Horizons Regional Council swimming water quality testing under way in Whanganui-Manawatū

One of Horizons' #swiminourregion winning photos from last summer, taken at Vinegar Hill by Tui Bolger.

Weekly water quality testing is under way at swimming spots throughout the Whanganui region.

It's part of Horizons Regional Council's annual summer swim spot programme which monitors bacteria levels at more than 80 recreational sites in Manawatū-Whanganui between November and the end of April.

Horizons natural resources and partnerships group manager Dr Jon Roygard said the council collects, analyses and reports on swim spot monitoring over summer through the "Can I Swim Here?" module on the LAWA website to inform the public on when and where they can swim.

"Weekly water samples collected from each site are sent to an independent accredited lab for testing," Roygard said.

"Results are received within 48 hours and are updated on LAWA, as well as Horizons' website where interactive maps show each of the swim spots marked by a red, amber or green location maker to indicate that week's bacteria results.

"However, we do urge public and their animals to stay out of the water if they are at a river and see black, slimy mat-like growth on the stones that may also be musty smelling. In lakes, potentially toxic algae are visible as bright green 'blooms' with surface scum often found at the lake edge."

Because sampling is weekly, the results may not reflect the water quality for the whole week, especially if it has rained. Roygard said generally it is safe to swim if the water looks clear or it's three days after rainfall.

Information about swim spots is online at www.lawa.org.nz and www.horizons.govt.nz/managing-natural-resources/swimming