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.
Highlights
Since the signing of the Ramsar convention in 1971, great importance has been accorded to wetlands’ ecosystem services, and studies on wetlands have gained momentum worldwide
The Akagera Complex Wetland comprises a transboundary network of wetlands lying between 1◦18 –02◦11 S and 30◦33 –31◦01 E, where it forms the borderland between Rwanda and Tanzania in East Africa
The wetland is traversed by the Akagera River that flows northwards into Lake Victoria, the name of Akagera
Summary
Since the signing of the Ramsar convention in 1971, great importance has been accorded to wetlands’ ecosystem services, and studies on wetlands have gained momentum worldwide. Wetlands have the potential to regionally increase food security by sustainably increasing food production and supporting the uncoupling of food supply from global market price fluctuations They provide important ecosystem services to numerous stakeholders and need to be protected from either exhaustion or extinction. They act as a buffer in flood or overflow plains, reducing maximal flow rates during the rainy season and maintaining relatively high flow rates during the dry season [2]. The present study, seeks to: (1) generate a clear Akagera wetland delineation map; (2) monitor the wetland through analysis of remote sensing longitudinal imagery; and (3) identify and provide the estimates of different wetland cover classes and, where possible, detect changes over time. The authors elaborate on the methods and materials used (Section 2); the results obtained (Section 3); the discussion and analysis of results (Section 4); and, the conclusion (Section 5)
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