Abstract

SEAMAN, Maitland et al. DRIFT-ARID: Application of a method for environmental water requirements (EWRs) in a non-perennial river (Mokolo River) in South Africa. Water SA [online]. 2016, vol.42, n.3, pp.368-383. ISSN 1816-7950.  http://dx.doi.org/10.4314/wsa.v42i3.02.

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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