In Europe, the Loire, Po, Rhine and Danube rivers have all reached record-low levels in recent weeks, after prolonged hot and dry conditions. While the low water levels are prompting fascinating discoveries for historians as previously submerged artifacts are exposed, scientists say the shrinking rivers are a troubling sign of a deepening global water crisis. And it's not just the northern hemisphere that is impacted- Australian rivers are shrinking, too, and experts say there are dire consequences.
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TRANSCRIPT
Bosnia and Herzegovina's largest river, the river Bosna, typically flows as a deep, wide mass of water.
Parts of the the 271-kilometre-long river are now more rock than water, after multiple heatwaves and a prolonged drought.
There are rising concerns if conditions don't east, drinking water will run short, and local Fisherman Armin Fojskic says he expects large numbers of the river's fish to die.
“Low levels of water are critical for the fish, especially if it is extremely low, and these past days it has really been extremely low. The main danger for fish is oxygenation of the river, when water flow drops, the river loses oxygen and fish start to suffocate.”
The Bosna is one of a number of European rivers experiencing major water level declines, with the Loire, Po, Rhine and Danube rivers all reaching record-low levels in recent weeks.
Receding levels in the Danube have left Hungary struggling to cool its nuclear reactors to keep plants open, and Romania was forced to shut its last working reactor last week.
In Bulgaria, the remains of what is believed to be an ancient mammoth have been revealed, and in Serbia, the shrinking Danube river has uncovered shipwrecks from World War two.
Serbian Fisherman Zoran Lovric says he's never seen anything like it.
"This has literally never happened before, these wrecks we're heading towards right now have never been visible like this. They've always been completely submerged; what we're seeing now is utterly unprecedented."
While they might be prompting fascinating discoveries for historians, scientists say the shrinking rivers are a troubling sign of a worsening global water crisis.
The European Commission says about half of Europe’s land area is currently experiencing drought, with prolonged, poor rainfall combined with recurrent and severe heatwaves worsening conditions in recent months.
It comes as major wildfires continue to burn across the continent.
Hydro-climatologist and co-Founder of the Pacific Institute in California, Peter Gleick says what Europe is experiencing is not in line with normal weather fluctuations.
"Weather is always variable. We always have droughts. We always have floods somewhere at some time. We always have heat events and cold events. But what we're seeing now is extreme events worsened by human-caused climate change. We know that we're dumping greenhouse gases into the atmosphere. We know that's warming the planet. We know that it's altering these extreme events by making them more extreme, more frequent, and more intense."
He says the extreme patterns affecting rivers in Europe are similarly impacting water systems across the globe.
"So in the United States, for example, in the Western United States, the Colorado River, which is the largest river in the southwestern arid, dry part of the United States, shared by 7 states and Mexico, is at record low levels. Some of the largest reservoirs in the world are built on the Colorado River, and they're now at record lows. The amount of water in those reservoirs is lower than it's been since those reservoirs were built 80 or 90 years ago."
And it's not only rivers in the northern hemisphere that are losing water.
Water flows in Australia's largest river system, the Murray-Darling Basin, have been declining for decades.
There are 77,000 kilometres of rivers in the Basin, its vast networks stretching through most of New South Wales, all of the ACT, and parts of Queensland, South Australia and Victoria.
Director of Freshwater Ecosystems at LaTrobe University, Nick Bond, says since the 1997 to 2010 Millennium Drought, declining water levels have been especially notable.
"Rivers across the basin have shown declining patterns of runoff. And in particular, certain parts of the Basin, we're seeing much longer periods of cease to flow, so periods when the rivers actually stop flowing altogether."
The drastically low levels in the Basin have largely been blamed on water extraction, with multiple disasters, including mass fish kills, wetland loss and algal blooms attributed to over-use.
The Murray-Darling Conservation Alliance says irrigated agriculture is the major water use in the Murray-Darling Basin, accounting for around 80-90 per cent of water extraction.
