Heavy rains are great news for Sydney’s dams, but they come with a big caveat


Ian Wright, Western Sydney University and Jason Reynolds, Western Sydney University

Throughout summer, Sydney’s water storage level fell alarmingly. Level 2 water restrictions were imposed and the New South Wales government prepared to double the capacity of its desalination plant.

But then it began to rain, and rain. Sydney water storages jumped from 41% in early February to 75% now – the highest of any capital city in Australia.

This is great news for the city, but it comes with a big caveat. Floodwaters will undoubtedly wash bushfire debris into reservoirs – possibly overwhelming water treatment systems. We must prepare now for that worst-case pollution scenario.

Reservoirs filled with rain

The water level of Sydney’s massive Lake Burragorang – the reservoir behind Warragamba Dam – rose by more than 11 meters this week. Warragamba supplies more than 80% of Sydney’s water.

Other Sydney water storages, including Nepean and Tallowa dams, are now at 100%.
WaterNSW report that 865,078 megalitres of extra water has been captured this week across all Greater Sydney’s dams.

This dwarfs the volume of water produced by Sydney’s desalination plant, which produces 250 megalitres a day when operating at full capacity. Even at this rate, it would take more than 3,400 days (or nine years) to match the volume of water to added to Sydney’s supply this week.

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The Warragamba Dam before the drought and after the recent heavy rains.

But then comes the pollution

Thankfully, the rain appears to have extinguished bushfires burning in the Warragamba catchment for months.

But the water will also pick up bushfire debris and wash it into dams.

Over the summer, bushfires burnt about 30% of Warragamba Dam’s massive 905,000 hectare water catchment, reducing protective ground cover vegetation. This increases the risk of soil erosion. Rain will wash ash and sediment loads into waterways – adding more nitrogen, phosphorous and organic carbon into water storages.




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Bushfires threaten drinking water safety. The consequences could last for decades


Waterways and ecosystems require nutrients like phosphorous and nitrogen, but excess nutrients aren’t a good thing. They bring contamination risks, such as the rapid growth of toxic blue-green algae.

Drinking water catchments will always have some degree of contamination and water treatment consistently provides high quality drinking water. But poor water quality after catchment floods is not without precedent.

We’ve seen this before

In August 1998, extreme wet weather and flooding rivers filled the drought-affected Warragamba Dam in just a few days.

This triggered the Cryptosporidium crisis, when the protozoan parasite and the pathogen Giardia were detected in Sydney’s water supplies. It triggered health warnings, and Sydneysiders were instructed to boil water before drinking it. This event did not involve a bushfire.




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The Canberra bushfires in January 2003 triggered multiple water quality problems. Most of the region’s Cotter River catchments, which hold three dams, were burned. Intense thunderstorms in the months after the bushfire washed enormous loads of ash, soil and debris into catchment rivers and water reservoirs.

This led to turbidity (murkiness), as well as iron, manganese, nitrogen, phosphorus and carbon in reservoir waters. The inflow of organic material also depleted dissolved oxygen which triggered the release of metals from reservoir sediment. At times, water quality was so poor it couldn’t be treated and supplied to consumers.

The ACT Government was forced to impose water restrictions, and built a A$38 million water treatment plant.

Have we come far enough?

Technology in water treatment plants has developed over the past 20 years, and water supply systems operates according to Australian drinking water guidelines.

Unlike the 1998 Sydney water crisis, WaterNSW, Sydney Water and NSW Health now have advanced tests and procedures to detect and manage water quality problems.

In December last year, WaterNSW said it was aware of the risk bushfires posed to water supplies, and it had a number of measures at its disposal, including using booms and curtains to isolate affected flows.

However at the time, bushfire ash had already reportedly entered the Warragamba system.

The authors crossing the Coxs River during very low flow last September.
Author provided

Look to recycled water

Sydney’s water storages may have filled, but residents should not stop saving water. We recommend Level 2 water restrictions, which ban the use of garden hoses, be relaxed to Level 1 restrictions which ban most sprinklers and watering systems, and the hosing of hard surfaces.

While this measure is in place, longer term solutions can be explored. Expanding desalination is a popular but expensive option, however greater use of recycled wastewater is also needed.




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Highly treated recycled water including urban stormwater and even treated sewage should be purified and incorporated into the water supply. Singapore is a world leader and has proven the measure can gain community acceptance.

