Study On Behaviors Of Algal Blooms In Three-Gorges Valley Using Self-Organized Criticality And Sandpile Model

Eutrophication is one of the most important aspects in water environmental protection, and the possible impacts on environment of Three-Gorges reservoir are always the focus of our care. Since the three-Gorges reservoirs begin to intercept water, the self-clarification ability of water bodies have decreased because of the lower velocity of flow, the formation of water-level-fluctuating zone, and the inner tides movements. The water bodies are facing serious risk of eutrophication, so it's an important and urgent task to do some research on eutrophication prediction along Three-Gorges reservoir. The causes and mechanisms of eutrophication were analyzed, and the possibilities were discussed on the occurrence of valley eutrophication before and after completing Three-Gorges reservoir along with the analysis on the factors resulting in the valley eutrophication such as the ratio between TP and TN, reservoir-operated circumstances, the weather in the reservoir area, hydrological status and the water quality. The critical concentrations of TP and TN which would lead eutrophication can be the references for further study and prediction on eutrophication in the reservoir area. As the increasing understanding of eutrophication mechanism and the development of computer technology, more and more eutrophication studies focus on the mathematic modeling of eutrophication. After the systemic introduction of the mathematic modeling of eutrophication, this paper presented our studies on behaviors of algal blooms along Three-Gorges reservoir with the help of the theory of Self-Organized Criticality (SOC). Based on BTW sandpile model, the conceptions of multi-quadrants, priority and apparent friction coefficient were proposed, two improved sandpile model were founded. Through a mass of simulation computing, the impacts of some parameters on the sandpile's SOC characters were studied, and the thermodynamic analysis of the model concerning total energy, structural entropy and free energy were also carried on. The results show the consistencies of SOC features with some statistical principles and complicated nonlinear relationships presented during algal blooms. It is obvious that the SOC features of the model have strong relevancy to the phenomena of algal blooms, and consequently, SOC could be a new way to study the complex behaviors of algal blooms.