Swim spots in Tasman among best
Tackling the source of seasonal E coli in Golden Bay’s Tukurua Stream has helped boost the region’s swimmability rates.
The latest Tasman District Council summer recreational bathing water monitoring report reveals a 98.6 per cent compliance rate with the national microbiological water quality guidelines in dry weather conditions for summer 2016-17.
That’s up from the average 97 per cent dry weather compliance rate over the past 10 years. Over all weather conditions during summer 2016-17, almost 95 per cent of the sites sampled met the guidelines.
A 98.6 per cent rate is also higher than Ministry for the Environment-commissioned modelling, suggesting that ‘‘swimmability’’ in the district is 97 per cent, which puts it second nationally behind the West Coast.
Deputy mayor Tim King said the report reaffirmed ‘‘what we already know – that our district provides some of the best places to swim in the country’’.
In a report outlining the results, TDC resource scientist Trevor James and environmental monitoring officer Jonathan McCallum say high levels of faecal indicator bacteria in Tukurua Stream has been an ongoing problem for years and many investigations have been undertaken to determine the source.
‘‘These high levels have nearly always occurred during/after rain, and often during dry weather,’’ they say in the report.
‘‘Prior to this season a third significant on-farm source was found in the form of a winter feed pad. Even though the discharge from the pad occurred out of the bathing season, faecal bacteria are well known to be stored in the bed and bleed off into the water column over many months following removal of the source.’’
The feed pad was identified in July 2016 and rectified before Christmas.
In total, seven freshwater and six marine sites were sampled for faecal indicator bacteria between mid-November 2016 and early March 2017.
All sites were sampled weekly, except during December to January when they were sampled twice weekly.
There were 16 exceedances found in the 286 samples taken. Seven of those were at three freshwater sites: five at Tukurua and one each at both the Lee and Roading rivers.
The nine coastal exceedances were at Pohara, which had four, Ligar Bay with three, and one each at Kaiteriteri and Rabbit Island.
The report says that for most sites, particularly freshwater sites, an exceedance of the microbiological water quality guidelines is likely after more than 20mm of rainfall in 24 hours.
‘‘To keep the public aware of this risk, council issues standard guidance for people to avoid swimming within 48 hours of rain.’’
King said the good results did not mean TDC would be lessening its ‘‘vigilance on water quality’’.
‘‘However, results as consistently good as we have been receiving throughout the district’s main waterways and beaches mean we can now concentrate on smaller tributaries and their local environment to eliminate the risk to our major rivers,’’ he said.
The results were ‘‘due in no small way to the work landowners and volunteer groups working with the council do to manage the land and activity around our waterways’’.
Sampling is set to occur at a larger suite of 20 bathing sites next summer.