Detecting chlorophyll, Secchi disk depth and surface temperature in a sub-alpine lake using Landsat imagery.

Area of Science:

• Environmental Remote Sensing
• Aquatic Ecosystem Monitoring
• Geospatial Analysis

Background:

• Sub-alpine lakes require regular monitoring of biophysical parameters.
• Satellite remote sensing offers a synoptic approach for large water body assessment.
• Landsat Thematic Mapper (TM) data provides valuable spectral information for water quality studies.

Purpose of the Study:

• To map chlorophyll a concentration, Secchi disk depth, and water surface temperature in Lake Iseo.
• To validate the use of atmospherically corrected Landsat TM data for aquatic parameter retrieval.
• To assess the spatial distribution of key limnological variables.

Main Methods:

• Atmospheric correction of Landsat TM data using a partially image-based method.
• Development of empirical models relating spectral reflectance to in situ measurements.
• Application of scene-independent procedures for surface temperature derivation.

Main Results:

• High determination coefficients achieved for chlorophyll (R2 = 0.99) and Secchi disk depth (R2 = 0.85).
• Spatial distribution maps generated for chlorophyll and Secchi disk depth with specified contour intervals.
• Accurate derivation of lake surface temperature with a root mean square error of 0.3°C.

Conclusions:

• Landsat TM data, when properly processed, is effective for mapping key biophysical parameters in sub-alpine lakes.
• Empirical modeling provides a reliable method for quantifying chlorophyll and Secchi disk depth from satellite imagery.
• Remote sensing techniques enable efficient and accurate monitoring of lake water quality and thermal characteristics.