River water temperatures (July, August, September)
Winter river water temperatures were mostly in the range 4-12oC in both islands and a little lower in alpine-fed rivers of South Island. There is the usual trend of decreasing temperature with increasing altitude (moving into mountainous areas) and a weaker trend of decreasing temperature moving south (increasing latitude).
The temperature anomaly map shows that river temperatures were near-normal for winter over most of the country, although rivers in Northland, and parts of South island were unusually cool.
River water temperature, July — September 2015.
Temperature anomaly, July — September 2015.
Visual clarity of rivers (July, August, September)
Visual clarity of New Zealand rivers over winter ranged widely (from <0.2m to >6 m) – reflecting the wide range of soil and rock types interacting with vegetation cover. Rivers in clay soils and under pastoral land use tend to have low clarity.
The clarity ranking map shows that numerous rivers were appreciably clearer than typical, particularly in the east of both islands, probably reflecting atypically low flows.