A one dimensional water quality model for rivers and estuaries

Pao Yue-kong Library Electronic Theses Database

A one dimensional water quality model for rivers and estuaries

 

Author: Cheung, Wai-hung Tony
Title: A one dimensional water quality model for rivers and estuaries
Degree: M.Sc.
Year: 1993
Subject: Water quality -- Mathematical models
Water quality -- Data processing
Rivers -- China -- Hong Kong
Estuaries -- United States
Hong Kong Polytechnic -- Dissertations
Department: Dept. of Civil and Structural Engineering
Pages: 131 leaves : ill., maps ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1132501
URI: http://theses.lib.polyu.edu.hk/handle/200/274
Abstract: A one-dimensional transient water quality model is developed based on the split-operator method due to Li1. The model can produce the transient solution of the dissolved oxygen, BOD, organic nitrogen, ammonia nitrogen, nitrite and nitrate nitrogen, and phosphate concentrations in one-dimensional estuaries and rivers of variable cross-sectional area, spatially variable dispersion coefficient, and decay coefficient. It can take into account the different formulations at the aerobic and anaerobic regions. For the occurrence of anaerobic condition in rivers and estuaries, the oscillatory behaviour of the solution produced by using the direct iterative method (e.g. the finite segment model) can be prevented by using the present split-operator method, which includes the use of the minimax characteristics method for the advection step, the central difference method for the dispersion step, and a semi-analytical method for the decay step. The model was verified by several test cases which have exact solutions. The agreement between the numerical and the exact solution is in general satisfactory. However, the difference between the two solution was apparent around the source region, which is due to the use of different source condition: the numerical model uses a triangular distributed source condition because of the finite grid size, while the analytical solution uses a point source condition. Practical application of the numerical model is demonstrated through the study of the spatial variation of water quality in the Ho Chung River of H.K. and the Delaware Estuary of USA.

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