The long and ‘catastrophic’ road to Murray-Darling water reform

It seems that many people in the water industry believe that water reform in Australia, and in the Murray-Darling Basin in particular, started with the National Water Initiative in 2004. But, this is selective memory and back-slapping on the part of the current cohort of water bureaucrats.

The long road to MDB water reform started over 40 years ago, in the late 1960’s not in the 2000’s.  In drawing attention to this much longer water reform timeline, I want to emphasise the central role of ‘catastrophes’ in creating the right political, social and economic environment for change.

The first of these policy-changing catastrophes for the MDB was the 1967 drought. This revealed to all who were on the land at that time what the Egyptian Pharaohs had learned over three millennia ago. If you get the water balance wrong on poorly-drained irrigated lands then massive salinisation problems will follow as surely as night follows day. The first major investigation into Murray Valley salinisation was prepared by consultants Gutteridge, Haskins & Davey in 1970 for the River Murray Commission (as it was known in those days).

The machinery of government and the bureaucracy moved slowly for another decade until the next big drought in 1982-3 yet again revealed the lurking threat of salinity. At the same time, in concert with rapidly growing and often poorly conceived upstream water allocation agreements, this drought caused the first recorded closure of the Murray Mouth (where the river system discharges to the sea in South Australia) since European settlement.

These catastrophic landscape events – and indeed they were catastrophic for both farmers and aquatic ecosystems affected – prompted a major, coordinated policy response by the Murray-Darling States and the Commonwealth Government. 1985 saw the first Meeting of the Murray-Darling Basin Ministerial Council and in 1988 the (revamped) Murray Darling Basin Commission1 (MDBC) was established with the objective to: “Promote and coordinate effective planning and management of the equitable efficient and sustainable use of the water, land and other environmental resources of the Murray-Darling Basin.”

The first actions of the new MDBC were to agree the MDB Salinity and Drainage strategy in 1988, and to implement the first integrated land and water, Natural Resources Management Strategy from 1989.

It was another catastrophe, in another decade, that re-activated the water reform process in the 1990’s. This time it was the infamous 1000 km long bloom of toxic blue-green algae in the Darling River in the summer of 1991.

This event generated saturation media coverage for weeks right across Australia (and even globally). There can be no doubt for any of us old enough to remember that the Darling River toxic algal bloom was a pivotal event that galvanised public and political opinion for radical policy change. The fact that around the same time the Murray Mouth closed yet again only added fuel to the fire that was public outrage about the over-exploitation of the Murray-Darling’s waters. Even the most conservative of agricultural and irrigation organisations realised that change had to come.

And come it did, and in pretty rapid time considering the normally glacial pace of political and bureaucratic policy reform. 1994 saw the first official COAG2 Water Reforms agreed. Forget what people may tell you about the National Water Initiative in 2004, it was the 1994 COAG Agreement that set the Murray-Darling and the rest of Australia, cities included, on the path to the re-visioning of ‘sustainable’ water use that we see today. To quote directly from the February 1994 COAG Communique: “while progress is being made on a number of fronts to reform the water industry and to minimise unsustainable natural resource use, there currently exist within the water industry

  • approaches to charging that often result in commercial and industrial users of water services, in particular, paying more than the costs of service provision;
  • major asset refurbishment needs in rural areas for which, in general, adequate financial provision has not been made;
  • impediments to irrigation water being transferred from low value broad-acre agriculture to higher value uses in horticulture, crop production and dairying;
  • service delivery inefficiencies; and
  • a lack of clear definition concerning the role and responsibilities of a number of institutions involved in the industry”

The policy and managerial flow-on from these concerns can be clearly seen in the way we trade, price, allocate and manage water across Australia today.

The following year, 1995, saw the imposition of the MDB Cap on surface water use, and in 1996 the landmark ARMCANZ ‘National Principles for the Provision of Water for the Environment’ were published.

It was just one more drought in one more decade – but this time the worst of all – that lead to the National Water Initiative in 2004 (which in many ways only reaffirmed the 1994 reforms and provided updated roadmaps for implementation), the Commonwealth Water Act in 2007, and ultimately, the Murray-Darling Basin Plan, agreed in 2012.

