Mapping and Monitoring the Akagera Wetland in Rwanda

Abstract

Wetland maps are a prerequisite for wetland development planning, protection, and restoration. The present study aimed at mapping and monitoring Rwanda's Akagera Complex Wetland by means of remote sensing and geographic information systems (GIS). Landsat data, spanning from 1987 to 2015, were acquired from different sensor instruments, considering a 5-year interval during the dry season and the shuttle radar topographic mission (SRTM) digital elevation model (30-m resolution) was used to delineate the wetland. The mapping and delineation results showed that the wetland narrowly extends along the Rwanda-Tanzania border from north to south, following the course of Akagera River and the total area can be estimated at 100,229.76 ha. After waterbodies that occupy 30% of the wetland's surface area, hippo grass and Cyperus papyrus are also predominant, representing 29.8% and 29%, respectively. Floodplain and swamp forest have also been inventoried in smaller proportions. While the wetland extent has apparently remained stable, the inhabiting waterbodies have been subject to enormous instability due to invasive species. Lakes, such as Mihindi, Ihema, Hago and Kivumba have been shrinking in extent, while Lake Rwanyakizinga has experienced a certain degree of expansion. This study represents a consistent decision support tool for Akagera wetland management in Rwanda.

Physical Geography and Environmental Sustainability

“…Due to urbanization and its impact on land-use, several studies here have also examined land-use and land-cover changes (e.g., [1,2]) through mapping. So, urban environments are increasingly being addressed by physical geographers, as for instance geomorphologists as part of urban geomorphology [13,14] or what has been a growing "human geomorphology" (e.g., [15]).…”

“…A variety of methodological approaches are incorporated here, with spatial technology (remote sensing, GIS, etc.) included in several studies (e.g., [1][2][3][4]), serving to portray the role of technology on data compilation and analysis in geographical research. Data visualization is evident in paper [11] for modelling and, earlier in the Special Issue, [1] explores data-sharing based on data acquired from Earth observation.…”

A New Conceptual Framework for Integrating Earth Observation in Large-scale Wetland Management in East Africa

“…For the objective of developing coherent and adoptable methods towards wetland mapping, we therefore valued the accessibility and availability of the SRTM DEM, substantiated with a large body of literature successfully using it for large-scale wetland mapping (e.g. Bwangoy et al 2010;Ndayisaba et al 2017;Ludwig et al 2019) over the higher performance of the TanDEM-X DEM.…”

Mapping spatio-temporal variations in water hyacinth (Eichhornia crassipes) coverage on Rwandan water bodies using multispectral imageries

“…5). The studies investigating threats to the Akagera Wetland from 1987 to 2015 showed water hyacinth to be the main problem, particularly in the 2000-2002 period (Twongo et al 2002;Ndayisaba et al 2017). However, these studies did not quantify the coverage of water hyacinth in the wetland during this period.…”