National indicator data for river condition in New Zealand

National indicator data for river condition in New Zealand - collected by Regional Councils and the National Institute of Water and Atmospheric Research (NIWA), collated and processed by NIWA and protected by copyright owned by the Ministry for the Environment on behalf of the Crown. The dataset consists of physical-chemical water quality and macro-invertebrate data from the regional council State of Environment (SoE) and National River Water Quality Network (NRWQN) programmes. The physical-chemical water quality variables are water clarity (CLAR), Escherichia coli concentration (ECOLI), nitrate-nitrogen concentration (NO3N[1]), ammoniacal nitrogen concentration (NH4N), total nitrogen concentration (TN), dissolved reactive phosphorus concentration (DRP), total phosphorus concentration (TP), temperature (TEMP), dissolved oxygen concentration (DO[2]) and percent saturation (DOSAT), suspended sediment (SS), and turbidity (TURB).

The invertebrate variables are taxa lists and counts or coded-abundance classes for each taxon. The raw invertebrate data were post-processed to generate four variables: total number of taxa in a sample (TAXA), the number of taxa from the insect orders Ephemeroptera, Plecoptera and Trichoptera (EPTtaxa), the percentage of individuals in a sample from EPT taxa (%EPTabund), and the Semi-Quantitative Macroinvertebrate Community Index for hard-bottom streams (SQMCI-hb). REC reach numbers where added to site information based on best guesses.

In the dataset used for the 2012 study, the start dates for all monitoring site records were 1 January 2006 or earlier, and the end dates ranged from June 2009 to February 2012. The range of end dates poses some potential problems due to temporal variation in water quality. Further, we carried out temporal trend analyses in the current study and recent data were needed to ensure that the analyses corresponded to recent conditions. For these reasons we requested updated physical-chemical water quality data from five regional councils, to fill the most severe gaps in recent data. Each of the five regional councils provided updates, and the ending dates in the current dataset range from January 2011 to December 2012. Note that start and end dates can vary among sites within councils, and among variables within sites.