This is the Wairoa River, flowing north into Tauranga Harbour at the western end of the Bay of Plenty on the North Island. Back in the mid-1970s, there was a plan for a hydroelectric power scheme here, proposed by the Tauranga Joint Generation Committee, involving both this river and the Opuiaki River. A group called the Kaimai Canoe Club, which had just been formed by Barry Anderson, Bill Ross, Kerry Smith, and Peter Entwistle, actually fought against it. They argued at the water rights hearings that it would ruin the fishing, sports, and recreation for everyone, now and in the future.
They ended up reaching a compromise: water would be released 26 days a year specifically for whitewater recreation. If you follow the river, you'll see the last dam diverts water around the riverbed to the Ruahihi Power Station. TrustPower is currently the manager of the power scheme on the river.