Tharwa Fish Habitat Improvement Project
The Tharwa Fish Habitat Project used engineered log jams to improve fish habitat in the river adjacent to Tharwa and also augmented some existing constructed rock groynes (outcrops of rock). The log jams were made of interlocking hardwood logs and rock. Some of the logs still have their roots attached, which helps the log jams maintain stability and provides the woody habitat that is an important native fish habitat. The materials used in the second phase of the project were recycled from ACT development sites.
The river scours the sand between the structures, deepening the channel and creating pools that make it easier for the fish to pass and live in this section of river. The structures also provide complex habitat for fish and the food they eat. The river corridor has been further improved and stabilised with tree planting under the ACT Million Trees Program. Shrubs and macrophytes (plants that grow in or next to water) have been planted on the sand bar and river edge, and larger trees and shrubs planted further up the bank . Weed control and site rehabilitation accompanied the planting. The ACT Government and community groups such as Waterwatch are monitoring the site and its aquatic life before and after the log jams were constructed to measure the effectiveness of the project and its potential for use at other locations.