Our latest water quality data from around the country, showing results from July to September 2011.
River water temperatures were fairly typical for winter months with no large anomalies, although temperatures of the Hurunui and Waimakariri Rivers (Northern Canterbury) were colder than usual. River water temperatures ranged from <4oC in the southern South Island and alpine catchments to >12oC in the north of North Island - showing the typical trend with altitude super-imposed on a weak (S-N) latitudinal trend.
Visual clarity ranges widely, being typically high in catchments draining erosion-resistant rocks and low in areas of soft sedimentary rock and in pastoral catchments – with the Waipaoa River near Gisborne being unusually 'turbid' (as is typical). Visual clarity was fairly typical at most river sites consistent with fairly normal flows in the past winter (visual clarity is strongly inversely related to flow condition in rivers). However, there were some high to very high visibilities recorded in Northland, Bay of Plenty, Wairarapa (Ruamahanga R.), and central SI (Haast R. and Opihi R.) all apparently attributable to lower than normal flows. The lower Mataura River (Southland) had high flows and unusually low clarity.
Note that the data are preliminary, and subject to amendment after quality assurance procedures. We thank NIWA field teams, regional and district councils, and hydro-power companies for providing this information.
