Modelling flow and sediment transport change on the ecosystem in the large fresh water lake-Poyang Lake

Abstract

River connected lakes exchange substances such as water and sediment with the rivers frequently, which means the ecosystem is significantly influenced by the relationship between the lake and the rivers. Affected by the construction and operation of the upstream reservoirs and the evolution of the climate conditions, the relationship between the lake and the rivers connected to Poyang Lake (PYL) has changed remarkably. The changed relationship has a direct impact on the inflow and outflow conditions of the water and sediment, which are most important state variables and driving variables in the aquatic ecosystem, specifically, the inorganic environment of an aquatic ecosystem is mainly composed of water and various forms of sediment and the transport of water and sediment drives the transport of nutrients and biological elements and forms the aquatic habitat. To study the impact of the flow and sediment transport change on the ecosystem in PLY, this study builds the food web model and simulates the evolution of the aquatic ecosystem by virtue of AQUATOX, which is a comprehensive eco-model developed by Environmental Protection Agency. The results illustrate there is a degeneration of the ecosystem in PYL when the sediment transport is decreased significantly, and the water discharge of Hukou is increased in dry season. In the 30 years’ simulation period, the biomass concentration of chlorophyll a increased significantly in summer and autumn, and the biomass concentration of benthos decreased significantly from 2012 to 2030.