By the new Millennium just about everyone had had enough of watching productive farming lands run out of water, and river vegetation and wildlife being ravaged by drought or poisoned by acid-sulfate sediments.

There is no doubt that the National Water Initiative and the Murray-Darling Basin Plan are pinnacle water reform policy achievements, both for Australia and for the world.   But it is worth remembering they were a long time coming, and we had to suffer near-decadal catastrophe after decadal catastrophe to really galvanise ourselves to action.

It has indeed been a long and catastrophic path to water reform in the Murray-Darling Basin …let‘s hope we don’t need more in the coming decades to keep us vigilant. The political signs right now are not at all encouraging.

Footnotes:

1 This was the second major policy change in the MDB’s management history – the first being the establishment of the River Murray Commission in 1917. It saw a fundamental shift from seven decades of ‘management for supply’ to a new era of ‘management for sustainability’.

2 COAG is the Council of Australian Governments, and the peak inter-governmental (federal-state) policy-setting forum in Australia.

This blog is an edited version of an opinion piece published in the Newsletter for the Peter Cullen Trust in 2013.

The California Water Market 2014

Worth reading this interesting article on the Californian drought and water trading by Wes Strickland (see Bloomberg article attachment too)

Private Water Law

There has been no shortage of news articles on the California drought this year. Many have helped inform the public about critical issues related to the conservation and development of water resources in the state, and about changes or potential changes in the laws and regulations concerning urban water use and groundwater. There have also been a number that focus on the existence of and increased activity in a market for water rights and supplies, including this article from today in Bloomberg.

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Developing Australia’s tropical water resources – Part 3

Part 3.  Conclusions

Australia already produces enough food to feed 60 million people, of which we export almost two thirds. Australia is number ten among net food exporting countries in the world. We have more than enough food to feed ourselves for many decades, if not centuries, to come.

We have learned much from the environmental mistakes made over the past century in developing profitable agricultural production in southern Australia, the Murray-Darling Basin in particular. Agricultural productivity and efficiency are continuously improving and, at the same time, water is being recovered for the environment to remedy past impacts on river and floodplain ecosystems.

In theory, it should be possible to to expand irrigated agriculture in the north in a resource-sustainable way while avoiding significant ecological damage.

The tough questions remaining, however, are these:

  1. We may have the knowledge, but do we have the political will to fund and implement agricultural practices in the tropical north in a sustainable manner, or will northern Australia simply repeat the mistakes made in the Murray-Darling Basin and elsewhere?
  2. Even if the political will exists, are the apparently modest economic gains from irrigated agricultural expansion in northern Australia worth the risk of losing the cultural, tourism and other benefits of such pristine and biodiverse tropical lands and river systems?

As has been noted by other authorities, there is probably a far better case for driving greater irrigation efficiencies and productivity in southern Australia than for further developing the north. Here there are already well established food production and market-delivery systems, and the scale of agricultural production is an order of magnitude greater than anything that appears viable in Northern Australia. And to be frank, in the south the ecological damage has already been done and is now, if slowly, being repaired. 

Developing Australia’s tropical water resources – Part 2

Part 2.  Is there a case for major expansion of irrigation in Northern Australia?

Earlier this week in Part 1 I argued that ecologically-sustainable irrigated agriculture is, at least, technically feasible (if politically unrealistic!) …….the remaining fundamental question is this – is Australia’s tropical north the potential agricultural utopia it is claimed by many to be?

The northern regions in question stretch from Broome in Western Australia to Cairns in north Queensland. There is already rangeland grazing through the region, and some irrigated agriculture, for example in Western Australia (Ord River), Queensland (Flinders and Gilbert Rivers) and the Northern Territory (Daly River).

