Where does Coochiemudlo Island’s tap water come from?
By Angela Hoskins
Soon after moving to Coochiemudlo Island, I asked a long-time resident about our tap water, where it comes from. His simple, short answer: ‘From Straddie.’
That’s short for North Stradbroke Island, also known as Minjerribah, and the answer to my question surprised and intrigued me. I figured that it must be Straddie’s groundwater that is supplying us with tap water. From Morwong Beach I looked out to Minjerribah and imagined a deep, underwater pipe stretching across the bay, from that island across to Coochiemudlo Island, just for us. My imagination had got away on me (ahem)!
Of course, getting tap water to Coochiemudlo Island is not as straightforward as that.
On Morwong Beach, the northern shore of Coochiemudlo Island, with Minjerribah (North Stradbroke Island) in the background.
Coochiemudlo Island’s water arrives via a roundabout, complex system that services the Southern Moreton Bay Islands (SMBIs) and mainland communities on the way. Groundwater from Minjerribah is part of our water supply, along with bulk water fed into the system from a range of other sources and catchments.
What is groundwater?
Water on the Earth’s surface can seep into the ground and accumulate within aquifers — cracks or pores in rocks deep in the ground — forming a groundwater resource. Not all groundwater is suitable for human consumption. Australia’s groundwater makes up approximately 17% of the country’s water resources, accounting for over 30% of total water consumption. (Geoscience Australia)
Generally, groundwater has accumulated over untold years and replenishes only when rainfall is sufficient to infiltrate soil and rock meaning that groundwater can be either a finite or slowly replenished resource. In temperate and sub-tropical areas like south-east Queensland, when the rainfall is high, groundwater extraction can be managed on a renewable basis. However, in many instances Australia-wide where groundwater extraction is approaching or beyond sustainable limits. (Geoscience Australia)
In 2020, Redlands2030 published an article that expressed concern for Minjerribah’s aquifer, that it doesn’t have the capacity to keep supplying 60% of Redlands’ water needs without resulting in environmental harm. Minjerribah’s aquifer levels had dropped significantly during the millennium drought in 2007. With ongoing population growth and development on the Redlands Coast — and an unpredictable, changing climate — over-extraction could risk the replenishment process.
Redlands bulk water supply ratio (October 2024)
Redland City Council (RCC) reported that the ratio of our water supply sources varies a lot throughout the year. The ratio is dictated by Southeast Queensland Water (Seqwater) based on demand throughout the wider Seqwater interconnected water grid. As of October 2024, the mainland (including Coochiemudlo Island) and SMBIs water supply came from:
North Stradbroke Island (Minjerribah) groundwater 40%
Brisbane (Eastern Pipeline Interconnector) 33%
Capalaba Water Treatment Plant 27%.
Redlands Coast water supply
Seqwater and RCC are the government agencies responsible for our water supply. Seqwater takes care of catchment management, and raw water treatment including fluoridation and monitoring. RCC deals with the receipt of bulk water that is bought from Seqwater, and the delivery of water to customers through Council’s distribution network. RCC also is responsible for extensive water quality monitoring to ensure compliance with the Australian Drinking Water Guidelines.
Redland City Council Water Supply Zones (page 7 RCC Drinking Water Service Annual Report 2022/2023)
Groundwater on Minjerribah
On Minjerribah, three standalone water treatment plants (WTPs) process water for their local communities: at Dunwich, Amity Point and Point Lookout. A fourth WTP, on the south of island, is dedicated to the supply that is taken off island. This treated water is sourced from a combination of groundwater and water from Herring Lagoon on the eastern side of Minjerribah. An underwater pipe from the southwest of the island, at the closest point to Russell Island, distributes Minjerribah groundwater through a network of pipes to service the SMBIs, then onto reservoirs on the mainland at Mount Cotton. Technically, it is possible to reverse the flow of water so that the SMBIs can get access to water from the reservoirs on the mainland.
Heinemann Road Reservoirs
Coochiemudlo Island gets its tap water directly from the Heinemann Road Reservoirs.
The Heinemann Road Reservoirs, west of Redland Bay, is managed by Seqwater. Here, the groundwater from Minjerribah merges with bulk water from geographically diverse catchments — Brisbane, and potentially from as far as the Darling Downs — via the Eastern Pipeline Interconnector. From there, the water journeys through RCC’s reticulation network to supply tap water to Mt Cotton, Redland Ray, Victoria Point, Thornlands, and Coochiemudlo Island.
