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DRIFT-ARID: Application of a method for environmental water requirements (EWRs) in a non-perennial river (Mokolo River) in South Africa


Maitland Seaman
Marie Watson
Marinda Avenant
Alison Joubert
Jackie King
Charles Barker
Surina Esterhuyse
Douglas Graham
Marthie Kemp
Pieter le Roux
Bob Prucha
Nola Redelinghuys
Linda Rossouw
Kate Rowntree
Frank Sokolic
Leon van Rensburg
Bennie van der Waal
Johan van Tol
Tascha Vos

Abstract

Methods developed to determine the amount of water required (EWR) to sustain ecosystem services in non-perennial rivers need a different approach to those used in perennial rivers. Current EWR methods were mostly developed for use in perennial rivers. Non-perennial rivers differ from perennial ones in terms of variability in flow, periods of no-flow and related habitat availability. A DRIFT-ARID method (an adaptation of the Downstream Response to Imposed Flow Transformation (DRIFT) method) was developed, tested and adjusted, using the semi-permanent Mokolo River. Field data from five study sites was collected from April to May 2010 by a multidisciplinary team. The results were used in a DRIFT-ARID Decision Support System (DSS) to determine the impact of five chosen development scenarios in the Mokolo River Catchment. An integrated groundwater–surface water MIKE-SHE hydrological model was used to simulate the hydrology of the chosen scenarios. Specific non-perennial river indicators such as onset of dry phase were identified and included in the DRIFT-ARID DSS. DRIFT-ARID has the potential to be used in non-perennial rivers and, once set up, can provide results for future scenarios. The method now needs to be tested on other non-perennial river types, especially episodic rivers where data are scarce or non-existent.

Keywords: DRIFT-ARID, non-perennial, EWR, flow method, Mokolo River


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eISSN: 1816-7950
print ISSN: 0378-4738