Habitat management

Weir remediation

NSW DPI is leading the way in the use of weir removal as a management tool to address river degradation. The removal of weirs is a complex process that needs to address the requirements of the environment as well as the cultural, heritage and social issues of the community.

Overview of what weirs are and the problem they cause for aquatic habitats

Weir removal

Since the construction of many weirs, circumstances and community needs have changed. For example, an alternative water supply may now be available and an old weir may no longer serve its original purpose. Some of these structures, particularly those near towns, may have developed secondary uses such as recreational and visual amenities for local communities, but others are now redundant and should be removed.

Weirs may be able to be removed where they are no longer serving a useful purpose. NSW DPI has commenced a Weir Removal Program with funding from the recreational fishing license. A number of weirs have now been removed, improving fish passage to hundreds of kilometres of waterways in NSW.

Weir modification

A number of older weirs need major maintenance or refurbishment. Before significant expenditure is incurred, the owners and the community should consider if the cost would be better spent on an alternative water supply, or upon significant design changes that will reduce the environmental impact of the structure. Such modifications may include the instalment of fishways which improve fish passage.

The modification of the Stroud Weir, on the Karuah River, to include a rock-ramp fishway is one example. (Note: this page contained many photographs and may take a while to load).

Benefits

Removal or modification of barriers to fish passage such as weirs will result in improved stream connectivity, better water quality, increased biodiversity, and enhanced recreational angling benefits.

The removal of instream barriers results in the reclamation of valuable habitat for aquatic fauna and the reinstatement of normal fish migratory processes. Many native fish species have a migratory component within their life-cycles, whether for the purpose of reproduction or for habitat expansion. Migration also acts to increase the genetic diversity of fish populations and improve the genetic health of native fish stocks.

Detailed Weir Review

In 1999, the then NSW Fisheries (now DPI) and the Department of Land and Water Conservation undertook the NSW Initial Weir Review which aimed to make a provisional assessment of all licensed dams and weirs within NSW, and evaluate their impact on fish passage for the purpose of identifying priority sites for remediation.

Following the production of the initial weir reviews, it was acknowledged that more comprehensive weir reviews were required to assess additional social, cultural, ecological, and logistical issues pertaining to highlighted priority sites prior to the implementation of on-ground works.

In 2003 NSW Fisheries (now DPI) initiated the NSW Detailed Weir Review project on behalf of the NSW Environmental Trust. The project aimed to conduct thorough investigations into 80 high priority structures across NSW to better determine appropriate remediation actions.

The Detailed Weir Review project is now complete, with a total of 109 weir structures across the 13 CMA regions of NSW investigated. The individual detailed reviews can be found in the reports below that cover each CMA region.

Case Study

The Branch River Crossing

The Branch River Crossing is located near Port Stephens on the Karuah River catchment, approximately 22 km north-east of the township of Karuah, NSW. The crossing was situated on a natural rock bar at the upper end of the tidal limit. The removal of the Branch River Crossing was part of a larger weir removal project being undertaken by DPI, WWF Australia and the NSW Environmental Trust. This project aims to increase public awareness of the environmental effects of in-stream barriers. It provides a framework to facilitate community based weir removal projects and demonstrates the ecological benefits of improved river health.

An excavator and rock breaker were used to break the concrete cap on the Branch River Crossing (left). A couple of metres of the crossing was left near the edge to maintain bank stability (right). In less than four days fish passage was re-instated to approximately 30km of the Branch River for the first time in 52 years.