Waipoua River 20130219.pdf - Northland Regional Council

Figure 4 Monitoring sites in the harbour and its catchment3.2 Water quality and the river ecosystemThe ecological health, or integrity, of the river ecosystems are related to a number ofenvironmental factors including, but not limited to, the availability of suitable habitat types(e.g. diverse range of substrate sizes, aquatic plants, large woody debris and varied flowtypes), food and light availability, disturbance and high water quality. It is important to notethat the relationship between ecosystem health and environmental factors is often verycomplex and unpredictable.In rivers the water quality parameters of concern in terms of ecological health are, in noparticular order, temperature and dissolved oxygen, clarity, nutrients, suspended solids.Faecal pathogens are not known to affect aquatic ecosystems. The state of water qualityfrom a human health perspective is discussed in section 3.2.5 below. Biological monitoringinformation, such as invertebrates, periphyton, habitat assessment and fish, can be used tohelp determine the impacts of water quality, if any, on river ecosystems, however, asmentioned above causal effects are not always clear.The Council has adopted a river classification based on a system developed by Cawthron(Wilkinson, 2007). Rivers are classified into five classes; Excellent, Very Good, Moderate,Degraded and Very Degraded, based on a number of connected water quality indicators;nutrients, physical properties, clarity, bacteriological and invertebrates (Table 4).22