It’s too early to tell what impact the combination of bushfires and floods will have on water storages. But as extreme weather events increase in frequency and severity, all options should be on the table to shore up drinking water supplies.The Conversation

Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University and Jason Reynolds, Senior Lecturer in Geochemistry, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bushfires threaten drinking water safety. The consequences could last for decades



Warnings about poor drinking water quality are in place in some areas affected by the bushfires.
From shutterstock.com

Stuart Khan, UNSW

Bushfires pose serious short- and long-term impacts to public drinking water quality. They can damage water supply infrastructure and water catchments, impeding the treatment processes that normally make our water safe to drink.

Several areas in New South Wales and Victoria have already been issued with warnings about the quality of their drinking water.

Here’s what we know about the short- and long-term risks.




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Short-term risks

Bushfires can damage or disrupt water supply infrastructure as they burn. And the risks can persist after the fires are out.

A loss of power, for example, disables important water treatment processes such as chlorine disinfection, needed to kill microorganisms and make our water safe to drink.

Drinking water for the towns of Eden and Boydtown on the NSW south coast has been affected in this way over recent days. Residents have been advised to boil their water before drinking it and using it for cooking, teeth brushing, and so on.

Other towns including Cobargo and Bermagui received similar warnings on New Year’s Eve.




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In some cases, untreated water, straight from a river supply, may be fed directly into drinking water systems. Water treatment plants are bypassed completely, due to damage, power loss, or an inability to keep pace with high volumes of water required for firefighting.

We’ve seen this in a number of southern NSW towns this week including Batlow, Adelong, Tumbarumba, and the southern region of Eurobodalla Council, stretching from Moruya to Tilba. Residents of these areas have also been urged to boil their drinking water.

Untreated river water, or river water which has not been properly disinfected with chlorine, is usually not safe for drinking in Australia. Various types of bacteria, as well as the parasites giardia and cryptosporidium, could be in such water.

Animals including cattle, birds and kangaroos can excrete these microorganisms into river water. Septic tanks and sewage treatment plants may also discharge effluents into waterways, adding harmful microorganisms.

Human infection with these microorganisms can cause a range of illnesses, including gastrointestinal diseases with symptoms of diarrhoea and vomiting.




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Long-term risks

Bushfires can damage drinking water catchments, which can lead to longer term threats to drinking water. Drinking water catchments are typically forested areas, and so are vulnerable to bushfire damage.

Severe impacts to waterways may not occur until after intense rainfall. Heavy rain can wash ash and eroded soil from the fires into waterways, affecting drinking water supplies downstream.

For example, bushfire ash contains nutrients, such as nitrogen and phosphorous. Increased nutrient concentrations can stimulate the growth of cyanobacteria, commonly known as “blue-green algae”.

Cyanobacteria produce chemicals which may cause a range of water quality problems, including poor taste and odour. Some cyanobacteria can produce toxic chemicals, requiring very careful management to protect treated drinking water.

Boiling water will kill microorganisms, but not chemical substances.
From shutterstock.com

Many water treatment plants include filtration processes to filter small suspended particles from the water. But an increase in suspended particles, like that which we see after bushfires, would challenge most filtration plants. The suspended particles would be removed, but they would clog the filters, requiring them to be more frequently pulled from normal operation and cleaned.

This cleaning, or backwashing, is a normal part of the treatment process. But if more time must be spent backwashing, that’s less time the filters are working to produce drinking water. And if the rate of drinking water filtration is slowed and fails to keep pace with demand, authorities may place limitations on water use.




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Boiling water isn’t always enough

In order to reduce the risk of gastrointestinal and other illnesses, water suppliers and health departments may issue a boil water alert, as we’ve seen in the past week. Bringing water to a “rolling boil” can reliably kill most of the microorganisms of concern.

In cases where water may be contaminated with chemical substances rather than microorganisms, boiling is usually not effective. So where there’s a risk of chemical contamination, public health messages are usually “do not drink tap water”. This means bottled water only.

Such “do not drink” alerts were issued this week following bushfire impacts to water treatment plants supplying the Victorian towns of Buchan and Omeo.




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Impacts to catchments from bushfires and subsequent erosion can have long-lasting effects, potentially worsening untreated drinking water quality for many years, even decades.

