Environmental Issues
Since the construction of the Canning Dam, among other drinking water supply dams, water flow into the Canning River has been reduced by up to 96%. A number of freshwater fish species which are endemic to the south-west of Western Australia are found in the Canning River system, however studies of fish and fish habitats in the area have shown that fish numbers are low due to a loss of habitat and a loss of linkage between breeding areas due to low flows, preventing fish migrating upstream and reaching important breeding and nursery grounds. Stagnant water caused by a lack of water flow has provided a suitable habitat for successful breeding of an introduced pest, the mosquitofish.
Damming of the Canning caused dramatic flow reductions that significantly altered downstream aquatic macroinvertebrate communities. The lack of water flow has also resulted in a poor flushing effect below the dam wall. An excessive amount of nutrients from fertilizers and animal waste has caused algal blooms and eutrophication.
Many river pools which are an important summer refuge and habitat for aquatic and terrestrial flora and fauna have been lost due to sedimentation and modification of the flow regime caused by impoundments in the Canning River.
Periodic flooding of the Canning River from the dam is required to disperse seed, stimulate germination and ensure seedlings survive, recharge shallow groundwater tables that are important during periods of drought and to discourage and prevent weed growth. However during times of low rainfall periodic flooding is reduced.
Read more about this topic: Canning Dam
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