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

64 where dt ds is development rate at absolute temperature T (K); r = 1.987 is the universal gas constant (in calories/degree/mole); RHO25 is the development rate at 25oC (298.15 K) ; and TL, HL, TH, HH and HA are the remaining fitted parameters. For the pig-nosed turtle, the coefficients of the curve of best fit were RHO25 = 0.7571, HA = 29605.4896, TL = 297.0371, HL = -80893.0886, TH = 308.7106, HH = 161214.3066 (Figure 34). Figure 34. Development rate curves of best fit to known development increments for eggs of Carettochelys insculpta incubated under constant and fluctuating temperature regimes in the laboratory, and regimes in natural nests. Development rate is incremental change in head width, expressed as a percentage of final hatchling head width, per day. Note that only data for the constant temperatures can be shown, and as such, the data shown is a small part of that used to derive the model. A standard station for monitoring sand, water and air temperatures was set up on a small sand bar used for nesting by Carettochelys insculpta in May of each year (1996-98), immediately after the preceding wet season. Temperatures were monitored at 15 min intervals at the sand surface and at 10 cm depth intervals to 50 cm. Water and air temperatures were taken in the shade. Temperatures were recorded with four-wire RTD probes fitted to a datalogger (Datataker Model DT500) and calibrated against a mercury thermometer certified as accurate to 0.1oC by the National Association of Testing Agencies (NATA). The apparatus was removed from the riverbank in late November/early December at the first sign of wet-season flooding. Predictive relationships between nest data for 1997 and 1998 and data from this monitoring station were used to extrapolate presumptive nest temperatures for the entire dry season. Development increments occurring within each time interval between temperature measurements were summed (deCandolle 1855; Reibisch 1902). Point temperatures taken at 15 min intervals were again interpolated using cubic splines (PROC EXPAND, SAS_Institute 1988) to yield temperatures that were evenly spaced at equal but arbitrarily small intervals (t = 7 x 10-4 days). The amount of development to occur over time increments t = 1 to t = t was then calculated as tdt dsS tt t = = = ' 1 ...........................................................................................[13]