In 2012, an agreement between the Australian Government and all Basin states was established, setting legal limits on water extractions, with the aim of balancing farming needs with river health.
Mr Bond says while over-extraction is undoubtedly a major contributor to receding water levels, human-induced climate change is also playing a part.
"There's no doubt that water extraction is impacting on stream flow patterns. And as the climate dries, those impacts become more acute. But even when we look at some of the head-water catchments where there's really limited water extraction, we are seeing in those catchments a drying trend as well. And so there's a very clear climate signal associated with the drying pattern."
This year, the Murray-Darling Basin Authority is reviewing the basin plan, to consider if changes are need to make it work more efficiently and effectively.
One of the areas the review is considering is how the latest science can inform how the plan responds to a changing climate, including hotter, drier weather and more extreme droughts.
Mr Bond says the impacts of climate change on the river system are manifold, and are expected to get worse as global temperatures continue to rise.
He says one key issue is that as water levels recede, water quality also declines.
"There's a number of issues that are arising, that's for sure. I guess one of the most obvious ones that people most directly experience is declining water quality. So we're seeing more examples of blue-green algal blooms, and incidents where, or situations where the water becomes undrinkable. From a biodiversity perspective, we're also seeing the loss of species in rivers that are drying out. That includes fish, important species like river mussels. So yeah, there's, there's clear biodiversity impacts that are occurring as a result of this drying."
He the vast networks of small streams that feed into the larger rivers are seeing significant impacts that are often overlooked.
"Those small waterways actually make up the large proportion of the entire river network when you, when you look at them on the map. And so the, the loss of flow and the loss of biodiversity in those systems is definitely a really important, really important issue."
Kamilaroi man Professor Bradley Moggridge is a hydro-geologist at the University of Technology, Sydney.
He says Aboriginal and Torres Strait Islander communities are experiencing some of the worst impacts of poor water quality as water flows reduce.
"It's a basic human right to have access to clean water, and then there's a lot of majority Aboriginal communities and Torres Strait Islander communities on the continent that struggle to get access to clean, healthy water or flushing toilets."Some communities draw straight from groundwater, some communities draw from rivers, and the health of those water bodies is questionable. There's been many reports done."
Professor Moggridge says as the Murray-Darling, traditionally known as the Baaka, shrinks, there are also deep cultural implications.
He says the river passes through the lands of more than 40 different Indigenous nations, each with different connections, stories and language linking them to the water.
"The Barkindji say, you know, they saw the river change and they could do nothing about it. And I suppose for them, they had to adapt. The Barkindji, are very much closely connected to the Baaka. They are the river people, the Baaka people. And I suppose it's, you know, for them to feel helpless on their own land, you know, I think the management has to change. But also, what is happening upstream to cause these low flows?"
As the combined impacts of water extraction and global warming threaten to further damage the river and its biodiversity, Mr Moggridge says a new approach is urgently needed. He says First Nations wisdom and knowledge about the river, stretching back tens of thousands of years, must be integrated into river management and protection.
"Understanding country and having those long associations, those long observation relationships over thousands of generations, Aboriginal people do hold that knowledge. And, you know, whether they're in stories, songs, but also part of the oral traditions is passed down through the generations. "
Mr Gleick says at a global level, as rivers continue to shrink across continents, it's clear a decisive shift is needed in how the world's water resources are managed. The World Meteorological Organisation says the powerful El Niño currently intensifying in the Pacific is increasing the likelihood of above-normal temperatures across much of the world, and driving significant shifts in rainfall patterns. Mr Gleick says greenhouse gas emissions need to be reduced to slow the rate of climate change as much as possible.
But he says global governments also need to adapt to those human-caused impacts that can now no longer be prevented.
"We have to build resilience to the extreme events that we're seeing. We have to learn how to deal better with floods and droughts and more extreme floods and droughts that are coming. So building resilience to the water system, to the climate impacts that we can no longer avoid is another piece of the puzzle."
