PROGRAMS AND PLANS--Transport Modeling System Announced

In Reply Refer To:                      January 5, 1990
WGS-Mail Stop 415


SUBJECT:  PROGRAMS AND PLANS--Transport Modeling System Announced

The Offices of Surface Water and Water Quality have been
attempting to develop a flow and transport modeling system for the
past several years.  The main elements of this system are two flow
models and one transport model.  One flow model (BRANCH) and the
transport model (BLTM) have been previously documented and rather
extensively used in Water Resources Division (WRD).

The purpose of this memorandum is to announce the publication of
the third model via "Users Manual for an Open-Channel Streamflow
Model based on the Diffusion Analogy" (DAFLOW) by Harvey E. Jobson
as Water-Resources Investigations Report 89-4133.  These three
models offer a flexible and robust transport modeling system.

The DAFLOW model is designed to predict discharge and flow
velocity using a minimum of field data for a system of one-
dimensional open channels.  The model requires relatively few data
(it does not require cross sections for example), is very easy to
apply and understand (the code contains only 772 lines), and is
most accurate for upland streams with steep slopes.  The DAFLOW
model is a version of the old CONROUT model that was successful in
many WRD applications.  The required data are bed slope, an
average top width at one flow, and either a Manning's n or the
wave speed for one flow.  The model is menu driven and incorpo-
rates the hydraulic geometry coefficients developed in the field
of geomorphology to enhance its predictive capability.

The BRANCH model has been in use for some time, however, it
suffers a few limitations.  It is data intensive and requires a
fairly high level of skill to use.  It also tends to be unstable
for upland streams where the frictional slope is approximately
equal to the bed slope.  The BRANCH model works well, however, for
low gradient streams and estuaries.  Together the BRANCH and the
DAFLOW models, therefore, complement each other very well in
covering the entire range of flow situations encountered by WRD.

Either BRANCH or DAFLOW can be used to drive a transport model
such as the BLTM.  The BLTM model can be used to route any number
of dissolved constituents through a system of one dimensional
channels.  The kinetics of the constituents are defined in a
subroutine called FINK.  FINK subroutines are available for
temperature, the nitrogen cycle, the QUAL II kinetics, bass-egg
development, and fine sediment.

Attached is a list of past and potential transport projects that
have used one or more of the models.  Copies of DAFLOW and or BLTM
model documentation and codes (for either the prime or a PC) can
be obtained from the Office of Surface Water.  Copies of the
BRANCH flow model are available through David Thompson at the
Office of Surface Water's Flow and Transport Modeling group at
Stennis Space Center.

                                    Charles W. Boning
                                    Chief, Office of Surface Water