Author(s): Keitaro Yamada

Linked Author(s):

Keywords: Remote Sensing; Cambodia; Chlorophyll; Total Phosphorus; MODIS;

Abstract: Cambodia is located in the downstream area of the Mekong River. Large floods in the Mekong River occur annually and form floodplains widely. In these floodplains, abundant nutrients transported by the flooding become beneficial for agricultural production. In recent years, there is a need for impact assessment of floods and rapid urbanization on agriculture. In this study, we estimated the total phosphorus concentration in the Mekong River floodplains using satellite images. We first estimated chlorophyll-a concentration and then utilized this estimation to evaluate the total phosphorus concentration since various phosphorus types in the water makes it difficult to directly estimate using satellite images. Since floodplains have higher chlorophyll-a concentration and turbidity compared to ocean data, we considered the spectral reflection characteristics of eutrophicated waters and modified the used satellite bands in order to apply previous models (O'Reilly et al.,1988) mainly used for oceans. Our results show that the coefficient of determination improved from 0.30 to 0.54. Using the obtained model, monthly concentrations of total phosphorus in floodplains were estimated. The variance values of total phosphorus concentration in rainy and dry seasons were 0.0820 and 0.0144, respectively, and we found that the phosphorus concentration was larger in the rainy season. The median of the concentration increased in the dry season. This suggests that the effect of condensation to the total phosphorus concentration is large.

DOI: https://doi.org/10.3850/38WC092019-1316

Year: 2019