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Understanding the Darling River against a background of climatic realities, water mismanagement and theft – #riparian #WaterTheft #environment

Back in the 1980s I worked with the NSW Department of Education as Project Officer for the Country Areas Program (CAP). I enjoyed the work. It allowed me to deepen my knowledge of rural life and travel the state.

On my first trip to Bourke, somewhere around 1983, I remember seeing signs of windblown sand along the Mitchell Highway where geographic reason told me there should be none. I reflected on the loss of woodlands in the face of sheep, wheat and cattle. Closer to Bourke, in places irrigation water from the Darling River touched the land with a green hue.

I’d already been to the Menindee Lakes, Broken Hill and Silverton and crossed Nullabor to Perth, appreciating desert where I expected to find it.  Later I spent time travelling through South Australia where encounters with abandoned farmhouses were a testimony to the folly of agriculture on the fringes of the desert.

Educated during the 1950s and 1960s, I’m part of the generation taught that Australia rides on the sheep’s back and that our inland waterways were critical in ‘opening-up’ the interior affording an opportunity for the sheep wheat industry to thrive becoming a fundament of our wealth.

This first trip to Bourke came as a shock.  My sense of the place seemed wrong. Images used to illustrate a series of CAP readers for children compounded my disquiet as one, a tale of paddle steamers plying the river as far as Brewarrina and Walgett (see figure 1), had left me with an expectation of a healthy riparian world flush with water, at least in the wet season.

bcp_05662h
Figure 1: Paddle steamer ‘Brewarinna’ and barge ‘Coledida’ with Narrara wool on the Barwon. From the collections of the State Library of New South Wales

What I saw was a trickle and I wondered how anyone could survive on it. Yet it had once been a mighty riparian system. In 1950 Bill Wheate (see Figure 2) writing in the Walgett Spectator lamented the demise of paddle steamers.

paddle_steamers_gone
Figure 2: The Walgett Spectator – Gone are the days of Paddle-Steamers

Taking the Darling’s Water

Since my first visit to the Menindee Lakes in 1967 then Bourke in 1983, there has been a steady and relentless extraction of water from the Darlings’ tributaries in southern Queensland and Northern NSW. Most tragically the development of massive storage ponds to support the cotton industry has been a feature of this extraction.

That we have a cotton industry on the upper reaches of the Murray Darling system strikes me as an absolute absurdity. Why on earth would the world’s driest inhabited continent attempt to cultivate and export a crop that is so water intensive? In reality, we are exporting water.

Perhaps one reason that more Australian’s are protesting about this is that they aren’t sufficiently aware of the prevailing climatic and riparian conditions. As more than 85% of us live within 50 kilometres of the coast this is understandable. So, I thought I should begin with the basics and with apologies to my geographically literate readers.

Australia’s geographic context

Australia is the world’s second-driest continent (after Antarctica), with average (mean) annual rainfall below 600 millimetres (mm) per year over 80% of the continent, and below 300mm over 50%. Year Book Australia, 2006 [1]

Annual average rainfall for Australia

Figure 3: Mean precipitation is low for several reasons [2]

Continentality

Distance from maritime influences ensures greater aridity and a relative absence of the moderating effects of oceans meaning that summers tend to be hotter than coastal locations at a similar latitude and winters cooler. the distance from maritime influences;

Latitudinal position

Australia’s latitudinal extent is from 10° 41′ 21″ S  to 43° 38′ 40″ S.  The Horse Latitudes, areas around 30° north and south latitude, have a large impact on continental Australia. Latitude 30°S, runs from Woolgoolga, NSW to Leeman, WA. Significantly it passes close Bourke on the Darling River, close to the confluence of the Darling’s main tributaries the Barwon, Culgoa, Warrego, Paroo, Gwydir and Namoi.

Orographic rain in Eastern Australia

Figure 4: Rainshadow effects of the Great Dividing Range are evident with decreasing westward precipitation.

 

ENSO

The ENSO effect (El Niño Southern Oscillation). This refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. It causes a seasonal variability in rainfall throughout Australia, the South West Pacific and the Indonesian archipelago in particular. During an El Niño year, drought is common

The Indian Ocean Dipole

The Indian Ocean Dipole refers to the changes in the difference between sea surface temperatures in the tropical western and eastern Indian Ocean. Its positive phase has a significant impact on agricultural output in the northwestern parts of Australia as cooler water builds up along the coast increasing aridity.

Evaporation rates

These factors combined ensure that evaporation exceeds precipitation over approximately 80% of the continent as illustrated in the Australian Bureau of Meteorology maps below.

Figure 5: Annual average evaporation for Australia [3]

 

The Murray Darling Basin (MDB)

Figure 7: Boundary of the Murray Darling Basin (MDB)

The Murray and Darling are the principal sources of water from south-east Queensland to South Australia. While the Murray rises in the wet Southern Alps, the confluence of the Darling’s tributaries is in an area characterised by aridity and high evaporation.

