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DRIFT-ARID: A method for assessing environmental water requirements (EWRs) for non-perennial rivers


Maitland Seaman
Marie Watson
Marinda Avenant
Jackie King
Alison Joubert
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

Environmental water requirement (EWR) assessment methods, for ascertaining how much water should be retained in rivers to sustain ecological functioning and desired levels of biodiversity, have mostly been developed for perennial rivers. Despite non-perennial rivers comprising about 30–50% of the world’s freshwater systems, data on their hydrology, biota and ecological functioning are sparse. Current EWR assessments require hydrological and other data that may not be available for such rivers and some adaptation in the methods used seems necessary. DRIFT is an EWR method for perennial (or near-perennial) rivers that has been developed in South Africa over the past two decades and is now widely applied nationally and internationally. When applied to the semi-permanent Mokolo River, challenges particular to, or accentuated by, non-perennial rivers included the reliable simulation of hydrological data, the extent of acceptable extrapolation of data, difficulties in predicting surface-water connectivity along the river, and the location and resilience of pools, as well as whether it was possible to identify a reference (natural) condition. DRIFT-ARID, reported on here, is an adaptation of the DRIFT approach to begin addressing these and other issues. It consists of 11 phases containing 29 activities.

Keywords: EWR, non-perennial, DRIFT, DSS


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eISSN: 1816-7950
print ISSN: 0378-4738