Evaporation and abstraction determined from stable isotopes during normal flow on the Gariep River, South Africa

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dc.contributor.author Diamond, Roger E.
dc.contributor.author Jack, Sam
dc.date.accessioned 2018-06-01T10:08:36Z
dc.date.issued 2018-04
dc.description.abstract Changes in the stable isotope composition of water can, with the aid of climatic parameters, be used to calculate the quantity of evaporation from a water body. Previous workers have mostly focused on small, research catchments, with abundant data, but of limited scope. This study aimed to expand such work to a regional or sub-continental scale. The first full length isotope survey of the Gariep River quantifies evaporation on the river and the man-made reservoirs for the first time, and proposes a technique to calculate abstraction from the river. The theoretically determined final isotope composition for an evaporating water body in the given climate lies on the empirically determined local evaporation line, validating the assumptions and inputs to the Craig-Gordon evaporation model that was used. Evaporation from the Gariep River amounts to around 20% of flow, or 40 m3/s, of which about half is due to evaporation from the surface of the Gariep and Vanderkloof Reservoirs, showing the wastefulness of large surface water impoundments. This compares well with previous estimates based on evapotranspiration calculations, and equates to around 1300 GL/a of water, or about the annual water consumption of Johannesburg and Pretoria, where over 10 million people reside. Using similar evaporation calculations and applying existing transpiration estimates to a gauged length of river, the remaining quantity can be attributed to abstraction, amounting to 175 L/s/km in the lower middle reaches of the river. Given that high water demand and climate change are global problems, and with the challenges of maintaining water monitoring networks, stable isotopes are shown to be applicable over regional to national scales for modelling hydrological flows. Stable isotopes provide a complementary method to conventional flow gauging for understanding hydrology and management of large water resources, particularly in arid areas subject to significant evaporation. en_ZA
dc.description.department Geology en_ZA
dc.description.embargo 2019-04-01
dc.description.librarian hj2018 en_ZA
dc.description.sponsorship SJ received funding from the Plant Conservation Unit at the University of Cape Town and the South African Environment Observation Network. RD received funding from the Water Research Commission and the National Research Foundation. en_ZA
dc.description.uri https://www.elsevier.com/locate/jhydrol en_ZA
dc.identifier.citation Diamond, R.E. & Jack, S. 2018, 'Evaporation and abstraction determined from stable isotopes during normal flow on the Gariep River, South Africa', Journal of Hydrology, vol. 559, pp. 569-584. en_ZA
dc.identifier.issn 0022-1694
dc.identifier.other 10.1016/j.jhydrol.2018.02.059
dc.identifier.uri http://hdl.handle.net/2263/65072
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2018 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Journal of Hydrology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Journal of Hydrology, vol.559, pp. 569-584, 2018. doi : 10.1016/j.jhydrol.2018.02.059. en_ZA
dc.subject Evaporation en_ZA
dc.subject Stable istopes en_ZA
dc.subject Hydrology en_ZA
dc.subject Temperature en_ZA
dc.subject Evapotranspiration (ET) en_ZA
dc.subject Precipitation (chemical) en_ZA
dc.subject Oxygen en_ZA
dc.subject Hydrogen en_ZA
dc.subject Lakes en_ZA
dc.subject Western Cape Province, South Africa en_ZA
dc.subject Fractionation en_ZA
dc.subject Water balance en_ZA
dc.subject Gariep River, South Africa en_ZA
dc.title Evaporation and abstraction determined from stable isotopes during normal flow on the Gariep River, South Africa en_ZA
dc.type Postprint Article en_ZA


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