Landsat 8-observed water quality and its coupled environmental factors for urban scenery lakes: A case study of West Lake.

Abstract

Urban scenery lakes are not only popular sites for recreation, water sport, and visit of citizens and tourists, but also function for urban water drainage and storage, and hence their water quality is a sensitive indicator of urban aquatic environment. This study focused on two important water quality parameters, TSM (total suspended matter) and CDOM (colored dissolved organic matter) in West Lake, a world famous urban scenery lake in Hangzhou, China. Based on Landsat-8 images, remote sensing inversion models for TSM and CDOM in West Lake were compared and the best ones were determined using exponential functions and green/red band ratios. Results show that the accuracy of TSM models is relatively better while CDOM models performed relatively poor, indicating that empirical estimation of CDOM for inland complex waters remains a challenge. The Landsat-derived results in West Lake from 2013 to 2017 show that TSM presented diverse distributions in different sections and months/seasons - the relatively high-concentration TSM was usually found in the north section and during spring festivals, holidays and summer vacations. These spatiotemporal patterns demonstrate the evidence that TSM in West Lake was highly linked to anthropogenic impacts, such as tourist visits, commercial activities, and urban drainage projects in Hangzhou. The relations between TSM and precipitation were also examined, but no significant correlations were found, showing that the impacts of rainfall on water quality of urban lakes are complicated, and using remote sensing for such studies is still with limitations.