Water quality maps and information, Summer 2015

River water temperatures (OND)

River water temperatures (JFM)

Summer river water temperatures were mostly around 20oC in North Island and a little cooler in South Island. As is usual there is a weak trend of decreasing temperature moving south (increasing latitude) and somewhat stronger trend of decreasing temperature with increasing altitude of catchments, particularly in the South Island. The temperature anomaly map shows that river temperatures were unusually warm in south-central North Island and central South Island. Conversely some Bay of Plenty and East Cape rivers, and also rivers in Southland, were cooler than usual.

Temperature, Freshwater 65 Anomaly map FU 65

Visual clarity of rivers (JFM)

Visual clarity of rivers across New Zealand ranged widely (from about 20 cm to more than 10 m over the past summer), as is typical, reflecting the diversity of soil and rock types (rivers draining clay soils and/or weak rocks tend to be turbid) and vegetation cover (rivers draining livestock pasture are characteristically less clear than rivers draining forest). Flow state also strongly influences visual water clarity, and rivers are typically clearer under lower flow conditions. The visual clarity ranking map shows that most rivers across the country were comparatively clear through summer, and some were unusually clear, probably reflecting low flows in a fairly dry summer.

Clarity map FU 65 Ranking map FU 65