The idea that northern Australia should be a good place to develop agriculture has been pervasive for many decades, in spite of well-documented arguments to the contrary (for example, Davidson, 1965). The region has almost 50 per cent of Australia’s total surface water runoff, a big contrast to the runoff in the Murray Darling Basin of only six per cent, and where there is already billions of dollars-worth of agricultural productivity. It is captivating in a food-hungry world to think we might harness those northern water resources and have more agriculture and more production. Naturally, it is not quite that simple, or development would have proceeded long ago (notwithstanding the initial faltering attempts for the Ord Irrigation scheme).

A relatively recent set of scientific, economic and cultural studies into the development prospects of the north was reported by the Northern Australia Land and Water Taskforce (CSIRO 2009). One key point from that investigation is that, despite the high average rainfall, the north is seasonally water limited. This is not unusual in the tropical latitudes, being also the case in the Philippines, Indonesia and parts of southern India. In all of those countries, a higher than average annual rainfall does not guarantee a year-round water supply.

A further important point noted by the Northern Australian Land and Water Task Force (CSIRO, 2009) is that the most useful rainfall tends to be away from areas where the soils are suitable for irrigation. Also, there are not very many good locations for big dam sites in the north (notwithstanding the major ecological impacts of large dams already discussed). Although Lake Argyle, the second largest dam in Australia, has been built on the Ord River in northern Western Australia, there are not many dam sites like that and, as already noted, it is to be hoped we are wise enough now to know that building large dams like that is not the way of the future.

CSIRO and others acknowledge, however, that there is potential for some new irrigated agricultural development in northern Australia, largely based on complementary use of surface water and groundwater, between wet season and dry season. But the extent of this is nowhere near that suggested by some.

Prior to the 2013 federal election, the Liberal-National opposition (now government) released ‘Coalition 2030 Vision for Developing Northern Australia’, their vision for developing northern Australia. That policy document stated that Australia’s agricultural production could be doubled by 2030 with such northern development.

However, CSIRO and the northern Australian Task Force had already concluded that only about 600 gigalitres (GL) of groundwater is available to sustainably support production, which is a very small amount when compared to the greater than ten thousand gigalitres of water typically used by irrigated agriculture across Australia (in non-drought years). On an area basis this would mean an additional 40,000-60,000 hectares of irrigated farmlands,[i] which is minor compared to that already in Australia of 1.8 million hectares.

It was concluded that achievable extra irrigated agricultural production in Northern Australia is likely to be only around three to four per cent – a long way from the doubling proposed by the (now) Federal Government.

The Flinders and Gilbert catchments in the elbow of the Gulf of Carpentaria feed significant river systems and, during 2013, the Queensland Government released about 94 GL of that surface water for new irrigation developments there. Again, this is not very much water in comparison with the volumes in use for irrigation in southern regions, although it is evidence that some new agricultural development is underway in the north.

From an ecological perspective, there is a pertinent warning by Georges et al. (2002) based on work in the Daly River that overuse of groundwater is likely to interfere with habitat for at least some of the north’s unique freshwater species, especially turtles and other amphibians.

One other important aspect that must be understood and respected in the north, particularly around the Gulf of Carpentaria, is that successful coastal commercial and recreational fisheries for Barramundi and Banana Prawns are highly dependent on the amounts of water that flow down the rivers and out to sea. If too much water is taken out for agriculture upstream, the coastal fisheries are likely to suffer. This point was made recently by Professor Michael Douglas who leads the Tropical Rivers and Coastal Knowledge (TRaCK) research hub based in Darwin (TRaCK 2012):

There is a perception that wet season flows in the north are ‘wasted’, but our research has shown a direct correlation between river flows and the commercial and recreational catches of coastal fish such as barramundi, king threadfin, and prawns…..Large floods that spill over the banks allow fish to move onto the floodplains to feed then move back out to the river as the floodplains dry….This means that much of the meat on barramundi in the upper reaches of river systems may have been ‘grown’ on the floodplains, potentially many months before and hundreds of kilometres downstream, and similarly, freshwater flows into estuaries play a significant role in determining the numbers and sizes of fish that live there….These floods are also necessary to connect the floodplains to the river and allow movement throughout the entire river system, while maintaining dry season flows may be essential for the life cycles of important species such as barramundi and freshwater prawns.”

