Bathing water quality in streams

Image/logo for showing indicator 'Steady'.

Escheria coli (E.coli) counts at bathing sites 

Purpose of indicator

Monitoring bathing water quality provides an indication of whether or not water is safe to swim in and enjoy. Run-off from surrounding land can contain bacteria such as E.coli which at elevated levels is a health risk to humans. Vegetated riparian margins and exclusion of stock help to reduce this risk.

Current information and trend

Popular recreational bathing waters and shellfish beds are surveyed annually over warmer months from October to March by Bay of Plenty Regional Council. The surveys monitor and identify risks to public health from pathogens indicated by E.coli, which is an indicator of faecal matter. This information is used by public health services and local authorities to assess the risk to human health and to inform the public whether it is safe to use these waters. Table 1 shows the Ministry for the Environment and Ministry of Health ‘traffic light’ system guidelines, using sample counts to determine recommended action or management response.

Since 2005/06 most surveyed sites shown in figure 2 have remained relatively stable. Rotoehu Soda Springs shows some improvement since 2005/06, likely due to land management improvements around the springs in 2006. The Ngongotaha and Puarenga Streams have been non-compliant with recreational guidelines at times, due to a combination of environmental and human induced factors, and seasonal variations. For example, bacteria levels in the water during wet summers are often high when compared with dry summers. During a wet summer with frequent rain more faecal matter (E.coli) is contained in run-off from land into rivers, streams and lakes. Ngongotaha stream has shown some improvement following riparian vegetation planting.

Table shows 'traffic light' system guidelines 
 
Table 1
Source: Ministry for the Environment and Ministry of Health, 2011
 
Line graph for the trends in Log E.coli
Figure 2. Trends in Log E.coli counts per 100 ml of sample
Source: Bay of Plenty Regional Council, 2011

The sites shown here are located in the Bay of Plenty Regional Council area of the Rotorua district. Future reporting will also show water bodies monitored in the Waikato Regional Council area of the Rotorua district.

In Summary

  • Most streams show a steady state of faecal counts
  • Ngongotaha Stream has shown improvement following riparian planting
  • Rotoehu Soda Springs has improved (less numerous) E.coli counts, likely due to land management improvements
  • Ngongotaha and Puarenga Streams have been non-compliant with recreational guidelines at times, often during high rainfall.
 
Page reviewed: 21 Jan 2016 11:26am