Remote surveillance: assessing water quality

Posted on June 1, 2016

Remote sensing technology gives natural resource managers and landowners the ability to monitor environmental conditions in new and powerful ways. However, the remote assessment of water quality in lakes and ponds is complicated by wide variations in the inorganic and organic composition of suspended particles, which affect the optical environment, and the moderate- and medium-resolution remote sensing systems that are used routinely for the spectral analysis of marine waters can’t be used to monitor water quality in freshwater bodies less than 1.5-2.0 km2 in area. Czech investigators tested the capacity of an alternative sensing system with higher spectral and spatial resolution (2.4 nm and 0.4-6.0 m respectively), mounted in a single-engine light aircraft, to measure reflectance from the surfaces of quarry lakes and turbid, eutrophic fishponds in South Bohemia. Comparative measurements were also made in the field with a handheld spectral scanner, and water samples were taken to measure concentrations of algal chlorophyll and suspended solids. When patterns of reflectance at different optical frequencies were examined, it was found that concentrations of chlorophyll a were best predicted by the ratio of reflectance values at 714 and 650 nm, and that total suspended solids were best predicted by the reflectance at the near-infrared wavelength of 806 nm. The fact that reflectance explained most of the variation in the data (96% and 89% for chlorophyll and suspended solids respectively) shows that airborne
hyperspectral scanning is an ideal tool for monitoring surface water quality in multiple water bodies scattered across the landscape.

Reference: Vinciková, H. et al. 2015. Spectral reflectance is a reliable water-quality estimator for small, highly turbid wetlands. Wetlands Ecology & Management 23, 933–946.