[i] Currently there are about 34,000 hectares of irrigated lands in northern Australia (CSIRO 2009).

Developing Australia’s tropical water resources – Part 1

In a paper presented to the 2013 Fenner Conference in Canberra, I described the economic opportunities and environmental risks that may arise from the proposed agricultural expansion in Australia’s tropical north. I had blogged on that same topic back in Nov 2011 (Northern Australia’s fascinating wetness) and this was a chance to update my own thinking, based on extensive scientific and economic analysis undertaken by CSIRO and the Northern Australia Task Force.  The new liberal (read ‘conservative’ for foreign readers) government in Australia had just re-activated calls for a new Australian ‘food bowl for the world’ in our tropical north, built on the perception of abundant water and fertile soils, so it seemed most timely to do so.

The proceedings of that Fenner Conference will be out soon, so I thought it might be useful to highlight here some of the key points I make in that paper, broadly addressing two main questions:

As Australia looks increasingly to its tropical northern lands as a prospective ‘food-bowl for Asia’ we should reflect on two important questions:
(i) Have we gained sufficient knowledge and wisdom from a century of unsustainable irrigation practices in southern Australia to do things differently in the future?
(ii) Is Northern Australia really the agricultural utopia that some in the community argue, and do the potential rewards justify the risks to our largely pristine and biodiverse tropical river basins?

In part one in this series (from the conference paper), I first describe the environmental consequences of water resources development in Australia’s south – in the Murray-Darling Basin.


Part 1. Understanding and managing the causes of environmental damage arising from irrigated agriculture

1.1  Landscape and Catchment impacts

The sustainable management of land and soils has always been a fundamental challenge for Australia and, unfortunately, it is something we were poor at for a very long time. The combination of unconstrained clearing of native vegetation, particularly in hilly terrains, combined with the erosive power of high-intensity Australian rainfall led to massive soil erosion problems in many farming areas.

This led to a double-whammy outcome where (i) farmers lost fertile top-soils and damaged their lands through gullying, and (ii) the river environment down-stream of these agricultural areas suffered as farm soils and sands were washed away during heavy rainfall, muddying river waters and smothering stream-bed habitats essential for the survival of riverine biota.

Along with soil and fine sediment, fertilisers and pesticides may be transported from farms into rivers, wetlands and coastal water, especially when they are applied poorly or in excess of crop needs. These too have a negative impact on receiving waters – either by stimulating unwanted algal blooms or by being toxic to native animals in the river system.

The positive news is that thanks to a combination of good scientific and agronomic research over the past two to three decades, combined with extensive on-ground trials by land-holders (funded and carried out through various programs such as Landcare and various regional National Resource Management groups) we now have a reasonably good handle on the most appropriate agricultural practices for stopping erosion and retaining soils on-farm, and for minimising fertiliser and pesticide run-off. For example, in the Great Barrier Reef coastal catchments, where restoration and prevention programs are in now place to improve farming practices which will minimise soil and fertiliser wash-off.

Another major problem in Australia agriculture has been soil salinisation. This has two different settings and causes, arising separately on dry-land and irrigation farms. In both cases, mobilised salt can travel from farms back into adjacent rivers – by natural run-off processes or via irrigation drains – causing river salinity problems tens or hundreds of kilometres downstream. This was the situation in which the people of Adelaide found themselves in the 1960s and 1970s, eventually necessitating huge engineering interventions[i] to stop the salt from reaching the River Murray and Adelaide’s water supplies which are drawn from it.

From a river ecosystem perspective, the biggest impact arising from the development of irrigated agriculture in southern Australia, indeed throughout the world, has been the building of large dams on rivers to store and distribute water . Dams on rivers have two major types of ecological impact. First, there are physical impacts – they are a barrier to the necessary upstream and downstream movement of aquatic animals, especially fish. Second, there are hydrological impacts – by capturing water for irrigation, dams reduce downstream flow volumes and velocity, and also change the timing and pattern of flows.

