The amount of E. Coli in Taranaki rivers will have to drop between 60 and 90 percent to achieve the government's "swimmability" targets, according to a new report.
Photo: RNZ / Rebekah Parsons-King
In 2017, as part of the National Policy Statement for Freshwater the government set a target of 80 percent of large rivers being "swimmable" by 2030, and 90 percent by 2040.
In Taranaki the aim is 67 percent of large rivers - by length - will meet the swimmable standard by 2030.
But new research done by consultants Land Water People - for the regional council - indicates that will be difficult to achieve.
It estimates only 20 percent of the region's rivers currently meet the standard "for primary contact".
In rivers concentrations of E. Coli - an indicator bacteria for the presence of pathogens that could make humans sick - are used to predict the risk of infection to people ingesting water during water-based activities.
"Swimmable" is defined as being in Band C or higher under the National Objective Framework for E. Coli where Band A is rated top and Band E is bottom of the class.
In Band C, E. Coli levels can exceed 540/100ml 10 to 20 percent of the time and the predicted average infection risk is 3 percent.
At time the national standards were set a Ministry for the Environment taskforce estimated 39 percent of Taranaki rivers (by length) and 97 percent of its lakes were swimmable.
It reckoned interventions under way in Taranaki including the regional council's riparian planting programme and the diversion of dairy shed effluent to land, could result in about 67 percent of the province's large rivers being swimmable by 2030.
The regional council argued that was too optimistic.
It's Our Place: Taranaki State of Environment 2022 report revealed only two monitored freshwater sites had achieved the swimmable standard between 2015 and 2020.
It found E. Coli concentrations had also increased at 70 percent of its monitored sites over the last 10 years.
Waiwhakaiho River at New Plymouth has a permanent health risk warning not to swim there posted. Photo: RNZ / Robin Martin
The regional council set itself a more modest target of 50 to 55 percent of rivers reaching swimmable standard by 2030.
Now the Land Water People research has reinforced how difficult it will be to achieve even that goal.
It divided the region's rivers into three management classes defined as mountain, hill and lowland rivers, with corresponding objectives of A, B and C band, respectively.
This approach acknowledged that lowland rivers would be most impacted by upstream land use activities and were in the poorest current state.
The results of the analysis illustrated that reductions in E. Coli loads of approximately 60 to 90 percent would be required to achieve freshwater objectives in Taranaki.
The report did not address what measures would be required to achieve E. Coli load reductions, how those limits might be implemented, or over what timeframes.
The regional council will consider the report tomorrow.