Following these bushfires, many water treatment plant operators and catchment managers will need to adapt to changed conditions and brace for more extreme weather events in the future.The Conversation

Stuart Khan, Professor of Civil & Environmental Engineering, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

‘New Bradfield’: rerouting rivers to recapture a pioneering spirit


Waters from the Herbert River, which runs toward one of northern Australia’s richest agricultural districts, could be redirected under a Bradfield scheme.
Patrick White, Author provided

Patrick White, James Cook University and Russell McGregor, James Cook University

The “New Bradfield” scheme is more than an attempt to transcend environmental reality. It seeks to revive a pioneering spirit and a nation-building ethos supposedly stifled by the bureaucratic inertia of modern Australia.

This is not a new lament. Frustrated by bureaucracy, politicians in North Queensland have long criticised the slow pace of northern development.




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In 1950, northern local governments blamed urban lethargy. One prominent mayor complained:

… these young people lack the pioneering spirit of their forebears, preferring leisure and pleasure to hardships and hard work.

These sentiments were inspired by an agrarian nostalgia that extolled toil and toughness. Stoic responses to the challenges of life on the land are part of the Australian legend.

With drought devastating rural and urban communities and a state election looming in Queensland in 2020, both sides of politics have proposed a “New Bradfield” scheme.

An idea with 19th-century origins

Civil engineer John Bradfield devised the original scheme in 1938. His plan would swamp inland Australia by reversing the flow of North Queensland’s rivers. Similar proposals go back to at least 1887, when geographer E.A. Leonard recommended the Herbert, Tully, Johnstone and Barron rivers be turned around to irrigate Australia’s “dead heart”.

Blencoe Falls, on a tributary of the Herbert River, North Queensland, during the dry season.
Patrick White, Author provided

As the “dead heart” became the “Red Centre” in the 1930s, populist writers revived the dreams of big irrigation schemes.

These schemes have always been contested on both environmental and economic grounds. A compelling history of Bradfield’s proposal reveals many errors and miscalculations. But what the scheme lacked in substance it made up for in grandiose vision.

Water dreaming has been a powerful theme in Australian history. The desire to transform desert into farmland retains appeal and discredited schemes like Bradfield keep reappearing.




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The keys to unlock Northern Australia have already been cut


Contempt for nature and country

While less ambitious than the original plan, the “New Bradfield” scheme still engineers against the gradient of both history and nature. It would have irreversible consequences for Queensland’s environment, society and culture.

What’s more, the new scheme manifests much the same mindset as the old.

It’s an attitude that privileges the conquest of nature: in this case literally up-ending geography by turning east-flowing rivers westward. Its celebration of the human struggle against defiant nature reprises the pioneering ethos.

Like many pioneers, “New Bradfield” proposals disregard the interests and land-management practices of Indigenous people. The bushfires ravaging the eastern states show the folly of ignoring traditional ways of caring for country .

Overlooking native title realities can also cost governments and communities.




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Polarising debate neglects more viable projects

“New Bradfield” is promoted as “an asset owned by all Queenslanders for all Queenslanders”. But environmental destruction and disputes over water sales in the Murray-Darling Basin sound a warning.

The Queensland Farmers Federation has cautiously welcomed the new scheme. Others have dismissed it as a “pipe dream”.

Thus, northern Australia again sits amid a polarised debate about its utility to the nation. Such polarising contests diminish the likelihood of more viable projects being implemented.

Extravagant expectations of “untapped” northern resources have been proffered for nearly two centuries. Distant governments have fantasised the Australian tropics as a land of near-limitless potential. Northern communities have many times been disappointed by the results.

Today’s promises to “drought-proof” large areas of Queensland rely on similar images. “Drought-proofing” aims to keep people on the land but often defies economic and social reality.




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We can’t drought-proof Australia, and trying is a fool’s errand


Dam developments have an underwhelming record

The “New Bradfield” rhetoric echoes the inflated expectations of myriad disappointing northern development plans in the past. The Ord River project was touted as an agricultural wonder that would put hundreds of thousands of farmers into the Kimberley. Its success lies forever just over the horizon.

Much closer to the present proposal is the Burdekin Falls Dam. It sits in the lower reaches of the same river earmarked for the Hells Gates Dam that would feed the “New Bradfield” scheme. Damming Hells Gates has been advocated since at least the 1930s and has new supporters.

The proposed site for Hells Gates Dam is on Gugu Badhun country on the Burdekin River.
Dr Theresa Petray, Author provided

Back in the 1950s, damming the Burdekin was expected to generate hydro-electric power and irrigate vast swathes of farmland. After decades of political squabbling, the dam was completed in 1988. It does not generate hydro power. Although it irrigates some land downstream, the anticipated huge agricultural expansion never happened.

