Soil and water management in State forests

Forests play an essential role in the protection and maintenance of our soil and water resources. The conservation of soil and water contributes to catchment health and biodiversity for the benefit of the whole community.

Most major rivers in NSW have at least part of their headwaters in State forests. From these forests comes water that is used for town and rural water supplies. Forests filter rainwater and run-off entering watercourses, ensuring good water quality.

Conservation and maintenance of soil and water resources are fundamental aims of the management of State forests. The mechanisms for achieving this are incorporated into State Forests of NSW Codes of Practice.

Codes of Practice

Through its Codes of Practice, State Forests is committed to using world's best management practices to ensure that soil and water quality are not adversely impacted by timber harvesting, roading and other operations and to ensure that the amount and quality of water delivered to local communities is not adversely affected. Our forest management also aims to maintain the capacity of soils to support natural forest ecosystem processes.

The practices that State Forests uses are documented in State Forests Forest Practices Code for field operations, which specifies, amongst other things, the operational standards required for delivering clean water and meeting current regulatory requirements. The practices include many protection measures, such as the maintenance of undisturbed streamside filter strips, use of silt fencing, construction of appropriate road drainage and stream crossings and limits placed on road use during wet weather.

Environment Protection Licences

Effective implementation of soil and water protection is further assisted through the regulatory conditions prescribed in Environment Protection Licences issued by the Environment Protection Authority (EPA).

The EPA audits the implementation of Licence conditions. In accordance with these conditions, State Forests is undertaking a comprehensive program of water quality monitoring in many locations in New South Wales. The aim of the program is to monitor the effectiveness of the licence conditions in protecting the quality of water available to the aquatic environment and local communities.

Hydrology research

In addition to the prescribed water quality monitoring program, State Forests has been conducting hydrology research projects for more than 25 years, investigating the impacts of forest management activities on water quality and quantity. At present State Forests operates more than 35 stream gauging and water quality monitoring stations in a number of State Forests' regions, including North East, Mid North Coast, Hunter, South East, Hume and Macquarie regions.

Results of research projects and water quality monitoring have shown that runoff containing fine sediment from unsealed roads is the major potential source of water pollution in a managed forest environment.

Further research by State Forests, universities, CSIRO and the Cooperative Research Centre for Catchment Hydrology has demonstrated that due to strict sediment control measures State Forests' management activities do not have an adverse impact on water quality.

Results of hydrology studies

Hydrology studies have shown that the amount of water that is yielded from a native forest depends upon a number of factors, such as the age of the forest and the proportion of the forest that is affected by timber harvesting activities at any point in time.

Following harvesting, there is generally an increase in the amount of water that is yielded by a patch of forest. This is because there are fewer trees to intercept rainfall or to transpire water through their leaves; therefore more water infiltrates into the soil and/or flows over the soil surface and into streams.

Several years after harvesting, the amount of water flowing into streams from a patch of forest declines as the forest regrows and the young trees intercept and transpire more water.

Sometimes the amount of water yielded from a patch of younger regrowth forest can fall below that of an established, older forest. However, over time the amount of water yielded from a patch of forest levels out again as the forest reaches maturity.

Managing water yields

Silvicultural practices such as thinning can be used to speed up this process by removing some of the smaller regrowth trees to ensure that water yields are not significantly different to those prior to harvesting.

Another method employed by State Forests is to deliberately disperse harvesting operations over space and time, so that only a very small proportion of any catchment is affected at any point in time. This ensures that, on a catchment scale, forest management does not have an adverse impact on the quantity or quality of water available to local communities.