Environmental Engineering Reference
In-Depth Information
Table 6.1
Projections of average salinity levels in selected rivers of the Murray-
Darling Basin, in electrical conductivity (EC) units.*
River valley 1998 2020 2050
Murray River at Morgan 570 670 790
Murray River at Renmark 400 480 550
Murray River at Swan Hill 270 270 310
Murrumbidgee 250 320 350
Avoca 970 980 1480
Loddon 870 880 900
Goulburn-Broken 130 180 260
Lachlan 530 780 1150
Macquarie 620 1290 1730
Namoi 680 1050 1280
Condamine-Balonne 210 1040 1040
*Electrical conductivity of water is widely used to measure salinity. The World Health Organization
suggests a level of 800 EC units as the upper limit for human drinking water, and 1500 EC units as the
threshold for irrigation and environmental purposes.
Source:
The Salinity Audit of the Murray-Darling Basin
(1999).
the salt down a metre or so, but not enough to wash it out of the profile. The
salt can then be brought back to the root zone by rising groundwater.
In irrigation areas where excess water has been applied, the groundwater
has risen causing waterlogging, commonly bringing salt to the surface. Engi-
neering approaches to this problem have concentrated on providing drain-
age to remove the symptoms of the problem rather than addressing the
causes (an example is the large evaporating basins that have been created
from former wetlands).
Native Australian vegetation typically has deep root systems that can
extract water from deep in the soil profile. This is an adaptation to the
drought periods common in Australia. When deep-rooted vegetation is
replaced by shallow-rooted pastures or crops that do not use the rainfall that
falls, the watertable often rises, mobilising salt if it is in the profile. It is a
paradox that, in a dry country like Australia, a common form of land degra-
dation is due to excess water causing waterlogging and salinisation.
The Salinity Audit of the Murray-Darling Basin (1999) showed high salin-
ity levels in many of the tributaries of the Basin. The levels of salt in the Border
