Author(s): Bich Tran; Marloes Mul; Solomon Seyoum; Eddy Wymenga

Linked Author(s): Bich Tran

Keywords: Wetland; Inner Niger Delta; Evapotranspiration; Flood map; Inundation

Abstract: Wetlands are characterized by seasonal water abundance, which provides a wide variety of ecosystem services. Over the globe, the area of wetlands has been decreasing. Many different approaches have been developed to map wetlands and its dynamics using earth observation data. However, this is complicated by the fact that wetlands cover areas with open water and flooded vegetation, which have different spectral responses. In this study, a new approach for mapping wetlands dynamics using remote sensing derived actual evapotranspiration (ETa) data is presented and tested in the Inner Niger Delta (IND), Mali. High ETa was used to define the abundance of water and thereby able to classify both the open water and flooded vegetated areas as wetland. The water abundance maps were compared with existing inundation extent maps corresponding to maximum water level at a gauging station in the IND. The maximum water abundance surface area in peak flooding month was comparable with the inundated surface area (R2 = 0.89, p-value <0.05), ranging from 10,500 to 18,500 km2. However, the pixel-by-pixel comparison showed different spatial patterns in the inlet and outlet of the inner delta due to low ETa in shallow water and high ETa in saturated soil. Overall, the ETa-based method show potential as an operational method to assess dynamics of wetland when water level data or inundation map is not available. It can also be applied to other wetland areas, which are covered in global ETa data products but do not have observed data on their flood extent.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221154

Year: 2022