LAUSR

Small water bodies are an important part of the Earth's freshwater system, protecting biodiversity and providing ecosystem services. Because of various surrounding features, it is unknown to what extent we can obtain accurate remote-sensing reflectance (Rrs) of such an environment by the conventional above-water approach (AWA). In this study, we used both AWA and the skylight-blocked approach (SBA) side-by-side to measure Rrs in a typical small water body. It was found that the variation of Rrs in the UV-blue domain from AWA is around 50% and is inconsistent with the variation of the total absorption coefficient (at) obtained from water samples; on the contrary, the variation of Rrs obtained from SBA is highly consistent, with a coefficient of variation under ∼5%. These results highlight the large uncertainties in the measured Rrs from AWA due to the complexity of such an environment and further echo the robustness of SBA to measure Rrs in the field, even in such challenge environments.