The Study On The Ecological Water Quality Dynamic Modeling Of Bohai Bay

Due to the rapid economic development in the coastal area, Bohai Bay has received large amount of waste water from industrial, agricultural and domestic usage. The excessive accumulation of nutrients like ammonium, nitrate and phosphate in the ecosystem causes the worsening of the eutrophication problem, resulting in frequent occurrence of the red tide. During the period of a red tide, the depletion of oxygen in the water may lead to the death of many sea creations and reduce the production of the fishery business, which is posing potential threat to the sustainable economic growth. To control and reduce the red tide, it is necessary to understand the coastal eutrophication phenomenon. Therefore, to establish a dynamic water quality model that can be used to describe the evolution of the ecosystem and the related water quality indicators is of great theoretical and practical significance.A 2-dimentional ecological water quality dynamic model has been set up. This model includes two sub-models: one is hydrodynamic model and the other is ecosystem dynamic model. The basic equation of the ecological water quality dynamic model is a convection-diffusion equation with source functions. The ecosystem dynamic model is working as its eco-source. A 2-dimentional hydrodynamic sub model is adopted to solve the synchronized fluid field and to provide the ecological water quality dynamic model with the hydrodynamic parameters.The ecosystem dynamic model is the key to the ecological water quality dynamic model since the interaction amongst different elements of the ecosystem is the inner driving force of the evolution of the system. The ecosystem dynamic model set up here, based on a hypothetical phytoplankton-dominated ecosystem, describes the evolution of phytoplankton, the relevant environmental elements and the consequential changes of the dissolved oxygen. This sub model has eight variables, including phytoplankton (P), detritus nitrogen (ND), detritus phosphorous (PD), ammonium (A), nitrate (N), phosphate (P1), carbonaceous biological oxygen demand (CBOD) and dissolved oxygen (DO). Taking CBOD and DO into account is the main feature of the ecological water quality dynamic model in this paper.To facilitate the model program debugging and validating,numerical experiments...