US-CHINA WORKSHOP ON ADVANCED COMPUTATIONAL MODELLING IN HYDROSCIENCE & ENGINEERING September 19-21, Oxford, Mississippi, USA MODELING HYDRODYNAMICS, CHANNEL MORPHOLOGY, AND WATER QUALITY USING CCHE1D
CCHE1D is a one-dimensional model for the simulation of unsteady flows, sediment transport, and water quality in stream networks. The model can be applied to a variety of engineering problems, but it is particularly useful in the determination of channel–watershed system responses to natural and man-made changes in both channels and upland areas. The model can be used in combination with the watershed model AGNPS in the analysis of watershed hydrology and nonpoint source pollution problems caused by erosion or pollutants such as nutrients and pesticides. CCHE1D’s flow module – CCHE1D-FL – computes one-dimensional unsteady flows in dendritic channel networks of arbitrary cross-sectional shapes. The sediment transport module – CCHE1D-ST – simulates the transport of sediment mixtures using a nonequilibrium approach, predicting sediment yields and channel morphological changes. The recently developed water quality module – CCHE1D-WQ – simulates transport and fate of pollutants in streams for continuous, unsteady flow conditions. The model computes advective-dispersive transport of a number of pollutants, simulating the biogeochemical processes of the main nutrient cycles, phytoplankton growth, and the process of eutrophication. GIS-based graphical software complements the modeling system, providing automated methods for watershed delineation, channel network generation, data transfers and conversions, and visualization.
Effects of Stream Tube Numbers on Flow and Sediments using GSTARS-3-A Case Study of the Karkheh Reservoir Dam in Western Dezful
Simulation of the flow and sedimentation process in the reservoir dams can be made by two methods of physical and mathematical modeling. The study area was within a region which ranged from the Jelogir hydrometric station to the Karkheh reservoir dam aimed at investigating the effects of stream tubes on the GSTARS-3 model behavior. The methodologies was to run the model based on 5 stream tubes in order to observe the influence of each scenario on longitudinal profiles, cross-section, flow velocity and bed load sediment size. Results further suggest that the use of two stream tubes or more which result in the semi-two-dimensional model will yield relatively closer results to the observational data than a singular stream tube modeling. Moreover, the results of modeling with three stream tubes shown to yield a relatively close results with the observational data. The overall conclusion of the paper is with applying various stream tubes; it would be possible to yield a significant influence on the modeling behavior Vis-a Vis the bed load sediment size. Keywords—Karkheh, stream tubes, GSTARS-3 Model, Jelogir hydrometric station.
One-Dimensional Mathematical Model for Suspended Sediment by Lateral Integration
Although a one-dimensional (1D) mathematical model based on the nonequilibrium transport of sediment is rational in principle, its application to rivers requires empirical determination of a key coefficient in the basic equation of transport, this is known as the adjustment coefficient. It also requires, as all 1D models do, empirical and rather arbitrary apportioning of the computed total scour or deposition to the wetted perimeter. In this paper an attempt is made to avoid both. The equation of sediment transport is written for a vertical stream tube of infinitesimal width for which the adjustment coefficient has been rationally determined. A procedure of lateral integration is then applied to obtain the global values of the said coefficient for the entire cross section and the distribution of deposition/erosion to the wetted perimeter. The shape of the cross section is thus determined along with the amount of deposition/erosion. Results obtained with this model compare favorably with those of depth-int...