Changes to water monitoring programme includes more sites

Waikato Regional Council will trial modelling as part of next summer’s recreational water quality monitoring programmes to assess risks at a greater number of sites.

Proposed changes to the monitoring programmes and a summary of the 2021-2022 summer recreational monitoring in fresh water, estuaries and open-coast beaches were presented at the Environmental Performance Committee meeting yesterday.

Monitoring manager Ed Brown said the changes, including modelling information to include more river sites and greater use of education via web platforms and signs, would better empower people to decide where and when to go swimming.

“This modelling of E. coli health warning levels has been assessed by our staff using data from our existing long-term monthly monitoring of 125 sites and has shown that E. coli levels across the 125 sites can confidently be inferred by only taking water samples at those 16 sites.

“We will be trialling using the monitoring results of those 16 reference sites to estimate E. coli levels across the remainder of the region for unmonitored rivers.

“Some other regional councils are already using a mix of monitored and modelled results, for example Wellington and Auckland.”

Mr Brown said the council would also extend reporting to a greater number of lakes where the risk of harmful algae blooms was often high.

“With these lakes, actual sampling may give a false impression that it’s OK to swim there as the monitoring may give a green light for swimming but, in actual fact, the situation at these lakes changes quite dramatically, say when the wind changes direction causing algae to accumulate on the opposite shore.

The council will look to create permanent alerts for high-risk lakes on the “Can I swim here” LAWA page using available information.

The council has implemented recreational water quality monitoring programmes during the summer months since 1985.

The programmes currently include 34 monitoring locations at popular open-coast, estuary, river and lake sites.

During the 2021/22 season, faecal indicator bacteria concentrations and/or cyanobacteria counts exceeded guideline values on several occasions.

• Open beaches were mostly suitable for swimming, with two exceedances of the guidelines for enterococci, one at Buffalo Beach and Port Waikato Beach.
• Five estuary sites were monitored this summer for enterococci and E. coli bacteria at sites in Kāwhia, Maraetai Bay, Raglan, Tairua and Whangamatā. There were five exceedances above the enterococci guideline, four at the Tairu Pepe Stream and one in Kāwhia; there were four exceedances above the E. coli guideline, one at Raglan motorcamp and three at Tairua Pepe Stream
• Nine river sites were monitored weekly for E. coli from December to February (excluding Waikato River hydro-lakes), with 22 exceedances above the recreational guideline. All rivers sampled were impacted except for the Waikato River at Horahora domain, where all results were suitable for swimming.
• Water quality in lakes is measured for E. coli (Lake Taupō and shallow lakes) and cyanobacteria bio volume (Lake Taupō, shallow and hydro-lakes). There were three exceedances of the recreational guideline for cyanobacteria in Lake Ohakuri and one exceedance in Lake Maraetai.