The West Coast Regional Council focuses its monitoring effort on waterways where there is human activity rather than keeping track of water quality across the entire region. Therefore results indicate the level of impact of human activities in the minority of catchments where people live. Monitoring sites are designed to cover a representative combination of the major land use activities, e.g. mining, agriculture and urban drainage. Sampling of bugs in streams () shows water quality is good in the top three quarters of monitoring sites, with the bottom quarter consistently rating moderate to poor. There has been some recent improvement in results for , , , and .
Nutrient monitoring in the Grey and Buller rivers indicates that while ammoniacal nitrogen has decreased, other forms of nitrogen - total nitrogen and nitrate - have increased. Nitrogen levels, although increasing, are still low. The region’s frequent rainfall means we seldom see any algal growth related to high nutrient levels.