Study on the algal dynamic model for West Lake, Hangzhou

Abstract

An algal dynamic model describing the ecosystem of West Lake, Hangzhou, one of the typical shallow and eutrophic lakes, was proposed. The model consists of 13 state variables such as biomass of four main algae (Cyanophyta, Chlorophyta, Cryptophyta and Bacillariophyta) and respective content of phosphorus, biomass of zooplankton, the content of phosphorus in zooplankton, orthophosphate, phosphorus in detritus and phosphorus in sediment. Model simulation was carried out on year time scale to describe the dynamic change of four main algae and zooplankton. The result of model calibration and verification shows that the model can reasonably respond to the changes of forcing function in lake ecosystem. The model compares the possible changes of water quality with changes of drawing water quantity, phosphorus content of drawing water and stream water and removing quantity of sediment. The model has been used to simulate the dynamic changing of the four main algae with the measure taken. It shows that the measure by removing phosphorus in sediment is most available, and the biomass of Cyanophyta, Chlorophyta, Cryptophyta will descend obviously. Furthermore, the improvement of water quality with above measures is also evaluated. On the basis of the results of the simulations, the best management strategy limiting eutrophication processes in West Lake has been pointed out.