"Immediately downstream of the Gravelotte road bridge, the Selati River is partially impounded by a series of 10 small weirs over a distance of some 20 kilometres.  These weirs mark the points where irrigation water is abstracted for large-scale commercial irrigation farms.

In its upper reaches, the Selati River is perennial.  However, the combination of little or no inflows from seasonal tributary streams in its middle and lower reaches, coupled with large-scale water abstractions in the middle reaches, has resulted in the Selati River being a seasonal river over most of its lower reaches.  At the town of Phalaborwa, discharges of treated domestic effluent and seepage from large-scale tailings dams provide a source of “perennial” flows for the final few kilometres before it joins the Olifants River.  In effect, the final few kilometres of the Selati River only contain effluent during the dry winter months, though this becomes “diluted” when normal summer flows resume." (Ref 2)