
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