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Bega Valley Shire CouncilBega Valley Shire Council

Tantawanglo-Kiah water supply system

The following image shows the location of the Tantawanglo-Kiah water supply system. The image shows the three sources from which water is extracted, the major water storages (Yellow Pinch dam and Ben Boyd dam) and the main components of the reticulation system including reservoirs, chlorinators and pipelines.

A map of the Tantawanglo-Kiah water supply system.

Water sources

  • Tantawanglo Creek
  • Towamba River alluvial aquifer (Kiah borefield)
  • Bega River alluvial aquifer (Bega borefield) via the Bega to Yellow Pinch Dam pipeline

Water storagesAerial image of Tantawanglo Dam.

Dams

Yellow Pinch Dam in the north (capacity of 3,000 mega litres) and Ben Boyd Dam in the south (capacity of 800 mega litres). Both are off-stream dams with small catchments, filled with water transferred from their respective sources.

Current dam levels (% capacity)

Yellow Pinch Dam: 89% (as at 9 September 2019)

Ben Boyd Dam: 100% (as at 9 September 2019)

Aquifers

The alluvium (depositional sands and gravels) associated with the Bega River and Towamba River contains groundwater. This groundwater is called an aquifer because it yields a usable quantity of water.  A large volume of water is estimated to be stored in the Bega River alluvial aquifer, approximately 12,000 ML in the arm of the Bega River upstream of the Brogo River confluence. A relatively large volume of water is estimated to be stored in the Towamba River alluvial aquifer, approximately 3,000 ML in the Lower Towamba River at Kiah. Both alluvial aquifers are fully charged when a surface flow is present in the river.

System operation

North:

Water from Tantawanglo Creek is withdrawn from Tantawanglo Creek Weir - a pipehead weir located in the South East Forest National Park, about 30km south-west of Bega. The amount of water extracted depends on the flow in the creek and the licensed daily extraction limits. Daily extraction volumes range from 0 ML/d (during very low drought flows) to a maximum of 5 ML/d (for creek flows that are greater than 10 ML/d). 
Water from Tantawanglo Creek weir is piped to Yellow Pinch Dam (approximately 35 km). Water in the pipeline flows by gravity and is boosted by Wolumla booster pump station. The pipeline from Tantawanglo Creek to Yellow Pinch Dam supplies water to Candelo, Wolumla and 176 rural properties upstream of Yellow Pinch Dam.

Tantawanglo Creek is the main source of water for Yellow Pinch Dam. The Bega River, via the Bega to Yellow Pinch Dam pipeline, is another source of water for Yellow Pinch Dam. It is used to fill the dam during moderate to high flows in the Bega River at Bega. Another minor source of water for Yellow Pinch Dam is the small catchment area of the dam.
Water stored in Yellow Pinch Dam is used throughout the year and to meet peak holiday supply needs. Yellow Pinch Dam supplies water to Merimbula, Tura Beach, Pambula Beach, Pambula and 70 rural properties downstream of Yellow Pinch Dam.

Water availability from Tantawanglo Creek becomes limited during drought.  Less water is extracted as the flow in the creek lowers. Water stored in Yellow Pinch Dam is pumped upstream during dry times to maintain the supply of water to Candelo, Wolumla and rural properties upstream of Yellow Pinch Dam (ie. the flow is reversed).

South:

Water from the Kiah borefield is withdrawn from five shallow bores located in the alluvial aquifer of the lower Towamba River. The amount of water extracted depends on the flow in the Towamba River and the licensed daily extraction limits. Daily extraction volumes range from 1 ML/d (during very low drought flows) to a maximum of 5 ML/d (for river flows that are greater than 15 ML/d). The maximum licensed daily extraction limit is 12 ML/d (for river flows greater than 34 ML/d) however supply system augmentations are needed to achieve this.

Water from the bores is pumped to Boydtown Balance Tank from where it flows by gravity to Eden Reservoirs (and Ben Boyd Dam when the dam is being filled). Water stored in Ben Boyd Dam is used to supplement supply from the Kiah borefield to meet high water usage periods and to maintain supply during dry times when water from the Kiah borefield source is limited.

The Kiah borefield and/or Ben Boyd Dam supplies water to Boydtown, Eden, South Pambula and 160 rural properties between Kiah and South Pambula. Water from the south can also supplement water from the north during dry times.

The system at a glance

Towns/villages served Candelo, Wolumla, Tura Beach, Merimbula, Pambula Beach, South Pambula, Eden and Boydtown.
Water Sources Tantawanglo Creek (weir)
Towamba River alluvial aquifer at Kiah (bores)
Bega River alluvial aquifer (Bega to Yellow Pinch Dam pipeline)
Off-stream water storages(dams) Yellow Pinch Dam 3,000 ML & Ben Boyd Dam 800 ML
Licence Entitlement - high security (ML/a) 1,500 Tantawanglo Creek
1,400 Towamba River alluvial aquifer
2,640 Bega borefield (total for Bega borefield including Bega to Yellow Pinch pipeline and Bega-Tathra water supply system).
Avg annual water extracted from water sources (ML/a) ~1,700 (900 from Tantawanglo, 600 from Kiah, 200 from Bega borefield (as of June 2018))
Maximum source extraction capacity (ML/a) ~2,900 (1,500 from Tantawanglo, 900 from Kiah, 5,000+ from Bega borefield)
Estimated future (2030) avg annual water extraction needs (ML/a) ~2,900

 

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