Passage 3 Sea Change for Salinity

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READING PASSAGE 3 
 
You should spend about 20 minutes on 
Questions 1-14
, which are based on Reading 
Passage 3.
 
Sea Change for Salinity 
 
One of the most serious problems facing Australian farmers is an increase in the salt 
content in the soil. However, there are new weapons emerging in the fight against 
salinity 
 
A
Beneath the flat, impassive surface of Australia lie hidden mountains, valleys and 
gorges - ancient traps and channels for the deadly salt that is stealthily killing so 
much of the Australian landscape. The war on salt is calling forth new weapons. 
A suite of high technologies used by geologists to see underground and prospect 
for gold and minerals is now being used to pinpoint the presence of salt beneath 
the landscape, and predict where it might move. 
B
Unless this process is clearly understood, warns Chief of Exploration and Mining 
Dr Neil Phillips, the hard work now underway of planning and tree-planting on the 
surface may be rendered ineffective: salt can still sneak past and erupt, following 
one of the ancient river channels formed millions of years ago. The use of 
airborne electromagnetic to detect salt hidden beneath the landscape has been 
around for a decade, but the past two years have seen a major development in 
its precision and powers of detection. Like the use of radar in battles, it has the 
potential to turn the tide of the struggle in favour of the defence by helping to 
pinpoint, plot and predict the movements of the foe. 
C 
Angus Howell, who farms near Warrenbayne, in Southeast Australia, saw his 
first outbreak of salt in 1948. Over the ensuing decades the patches spread and 
multiplied until they consumed almost 100 hectares. By the late 1970s, Howell 
and his fellow farmers had decided it was time for action and established a 
government-funded "Landcare' group in a bid to save Australia's farmland. But 
despite a mounting effort by scientists, farmers and governments, the 'white 
death' continued to encroach. Small successes were eclipsed by larger defeats 
and fresh outbreaks. 
D 
‘The technical solutions just aren't there yet for dealing with broadacre salinity, 
nor are the social and economic solutions. How do you introduce the land-use 
changes that are needed when people still need to make a living?' Howell asks. 
There is no satisfactory solution yet. Part of the problem has lain in salt's ability 
to mount ambushes, emerging somewhere new, sometimes unexpected and 
unexplained, beating plans to intercept it. Only now are scientists starting to 
really disclose its secret subterranean stores and passages. 

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E 
The need for such knowledge is pressing. Salt has already afflicted six million 
hectares of once-productive country. At present rates it is predicted that, by 
2050. it will have sterilised a total of 17 million hectares and the waters of 
Australia's Murray River will regularly exceed the World Health Organisation's salt 
limits for drinking water. Defeating this assault may take centuries, not decades. 
F 
Electromagnetic surveys measure the electrical conductivity of soil to reveal the 
distribution of salt and the nature and variability of the regolith - the weathered 
rock and sediment that may lie above the bedrock. Magnetic surveys measure 
small differences in the Earth's magnetic field, enabling scientists to probe the 
deep past and reconstruct ancient landscapes - rivers, basins and faults now 
buried under tens of metres of sediments. These features help to reveal where 
groundwater is stored, dictate the direction of groundwater movement, and are 
critical to predicting or ruling out salinity hot-spots. 
G 
Radiometric analysis is based on the detection of radiation emitted by elements 
contained in rocks and soils, allowing scientists to delineate landforms. These 
factors influence the mobility of salt through the soil profile and help determine 
where to plant particular crop species to tackle the problem. 
Using data from the Murray River region, scientists have revealed a network of 
ancient drainage channels buried metres beneath the current landscape. These 
buried channels may carry salt and sometimes run at right angles to channels on 
the surface. This implies that the salt could move underground in quite a 
different direction to what one would expect by looking at surface slope and 
drainage. 
H 
One of the biggest advances in detection, says Professor Neil Phillips, has come 
with the integration of different techniques such as magnetics, electromagnetics 
and radiomagnetics, and ground mapping. Individually, these technologies only 
gave clues to what was going on underground. Together they provide a far more 
revealing picture of the subsurface landscape, several hundred metres deep. 
Advanced airborne electromagnetics, in particular, enables scientists to take ‘slices’ of 
the landscape at depths of five metres, ten metres, fifteen metres and so on, to 
determine where salt may be stored at depth. This is building up a four-dimensional 
picture of the subsurface landscape, enabling researchers to understand movements 
of salt in width, depth, breadth and time. 
From such technologies it will be possible to locate salt stores, identify how saline 
they are, look at man-made and natural changes to the landscape that may 
cause it to mobilise, and then predict where it will head to and over what time 
span. This in turn will give the salt warriors time to model various ways of 
containing or curbing the menace, see what works best and then try it out on the 
ground. 

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