The hydrological changes can be highly detrimental to river biota, especially to the plants and animals living or breeding on the river’s floodplain. They rely on regular flooding to sustain their growth or to stimulate seed germination or animal breeding. Small to medium sized floods, occurring every year or so are of particular ecological benefit and it is these that are most reduced by dams (large floods pass through a river system more or less unaffected).

The dampening of the natural variability in downstream flows by dams also impacts on fish in the river channel, which rely on certain flow velocities or water depths eg. as a cue for migration. Water released from large dams is also often much colder than that naturally flowing in a river and this may also impact negatively on fish breeding.

On-farm dams – large and small – can also cause serious eco-hydrological problems, even if individually they are much, much smaller than on-river dams. When there are many in a catchment, across many farms, their combined impact on run-off and river flows can be significant (Nathan and Lowe 2012).

Further, in the so-called unregulated reaches of the northern Murray Darling Basin where there are no large dams on rivers, large on-farm dams harvest river waters during flood times for later use on crops, mostly cotton (these are often known as ‘ring-tanks’ because of the way they are constructed). While this might sound harmless enough, perhaps even beneficial, the combined impact of large ring-tanks on downstream river flows and biota can be serious.

Smaller weirs are built on rivers to provide a local head of water to allow gravity supply of water for irrigation (and for some towns). We learned early on that fish cannot move up and down the river to feed or breed if there are weirs blocking their path. Some weirs are removable or have gates that can be fully opened at certain times of the year to allow fish to move past. In other weirs, fish ladders were built to allow fish to move past them. Unfortunately our original designs were taken from Europe and were based on the behaviour of salmon. Salmon are fish that jump but our sluggish Australian fish are not much when it comes to jumping!

After some good local research in the 1980s and 1990s, we realised that ladders could be designed to better suit Australian fish (fig 4), and even fish lifts have been built where fish can swim in at the bottom, get lifted up in a cage and swim out upstream at the top.

Finally, one other thing that that has been learned is that clearing vegetation right down to the water line of the river is not a good idea. The stream-side or riparian vegetation plays many key roles in maintaining a healthy river. It filters out (some but not all) nutrients running off the land before they reach the stream, as well as stabilising river banks, shading smaller streams and otherwise providing habitat for animals, aquatic and terrestrial.

Now that we properly understand the importance of river riparian corridors and the impacts of clearing, much restoration work has been undertaken. This includes physical works to reshape river banks (where badly eroded) and the re-establishment of endemic vegetation (and the removal of invasive, exotic species such as Willows where required).

One other catchment-scale impact, while largely out of sight, that should not be ignored is the (unsustainable) use of groundwater. Where pumping by farmers exceeds the rate of replenishment,[ii] the groundwater level decreases, making pumping more expensive or even impossible in extreme cases. At the same time, unsustainable pumping can negatively affect so-called ‘groundwater-dependent ecosystems’ (Murray et al. 2003). These could include certain types of wetlands where water supply from below is important (other wetlands rely on surface run-off only), some woodlands and the mound springs of the Great Artesian Basin.

1.2  Local or Habitat impacts

The range of local impacts of agriculture on river and floodplain habitats – the places where plants and animals live, feed and reproduce – is broad. Many are directly linked to the catchment-scale impacts outlined above, while there are others that arise due to distinctly local factors. Habitat degradation linked to agricultural practices in a river’s catchment include:

(i)            Sand smothering of river bed habitats – impacts particularly on invertebrates that live and feed on the bottom of streams, and which are also the food source for many fish and other animals (eg. platypus) (fig. 2b).

(ii)          Fine sediment run-off – makes water more turbid with lower penetration of sunlight into the water. In turn, this affects the ability of plants to grow below the water’s surface. These submerged plants are an important part of healthy river ecosystem.

(iii)        Fertiliser run-off – stimulates the growth of nuisance, filamentous algae that grow on submerged logs and rocks – these crowd-out the formation of natural microbial biofilms which are a more palatable food source for river animals.

