Project Title: Project reference no: 23045
Dr A Georges, Dr I Webster, E Guarino, M Thoms, P Jolly and S Doody
CRC for Freshwater Ecology and the Applied Ecology Research Group, University of Canberra
Department of the Environment and Heritage, 2003
- Modelling Dry Season Flows and Predicting the Impact of Water Extraction on a Flagship Species - Summary (PDF - 75 KB)
- Modelling Dry Season Flows and Predicting the Impact of Water Extraction on a Flagship Species - Full Report (PDF - 970 KB)
About this report
The Daly River drainage is the third largest in the Northern Territory draining an area of 51,800 km² and with an annual discharge of 4180 x 106 m³. Katherine and Pine Creek are the only major urban centres in the catchment and there are no dams on the Daly River or any of its tributaries. Major uses of adjacent rural land are pastoral and to a lesser extent agricultural. There are proposals for major agricultural development adjacent to the Daly, and these will require concurrent development of water resources for agricultural use.
Potential environmental impacts from water resource development and agricultural development on adjacent lands are
- reduced connectivity in what is currently a year-round flowing river;
- reduced flows with consequential impact on flow-dependent species (eg. ribbon weed);
- altered timing of flow patterns which may cause species to mis-cue reproductive and other behaviours;
- increased turbidity in what is currently a clear-water river in the dry season;
- altered water quality by altering the mix of waters derived from different sources or input of nutrients;
- altered water temperatures, with attendant consequences for primary production and metabolism of poikilothermic animals (invertebrates, fish, turtles) higher up the food chain.
The aim of this project is to contribute to recommendations on environmental flows to ensure that they are consistent with maintaining the biota of the Daly River, given competing demands of agriculture, recreation and tourism, conservation and Aboriginal culture. Our focus is on flow, connectivity and water temperatures.
To achieve this aim, we modelled the impact of potential flow reduction on dry-season river connectivity and water temperatures in the Daly River and explored the impact this would have on the life history and viability of a flagship species, the pig-nosed turtle.
The pig-nosed turtle was chosen as the species for study because it is a high profile flagship species of considerable international concern (the sole remaining member of a once widespread Family), and the best Australian populations of the species reside in the Daly River. It is regarded as particularly sensitive to environmental perturbations, by virtue of its mobility, reliance on food sources that are themselves flow sensitive, and its peculiar mode of sex determination, which depends on temperature. Protecting the interests of the pig-nosed turtle will likely bring attendant benefits for a wide range of other species whose requirements are less stringent. It can therefore be regarded also as an umbrella species. Adverse impact on this species, and those fish and other aquatic life with concordant requirements, such as endangered freshwater shark, would be regarded as major degradation of the riverine environment.
Note: This report is related to the 'Recommended Environmental Water Requirements for the Daly River, Northern Territory, Based on Ecological, Hydrological and Biological Principles' report available from the Supervising Scientist Division web site.