HR: 0800h
AN: H31B-1314    [Abstracts]
TI: A Reaction-based Diagonalization Approach to Modeling Surface Water Quality
AU: * Yu, J
EM: ji324333@pegasus.cc.ucf.edu
AF: University of Central Florida, 4000 Central Florida, Orlando, FL 32816 United States
AU: Yeh, G
EM: gyeh@mail.ucf.edu
AF: University of Central Florida, 4000 Central Florida, Orlando, FL 32816 United States
AU: Zhang, F
EM: zhangf@ornl.gov
AF: Oak Ridge Natioinal Laboratory, P. O. Box 2008, Oak Ridge, TN 37831 United States
AU: Wu, T
EM: tien-shuenn.wu@del.state.fl.us
AF: Florida Dept. of Environmental Protection, W2600 Blair Stone Road, Tallahassee, FL 32399 United States
AU: Hu, G
EM: ghu@sfwmd.gov
AF: South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, FL 33406 United States
AB: There are many water quality models (e.g., WASP, QAUL2E/QUAL2K, CE-QUAL-ICM, RCA, RMA11, etc.) that have been employed by practitioners in surface water quality modeling. All of these models are similar to each others. The major differences among them are the number of water quality parameters included and the number of biogeochemical processes considered. Because of the limitation on the number of biogeochemical processes considered and, in a lesser extent, on the number of water quality parameters included, these models often perform only fairly in validation and their predictions may be unreliable, even though they can be adequately calibrated in most occasions and excellently in some occasions. Obviously, there is a need to develop a model that would allow the inclusion of any number of water quality parameters and enable the hypothesis of any number of biogeochemical processes. This paper presents the development of a numerical water quality model using a general paradigm of reaction-based approaches. In a reaction-based approach, all conceptualized biogoechemical processes are transformed into a reaction network. Through the decomposition of species governing equations via Gauss-Jordan column reduction of the reaction network, (1) redundant fast reactions and irrelevant kinetic reactions are removed from the system, which alleviates the problem of unnecessary and erroneous formulation and parameterization of these reactions, and (2) fast reactions and slow reactions are decoupled, which enables robust numerical integrations. The system of species governing equations is transformed into two sets: algebraic equations (either mass action equations or users' specified) of equilibrium variables and differential equations of kinetic variables. As a result, the model alleviates the needs of using simple partitions for fast reactions and uses kinetic-variables instead of biogeochemical species as primary dependent variables. With the diagonalization strategy, it makes the inclusion of arbitrary number of fast and kinetic reactions relatively easy, and, more importantly, it enables the formulation and parameterization of kinetic reactions one by one. To demonstrate the flexibility and generality, the eutrophication model in WASP5, QUAL2E, and CE-QUAL-ICM are recast in the mode of reaction networks. This illustrates that the model embeds the most widely used water quality models as specific examples. Based on these three examples, the deficiencies of current practices in water quality modeling are discussed and the actions that must be taken to improve these practices are addressed.
DE: 4804 Benthic processes, benthos (0408)
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4807 Chemical speciation and complexation
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
DE: 4899 General or miscellaneous
SC: Hydrology [H]
MN: Fall Meeting 2005