Historical channel change in the Okavango Panhandle, Botswana

Zacchary T. Larkin, Timothy J. Ralph, Stephen Tooth, Kirstie A. Fryirs, Terence S. Mccarthy

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    Abstract

    The Okavango Delta in northern Botswana is characterised by ongoing morphological, hydrological, and ecological adjustment and change over seasonal, interannual, and longer timescales. Understanding the natural, historical range of variability in the Okavango is critically important for implementing successful management strategies. The Okavango Panhandle is a ~10 km-wide entry corridor of permanent swamps with a meandering trunk channel that is anabranching in some reaches. By using historical aerial photographs for detailed geomorphological mapping and morphological analysis of channel variables, we investigated the types and rates of change occurring in the anastomosing channels of the Okavango Panhandle. Throughout the second half of the 20th century the main Okavango channel has been progressively losing water to the Filipo channel to the east. Vegetation encroachment into the failing Okavango channel has reduced the channel width from ~40-50 m to ~20 m, whilst the Filipo channel has either remained stable or increased in channel width up to ~55 m. Changes to the water balance between channels is largely manifest in channel width changes, and there is no evidence of discernible lateral channel migration along any of the channels investigated. Given low historical rates of channel migration, meander belts likely take decades to centuries to develop, but given the current rate of vegetation encroachment along the Okavango River, we estimate that the failing Okavango channel may be blocked in various sections and essentially abandoned in the near future. Our findings have implications for the community of Sepopa and local tourism lodges that rely on the failing Okavango channel for water and transport.
    Original languageEnglish
    Title of host publicationWIDS2017 Dynamic Landscapes
    Subtitle of host publicationproceedings of the Wetlands in Drylands Research Network Conference
    EditorsTimothy J. Ralph
    Place of PublicationSydney, Australia
    PublisherMacquarie University
    Pages18
    Number of pages1
    ISBN (Print)9781741384543
    Publication statusPublished - 24 Jul 2017

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    Larkin, Z. T., Ralph, T. J., Tooth, S., Fryirs, K. A., & Mccarthy, T. S. (2017). Historical channel change in the Okavango Panhandle, Botswana. In T. J. Ralph (Ed.), WIDS2017 Dynamic Landscapes: proceedings of the Wetlands in Drylands Research Network Conference (pp. 18). Sydney, Australia: Macquarie University.