This river has a 68,000ha catchment, which is largely pristinehttp://www.protectedplanet.net/sites/Mokihinui_Forks_Ecological_Area and within the conservation estate upstream of the coastal region. There are two small settlements in the low reaches and two large farms, one at the river mouth, the other in Seddonville, behind the coastal range. The Seddonville farm is a large industrial dairy farm that in 2004 was still discharging all dairy effluent into the river. It took a concerted effort on the part of local environmentalists to get the regional council to insist on the farm installing effluent ponds. These ponds then largely discharged into the river via a drain for many years, and were washed out during floods until a particular complaint in 2016 got the regional council to insist on an upgrade, and a shift to above the floodline. In September 2017 milk was discovered being discharged into the river via that same drain. Erroneous reporting in the local paper protected the farmer; it is not clear whether the erroneous reporting was the police, the regional council or reporter.Westport News 2017.09.26 https://www.wpn.co.nz/ Evidence points to the dairy company refusing the milk due to unacceptable penicillin levels. There does not appear to be any contingencies provided on the West Coast for milk rejected by Westland Milk Products. It is unsafe to venture down McIndoes Rd, where the milking sheds and effluent ponds are, due to farmer aggression. There has also been extensive land use change over the last decade on this farm, where 60ha or more of forest remnants/ wetlands have been destroyed for humped and hollowed pasture. Agrichemicals and fertilizers are indiscriminately discharged onto pasture, creating non-point discharge into the river, where algal build-up during low flow often creates thick, opaque mats, although these have decreased from their worst around 2010. The river at the popular swimming hole in Seddonville is perhaps cleaner in summer 2019 than it has been in many years, but there is still plenty of room for improvement.
