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Estimation of environmental flows at the Orange River mouth using an improved spatial interpolation approach.

IWRA World Water Congress 2008 Montpellier France
5. Water Governance and Water Security
Author(s): Billy Troy
Jean Marie Fritsch
(1) : IRD- Institut de Recherche pour le Développement, UMR G-eau, PO Box 542, Newtown 2113, Johannesburg, South Africa.

Keyword(s): environmental flows, flow duration curves, Orange River Mouth, Ramsar site, spatial interpolation approach, wetlands

AbstractEnvironmental flow requirements are often difficult to estimate due to missing or incomplete observed flow time series at the sites concerned. A spatial interpolation approach for daily flow regime simulation at ungauged sites was designed to address this matter and other hydrological issues. This paper presents improvements of this method, applied at the Orange River Mouth site (South Africa and Namibia), which shelters endangered wetlands of international importance. This modified spatial interpolation approach allowed to calculate simulated daily flow time series that better matched with observed water levels than the original method. These results were then used to estimate the flooding frequency at the mouth required to support wetlands conservation. These methodological developments are generic and could easily be included in future applications of this spatial interpolation approach.
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