Relationship between water color, water levels, and climate indices in large rivers: Case of the St. Lawrence River (Canada)

The relationship between the color (measured with Landsat Thematic Mapper and Enhanced Thematic Mapper sensors in bands 1, 2, and 3) of St. Lawrence River (SLR) water and water levels (in SLR and Lake Ontario) was first analyzed, followed by the analysis of the relationship between water levels and four climate indices for the period from 1984 to 2009. Although there is a statistically significant relationship between these first two variables, this link depends on the strength of two factors: the type of color (band) and inflows from tributaries. Bands 1 (blue) and 2 (green) were negatively correlated with water levels. This correlation, however, is spatially influenced by water inflows from tributaries. Band 3 (red) showed no significant correlation with either water level. Over the same period, water levels were negatively correlated with the Atlantic multidecadal oscillation index. Results suggest that the color of waters in the SLR may be used as an indicator to monitor environmental and climate changes in its watershed.