Yass Valley

Indicator: Water Use

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What the results tell as about Yass Valley

Yass has a very limited water supply, due to low flow in the Yass River and the on-going drought. The dam capacity is inadequate to maintain supply in drought without Level 3 restrictions on domestic users, which disadvantages residents. Bore supplies to Murrumbateman are barely adequate. Increased dam capacity is required.

Supply- how much water could we have?

Yass township, with a population of approximately 6,000, draws its water supply from the Yass Dam, which has the modest capacity of 872 Megalitres (one ML is 1,000 cubic metres of water, roughly one Olympic swimming pool). The dam is filled from the Yass River, which is highly subject to drought and resulting low water flows. Inflows to the river catchment over the last four years are amongst the lowest recorded. At present there are no additional water sources available for the town water supply, which has resulted in restrictions on water use.

Murrumbateman with a population of 330 has an independent water supply sourced from bores, which initially supplied 3.5 Litres/sec (11 ML/yr) for the local reticulation system. A second bore was recently drilled with a yield much less than expected, as it had been anticipated that 11 L/sec could be supplied. Due to the close proximity of the existing bore, the NSW Department. of Water and Energy issued a licence stating the volume of groundwater extracted from bores shall not exceed 56ML in any 12 month period. The current annual requirement is 45ML.

The non-urban population uses private supplies, which are not part of the reticulation system.

Yass Council are actively investigating a range of options for increasing water availability and reliability..

Table 1. Dam and bore capacity Yass Valley Shire
Sources of reticulated water (dams, rivers, weirs, bores, etc) Reticulated water supply for (town/village) 1999/2000 2003/04 2007/08
Yass dam Yass, Bowning and Binalong 875ML 876ML 872 ML
Murrumbateman bore Murrumbateman 3.5 litres/second 3.5 litres/sec 7.0 Litres / Sec
Estimate what % of the population is connected to reticulated water 95% urban; 5% rural   52% 52%
Estimate what % of the population uses non-reticulated water 95% rural; 5% urban   48% 48%

 

How much water is available?

Yass dam levels were at 100% of capacity continuously from mid-1998 to November 2001, when they dropped to 70% by January 2002. Each subsequent year up to 2007 the dam levels fell during the summer to about 70% of capacity and did not recover until June or July. In 2008 the dam level fell to 90% of capacity in March, April and May, compared to 67% in April 2007.

The Murrumbateman bore supply was increased by drilling of a second bore. As a consequence of the shortage of water due to the drought and limited dam capacity, water restrictions were successfully employed to reduce domestic and public water consumption in Yass and Murrumbateman. As can be seen from the table below, a 30% reduction in water use was achieved in Yass and 50% in Murrumbateman.

A comparison between dam storage capacity and average annual water consumption demonstrates that Yass has only one years water in storage when the dam is full.

Consumption – how much water was used?

Total use

Table 2. Total use of drinking water by Yass Valley Shire
  2004/05 2005/06 2006/07 2007/08
Total volume of surface water used per year in ML - from eg. dams, reservoirs, rivers etc. 815 837 842 748
Total volume of reticulated water used per year (ML) 758 783 765 685
Total volume of bore water used per year in ML 46.38 47.33 27.72 21.78
non-reticulated        

 

Use by sector

Table 3 shows that the commercial use of reticulated water in Yass has progressively increased up to the present, in contrast to the domestic use, which has been effectively controlled by water restrictions. In Murrumbateman the commercial use has remained constant, whereas the domestic use has halved.

Table 3. Water use by sector
Town/Village Sector 2004/05 2005/06 2006/07 2007/08
Yass Domestic 515 537 535 453
Commercial 100 102 114 122
Industrial 0 0 0 0
Rural/Irrigation 0 0 0 0
Bowning Domestic 17 30 22 31
Commercial 3 3 3 2
Industrial 0 0 0 0
Rural/Irrigation 0 0 0 0
Binalong Domestic 73 59 56 49
Commercial 9 10 8 7
Industrial 0 0 0 0
Rural/Irrigation 0 0 0 0
Murrumbateman Domestic 36 36 22 17
Commercial 5 6 5 4
Industrial 0 0 0 0
Rural/Irrigation 0 0 0 0
Total Domestic 641 662 635 550
Commercial 117 121 130 135
Industrial 0 0 0 0
Rural/Irrigation 0 0 0 0

 

Environmental flows

The drought has caused many of the creeks in the Shire to become interrupted watercourses. No flow data was provided for the Yass River, or environmental flow information.

Managing water use and demand

Water restrictions

Water restrictions have been in place in Yass each year from 2001. During the reporting period there have been continuous restrictions from mid-2005 until the present. Level 3 restrictions applied for 43 days in 2004-2005, four days in 2005-2006 and 198 days in 2006-2007. During 2007-2008 Level 2 restrictions applied for 260 days and Level 1 for 106 days. Since 2005 the restrictions policy has had 5 stages, in line with the ACT.

Murrumbateman entered water restrictions in 2006-2007 and 2007-2008, with 191 days of restriction in 2006-2007 and a whole year of restriction at Levels 3 and 4 in 2007-2008.

Recycling – making the drop go further

Yass Sewage Treatment Plant has processed 126 ML of water per year, which is used to irrigate pastoral land owned by the Council, and discharged to Banjo Creek which feeds into the Yass River. The phosphorus content of the discharge leads to algal blooms downstream in the river. An upgrade of the treatment plant is in progress.

Future supply

It is apparent that the present availability of water to Yass is not adequate, and has resulted in water restrictions since 2001, with Level 3 in place during 4 of the last 6 years. The Yass Council have explored a range of options in order to identify the most cost-effective resolution of the problem.

One option that was explored was a pipeline from the ACT supply. This appeared to be technically feasible and an ultimate long-term solution but requires significant capital expenditure and support from the ACT Government.

The ACT Government is currently investing substantial capital works to greatly increase the reservoir capacity supplying Canberra and Queanbeyan, and also a pipeline from the Murrumbidgee River. ACT dam storages fell to about 30% of capacity in 2008, with Level 3 water restrictions in force.

The construction of an off-river storage for Yass has been explored, at a site 3 km upstream of Yass Dam. This would increase water harvesting from the river during higher flows, to be released during low flow periods to allow subsequent extraction. The proposed site allows construction of 450 ML storage. Geotechnical investigation and concept design have been completed. The cost-benefit arising from this project is however lower than the alternative of raising the dam wall of the present reservoir. This proposal is to raise the wall by three metres, which will increase storage capacity by 1,500 ML, almost tripling the existing water storage. The design and tender documents are under preparation, with a completion date of December 2011.

About the data

Quantitative data received from Yass Shire Council

 

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