The Burdekin Falls Dam has helped the regional economy and could help to overcome the water shortages of the nearby city of Townsville. But it has not met the inflated expectations widely proffered decades earlier. The benefits that would flow from another dam further upstream are likely to be even more meagre.




Read more:
Damming northern Australia: we need to learn hard lessons from the south


Grandiose visions of northern development have a habit of failing. A “New Bradfield” scheme, animated by an old pioneering ethos, is unlikely to be different.

Drought-affected communities would derive more benefit from sober proposals that acknowledge the past, integrate Indigenous knowledge and incorporate agricultural innovation.The Conversation

Patrick White, PhD Candidate in History and Politics, James Cook University and Russell McGregor, Adjunct Professor of History, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Researchers allege native logging breaches that threaten the water we drink



Researchers have uncovered what appears to be widespread logging of steep slopes in Victoria, which has the potential to damage critical water supplies.
Chris Taylor, Author provided

David Lindenmayer, Australian National University and Chris Taylor, Australian National University

The Victorian government’s logging business is cutting native forests on steep slopes, in an apparent rule breach that threatens water supplies to Melbourne and rural communities.

Our research indicates that across vital water catchments in the Central Highlands of Victoria, state-owned VicForests is logging native forest on slopes steeper than is allowed under the code of practice. Logging also appears to be occurring in other areas supposedly excluded from harvesting.

Logging operations are prohibited from taking trees from slopes steeper than a certain gradient, because it can lead to soil damage which compromises water supplies. There are far better commercial alternatives to this apparent contravention of the rules, which must immediately cease.

A steep slope recently logged measuring 33 degrees on site near Mount Matlock in the Upper Goulburn Catchment.
Chris Taylor

Logging on steep slopes matters

Water catchments are areas where the landscape collects water. They are defined by natural features such as mountain ridgelines and valleys. Rain drains into rivers and streams, which supply water to reservoirs.

Forest cover protects the soil in water catchments by preventing erosion and other damage which can pollute water.

Areas that provide water for drinking, agriculture and irrigation are known in Victoria as special water supply catchments. Under the state’s Code of Forest Practice, logging in these catchments is prohibited on slopes steeper than 30 degrees (or 25 degrees in some catchments). VicForests claims it does not log trees on such slopes.

Sobering evidence

Water in some affected catchments ends up in Melbourne’s drinking water supply.

We analysed slopes across multiple special water supply catchments. We first examined the relationships between slope and logging disturbance using data from the Victorian government, Geoscience Australia, and the European Space Agency. To confirm the results, we visited multiple sites in the Upper Goulburn catchment, which supplies water to Eildon Reservoir, to measure the slopes ourselves.

We found logging in many areas steeper than 30 degrees. In larger catchments such as the Upper Goulburn, around 44% of logged areas contained slopes exceeding this gradient. In many instances, logged slopes were far steeper than 30 degrees and some breaches covered many hectares.

In the Thomson, Melbourne’s largest water supply catchment, 35% of logged areas contained slopes steeper than 30 degrees.

We also found areas that should have been formally excluded from logging but where the forest had been cut. Many of these exclusion zones were around steep slopes. In the Upper Goulburn catchment, nearly 80% of logged areas contained exclusion zones that should not have been cut.

Recently logged areas near Mount Matlock in the Upper Goulburn Water Catchment. The top map shows where we detected slopes exceeding 30 degrees in logged areas (red). The bottom map shows areas designated by the Victorian government as exclusion zones (magenta).
DELWP 2019, ESA 2019, Gallant et al. 2011

Why is this happening?

Last week, VicForests rejected our allegations of slope breaches. VicForests claimed it was complying with a rule under which 10% of an area logged can exceed 30 degrees. This rule applies to general logging areas; our interpretation is this exemption does not apply to the special water supply catchments.

Forest on steep and rugged terrain is economically marginal for wood production because the trees are relatively short and widely spaced. Almost all timber from these areas is pulpwood for making paper.

So why are such areas being logged at the risk of compromising the water catchments that supplies Melbourne and regional Victoria?

We suspect pressure to log steep terrain is tied to the Victorian government’s legal obligation to provide large quantities of pulp logs for making paper until the year 2030 (coincidentally the year the government plans to phase out native forest logging).

