QUAL2K is a Microsoft Windows based application for river and stream water quality modeling. QUAL2K is an updated version of QUAL2E with improvements in model segmentation, forms of carbonaceous BOD evaluated, particulate organic matter simulation, anoxia and denitrification modeling, sediment-water dissolved oxygen and nutrient fluxes, explicit simulation of attached bottom algae, light extinction calculation, enhanced pH simulation, and pathogen removal functions. The ecologically-focused model simulates daily water quality, as either steady-state or dynamic system.  Includes estimation of biological oxygen demand, nitrogen, phosphorus, coliforms and pH.

 

Website:  http://www.qual2k.com

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.

Description:  OTEQ.pdf.    Website: https://water.usgs.gov/software/OTEQ/

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OTIS is a mathematical simulation model used to characterize the fate and transport of waterborne solutes in streams and rivers. OTIS is often used with data from field-scale tracer experiments to quantify the hydro-logic parameters affecting solute transport. Additional applications include analyses of non-conservative solutes that are subject to sorption processes and/or first-order decay. The governing equation underlying the model is the advection-dispersion equation with additional terms to account for transient storage, lateral inflow, first-order decay, and sorption. This equation and the associated equations describing transient storage and sorption are solved using a Crank-Nicolson finite-difference solution.

Description: OTIS.pdf   Website:  https://water.usgs.gov/software/OTIS/

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LOAD ESTimator (LOADEST) is a FORTRAN program for estimating constituent loads in streams and rivers. Given a time series of stream-flow, additional data variables, and constituent concentration, LOADEST assists the user in developing a regression model for the estimation of constituent load (calibration). Explanatory variables within the regression model include various functions of stream-flow, decimal time, and additional user-specified data variables. The formulated regression model then is used to estimate loads over a user-specified time interval (estimation). Mean load estimates, standard errors, and 95 percent confidence intervals are developed on a monthly and(or) seasonal basis

Description:  LOADEST.pdf   Website:  https://water.usgs.gov/software/loadest/

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