The colonial exploration of the Upper Wairau in April 1855 saw Travers, Locke, Maling and Oldham accompanied by Maori guides heading into the region, and in their descriptions of the journey they wrote:
“… Te Kopi o Uenuku (the Rainbow River) had its source in the mountains above Lake Rotoroa”.
The Nelson Examiner
published a number of original articles written by Travers, the first of these was dated 5 May 1855. In his articles, Travers described the explorers slog through foul weather into the area, before being forced to turn back from somewhere near Tarndale. A few years later, on 14 March 1860, Travers reported:
“From the size of the river at the point where we first struck it, and from the appearance of the valley towards the north, I should suppose the river-course to this point to be about 10 miles, through a glen bounded on either side by rugged mountains, the Clarence, the Wairau, and the Te Kopi-o-Wenuku or Rainbow River, rising amongst those which lie on its eastern side”.