The underwater pipe for Coochiemudlo’s water supply reaches the island on the southwest shoreline, one of the closest stretches of water from the island to the mainland.
Southwest shoreline/point of Coochiemudlo Island where the water supply reaches the island. [Photo by Sure Shot Film]
Leslie Harrison Dam
Also known as the Tingalpa Reservoir, the Leslie Harrison Dam is located west of Capalaba. From here, the water is processed at the nearby Capalaba Water Treatment Plant before distribution to customers in the northern suburbs of the Redland City Scheme, about 25% of the Redlands population. Water from Heinemann Road reservoirs can also be distributed to the northern suburbs via the Alexandra Hills Reservoir.
Water usage in the Redlands
The Redlands City is generally the biggest user of water in Southeast Queensland. The region uses 200 litres of water per person each day. As a comparison, the Gold Coast uses 160–180 litres of water per person each day. There hasn’t been research into why the Redlands is the biggest user of water. Could a contributing factor be that our region was not under water restrictions a few years ago when many other regions in SE Queensland were?
Responses to droughts and water restrictions
Seqwater’s interconnected water grid was built in response to the water supply crisis of the Millennium Drought (2001-2009). Before the SEQ water grid, the different regions’ water supplies (dams, reservoirs etc.) were not connected. In times of drought, each local government area could have different water restrictions in place depending on their water supply levels. This meant Redland City might not reach the same restrictions as other areas if local water levels were high.
Now, with the interconnected grid, water restrictions are triggered regionally when combined overall dam levels reach a certain percentage.
Some water providers, such as Unity Water on the Sunshine Coast, sponsor school education programs about water cycles, efficiencies, and water conservation. The information school kids learn about water consumption does filter through to their parents, plus kids eventually grow up to run their own informed households. RCC does not currently have school-based education programs, but it does take part in regional communications planning and water-wise messaging. Recent wet years means that currently (as at October 2024) no water restrictions are in place in SE Queensland. Seqwater service providers, including RCC, will rollout consistent messaging during restrictions to reduce residents’ water usage.
Redlands water consumption: summary for the 28 day period ending Wednesday, 25 September 2024*
| Zone | Daily production (ML) | Daily per capita consumption | Total rainfall | Average max daily temperature |
|---|---|---|---|---|
| SEQ Service Provider | 939 | 172 | N/A | N/A |
| City of Gold Coast | 182 | 181 | 15.2 | 25.1 |
| Logan City Council | 79 | 179 | 0.0 | 27.5 |
| Redland City Council | 42 | 202 | 4.0 | 24.8 |
| Unitywater | 197 | 164 | 34.0 | 25.8 |
| Urban utilities | 439 | 168 | 8.4 | 27.2 |
Complaints about water quality in the Redlands
According to the statistical breakdown over a 12-month period in the table below, reported complaints about our water quality are few and far between.
Redlands water quality complaint statistics from 2022-2023
| Water Supply Scheme | Connections* | Health Concern | Discoloured Water | Taste and Odour | Total per 1000 Connections |
|---|---|---|---|---|---|
| Redland City Mainland and SMBI | 70,014 | 0 | 58 | 25 | 1.19 |
| Dunwich | 475 | 0 | 0 | 0 | 0 |
| Point Lookout | 1,218 | 0 | 0 | 1 | 0.82 |
| Amity Point | 403 | 0 | 0 | 1 | 2.48 |
| Total | 72,110 | 0 | 58 | 27 | 1.18 |
Reporting water mains leaks and water quality issues
From time to time, RCC receives reports from Coochiemudlo Island residents about mains water leaks located on streets. As it turns out, some of these reports are made after significant rain, and what looks like a leak from the island’s water mains can actually be a result of Coochiemudlo’s groundwater surfacing. It is always best to report something, though, if you are unsure.
You can report a leak on a footpath, road or outside the boundary of your property on the Redland Coast, or report a water quality issue — for example discolouration, strange taste, or suspected illness — by phoning RCC on 07 3829 8999.
Acknowledgements
Thanks to:
Water Quality Officer, RCC, for expertise and time taken with sharing much of this information.
Community Relations Officer, Seqwater, for emailed information.
References
Drinking Water Service Annual Report 2022/2023 (PDF)
Redlands Water and Water, Water Supply System Priority Infrastructure Plan (PDF)
