Protecting our water quality

City Forests has worked with the Otago Regional Council to set up an 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 other land uses.  Some of City Forests’ plantations form part of Dunedin’s water catchment network, including Flagstaff and Ross Creek forests, putting further need on ensuring water leaving the estate is of high quality.

Active water sampling points are currently established in a number of significant waterways across the estate.  In 2024, nineteen of these have been measured according to our monitoring protocols.  The water quality at these sampling points consistently rated highly.  Water points with rocky streambeds show the presence of indicator invertebrate species which designate good stream health.  Water monitoring for fish 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 originating from our thousands of hectares of planted forest is a valuable local resource for both people and flora and fauna.  In more than eighteen years of routine water quality measurements to 2024, there has been no evidence of significant deterioration in water quality in monitored waterways.