This pressure is reflected in recent reductions in log yields. Some commentators have blamed efforts to protect the critically endangered Leadbeater’s possum for this trend. However, only 0.17% of the 1.82 million hectares of forest allocated to VicForests for logging has been taken out of production to protect this species.

In our view, other possibilities for declining yields are past over-cutting and bushfires. VicForests failed to take into account the effects of fire on its estimates of sustained timber yield – despite some of Victoria’s forests being some of the world’s most fire-prone environments.

There are alternatives

Pulp logs sourced from native forests is not a commercial necessity; there are viable alternatives. Victorian hardwood plantations produced 3.9 million cubic metres of pulp logs last year. Most of this was exported.

If just some of these logs were processed in Victoria, it would be enough to replace the pulpwood logged from native forests several times over. Plantation wood is better for making paper than native forest logs, and processing the logs in Victoria would boost regional employment.

Degrading soil and water by logging steep terrain is not worth the short-term, marginal gain of meeting log supply commitments, especially when there are viable alternatives. The Victorian government must halt the widespread breaches of its own rules.


In a statement, VicForests said it “strongly rejects” the allegations raised by the authors.

In addition to the refutations included in this article, the company said:

  • Any concerns about its practices should be referred to the Office of the Conservation Regulator

  • VicForests does very little harvesting in catchments, where restrictions are in place

  • In the Thompson catchment, VicForests only harvests on average 150ha a year out of about 44,000ha in the catchment – which is 0.3%, or around 3 trees in 1000

  • VicForests only asks contractors to harvest on slopes if it complies with regulation.The Conversation

David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University and Chris Taylor, Research Fellow, Fenner School of Environment and Society, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

80% of household water goes to waste – we need to get it back


Roberta Ryan, University of Technology Sydney

As regional Australian towns face the prospect of running out of water, it’s time to ask why Australia does not make better use of recycled wastewater.

The technology to reliably and safely make clean, drinkable water from all sources, including sewage, has existed for at least a decade. Further, government policy has for a long time allowed for recycled water to ensure supply.




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The greatest barrier to the widespread use of recycled wastewater is community acceptance. Research from around the world found the best way to overcome reluctance is to embrace education and rigorously ensure the highest quality water treatment.

In 2006 Toowoomba voted against introducing recycled water, despite extensive drought gripping the area.
Allan Henderson/Flickr, CC BY

Why not use stormwater?

Many people are happy to use recycled stormwater, while being reluctant to cook, drink or wash with recycled household wastewater. But there are technical, cost and supply issues with relying on stormwater to meet our country’s water needs. Stormwater has to be cleaned before it is used, the supply can be irregular as it is reliant upon rain, and it has to be stored somewhere for use.

On the other hand, household wastewater (which is what goes into the sewerage system from sinks, toilets, washing machines and so on) is a more consistent supply, with 80% or more of household water leaving as wastewater.

Furthermore, wastewater goes to treatment plants already, so there is a system of pipes to transport it and places which already treat it, including advanced treatment plants that can treat the water to be clean enough for a range of purposes. There are strong economic, environmental and practical arguments for investing more effort in reusing wastewater to meet our water supply needs.

This water can be used for households, industry, business and agriculture, greening public spaces, fighting fires, and topping up rivers or groundwater.

The water cycle

Technically, all water is recyled; indeed we are drinking the same water as the dinosaurs. Put very simply, water evaporates, forms clouds and falls as rain, and is either absorbed into the earth and captured underground or filtered through rock and goes back again into oceans and rivers.

When we capture and reuse water, we are not making more water, but speeding up the water cycle so we can reuse it more quickly.

Not pictured: the many, many animals and people every drop of water has passed through over millennia.
Wikimedia Commons, CC BY-SA

We do already reuse wastewater in Australia, with many parts of regional Australia cleaning wastewater and releasing it into rivers. That water is then extracted for use by places downstream.

Despite this, there have been significant community objections to building new infrastructure to reuse wastewater for household use. In 2006, at the height of the Millennium drought, Toowoomba rejected the idea entirely.

However, since then a scheme has been successfully established in Perth. We must examine these issues again in light of the current drought, which sees a number of Australian regional centres facing the prospect of running out of water.




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Lessons from overseas

Singapore has had enormous success in reusing wastewater for all kinds of purposes.
EPA/HOW HWEE YOUNG

Despite initial reluctance, many places around the world have successfully introduced extensive wastewater recycling. Places such as Singapore, Essex, California, New Mexico, and Virginia widely use it.

Recent research from the Water Services Association of Australia, working with other research bodies, found several key lessons.

