Territory Stories

Modelling dry season flows and predicting the impact of water extraction of flagship species



Modelling dry season flows and predicting the impact of water extraction of flagship species


Georges, Aurthur; Webster, Ian; Guarino, Fiorenzo; Jolly, Peter; Thoms, Martin; Doody, Sean; CRC for Freshwater Ecology (Australia); University of Canberra. Applied Ecology Research Group


E-Publications; E-Books; PublicationNT; 57/2002; National River health program




Daly River


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.


Made available by via Publications (Legal Deposit) Act 2004 (NT); Submitted to the Northern Territory. Department of Infrastructure Planning and Environment

Table of contents

1. Project Details -- 2. Executive Summary -- 3. Interpretation of the Brief -- 4. Variation of the Brief -- 5. Background -- 6. The Daly Drainage -- 7. The Pig-nosed turtle -- 8. Analysis of Historical Flow Data -- 9. Analysis of Contemporary Flow Data -- 10. Modelling Flow Reduction -- 11. Water Temperature Versus Flow -- 12. Impact on Flagship Species -- 13. References




Environmental Flows; Modelling; Biota

Publisher name

Northern Territory Government

Place of publication



Final Report


57/2002; National River health program


75 pages ; 30 cm

File type



Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government



Parent handle


Citation address


Page content

5 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. Flow Characterization Sources of flow to the Daly River include overland runoff, during periods of intense rainfall, and subsurface interflow in the period during and immediately following the wet season; seasonal recharge and discharge to and from local offstream bank storage and offstream aquifers; diffuse recharge to regional aquifers and subsequent discharge; and to a minor extent, inflows from groundwater sources adjacent to the Daly River catchment. The Daly River is in the wet-dry tropics of the Northern Territory. As such it experiences the extremes of high rainfall during the monsoonal wet seasons and the near absence of rainfall in the intervening dry seasons. This pronounced seasonal pattern is reflected in river flows. Throughout this report, flows are those measured at G8140067, the DIPE gauging station located upstream of the Dorisvale Crossing on the Daly River. Flow categories are defined in terms of percentiles calculated from daily flows: 1+ Record High Flow: The maximum high flow recorded (8100 cumecs, January 1998) 1. Extreme High Flow: Flow > 95th percentile (740 cumecs) 2. High Flow: Flow > Q3 (50 cumecs) 3. Transitional Flow: Median < Flow < Q3 (10 to 50 cumecs) 4. Low Flow: Flow < Median (10 cumecs) 5. Extreme Low Flow: Flow < 5th percentile (3 cumecs) 5+ Record Low Flow: The minimum flow recorded (ca 2 cumecs, November 1966) Several distinct phases in the annual flow cycle are also recognised. 1. Flood -- Flows High to Extreme High; highly variable; frequency of daily rises and falls exceed the frequency of steady state ( < 1 cumec) conditions; inputs dominated by overland runoff and subsurface interflow; recharge of offstream storages and aquifers; often occurs in the months of January to March.

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