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

13 rivers has contributed to the decline of populations of migratory fish, such as Australian bass, Macquarie perch, and Golden perch (Lake and Marchant 1990, Barmuta et al. 1992). So alteration to flow regime may in turn alter the physical environment, the cues used by the biota to time critical life history events, and connectivity of aquatic environments important for the persistence of aquatic species where migration or movement is an important part of their life histories. Depending upon how attuned a species is to the cues it draws from a natural flow regime, some species may fall into what is called an ecological trap (Schlaepfer et al. 2002). Such traps occur when organisms make maladaptive behavioural or life-history choices which were formerly based on reliable environmental cues. Organisms often base behavioural and life-history decisions on environmental cues such as when to reproduce, places to eat, what to eat, where to shelter, when to move and so on (Bjorndal 1994; Visser et al. 1998; Buse et al. 1999). Hence, when such environments are suddenly altered, these formerly reliable cues are no longer associated with beneficial outcomes (Schlaepfer et al. 2002). In such cases, organisms can become trapped by their evolutionary responses to the cues and consequently experience reduced survival or reproduction. Although ecological traps are similar to natural cycles of disturbance, energy flow, and fragmentation etc., they differ in frequency because ecological traps are induced by people and occur on a shorter temporal scale than those induced in nature (Schlaepfer et al. 2002). If we are to minimise short-term losses to natural populations by virtue of human activities such as water extraction, we need to consider what attributes of a species may cause it to fall into that trap. An example of this is the boom-bust ecology of many aquatic dependant fauna (Walker et al. 1995; Kingsford et al. 1999). In energetic terms, a boom period occurs when resources are such that the organisms can not only meet their immediate needs for maintenance, growth and reproduction, but can also replenish the resources that were drawn upon unsustainably in preceding "bust" periods. In terms of population dynamics, a boom period occurs when resources are such that reproductive output not only ensures that current population levels are sustained, but is also sufficient to fully offset low recruitment that that would have otherwise resulted in population decline in preceding "bust" periods. Boom years may well be infrequent, and it is to be expected that the bust years would numerically dominate the boom years. Changing the frequency of boom relative to bust periods through flow alteration is likely to have substantial long-term impact on the population levels sustained locally, and may even result in local extinction if acting in concert with other factors that depress population numbers. The Daly River in the top end of Australia undergoes episodic high and low flows annually, the magnitude of which vary considerably from year to year. In this context, we determine how changes in the magnitude of flow effect water temperature and river connectivity in the Daly River and determine the likely consequences of this on a highly aquatic, flagship species, the pig-nosed turtle Carettochelys insculpta. Remarkably, there are relatively few examples of studies that directly address the issue of quantity and timing of flows and the life histories of freshwater biota. The Daly Drainage 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.


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