(iv)        Changed local water depth, flow velocity or water temperature caused by upstream dams – may impact directly on the local habitat suitability for many animals including fish, turtles and mussels.

Habitat degradation that is not linked to upstream catchment condition, but arises due to local farming impacts include:

(i)             Edge habitat destruction – caused by cattle given direct access to the river for watering. Many riparian restoration programs across Australia now fund farmers to fence off their lands from the river and to provide alternative watering points. Cattle defecating in streams under these circumstances also create local pollution problems as well as further downstream (including potential human health problems from drinking water which is contaminated by animal intestinal parasites such as Cryptosporidium and Giardia).

(ii)           Levees and block-banks on the floodplains – farmers with lands adjacent to rivers may construct levees to divert minor flood-waters away from, or towards, certain parts of their property. While the local ecological effects of this may be minimal, there are situations where such works cause the drying out of wetlands or woodlands further along the floodplain.

1.3  Lessons learned

The upside of this wide-range of impacts that have arisen through the development of irrigated agriculture is that, as scientists, managers, farmers and concerned citizens, we have learned a great deal about how not to go about developing and maintaining a large, productive agricultural system! For any new irrigation development, including any proposed for Northern Australia, we can reasonably claim knowledge of the impacts of past agricultural practices and that we have learned ways of carrying out irrigated agriculture far more wisely.

To summarise, we have learned that sustainable irrigated agriculture should include the following catchment and farm-scale practices:

(i)            Clearing land sufficient to grow crops and no more, retaining as much native vegetation on-farm as possible

(ii)          Protecting vegetation along riparian zones, including fencing where necessary, and on steeper slopes or other areas of higher erosion risk

(iii)        Adopting modern tillage and other agronomic practices that maximise water and soil retention on farm (and that enhance soil fertility)

(iv)        Applying water sufficient to meet crop needs and no more, using modern high-efficiency irrigation delivery systems (viz. micro-irrigation, pressurised supply, etc.)

(v)          Controlling the application of fertilisers and pesticides, at the lowest practical levels, and retaining any drainage waters on farm (unless otherwise proven safe to discharge)

(vi)        Avoiding or minimising the need for dams, especially large dams. If dams must be built (and, to be clear, this is not desirable) the combined storage volume of dams on a river system should be much less than the mean annual run-off upstream of where the dam is to be built. (Note: in the Murray-Darling Basin the combined dam storage volume is 1.5 times mean annual run-off, hence the huge magnitude of their ecological impacts.)

(vii)      Implementing regulatory controls on the construction of farm dams and floodplain banks and levees

(viii)    Adopting the combined and sustainable use of surface water and groundwater – for example, between wet and dry seasons. This should be optimised to maximise supply reliability and to minimise impacts on all water-dependent ecosystems.

(ix)        Applying ecologically-defined limits on the total amount of water that can be withdrawn for irrigation from a river or groundwater system in any season/year.

There are many other sustainable practices that should be adopted – this list is meant to be illustrative rather than inclusive. The key message is that ecologically-sustainable irrigated agriculture is technically feasible, if we have the intelligence and the conviction to implement it fully.

Whether or not politicians have the motivation or the will to fully implement the required approaches and practices is another question. Ecologically-sustainable irrigation comes at a cost – in increased system development and operating costs, in reduced area of agricultural farmlands or water available for production, or both. But the costs of environmental degradation itself are economically real – not just unforeseeable externalities – although they may not be observed for years or decades, certainly well beyond the life-time of most politicians.

Herein may lie the dilemma for irrigated agriculture in Northern Australia.

Endnotes

[i] These consisted of a network of salt interception bores and discharge/evaporation basins. See: <http://www.mdba.gov.au/annualreports/2009-10/chapter3-6.html&gt;.

[ii] Replenishment of ground-waters occurs by local rainfall infiltration or transport from further afield via connected aquifers.

 

 

 

 

 

 

 

Inside Water back on-line

Well, it has been a very hectic two and a half years for me in a work sense, and unfortunately no time for blogging.  My organisation eWater Cooperative Research Centre finished successfully and is now simply eWater.  But all progresses at a pace with our integrated water and river basin modelling work, in Australia and in the Asia-Pacific region.  Find out more at our web site.

