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This New South Wales town is diversifying its drinking water supply through harvested stormwater

In an Australian first, harvested stormwater from the urban water catchment in Orange, NSW, is being used as part of the drinking water supply, allowing Orange City Council to diversify water sources and, in turn, achieve more water security for the town.

Now, Orange City Council is expanding its scheme to further improve downstream water quality, building on the success of its diversification of water sourcing.

Stage 2 of Orange's Blackman Swamp Creek Stormwater Harvesting Scheme is currently being designed and will involve the construction of an off-line wetland. Stage 1 was completed in August 2009.

The town's Ploughmans Creek Stormwater Harvesting Scheme was completed the following year. This scheme consists of a series of constructed wetlands, which improve water quality in the creek system.

Both schemes then transfer water into the town’s drinking water supply, Suma Park Dam.

“We are currently working on the next stage of the Blackman Swamp Creek Scheme. What we're doing with Stage 2 involves constructing a new offline wetland, upstream of the existing extraction point for Stage 1,” Orange City Council Water and Sewer Strategic Manager Wayne Beatty said.

“The intention is to slow down peak flows in the Blackmans Swamp Creek, similar to the Ploughmans Creek scheme, and filter the water via the constructed wetland. This will mean that we will be able to extract more water over a longer period of time, along with the associated water quality improvements and environmental benefits downstream.

“We are currently doing a lot of flow modelling to assess environmental impacts. But, so far, modelling has shown us that creating these wetlands is actually beneficial for the local flora and fauna.”

Beatty said that the two schemes operate in distinctly different ways.

“The Ploughmans Creek scheme includes three constructed wetlands. The rain falls onto the urban catchment and flows into the series of constructed wetlands. We then pump water from those wetlands into a central holding pond," he said.

“The wetlands reduce peak flows in the creek system, improving water quality by natural filtration prior to transferring to Suma Park Dam.”

In contrast, the Blackman Swamp Creek Stormwater Harvesting Scheme extracts a large volume of water over a shorter time period, Beatty said. 

“At present, there are no wetlands in the Blackmans Scheme. It’s a quick and substantial flow that at the off-take point,” he said.

“The water from Blackman Swamp Creek is also drawn into the same 230 ML holding pond as the water from Ploughman Creek. The water then undergoes a natural settling process in the holding pond.”

From the holding pond, and before water enters the first of two batch ponds, alum is added to promote the settling of solids and attached contaminants.

“From there water is pumped to Suma Park Dam, which is our main water supply dam. There's minimal treatment involved, the process is predominantly about settling the water,” Beatty said.

Planning for the future

Beatty said diversification of water sources has been central to Orange City Council’s approach to water security issues in the past decade.

“Diversification of water supply has supported us through the drought. Further to the stormwater harvesting schemes, we have a pipeline from the Macquarie River, constructed a few years ago following the Millennium Drought,” Beatty said.

“There are conditions associated with the Macquarie pipeline. Our storage in Suma Park Dam has to be below 90% and the flow in the river must be greater than 108 ML/day. Assuming those conditions are met, we are able to pump 12 megalitres a day.

“We also use some groundwater. There's a range of different diversified supplies, which have managed to get us through a really dry period. This diversification of sources has been absolutely crucial.

“If we didn't have stormwater harvesting and we didn't have the Macquarie pipeline, the town may have needed to impose Level 6 restrictions on the community. 

Reaching that point of restriction on water use requires some difficult conversations with industry and businesses in terms of restricting operations. Level 6 is severe but with our diverse water sources and the change in weather conditions, we didn’t reach that point.”