Eco-hydrology and geomorphology of the largest floods along the hyperarid Kuiseb River, Namibia

Tamir Grodek, Efrat Morin, David Helman, Itamar Lensky, Ofer Dahan, Mary Seely, Gerardo Benito, Yehouda Enzel

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Flood-fed aquifers along the sandy lower reach of the Kuiseb River sustain a 130-km-long green belt of lush oases across the hyperarid Namib desert. This oasis is a year-round source for water creating dense-tall woodland along the narrow corridor of the ephemeral river valley, which, in turn, supports human activity and fauna including during the long dry austral winters and multi-year droughts. Occasional floods, originating at the river's wetter headwaters, travel ∼280 km downstream, before recharging these aquifers. We analyzed the flood-aquifer-vegetation dynamics at-a-site and along the river, determining the relative impact of floods with diverse magnitude and frequency on downstream reaches. We find that flood discharge that feeds the alluvial aquifers also affects vegetation dynamics along the river. The downstream aquifers are fed only by the largest floods that allow the infrequent germination of plants; mean annual recharge volume is too low to support the aquifers level. These short-term vegetation cycles of green-up and then fast senescence in-between floods are easily detected by satellite-derived vegetation index. This index identifies historical floods and their magnitudes in arid and hyperarid regions; specifically, it determines occurrences of large floods in headwater-fed, ephemeral Namib streams as well as in other hyperarid regions. Our study reveals the importance of flood properties on the oasis life cycle, emphasizing the impact of drought and wet years on the Namib's riparian vegetation.

Original languageEnglish
Article number124450
JournalJournal of Hydrology
Volume582
DOIs
StatePublished - 1 Mar 2020

Keywords

  • Aquifer recharge
  • Desert floods
  • Flood occurrence
  • Gobabeb
  • Kuiseb River
  • Namib desert
  • Normalized Difference Vegetation Index (NDVI)
  • Oasis valley
  • Vegetation dynamics

ASJC Scopus subject areas

  • Water Science and Technology

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