But, please stay tuned for more thoughts from down-under ‘Inside Water’.

Northern Australia’s fascinating wetness

Since at least the middle of the twentieth century, Australians have enviously eyed the wetness of our northern tropical regions — with some degree of frustration! Recent years are no different, with both the Federal Government and the Opposition looking at improving national water and food security via use of northern land and water resources.

Unlike the Murray-Darling Basin (MDB) drainage division, there are abundant water resources in the two huge drainage divisions that span the north of Western Australia, Northern Territory and Queensland.  Consider this: whereas the average annual outflow from the MDB is around 12,000 GL, the two northernmost drainage divisions (known as the ‘Timor Sea’ and ‘Gulf of Carpentaria’ divisions) average annual outflows of about 90,000 GL each. Those regions have mean annual rainfall of 800-900 mm across their range, and a lot more in sub-catchments closer to the coast, so you’d expect that the north would be an ideal area for food production.

Yet most irrigated agriculture is practised within the MDB, not the north. Other than the, only partial successful, Ord River irrigation scheme and parts or the Reef coast of northern Queensland, food production in the north is largely via pastoral grazing, focusing (e.g. in the Daly River catchment) on live-export of cattle, and supplies of feedstuffs to support that industry.

There are a number of reasons, and they need to be carefully evaluated before Australia goes down the track of developing new dams and irrigation lands in that region.

First, the apparently plentiful rain, which falls mostly (94–95%) in the summer 2–3 months only, and mainly near the coast, is relatively unpredictable. It can be as little as 300 mm or as much as 1800 mm annually and is counterbalanced by annual average evaporation of 1900–2000 mm.

An excellent reason to build dams to hold the flow, you might say, but unless there is a reason to use the water, there is little reason to build a dam, particularly considering the ecological issues Australia has experienced from damming rivers in the southern regions.

A second reason for little existing northern agriculture is the poor soils. In general they are unsuitable for agriculture (as opposed to pastoral grazing). They have very poor water-holding capability or are highly erodible, as has been identified by CSIRO’s surveys for the very purpose of assessing the north’s productive potential.

Before we invest in developing food production in the north, surely we will look at the lessons of the past in the south? One of those has taught us to regard potential salinity with caution. The salinity hazard of the northern regions may be rated in the lower part of the scale, but there is still much salt naturally stored in the soil profile, and CSIRO reports warn that significant rises in the water-table in those soils are liable to recreate the salinisation headaches we have seen in the WA and the MDB.

Ecologically, the north is a kind of Aladdin’s Cave of biodiversity, both in inland rivers and in the coastal waters fed by large rivers. There are numerous wetlands – the Directory of Important Wetlands in Australia lists 106 wetlands in northern Australia, 8 of which are Ramsar Wetlands of International Importance (the Ord River floodplain and several in Kakadu National Park, for instance). Another report says there are 1243 wetlands in the catchment of the Daly River alone.

The rivers also are rich in species, with the Daly River supporting 48 species of fish and more turtle species than any other river in Australia. Floods in the wet season drive fish spawning in the coastal waters, of Barramundi for instance which are harvested at a rate of hundreds of tonnes per year, both by recreational fishers and by Indigenous peoples.  Harvesting that water upstream for irrigation  may drive economic production in-land, but will almost certainly impact on the economy of coastal fisheries.  On purely economic grounds, trading off one food source against another may not be a wise choice, let alone the potential social, cultural and ecological impacts.

Clearly there are sound economic reasons — in fisheries and tourism for instance — as well as important Indigenous cultural reasons and ecological reasons to bring all available integrated thinking to bear before any development of the north’s water resources is agreed.  In coming decades, it may be that Australia must develop, at least some of, the land and water resources of the North – both to meet its own food needs and those of the rest of the world.

But let’s approach this challenge with our eyes open, and our minds fully engaged.  It seems perfectly possible that otherwise Australia may gain little but lose immeasurably.