This map shows river and stream sites monitored for Escherichia coli (E. coli) in the Waitaha Canterbury region in 2024/25. Sites are coloured according to grades that predict the average risk of bacterial infection for swimmers from random exposure. Grades A, B, and C (blue) correspond to infection risks of 1%, 2%, and 3% respectively. Grades D and E (dark blue) correspond to infection risks greater than 3% and 7% respectively.
| E. coli grades at monitored sites for rivers and streams | 2023/24 | 2024/25 | ||
|---|---|---|---|---|
| Percentage | Number of sites | Percentage | Number of sites | |
| Sites graded A | 31% | 29 | 29% | 30 |
| Sites graded B | 18% | 17 | 18% | 19 |
| Sites graded C | 7% | 7 | 8% | 8 |
| Sites graded D | 24% | 23 | 26% | 27 |
| Sites graded E | 20% | 19 | 19% | 20 |
| Totals (percentage; sites) | 100% | 95 sites | 100% | 104 sites |
Escherichia coli (E. coli) is a type of bacteria commonly found in the gut of warm-blooded animals (including people) and is excreted in faeces. The presence of E. coli in rivers and streams indicates faecal contamination, and the possible presence of other pathogens that could be harmful to human health, causing infections such as gastroenteritis.
Sources of E. coli outside of the body typically include human or animal waste discharge, bird droppings and stormwater run-off. E. coli can survive for long periods in the environment. If land or soil is contaminated with E. coli, rainwater seeping through the soil or irrigation water running off land can carry the bacteria into rivers, streams or groundwater.
Under the Canterbury Land and Water Regional Plan (CLWRP), there are freshwater quality outcomes for E. coli as required by the current legislation at that time, namely the National Policy Statement for Freshwater Management 2020 (NPS-FM) and the National Objectives Framework. When a site has exceeded health standards for E. coli, the water quality is not suitable for recreational activities involving contact with the water.
Monitoring and reporting on sites and concentrations of E. coli lets communities know about bacterial risk to swimmers and where we need to take further action to improve river water quality.
We visit over 100 river and stream sites monthly to collect freshwater samples. We sample for a range of water quality parameters, including E. coli. The sites we monitor cover a variety of river types and locations, from large alpine-fed braided rivers to small spring-fed streams.
Sampling follows Environment Canterburyβs standard procedures for the collection of freshwater quality samples, which is consistent with the National Environmental Monitoring Standard for river water quality sampling and data processing (NEMS, 2019). Water samples are sent to an accredited laboratory where they are tested using nationally approved methods. Lab results are electronically transferred to Environment Canterbury. Each monitored site is assigned a grade (AβE) which denotes the risk of bacterial infection, based on using E. coli concentrations as an indicator. Grades for a site are calculated based on the past five years of E. coli data using the attribute bands in Table 9 of Appendix 2A in the NPS-FM.
As the regional council for Waitaha Canterbury, we work with ngΔ Papatipu RΕ«nanga and our communities to set and implement environmental policies and rules that establish how resources, including river water, can be used sustainably. The NPS-FM and the National Objectives Framework set thresholds for both E. coli concentrations and the frequency that E. coli concentrations are exceeded based on infection risk through contact with river water. The CLWRP includes freshwater outcomes for E. coli in Canterburyβs rivers based on values for human health.
Environmental regulation and protection is a core service of Environment Canterbury. To help achieve outcomes, we undertake targeted consent compliance monitoring around the region. Consenting helps to sustainably manage and protect our natural environment and resources. We aim to avert environmental risks before they become incidents and cause damage. We work with land managers, individuals, and industry to improve compliance and ensure positive long-term environmental outcomes.
Our state of the environment monitoring programme enables us to measure and report on changes in freshwater quality, including reporting on E. coli in rivers. Monitoring and reporting tells us whether the actions weβre taking to address degrading water quality are having the desired effect over a reasonable timeframe.
Central government sets policy direction at a national level for local authorities to implement through laws, national policy statements and environmental standards.
Water users are required to comply with the rules and standards set out in regional plans. Consent holders are responsible for complying with conditions in their resource consent that are designed to maintain and protect Canterbury's natural resources.
Many landholders and water users go well beyond simply adhering to the rules and strive to improve environmental outcomes for water through best management practices and active restoration. Many community organisations are involved in riparian and wetland restoration work and contribute to our understanding of the environment through citizen science.
Data for monitored sites are updated annually on the Land Air Water Aotearoa (LAWA) website and River Quality topic.
You can also view our Water quality for contact recreation: Annual Summary Report 2023β24 Season (JPG file, 106KB).
