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

JOURNAL OF HYDROLOGY

卷:582

Article

Grodek, Tamir¹  Morin, Efrat¹  Helman, David^2,3  Lensky, Itamar⁴  Dahan, Ofer⁵  Seely, Mary⁶  Benito, Gerardo⁷  Enzel, Yehouda¹ 

[1] Hebrew Univ Jerusalem, Fredy & Nadine Herrmann Inst Earth Sci, Edmond J Safra Campus, IL-91904 Jerusalem, Israel

[2] Hebrew Univ Jerusalem, Robert H Smith Fac Agr Food & Environm, Dept Soil & Water Sci, IL-76100 Rehovot, Israel

[3] Hebrew Univ Jerusalem, Adv Sch Environm Studies, IL-91509 Jerusalem, Israel

[4] Bar Ilan Univ, Dept Geog & Environm, IL-5290002 Ramat Gan, Israel

[5] Ben Gurion Univ Negev, Zuckerberg Inst Water Res, IL-84990 Sede Boqer, Israel

[6] Desert Res Fdn Namibia, 7 Rossini St, Windhoek, Namibia

[7] CSIC, Natl Museum Nat Sci MNCN, Madrid 28006, Spain

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

DOI  :  10.1016/j.jhydrol.2019.124450

来源: Elsevier

【 摘 要 】

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 similar to 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.

【 授权许可】

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