Assessing hydrological alterations in Malibamatso River using River Flow Health Index

Abstract

ABSTRACT Hydrological regimes substantially influence the biodiversity of river ecosystems, and hydrological alteration is considered the primary driving force within these ecosystems. The River Flow Health Index method is used to investigate the hydrological alterations of the Katse Dam on the Malibamatso River. The method utilizes river discharges for 1986–2021 at a downstream gauge station in the basin. 171 hydrological parameters evaluated from the river flows are used to estimate the River Flow Health Index, which measures the conditions before and after the dam operation. The departure of the river flows from the natural state is provided on a 0–1 scale. Under the prevailing reservoir operation, substantial hydrological alterations are observed, especially for the rate of change component. In general, the Katse Dam impoundment alters the hydrological regimes, with the River Flow Health Index of 0.515 suggesting major alterations in different flow regime components. The study provides major insights for river scientists and managers to re-operate the dam and re-implement environmental flows to restore natural flow conditions.