Protecting our water quality

City Forests has worked with the Otago Regional Council to set up appropriate water and watercourse monitoring system for key waterways in the company’s forests.  Semi-permanent sample points are established in streams that are adjacent to impending, current, or post-harvesting operations, and are intended to monitor for changes in water or watercourse quality due to harvesting operations.

Attributes assessed are:

  • Water clarity (SHMAK rating)
  • Water temperature
  • Water conductivity
  • Any evidence of substrate sedimentation
  • Invertebrate types
  • Condition of riparian vegetation.

Evidence of such monitoring consistently shows the benefits of well-managed plantation forests to stream water quality, especially when compared to streams that cross farmland.

Some of City Forests’ plantations form part of Dunedin’s water catchment network, including Flagstaff and Ross Creek forests. This demands diligent monitoring and maintenance of the water quality whenever there is harvesting or roading activity taking place in the catchment.

Currently, active water sampling points are established in significant waterways. In 2023, 12 of these have been measured according to our monitoring protocols.  The water quality was consistently good or excellent as usual. Water points with rocky streambeds show high numbers of indicator invertebrates which designate good stream health. Water monitoring for species presence is also done prior to harvesting areas where significant waterways exist. This information impacts potential harvesting timeframes as harvesting must avoid fish spawning season in the case of some species. This information also contributes towards continually updating the national freshwater species database.

Water quality from our thousands of hectares of planted forest consistently remains virtually indistinguishable to that coming from natural forests.  In more than thirteen years of routine water quality measurements to August 2023, there has been no evidence of any significant deterioration in water quality in monitored waterways.