Dry valleys (mekgacha)

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNChapterpeer-review


Conventional rivers are absent from much of Botswana, with only the Okavango, Chobe and Zambezi systems in the extreme north containing perennial flowing water. Ephemeral rivers occur in the eastern hardveld, but the most extensive components of the surface drainage are the networks of fossil or dry valleys (termed mekgacha in Setswana and dum in various San languages) that cross the sandveld. This chapter presents the first holistic review of current knowledge about these enigmatic landforms. It does so using a range of evidence types, from radar remote-sensing to the analysis of historical documents written by missionaries and explorers. The chapter considers dry valley distribution, morphology, and contemporary and historical hydrology before discussing valley evolution over longer timescales. It concludes with a synthesis of the main arguments concerning how dry valley systems may have formed, including the balance between conventional fluvial incision and processes such as groundwater seepage erosion.
Original languageEnglish
Title of host publicationLandscapes and Landforms of Botswana
EditorsFrank Eckardt
Place of PublicationHeidelberg, Switzerland
PublisherSpringer Nature
Number of pages21
ISBN (Electronic)9783030861018
Publication statusPublished - 2 Apr 2022

Publication series

NameWorld Geomorphological Landscapes
PublisherSpringer Nature
ISSN (Print)2213-2090
ISSN (Electronic)2213-2104

Bibliographical note

Publisher Copyright:
© 2022, Springer Nature Switzerland AG.


  • Dry valley
  • Ephemeral drainage
  • Kalahari Desert
  • Long-profile
  • Drainage evolution


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