Assessment of the effects of cooling tower blowdown upon the ecology of the Coxs River

"April 1991".

Project Number: Biological assessment of the effects of Wallerawang Power Station blowdown upon the Cox’s River – YH/6/19/2 - M/04/201.

MDFRC item.

81 pages.

Although scientific interest in the Wallerawang area dates back at least to the time of Charles Darwin (Nichols and Nicholson 1989), the ecology of the area, and in particular the Coxs River system, is not well reported. The nature of the catchment has been modified considerably, first by farming and later by the mining of rich local coal deposits and the use of this resource in generating electricity. The Coxs River is also a valuable resource in terms of the local environment, for its recreational and aesthetic value, and as a water supply for local residents and industry and for Sydney via the Warragamba system. In recognising the potential for conflict between coal-powered generation of electricity at Wallerawang and maintaining the value of the Coxs River resource, the Electricity Commission of New South Wales (ECNSW) have sponsored this and other studies, as well as collecting water quality data over an extended period. The positioning of the power station straddling Coxs River and, more importantly, the return of water pumped from the Wallerawang Reservoir and used in the station’s two cooling towers present a potential threat to the river’s ecosystem which needs to be quantified. The present study aims at addressing this need by examining two important components of the Coxs River system; the macroinvertebrates (invertebrate aquatic animals such as molluscs, crustaceans, and insects larger than about ½ mm -see Appendix A) and fish. These groups are used because -They include animals high on the food chain and are therefore likely to reflect changes in the well-being of organism which constitute their food as well as changes in their own numbers, -They constitute diverse groups exhibiting a range of sensitivities to many environmental perturbations and therefore present an array of responses to changes in the aquatic environment, -Expertise is available to sample and identify these organism and detect and interpret changes n their populations. The survey of the two indicator groups is supported by concurrent water quality measurements and by other water quality data made available through ECNSW (see Section 3). Biological data are favoured over the use of water quality data alone (as a surrogate) in detecting ecological response to the perturbation in the Coxs River system.