Study On Algal Blooms Behavior For Typical Watershed Systems Along The Three Gorges Valley By Sandpile Experiments

For the forming reservoir along Three Gorges, owing to current velocity of flow of Yangtze River becoming slower, the self-clean capacity of the water body would be decreased obviously. At the same time the reservoir banks water area will form one of special periodic fluctuation movement and a new regional weather, which will change the mode of transfer, accumulation, distribution and evolvement for nutrient substance in the river valley of Yangtze Gorges. The water-level-fluctuating zones along the banks of the river valley and some main inferior rivers were appearing the algal blooms in different degree. And large quantities of living and industrial water containing P and N will feed into the body of the water area, which will make some heavy pollution to the whole Yangtze River. When the reservoir has been constructed, current velocity of flow will become so slower dramatically that the eutrophication would be an important task for protecting the water body environment of the Three Gorges reservoir. As we have known that the algal blooms system is one of the biochemical dynamical water area system which has the features, such as multi-factors coupling, multidimensional vanish-rising and self-organized criticality(SOC). The formation, eruption, spread, standing and disappearance of algal has complicated, non-linear and self-organized criticality relationships which are similar to the content of the water eutrophication substance. Sandpile model(SM) is the typical paradigm of SOC system, which has most true physical meaning. SOC and SM have been studied to these systems that are open systems with fluctuant behavior. And the typical eutrophicated valley is just an open system with substance and energy exchange simultaneously, so that we can use SOC, SM, biochemical reaction mechanism and the monitoring data to study fully and describe the inner-rules of Three Gorges eutrophication and algal blooms behaviors. By implementing the experiments of SM, we throw the particles on the underpan one by one, when the sandpile rises to the critical height (Hc), additional sand will lead to an avalanche. And then add the sands again; the avalanched sandpile will grow again. This continuous process may establish a correspond relationship with periodic fluctuation for algal bloom as described above. Based on the self-organized criticality theory, a true sandpile mode was designed. At the same time we used several different aspect ration particles for processing a mass of physical related experiments, which are much closer to the behavior of true sandpile. By sorting and analyzing lots of experimental data, a parameter is defined to describe the system's avalanche trends. These parameters might reveal the fluctuation feature of the sandpile system according to different details of the system and the dynamical behavior under different conditions in order to study a true algal bloom along the Three Gorges valley. According to these experimental measuring data and related statistical analysis, we obtained some general factors as follows: underpan diameter D, sand particle length L, sand particle radius r and sand particle density ρwhich would be associated with the SOC in the process of the sandpile evolution. By comparing these generalized factors with the sandpile avalanche trend, frequency and scale under different conditions, we would discover and describe some internal mechanism and evolution process for reflecting algal bloom. The results of the sandpile experimental might reveal the periodicity, fluctuation and the same movement direction during the process of the algal bloom. According to the water quality monitoring data from some typical watershed systems located along the Three Gorges which has being eutrophicated for some years, the complex SOC behaviors during the algal blooms/fluctuation in the slow flowing water systems have been studied. And the results are identical to the real measured, which means that the SM is effective when it was used to describe the evolution and SOC behavior for complex water area environmental system.