Territory Stories

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

Details:

Title

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

Creator

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

Collection

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

Date

2002-11-20

Location

Daly River

Abstract

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.

Notes

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

Language

English

Subject

Environmental Flows; Modelling; Biota

Publisher name

Northern Territory Government

Place of publication

Palmerston

Edition

Final Report

Series

57/2002; National River health program

Format

75 pages ; 30 cm

File type

application/pdf

Use

Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government

License

https://creativecommons.org/licenses/by/4.0/

Parent handle

https://hdl.handle.net/10070/885434

Citation address

https://hdl.handle.net/10070/885435

Page content

54 but the upstream site, Dorisvale, is consistently cooler than Jinduckin Creek by an average of 1.8 0C; temperatures at Jinduckin Creek are an average of 0.2 0C cooler than those at Cattle Creek, the site furthest downstream. The temperature increase between Dorisvale and Jinduckin Creek is attributed mostly to the discharge into the Daly River of the warmer water from the springs. Measured Temperatures 2001 July August Te m pe ra tu re (0 C ) 20 22 24 26 28 30 Claravale Jinduckin Creek Cattle Creek Period 1 Period 2 Figure 30. Comparison of measured water temperatures at three sites on the Daly River. Over the 58-day record the water temperature at the three sites showed longer period cycles of variation which had an amplitude of about 3 0C. This temperature variability appears to have been due to the weather. The relatively high water temperatures during the third week in July (Period 1 in Fig. 30) had an average wind speed of 11.4 ms versus 12.1ms in the last week of July (Period 2) and the third week had an average relative humidity of 68% in the third week versus only 43% in the last week. The stronger winds and lower relative humidity in the last week would have meant that evaporation would have been more vigorous than in the third week. This higher evaporation would have tended to increase the rate of cooling of the water column. Air temperatures were also an average of 6 0C cooler in the last week than in the third which would have contributed further to cooling the river during the last week of July. Interestingly, the estimated average downwelling irradiances in the third and last weeks of July were virtually identical being within -21Wm of one another, even though the short-wave radiation in the last week was measured to be about -250 Wm higher than in the third week. The radiation shortfall in the third week appears to have been up with a correspondingly higher downwelling long-wave contribution. Presumably, the variation in the meteorological conditions were due to the presence of a warm, cloudy, humid air mass deriving from the tropical ocean to the north of Australia in week 3 being replaced by a cooler, clear, and dry air mass from continental Australia during the last week in July. Figure 31 compares the measured and modelled river temperatures at Jinduckin Creek; Figure 32 shows a weeklong expanded section of Figure 31 to better illustrate the diurnal temperature variation. Overall, the model simulates the measurements well both with respect