Okarahia Stream

Ten sites are monitored in the WHZ as part of Environment Canterbury’s state of environment monitoring programme. These sites represent upper and lower reaches of alpine, hill-fed and spring-fed rivers.

As with many areas in New Zealand, increasing pressure is being placed on our water resources with intensifying landuse and increased demand for water take, with lowland areas being the worst affected. The best water quality is often observed in the upper reaches of rivers where there has been less degradation and anthropogenic activity. The poorest water quality is typically found at sites the further near the coast where waterways are under pressure from increasing landuse intensification.

The upper reaches of the WHZ have high water quality, low nutrient and bacteria concentrations. This is typical of alpine-fed rivers, with natural vegetation dominating the upper catchment. In the lower reaches of the catchment nutrient concentrations and bacterial indicators increase. Sources of bacterial contamination are likely to include the effects of intensive land use in the middle catchment area and birds colonising the riverbed. The bacterial quality of the river at SH1 is often poor during summer, which compromises the recreational value of the river.