Freshwater Update 78, September 2018

Freshwater Update 78 brings you the latest information from our Freshwater & Estuaries Centre, with articles that cross a broad spectrum of freshwater research, from archives to aquifers, periphyton guidance, geo-engineering and swimmability.

The value of archived biological collections: understanding the lake snow invasion

The diatom (Lindavia intermedia) that causes lake snow—nuisance slime in clean-water lakes that ruins angling and can block water intakes—was apparently introduced to New Zealand shortly before 2002, but was widespread by 2005. To obtain a clearer picture of when this diatom arrived in New Zealand, Otago Regional Council (ORC) commissioned NIWA to search archived diatom data and collections.

‘Swimmability’ of New Zealand rivers

Swimming is a popular activity in Aotearoa-New Zealand. Two attributes of waters that strongly affect aesthetic quality and safety for swimming are visual clarity and faecal contamination. It turns out that these two attributes are fairly well-correlated (inversely) in New Zealand rivers, such that (easily seen) visual clarity provides a rough-but-useful guide to (unseen) microbial quality.
Research subject: LakesRiversWater Quality