We do routine monitoring of river water quality under two main programmes. This monitoring provides information on the condition of the water so that we can assess its suitability for desired uses (for example, supporting healthy ecosystems, human recreation). The programmes are:
We have 10 sites on the Waikato River and 105 sites on other rivers and streams (including five NIWA sites).
Sites are grouped into two river reaches (upper and lower reaches of the Waikato River) and seven zones.
|River reaches and zones||Number of sites|
|Upper Waikato River||5|
|Lower Waikato River||5|
|Inflows to Lake Taupō||13|
|Upland tributaries of the Waikato River||12|
|Lowland tributaries of the Waikato River||26|
|Waipa River and tributaries||16|
Each site is visited at monthly intervals.
The Waikato Regional Council began monitoring sites on the Waikato River between 1980 and 1987. The regional rivers programme started monitoring between 1993 and 1994.
Water quality is measured by taking some measurements on site (for example, water temperature and water clarity) and taking samples of water back to the laboratory for analysis. More than 20 water quality variables are measured, including:
Three categories of water quality for ecological health were developed: excellent, satisfactory and unsatisfactory. These were based on ‘critical values’ for seven water quality variables we identified as relevant to the suitability of river water for ecological health:
Check out the table below for critical values for the three categories that were derived from national or other standards and guidelines, and from expert opinion.
At each monitoring site, the proportions of all samples collected during 2013-2017 for a given water quality variable which met the standard for excellent water quality were determined. Similarly the proportions which met the standard for satisfactory and unsatisfactory water quality were determined. This process was undertaken for all seven variables.
At each site, the average value of the proportions found to be ‘excellent’ for each of the seven variables was calculated. Average proportions for the ‘satisfactory’ and ‘unsatisfactory’ categories were also calculated.
The results for the individual sites were then aggregated according to site location. Results from the Waikato River sites upstream of Lake Karapiro were aggregated into an ‘Upper River’ result, while the other sites were aggregated into a ‘Lower River’ result. The results for the other sites were aggregated into seven ‘water zones’.
The table below lists the water quality guidelines and standards used.
|Water quality variable (units)||Relevance||Categories|
|Dissolved oxygen (% of saturation)||Oxygen for aquatic animals to breathe||>90||80–90||<80|
|pH (acidity)||Can affect plants and fish||7–8||6.5–7 or 8–9||<6.5 or >9|
|Turbidity (NTU)||Can restrict plant growth||<2||2–5||>5|
|Ammonia (g N/m3)||Toxic to fish||<0.1||0.1–0.88||>0.88|
|Temperature (°C)||Fish spawning May-Sep||<10||10–12||>12|
|Fish health Oct-Apr||<16||16–20||>20|
|Total phosphorus (g/m3)||Causes nuisance plant growth||<0.01||0.01–0.04||>0.04|
|Total nitrogen (g/m3)||Causes nuisance plant growth||<0.1||0.1–0.5||>0.5|
The aggregation of river water quality data within a zone or reach ignores any differences between the sites in a given zone or reach.
Tulagi, A. 2017. Waikato River Water Quality Monitoring Programme: Data Report 2016. Waikato Regional Council Technical Report 2017/14. Waikato Regional Council, Hamilton.