Affiliations: College of Environmental Sciences, Peking University,
Beijing 100871, China | Yunnan Institute of Environmental Science, Kunming
650034, China
Abstract: Lake eutrophication caused by excess phosphorus (P) loading from
point sources (PS) and nonpoint sources (NPS) is a persistent and serious
ecological problem in China. A phosphorus budget, based on material flow
analysis (MFA) and system dynamic (SD), is proposed and applied for the
agriculture-dominated Qionghai Lake watershed located in southwestern China.
The MFA-SD approach will not only cover the transporting process of P in the
lake-watershed ecosystems, but also can deal with the changes of P budget due
to the dynamics of watershed. P inflows include the fertilizer for agricultural
croplands, soil losses, domestic sewage discharges, and the atmospheric
disposition such as precipitation and dust sinking. Outflows are consisted of
hydrologic export, water resources development, fishery and aquatic plants
harvesting. The internal P recycling processes are also considered in this
paper. From 1988 to 2015, the total P inflows for Lake Qionghai are in a rapid
increase from 35.65 to 78.73 t/a, which results in the rising of P
concentration in the lake. Among the total P load 2015, agricultural loss and
domestic sewage account for 70.60% and 17.27% respectively, directly related to
the rapid social-economic development and the swift urbanization. Future
management programs designed to reduce P inputs must be put into practices in
the coming years to ensure the ecosystem health in the watershed.
Keywords: phosphorus budget, lake-watershed ecosystems, material flow analysis, system dynamic
