WORLD METEOROLOGICAL ORGANIZATION 
HOMS COMPONENT 

Explanation of the criteria for classification and numbering of components  K55.2.04 (DEC 99) 

Explanation of the dates on the component's description  
TRANSPORT MODEL FOR A ONE DIMENSIONAL SYSTEM OF OPEN CHANNELS (BLTM) 

1. Purpose and objectives BLTM is a computer code that can be used to simulate the fate of any
number of conservative or chemically interacting pollutants through a network of onedimensional open channels that may have reversing flow. 2. Description The BLTM model solves the convectivedispersion equation by using a Lagrangian reference frame in which the computational nodes move with the flow. The onedimensional equations are solved for any number of constituents moving in any number of branches which are connected at junctions. The unsteady hydraulics (discharge, area, top width, and tributary inflow) must be supplied to the model and constituent concentrations are assumed to have no effect on the hydraulics. Reaction kinetics of the constituents can be supplied by the user through a subroutine but subroutines are available for simple first order decay such as coliform, temperature, dissolved oxygen, and the nitrogen cycle. The advantages of the Lagrangian approach are: a) the scheme is very accurate in modelling the convection and dispersion terms, b) the model is
stable for any time step size, c) the model is economical to run, d) the model output includes information which is helpful in calibration and 3. Input BLTM requires 5 types of input:  Flow hydraulics including Discharge, crosssectional area, top Both DAFLOW (HOMS component K35.3.14) and BRANCH (K35.3.13) can provide the hydraulic input required by BLTM. 4. Output Tables or graphs of concentrations of any constituent at any point as a function of time, or at any time as a function of distance along the channel. Tables of the travel times of individual parcels of water.
Tables of the influence of any physical process (dispersion, tributary
inflow, production from a specified constituent, decay to a specified decay
product) on the concentration of a constituent at a particular point and time. 5. Operational requirements and restrictions The program is written in FORTRAN 77 and can be used on any microcomputer with MSDOS as well as on larger machines. A mathematical coprocessor is highly recommended. As executable code is provided a FORTRAN compiler is not necessary. The system must be onedimensional so no stratification or lateral concentration gradients should be present. All constituents are assumed to be dissolved, so sediment can not be handled. 6. Form of presentation Documentation (USGS Water Resources Investigation Report 874163) and
programs with dialogue are written in English. Both source and executable code are provided on a 3 1/2" floppy diskette or via the Internet. 7. Operational experience BLTM has been applied in a number of river and estuary systems in the
United States. 8. Originator and technical support U.S. Geological Survey, Office of Surface Water. 9. Availability From the HOMS National Reference Centre for USA for 3 1/2" floppy or printed documentation; or electronically on the Internet at: 10. Conditions on use Program and electronic version of the documentation are available free of charge; there is a charge for printed documentation.


(First entered:01 FEB 93  Last updated: 01 FEB 94) 