Date sent: Mon, 29 Apr 1996 17:51:14 +1000 Tom O'Callaghan ~~~~~~~~~~~~~~~ Questions: ~~~~~~~~~~ What conclusions can you come to regarding the issues we have considered in the Cooks River Valley and at Bicentennial Park? Are these issues becoming worse or are they being improved? What is the role of management in these changes? The issues that we looked at were: uses of the areas, both water and land, and their impacts; water pollution; visual water quality; impacts of fooding; role of mangroves; management strategies. The sites visited were: 1) Alexandra Canal 2) Occupation Road - Kyeemagh 3) Canterbury 4) Fifth Avenue - Campsie 5) Bicentennial Park - Homebush Area uses at site one have a considerable impact on the Cooks River. The land uses were residential, industrial, commercial, recreational, and also roads and the airport. Water uses were boating, fishing, waste disposal, storm water drainage, and possibly a scenic resource. The impact of the land uses are that they increase runoff, because of the surface being covered by buildings and impermeable surfaces, water cannot be absorbed by the ground; a further impact of these land uses is and increase in rubbish, and then possibly water pollution. The impact of the water uses is water pollution, caused by the boats themselves, and by waste disposal and the storm water drains, bringing rubbish from elsewhere. The uses at site two were land based. These uses were a market garden, and a bridge. The impacts of the market garden would be an increase in fertilizers, herbicides, pesticides, and some sedimentation in severe flooding that would effect Muddy Creek and Cooks River. The impact of the bridge would be "back-up flooding". This would be caused when debris such as branches would become stuck between the pylons of the bridge, thereby further reducing the flow (the presence of the pylons presently slows the flow down), this would then lead to back-up flooding. At the Canterbury section of Cooks River, there were only land uses. The area was predominately residential and recreational, with a small amount of agriculture, storm water runoff drainage, and the remains of an industrial building. There were facilities for boating, however, now they are not used. The was a very large amount of pollution in the water. However, there were some fish in the river, and a pelican and other water fowls. At the fourth site, the main land use was recreation, with some residential. The impact of these and the car bridge were not great, with not a great amount of visual pollution. At Bicentennial Park, the land uses were recreational, wildlife reserve, scientific research, and an educational resource. These uses with the water uses, boating, do not appear to have an impact upon this area. The water pollution in all sites was caused by industrial dumping, storm water drains, litter, and sediment. The number of industries dumping waste into the Cooks River has decreased from 110 in 1975 to 10 in 1991. The storm water drains bring rubbish, in addition to the rubbish that falls into the river directly. Due to the amount of bank erosion, there is a large amount of sediment, 25 000 tonnes. This sediment is so rich in heavy metals, that it could be mined. There are also approximately 150 points where raw sewerage can enter the river in times of heavy rain. The visual water quality varied from site to site. At Alexandra Canal, visually, the water appeared to be reasonably good. At Canterbury, the visual quality was at its worse, the river was covered in floating rubbish. Further upstream at Fifth Avenue, the visual water quality was not too bad (that is there was some rubbish in in the water). At Homebush Bay, the visual water quality appeared to constitute nothing. In a time of flood, the areas that would have an impact on the river would be sites 2,3 and 4. Site 2 could (if the flood was high enough) cause sediments, fertilisers, herbicides, and pesticides to be dumped in to Muddy Creek and Cooks River. The increase in fertiliser level could create and algal bloom, and the introduction of herbicides and pesticides could have adverse affects on the marine population. Sites 2 and 4 would have an impact because then the residential areas could be flooded, or the flow of rubbish would be disrupted. The role of Mangroves is to be a natural treatment of water pollution. The Mangroves achieve this by trapping pollutants in their net-like entanglement of roots. The Mangroves also supply a habitat for birds and aquatic life. The Mangroves provide the Paramatta River with oxygen. The Mangroves also provide a Scenic source, and trap sediment. The benefit of Mangroves is the large savings that they give, to replace the Mangroves with manmade sewerage treatment plants would cost US$123 500 per hectare, and to replace them with recreational amenities would cost US$8 105 per hectare. When compared with last years results, there does appear to be an improvement in the water quality. However, this was aided by the heavy rainfall. The management strategies seem to be working, however, the management strategies need to be extended, because they are not solving the problem completely. The Management Strategies were: - Protection of banks with rocks, concrete, or steel, to stop bank erosion, and hence sedimentation - Signs with fines for littering ($20 000 at Fifth avenue) - Storm water drains to stop urban flooding - Floating Booms to capture rubbish - Trash Racks to capture rubbish on a rack, in the storm water drains - Gross Pollutant Trap (this uses a deep well to trap sediment, and a trash rack to capture floating rubbish) - Water Quality Testing, to judge the effectiveness of these strategies - Mangroves at Bicentennial Park, pollutant trap, wildlife refuge. In conclusion, the management strategies do appear to be making an improvement to the Cooks River. However, the improvement is at a slow rate, and needs to be expanded to start to show any great signs of improvement.