ABSTRACT
T e looped solution algorithm described briefly previously for the water flow simulation again is applied to formulate the above dispersion equations for the pollutant transport in a looped-channel system. The unknown variables to be solved here are the concentration and the derivative of the concentration instead of the water level and discharge appearing in the water flow model. The details for the mathematical and numerical formulation which will not be stated here can be found in other articles such as Sauvaget {1985). Nonpoint source transport model For runoff simulation, this model can only take into account the infiltration and the surface runoff. For the infiltration computation, the SCS (Soil Conservation Service) formula (Chow, 1988) is coded in the model. The surface runoff is simply computed by using the volume conservation concept. The watershed to be simulated would be divided into several cells which will be considered as a computational node in the looped system. The conceptual layout of the cell-like divided watershed is shown as Fig. 1. In each cell the following water cohtinuity equation is used:
j=l (4)
in which Pm is the change of water volume in the cell due to the excess rainfall. The water depth change and the flow discharge between the neighboring cells can be simulated through the integration of this above relation into the looped water flow model.
