River water temperatures (OND)
Spring river water temperatures were mostly in the range 8-16oC in South Island and a little warmer in northern and coastal North Island. The usual trend of decreasing temperature moving south (increasingly latitude) is present but quite weak, and there is a more definite trend of decreasing temperature with increasing altitude of catchments. The temperature anomaly map shows that river temperatures were fairly typical for spring over much of the country, but unusually cool with snow melt in some large alpine rivers (e.g., Waimakariri, Hurunui, Haast), and also in central and lower North Island – possibly reflecting a rather cold wet spring. Conversely the Motueka River (northern NI), Hutt River (near Wellington) and Waipaoa River (near Gisborne) were all unusually warm.
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Visual clarity of rivers (OND)
Visual clarity of rivers through spring ranged widely (from <0.2m to >6 m) across New Zealand. This reflects the diversity of soil and rock types (rivers draining clay soils and/or weak rocks tend to be turbid), vegetation cover (rivers draining livestock pasture are characteristically less clear than rivers draining forest) and flow state (rivers are generally clearer under low flow conditions). The visual clarity ranking map shows that many rivers were unusually clear, particularly in northern NI, south-eastern SI, and central NZ (the Motueka, Waiau and Hutt Rivers) – probably reflecting lower than typical flows. The Whanganui River near Wanganui City was unusually turbid.
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