Monitoring variation of water turbidity and related environmental factors in Poyang lake national nature reserve, China

There are pronounced spatial-temporal patterns in water turbidity in Poyang Lake National Nature Reserve (NNR), China. A most suitable empirical model validated by the field data between Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance and Secchi Disk Depth (SDD) selected as the indicator of water turbidity is used to map the spatio-temporal dynamics. High water transparency values are observed during the summer season, while the most turbid situations always occur in winter. In different years, the trend is similar while the occurrence of detailed peaks is a little different in the same lake. Comparing the situation in different seasons, the most turbid places show in different directions. Different lakes have their specific situations. The turbidity difference in the low-water season is less than the varying in the other seasons. Statistical methods were used to quantify the influence of factors such as water level, wind speed, temperature and rainfall. Further statistic analysis is used to judge the accuracy of the model. Some ancillary environmental factors which can also play a role such as fishing, dredging, vegetation and bird's influence are analyzed by theoretical deduction, supported by field investigations and historical data.