The Auckland Council operates a long-term river water quality monitoring programme
throughout the region. The objectives of this monitoring include State of the
Environment (SoE) reporting, identification of major environmental issues and the
assessment of the efficacy of council policy initiatives and strategies. This report
provides a summary of the data collected during the 2015 calendar year.

Water quality is assessed monthly at 36 sites around the region covering a range of
parameters using a combination of field and laboratory based measurement. The
results are presented as box plots, which display the annual variation in the measured
parameters at each of the sites, and in tables, which provide a statistical summary of
each parameter at each of the sites.

Further, the data was used to produce water quality indices, which allowed sites to be
ranked and assigned a water quality class. This analysis allows the complex water
quality data to be communicated in a simple form. In 2015 the rivers with the highest
ranked water quality class were the Wairoa Tributary and West Hoe streams, followed
by Cascades Stream (Waitakere) and Opanuku Stream. The catchments of these
streams are mostly dominated by native forest. These were the only four sites
classified as having ‘excellent’ water quality in 2015. Poor water quality was observed
in streams with a mix of urban and rural land use, with Omaru Creek having the lowest
ranked water quality of those sites monitored.

Auckland Council technical report, TR2016/034

August 2016