Monitoring the river plume induced by heavy rainfall events in large, shallow, Lake Taihu using MODIS 250m imagery

Knowledge of stormwater river plume dynamics is important for the management of lake water quality because river discharge associated with rainstorms can be a major source of pollutants for lake waters. Total suspended matter (TSM) derived from the discharge of sediment-laden rivers is highly variable over a wide range of time and space scales. In the present study, the first use of remote sensing to monitor the river TSM plume was conducted to investigate the effects of heavy rainfall events on Lake Taihu by the largest inflowing river (Tiaoxi River) based on a calibrated and validated model using daily 250m MODIS imagery in band 1 (620–670nm). From 2004 to 2013, 48 MODIS images of 20 heavy rainfall events were obtained, showing that the area of the TSM plume significantly increased in the waters adjacent to the inflowing river, reflecting runoff input. The TSM concentration of the river plume after heavy rainfall was significantly higher than that before rainfall (ANOVA, p˂0.001). A significantly positive correlation between the TSM plume area and the rainfall amount in heavy rainfall events (p˂0.01) was also observed. The heaviest rainfall event, in October 2013, caused a river plume with an area of 302.8km2, which lasted for more than 10days. The significant increase in the frequency and rainfall amount of rainstorms and large rain in the past 50years (1965–2014) in Lake Taihu under global warming indicated an important role of remote sensing in monitoring the river plume resulting from heavy precipitation. The present study demonstrates that remote sensing tools can be valuable instruments in the detection and tracking of the effect of heavy rainfall events on the distribution and diffusion of the TSM concentration in the lake. The results obtained from the present study are valuable for further hydrological research on the Tiaoxi River, particularly for the immediate assessment of flood impacts on soil erosion of the catchment.