A Christchurch-based environmental consultancy has found swimmability in Horizons Region waterways improved 5 to 8 per cent between 2006 and 2016.
The independent study was by LWP, and commissioned by Horizons Regional Council and the Ministry for the Environment. It was part of the information needed to determine whether progress is being made on government's swimmability targets.
It focused on just two factors that influence swimmability - the sediment that affects water clarity and the presence of the faecal coli form bacteria E.coli.
Other water quality factors, such as nutrient loading and the health of freshwater life, will be looked at in time.
The report found a whole array of changes had contributed to the improvement. Among them were upgrading sewage and factory discharges, fencing and planting waterways and planting the most erodible land.