Plenty to be cranky about! Water expert puts forward alternatives

The NSW Governments latest Belubula River dam plan has come under sustained criticism following the release of a report recommending the Cranky Rock sites.

After closer analysis of the report released the Monday, there is mounting concern from water experts, cavers and environmental groups that the Cranky Rock site will have a significant negative impact on the Cliefden Caves and is being pursued over other more sustainable alternatives.

Having had time to research the report, the Save Cliefden Caves Association spokesperson, Bruce Welch says it’s clear that dams at Cranky Rock would flood the Cliefden Caves site and would be a disaster for the environment and future scientific research on the caves.

“NSW Water Minister, Kevin Humphries assured ABC Central West radio that the Cliefden Caves would not be affected.”

“Our examination shows that Needles Gap will be flooded with up to 50 metres of water if the Cranky Rock Dams go ahead – heavily impacting on a number of the caves, fossils and thermal spring.”

Other experts have expressed their concern.

Associate Professor Armstrong Osborne, one of Australia’s leading cave scientists at Sydney University is also concerned.

“The Cranky Rock proposals may also represent a threat to caves not flooded by the dams. We currently don’t know enough about the hydrology of the cave system at Cliefden to predict the effects of these proposed dams.” Associate Professor Osborne said.

Associate Professor Stuart Khan, a water expert from the University of NSW School of Civil and Environmental Engineering, has also provided arguments against the dam that go beyond the concerns about the caves.

“Clearly there is an impending need to augment water supplies in a number of NSW Central West towns. However, the construction of the proposed dam is only one of many ways that water supplies could be better managed.”

“I think its short-sighted to have a feasibility study that is essentially a Yes/No assessment for this one project. Instead, a study at this stage should be taking a much broader look at various available water management strategies and assessing them comparatively.”

In an article released today, Associate Professor Khan has outline a number of concerns beyond the impact on the caves including:

•         The impact on downstream users including irrigators and the inland riverine environment.

•         The precious little water flows down the lower reaches of the Belubula River anyway, due to existing dams further upstream (Carcoar Lake and Lake Rowlands)

•         Rainfall around Canowindra of around 700 mm/year, but evaporation is over 1000 mm/year. As such, storing water in shallow, high surface-area reservoirs will result in significant water losses, especially during the summer months.

•         Water security problems are projected by CSIRO to intensify by 2030 in southern and eastern Australia as a result of reduced rainfall and higher evaporation.

•         The proposed dam sites are just downstream from the Cadia Valley Operations open-pit gold mine and large mine tailings dam. These pose significant water quality risks for the proposed dams and would likely make them unsuitable storage locations for a drinking water supply.

Associate Professor Khan has identified a range of viable alternatives including urban stormwater harvesting, non-potable water recycling, indirect and direct potable reuse and managed aquifer recharge (MAR).

Mr Welch said that the NSW Government must rule out any dam that would have an impact on the Cliefden Caves site, provide guarantees about its future protection, and explore the many viable alternatives to the dam.

“This report is all about trying to sweep the issue aside until after the state election. Let’s have a proper evaluation of all the options, including those beyond dams, with all the facts on the table.”

 

Associate Professor Stuart Khan’s Assessment of Belubula Dams

Why a new dam on the Belubula River is unlikely to be an optimum water supply strategy.

Clearly there is an impending need to augment water supplies in a number of NSW Central West towns. A major El Nino event could rapidly exacerbate this need. However, the construction of the proposed dam is only one of many ways that water supplies could be better managed. As such, I think its short-sighted to have a feasibility study that is essentially a Yes/No assessment for this one project. Instead, a study at this stage should be taking a much broader look at various available water management strategies and assessing them comparatively.

There are a number of reasons for why I think the proposed Needles Gap Dam, or the alternative Cranky Rock Dam, is unlikely to  be the optimum strategy in this case. These include:

•         The devastating impacts to the Cliefden Caves, which apply to both the Needles Gap site and the Cranky Rock site, and have been described elsewhere on this website.

•         The Belubula River is an inland river and does not flow to the sea. Hence any water captured from it is water that is taken from downstream uses including irrigators and the inland riverine environment.

•         Precious little water flows down the lower reaches of the Belubula River anyway, due to existing dams further upstream (Carcoar Lake and Lake Rowlands)

•         Rainfall around Canowindra is around 700 mm/year, but evaporation is over 1000 mm/year. As such, storing water in shallow, high surface-area reservoirs will result in significant water losses, especially during the summer months.

•         Water security problems are projected by CSIRO to intensify by 2030 in southern and eastern Australia as a result of reduced rainfall and higher evaporation.

•         The proposed dam sites are just downstream from the Cadia Valley Operations open-pit gold mine and large mine tailings dam. These pose significant water quality risks for the proposed dams and would likely make them unsuitable storage locations for a drinking water supply.

There are a number of obvious alternative strategies that should be considered in parallel to the Needles Gap or Cranky Rock Dams. These include:

•         Urban stormwater harvesting: Nearby city of Orange is an excellent example of what can be achieved. The Blackmans Swamp Creek Stormwater Harvesting Scheme opened in 2009. This scheme involves capturing a portion of the town’s urban runoff produced during storm events, and transferring these into the nearby Suma Park Dam to augment the city’s bulk water supply. The high levels of treatment provided at the water treatment plant (using ozone and activated carbon) make this possible. Orange City Council has indicated that there are opportunities to at least double the capacity of the current stormwater harvesting system.

•         Non-potable water recycling: If carefully planned, treated municipal effluent (from sewage treatment plants) can be used for some important existing non-drinking water applications. If a suitable use can be found, this can be used to off-set (ie. replace) the demand on the drinking water supply. However, in most cases, there are limitations in how well this can be achieved without actually creating additional (unnecessary) water uses or without excessive distribution costs.

•         Indirect potable reuse: There are many options to treat municipal effluents to a very high level suitable for recharging drinking water supplies. One only has to look at the proximity of the Orange sewage treatment plant to the city’s main water supply of Suma Park Dam to see how simply this might be achieved. (Note that much of  the water from the Orange sewage treatment plant (about 10 ML/day) is currently allocated to Cadia Valley Operations for mining operations (~30 km away). However, one could look at sending the mining operations the waste brine from a reverse osmosis treatment process and supplementing that with improved reuse of wastewater from the mine tailings dams).

•         Direct potable reuse: There is a major emerging trend in the USA for inland cities (eg, Big Spring and Wichita Falls, both in Texas) to begin directly reusing advanced treated recycled water in their drinking water systems, without first storing it in an environmental buffer such as a reservoir. In some circumstances, there are many advantages to be gained from this approach, as described in a recently published report by the Academy of Technological Sciences and Engineering (for which I was the lead author).

•         Managed aquifer recharge (MAR): Instead of storing water in a surface water reservoir, water can be stored underground in an aquifer. There are a number of benefits in using an aquifer as a storage system including greatly reducing evaporation, delivering transportation and energy savings and lower construction costs compared to a large dam. Orange City Council is currently examining the possibility of using the Basalt Aquifer to the south of the city for MAR. This could be used for urban stormwater, highly treated recycled water (which is now happening in Perth), or even traditional surface water flows.

 

  • published this page in News 2015-02-11 23:08:32 +1100

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