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

6 2. High Flow Transitional (Wet-Dry) Flows High to Transitional; frequency of daily rises exceeded by, for the first time in the year, frequency of steady state conditions; inputs are a combination of overland runoff, subsurface interflow and discharge from offstream storages and aquifers; often occurs in April. 3. Low Flow Transitional (Wet-Dry) Flows Transitional to Low; inputs primarily discharge from offstream storages and aquifers; often occurs in May. 4. Low Flow Conditions Flows Low to Extremely Low; inputs primarily discharge from Oolloo and Tindalll aquifers; typically extends from June through October. Flows are groundwater fed, dominated by input from limestone aquifers. Flows decline in accordance with predictable recession curves. 5. Low Flow Transitional (Dry-Wet) -- Flows Transitional to Low; inputs primarily discharge from offstream storages and aquifers but influenced by early wet season rains; often occurs in November. 6. High Flow Transitional (Dry-Wet) -- Flows High to Transitional; frequency of daily rises exceeds, for the first time in the year, frequency of steady state conditions; inputs are a combination of overland runoff, subsurface interflow and discharge from offstream storages and aquifers; often occurs in December. The period of Low Flow Conditions is the primary focus of this study. The magnitude of flows during Low Flow Conditions and the time of onset, duration, and time of termination of Low Flow Conditions vary considerably from year to year. This provides a backdrop of high natural variability that presents a challenge for determining acceptable and unacceptable impact of water resource development on river flow. Spatial Pattern of Flows The study site was a 74 km stretch of the Daly River well above the tidal reaches between Dorisvale Crossing (131o 55'E, 14o37'S) and the inflow of Cattle Creek (131o13'E, 14o03'S) just downstream of Oolloo Crossing. This is adjacent to areas currently flagged for agricultural development. Our study spanned the 2000 and 2001 dry seasons. There was a nett increase in flow with distance downstream from Dorisvale Crossing. Much of the flow entered between Station 10 (Hot Spring) and Station 15 (Black Bull Yard), a consequence of a Claystone layer that capped the Oolloo Dolomite aquifer between Bradshaw Creek and Stray Creek. Groundwater input between Stations 10 and 15 was an order of magnitude higher than elsewhere in the study stretch. Given the source of dry season flow, and the interconnection between the surface flows and the groundwater of adjacent aquifers, any water allocation schedule would need to incorporate both surface and groundwater offtake. Modelling Flow Reduction Flow reduction was modelled using a steady state hydrodynamic model of the study stretch using the HecRas River Analysis System. At minimum flow conditions of 2 cumec, the Daly River between Dorisvale Crossing and Cattle Creek was severely fragmented with 26 small pools (79% of the river length), 7 intermediate pools (21%), and no larger or very large pools. Pools do not differ significantly in attributes apart from length. As we progressively flood the river, the number of pools declines in accordance with the relationship shown in


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