Monitoring Lake Simcoe Water Clarity Using Landsat-5 TM Images

This study focuses on utilizing satellite remote sensing to monitor the water clarity of Lake Simcoe, Ontario, Canada, which has been suffering from the overload of phosphorus (TP) and therefore eutrophication for decades. The dataset includes 22 cloud-free Landsat-5 Thematic Mapper (TM) images, as well as the nearly simultaneous in-situ observations from 15 stations on the lake. Compared to the general model used to estimate the Secchi Disk Transparency (SDT), a parameter for water clarity measurements, an improved model is developed, from the TM images. The results of these estimations are validated using the in-situ data by linear regression, and the accuracies are measured by the coefficient of determination R <Superscript>2</Superscript>. The results reveal an indication of high model fit between the majority of SDT predictions and the in-situ observations. Also, the improved SDT model provides higher prediction accuracies than the general one when applied to 68.2% (15 out of 22) of the images. The estimated clarity maps indicate that the turbid water is normally distributed at the nearshore areas and the northeastern region. Meanwhile, the southwestern lake has much clearer water than the other regions. In addition, the southern bay has always been suffering from a serious water quality problem even till now. The water clarity of Lake Simcoe shows strong seasonal patterns, that it is at its worst in August and September annually and much better in the other sampling seasons. On an overall scale, the lake water clarity kept relatively stable from 1987 until the fall of 1992, followed by a gradual increase until 2000, after a slight decrease, and lastly stayed consistent until the summer of 2008. Copyright Springer Science+Business Media B.V. 2011