Some of Australia's best quality groundwater is found in upper and lower southeastern South Australia and parts of southwestern Victoria.
But almost 200 years of use for agriculture, livestock and domestic use have changed surface drainage. Groundwater in some areas has collapsed and water quality is deteriorating, putting at risk not only a fragile natural ecosystem but also a $5 billion regional economy.
Some of the biggest drops are occurring near commercial forestry plantations, particularly blue gum plantations, where monitoring by the SA Environment Department shows drops in the water table of several metres.
The last alarm sounded in 2023, when a large algae bloom contaminated Piccaninnie ponds in southern Australia, likely caused by low water levels and high nutrient loads.
Private from the National Parks and Wildlife Service of that state who worked in kayaks was detained about 10 tons of algae sludge and closed the ponds to snorkeling and diving.
The famous cave diving site, known for its crystal-clear waters and aquatic plants, is a Ramsar-listed wetland of international importance, a conservation park and a rare Australian example of a spring-fed karst wetland, largely fed by inflows of water. underground.
Discharge of water from the spring system, which would be drained, used for livestock irrigation or remain as a surface wetland, is also decreasing.
In 2022, the download was the lowest on record.
South Africa's deputy governor and cave diver Dr Richard Harris described what he saw after a dive at Piccaninnie as “horrific” and said he feared for the future of the ponds.
“I am concerned that what is happening at Piccaninnie Ponds and the recent drop in levels at Ewens Ponds could represent a tipping point, one of those moments where, if it really gets out of hand, we could face a local disaster.” . he told SE Voice.
Ewens Ponds, another famous diving spot nearby, closed this year due to a reported 50cm drop in water levels. Both Piccaninne and Ewens Ponds remain closed.
Signs of stress in the aquifers have been reported for decades, but the unusually dry year has reinforced the urgency.
Fourteen years ago, a Low Limestone Coast working group reported drops in the water table over the “past five to ten years” and warned that the region could be “reaching the limits of sustainable water use.”
In the north of the region, blue gum plantations are blamed for a 6 meter drop in groundwater levels.
Large drops present another threat: increased salinity.
South Africa's second largest city, Mount Gambier, and the Coonawarra wine region depend on groundwater, as do countless other small towns and farms.
The Southeast is the largest user of groundwater in the state. There is no more water available to allocate in the managed areas, according to the Low Limestone Coast Water Allocation Plan.
Independent conservation ecologist Claire Harding, who has consulted with NPWS, said few aspects of the ponds' hydrology were monitored.
“As site managers, the NPWS has limited capacity to manage issues relating to water quality and quantity in the Piccaninnie ponds that are likely to be caused by landscape-scale pressures,” it said after the closure of the ponds.
The ponds are surrounded by large dairies, irrigated crops, mining, improved pasture operations and forestry.
Harding said all of these industries occur higher up the ponds, with groundwater flowing in the direction of the ponds.
“I am not aware of any systematic monitoring of agricultural contaminants, whether from runoff or groundwater, in this area.”
South Africa's Department of Environment and Water (DEW) said it believes reduced inputs and high nutrient levels “partially” caused the bloom and will “undertake further investigations.”
South Africa's Environmental Protection Agency, responsible for nutrient testing, did not respond to questions.
Over the next three years, Panorama South Australia (Limestone Coast) is reviewing its 2013 water allocation plan.
Planning and development manager Liz Perkins said while the impact of continued water extraction was accepted, the decline in groundwater “is not an acceptable impact”.
Acceptable effects still need to be refined, he said.
Perkins said the effects of long-term use of groundwater could be “irreversible.”
“In places where groundwater levels have decreased and recharge has been reduced, recovery may not be possible,” he said.
Wetlands once covered 44% of the southeast. The drainage of agricultural properties (there are around 2,500 kilometers of drainage in the region) and land clearing reduced wetlands to only 6% of the surface.
In the process, a clay lining broke, the pure seal that held back water recharge and maintained levels.
The Green Triangle, the highly productive area covering south-west Victoria and south-east South Australia, contains 17% of Australia's forestry plantations, covering around 328,000 hectares in 2020.
The industry, one of the south-east's top three employers, is facing changes to the way SA regulates water allocations using a framework that guides adjustments to achieve the necessary outcomes.
In public information sessions for the review of the water allocation plan, questions were asked about how forestry and other industries with permanent plantations would handle lower water allocations if that is what the framework recommends.
The South Australian Forest Products Association wants water drained to the sea to be returned to the land. Its chief executive, Nathan Pine, said its plantations “have shrunk over the past decade with around 30,000 hectares lost due to environmental and water policy that has stopped tree replanting in core forest areas”.
He wants to ensure that every felled tree is replanted so that plantations can increase.