Firstly, the language we use is important. Phrases like “toilet to tap” are unhelpful as they don’t emphasise the extensive treatment processes involved.




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The social media and news outlets can play an significant role here. In Orange County, California, wastewater was introduced through a slow process of building acceptance. Influential individuals were enlisted to explain and advocate for its uses.

Secondly, communities need time and knowledge, particularly about safety and risks. Regulators play an important role in reassuring communities. In San Diego, a demonstration plant gave many people the opportunity to see the treatment process, drink the water and participate in education.

We need to go beyond information to deep consultation and education, understanding where people are starting from and acknowledging that people
from different cultures and backgrounds may have different attitudes.

El Paso successfully introduced wastewater through strong engagement with the media and significant investment in community education, including explaining the water cycle.

Finally, quality of the water needs to be great and it needs to come from a trustworthy source. The more it happens, and people know that, the more likely they are to feel reassured.




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It’s clear the public expect governments to plan and act to secure our future water supply. But we can’t just impose possibly distasteful solutions – instead, the whole community needs to be part of the conversation.The Conversation

Roberta Ryan, Professor, UTS Institute for Public Policy and Governance and UTS Centre for Local Government, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Dams are being built, but they are private: Australia Institute



A senior water researcher at the institute said politicians don’t want to talk about private dams because “they do nothing for drought-stricken communities”.
Shutterstock

Michelle Grattan, University of Canberra

A report from The Australia Institute rejects government claims new dams are not being built, saying at least 20 to 30 large private dams have been constructed in the Murray-Darling basin in recent years.

While information on the number of private dams and the cost of their taxpayer subsidy is limited, the report says “it appears that just two of these dams cost taxpayers nearly $30 million”.

“Over $200 million was spent on dam-related projects [in the Murray-Darling Basin] according to official data, although not all of this will have been specifically on dams,” it says,

Maryanne Slattery, senior water researcher at the institute, said politicians don’t want to talk about these dams because “they do nothing for drought-stricken communities, the health of the river or struggling farmers”.

“These dams have been built on private land and are for the exclusive use of corporate agribusiness, such as Webster Limited,” she said.

“Politicians are reluctant to talk about why millions of taxpayer dollars have been spent subsidising dams that make the problems of the Murray Darling Basin worse”.

Water Minister David Littleproud has repeatedly berated the states for not building new dams. He said recently that of the 20 dams completed since 2003, 16 were in Tasmania.

“If NSW, Queensland and Victoria don’t start building dams, their water storage capacity will fall by more than 30% by 2030,” he said. “We put $1.3 billion on the table in through the national water infrastructure development fund in 2015 and have still had to drag most states kicking and screaming to build new dams.”

The report says new public dams would require public consultation, including with stakeholders who had environmental and economic concerns.

But private dams involved “minimal public consultation and can be approved and constructed based on environmental assessments commissioned from private consultants by dam proponents”.

The report looked at three dams in detail, on properties in the Murrumbidgee Valley owned by Webster Ltd – Glenmea, Bringagee and Kooba Station. The dams were funded out of the federal government’s $4 billion water efficiency program.

The report argues such dams are not the best way to save water. It points to the department of agriculture and water resources saying new dams can save water where they replace shallower ones (which have more evaporation), or where they collect recycled irrigation water.

“However, none of the three case-study dams in this report save water in this way. They are new dams, not replacing smaller, shallower dams. Water stored behind their approximately eight metre high walls would otherwise be stored in public headwater dams around 100 metres deep.”

These dams are designed to divert normal irrigation water and “supplementary water” – not to simply recycle irrigation water, the report says. Thus “they increase both evaporation and irrigation water use”.

Supplementary water is water that is surplus to consumptive needs. It is important environmentally and to downstream users, historically making up almost all the water flowing from the Murrumbidgee into the Murray, the report says.

“With major dams now targeting this water, the Murrumbidgee could be disconnected from the Murray in most years. This has implications for all NSW Basin water users, who are already grappling with how to meet downstream obligations within the Murray’s constraints and with no water coming down the Darling.”

The report says a Canadian pension fund had just been reported as “swooping” on Webster, “with specific mention of a property with one of these new dams”.

“The new dams that Australian taxpayers helped build appear to be highly valued by international investors,” the report says.The Conversation

Michelle Grattan, Professorial Fellow, University of Canberra

This article is republished from The Conversation under a Creative Commons license. Read the original article.