Monitored sites in the Te Wharau catchment
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Te Wharau
The Banks Peninsula Zone (BPZ) has an area of 8010 km2 and forms the most prominent volcanic feature of the South Island. Geologically the peninsula comprises of the remnants of two large volcanoes which means streams in this area have naturally higher phosphorus concentrations than other waterways in Canterbury. There has been vast vegetation clearance with estimates suggesting native forest once covered 98% of the peninsula, however less than 2% remains today.
Main pressures on streams within the BPZ come from agricultural activities, which results in further land modification, vegetation clearance and subsequent increased phosphorus runoff into the waterways. Because these streams are naturally higher in phosphorus, they are susceptible to excessive nutrient concentrations which may lead to degraded water quality and poorer instream aquatic communities.
Whilst streams within the BPZ, typically have high dissolved phosphorus concentrations they have relatively low dissolved nitrogen concentrations. This is largely due to phosphorus-rich soils and generally low input from groundwater. Bacterial concentrations are often very high due to the steep terrain and difficulty fencing out stock from streams draining the steep gullies. Good riparian management in this catchment can assist in reducing the likelihood of excessive phosphorus and bacteria entering streams.
Environment Canterbury
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