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