The reserves namesake is the Great Selati River, which traverses the northern sector of the reserve, flowing east to west. The water quality is affected by upstream agricultural activities and mining activity in the general vicinity.
In 2014, the Selati Research Initiative, in partnership with the South African Environmental Observation Network (SAEON), began assessing the quality of water at various points along the river. By taking measurements at different river stations, we can observe whether there are any significant changes in the aquatic biodiversity, both inside and outside the reserve. This information helps us conclude the general health of the river system, allowing us to further assess the viability of the system to self-sustain the diversity of aquatic life within the reserve.