Although distinct in riparian character, the two systems are still referred to as the Murray-Darling Basin (MDB). The MDB is well described by the Murray Darling Basin Authority (MDBA) which makes the following points:

  • It’s one of the flattest catchments on Earth;
  • 94%of the basin’s 530,000 GL of precipitation is lost through evapotranspiration and pan evaporation;
  • The average flow of water into the basin is 32,500 GL but Australia’s climatic variability means this can range from 7,000 GL (in 2006) to almost 118,000 GL (in 1956).
  • The Basin’s subdued topography, warm to hot semi-arid conditions in most regions, and slow-flowing nature of the creeks and rivers contribute to the high evaporation rates.
  • Rainfall is summer dominant in the north and winter dominant in the south.
  • Tributaries that rise in the Great Dividing make the largest contribute most water, despite their smaller size.
  • the upper Murray, Murrumbidgee and Goulburn–Broken rivers drain only 11% of the basin but contribute 45% of the Basin’s total annual runoff from
  • The Darling River and its tributaries cover 60% the Basin’s area but only contribute 32% of its water.
  • The Darling River covers 11% percent of the Basin’s area but contributes less than less than 0.5% of annual runoff.
  • 86% of the Basin’s waterways are ephemeral
  • Water from overbank full flows that spreads out onto floodplains evaporates quickly

One of the most telling realities about the MDB is that the Murray–Darling system is that mean annual discharge is 0.4 megalitres per second (ML/s). The Amazon is 290 ML/s and the Ganges–Brahmaputra is 38 ML/s.

The average annual flow of the Murray-Darling would pass through the Amazon River in less than a day.[6]

The entire water flowing in Australian rivers amounts to about 13% of the Amazon’s annual discharge.

The Australian Hydrological geospatial fabric data provides a more comprehensive analysis of the drainage systems of Australia.

 

hydrological
Figure 8: Australian Hydrological Geospatial Fabric.

For a video explanation of Australian Hydrological Geospatial Fabric follow this link

Australian soils

Salinity is a significant problem in soils across Australia’s arid region.  The Australian Bureau of Statistics[7] notes that Australia’s soils are susceptible to degradation by agricultural activities.

  • One of the most significant causes of soil degradation in Australia is salinity, which poses a serious threat to native species, ecological communities and functioning ecosystems (ANZECC 2001).
  • Salinity has been caused by extensive land clearing in Australia, predominantly for agricultural purposes. European farming practices, which replaced trees or other deep-rooted native vegetation with shallow-rooted crops and pastures that use less water, has resulted in rising water tables which can cause dryland salinity.
  • Dryland salinity is more difficult to remedy than irrigation salinity which is well understood and managed.
  • In 2000, 5.7 million hectares of Australia were assessed as having a high potential to develop salinity. Predictions indicate that unless effective solutions are implemented, the area affected could increase to 17 million hectares by 2050, most of which is agricultural land (more than 11 million hectares) (NLWRA 2001). In 2002, about 20,000 farms and 2 million hectares of agricultural land showed actual signs of salinity (ABS 2002). For many farms, salinity has meant the loss of productivity and income.
  • There are also many off-farm impacts of salinity, the most significant of which appears to be the salinisation of rivers which affects drinking and irrigation

 Native Title report 2008.  Case Study 2: The Murray-Darling Basin – an ecological and human tragedy

Rivers, interception of flows and salinity

The Murray-Darling Basin Authority is clear that:

  1. Salinity management is one of the most significant challenges in the Murray–Darling Basin. If it is not managed well, salinity has serious implications for water quality, plant growth, biodiversity, land productivity and the supply of water for critical human needs.
  2. Human activities such as irrigation development and land clearing often exacerbate salt mobilisation, causing it to concentrate in certain parts of the landscape and rivers.
  3. Unregulated, illegal interception of flows presents a risk for all water users in a catchment.  Not only does it mean lower levels of flow in main channels but it also has an impact on water table levels.

By reducing flows there is increased risk downstream to:

  • crop yields
  • pastures
  • drinking water in rural and urban communities.
  • the ecological health of streams and estuaries.

For these reasons, riparian flows in Australia, particularly in the Murray-Darling basin require careful management as a means of avoiding increasing salinity.

Overuse of water and water theft

It’s hard for an outsider to know much about these issues in detail. Looking at the state of the Darling and the Menindee Lakes is enough to show that there is gross mismanagement of the entire system.  While large water exporters like the cotton industry enjoy a privileged and profitable position, it is at the expense of all downstream water users.

Reading Helen Vivian’s  Cry me a river: Mismanagement and corruption have left the Darling dry, reminds us that:

The lower Darling River is in so much trouble that a 270-kilometre pipeline is being built to supply Murray River water to Broken Hill, which used to supplement its water supply from the Darling River via the Menindee Lakes.

Expecting taxpayers to fund the construction of a water pipeline from the Murray to Broken Hill confers an outrageous subsidy on upstream water mismanagers. It also masks increasing water theft

There is little point in me engaging in further commentary on the since Cry me a river does it so thoroughly. The large irrigator’s threadbare arguments that their interceptions of water and storage in deeper ponds reduce evaporation and that the Menindee Lakes are inefficient because they are shallow and have high evaporation rates, is a selfish position that ignores numerous inefficient practices where evaporation rated are extremely high.


[1] http://www.abs.gov.au/Ausstats/Abs%40.Nsf/46d1bc47ac9d0c7bca256c470025ff87/BBD307D0202CA25BCA2570DE00032610?opendocument=

[2]http://www.bom.gov.au/jsp/ncc/climate_averages/rainfall/index.jsp ©Commonwealth of Australia 2010

[3]http://www.bom.gov.au/jsp/ncc/climate_averages/evaporation/index.jsp “Evaporation is the amount of water which evaporates from an open pan called a Class A evaporation pan. The rate of evaporation depends on factors such as cloudiness, air temperature and wind speed. Measurements are made by the addition or subtraction of a known amount of water, which then tells us how much water has evaporated from the pan.” http://www.bom.gov.au/watl/evaporation/

[4]http://www.bom.gov.au/water/geofabric/documents/BOM002_Map_Poster_A3_Web.pdf

[5] W J Young (ed), 2001, Rivers as Ecological Systems: The Murray-Darling Basin, Murray-Darling Basin Commission Canberra, p3.

[7]http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/1370.0~2010~Chapter~Salinity%20%286.2.4.4%29

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