The Taranaki Regional Council says the overall health of its rivers and streams is improving.
The latest State of the Environment monitoring, which provides longer term water quality trends, shows ecological health has improved at 40 out of 57 sites, compared with a less positive picture two years ago.
Ecological health measures life forms found in rivers and streams.
The reports show nutrient and bacterial counts were mostly stable or had reduced, although bathing sites are not tested during high rain falls when levels are likely to be higher.
The council's environmental quality director, Gary Bedford, says bugs and insects are returning in ever-increasing numbers to the mid-catchment areas of rivers and streams especially, which is great news.
He says many factors, including riparian fencing, have helped.
"Many dairy farm effluent systems have been upgraded. Farmers are controlling their nutrients on their paddocks far better, so that they're not getting run-off of excess nutrients but they're actually utilising what they put on.
"All these measures together are showing now the benefits in terms of improved stream health as far as we can work out."
Mr Bedford says stopping large discharges from industry, such as the Eltham wastewater treatment plant into the Waingongoro River, has also made a difference, but there is still room for improving water quality.
The council is reviewing its fresh water plan which may stop Taranaki farmers putting water from treated effluent ponds into waterways.