Remote Sensing of Suspended Particulate Matter in Himalayan Lakes

This study presents satellite data and in situ measurements to estimate the concentration of suspended solids in highaltitude and remote lakes of the Himalayas. Suspended particulate matter (SPM) concentrations measured in 13 lakes to the south of Mount Everest (Nepal) in October 2008 and reflectance values of the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) onboard ALOS, acquired a few days after the fieldwork activities concluded, were combined to build a relationship (R2 5 0.921) for mapping SPM concentrations in lakes of the Mount Everest region. The satellite-derived SPM concentrations were compared with in situ data (R2 5 0.924) collected in the same period in 4 additional lakes, located to the north of Mount Everest (Tibet, China). The 13 water samples collected in lakes in Nepal were also used to investigate the absorption coefficients of particles ap(l) and colored, dissolved organic matter aCDOM(l), with the aim of parameterizing a bio-optical model. An accurate model (R2 5 0.965) to estimate SPM concentrations from ap(l) was found and could be adopted in the future for retrieving suspended solids from satellite imagery independently of ground measurements. In such a remote area, remote sensing was demonstrated to be a suitable tool to characterize the state of lakes, whose loads of suspended solids might be assumed to be direct and quick-responding indicators of deglaciation processes and glacier–lake interactions. As a macrodescriptor of water quality, the assessment of SPM in glacial lakes of the Himalayas might also be of interest for resource use in the downstream region.