| Salinity | 
| What is salinity ?
Salinity is the measure of the concentration of dissolved salts in solution (measured as milligrams per litre or EC units).
The salts that occur in significant concentrations in the River Murray are the chlorides, bicarbonates and sulphates of sodium, magnesium, calcium and potassium. In water, these salts dissociate into charged ions, which conduct electricity. The electrical conductivity of the solution increases in proportion to the concentration of ions and hence measuring conductivity is a convenient way of estimating. These units of electrical conductivity are referred to as EC units. An EC unit is 1.56 x ppm (parts/million).
<Back to Top...>
What is an EC unit?
EC or electrical conductivity units refer to the capacity of medium to pass an electric current.
<Back to Top...>
Where does the salt come from?
The River Murray flows through a highly saline groundwater environment. Most of the salt comes from deposits laid down in porous rock layers and is being mobilised on a massive scale by excess groundwater arising from existing land use.
The development of irrigation along the River, the construction of water control structures and leakage from basins accepting saline drainage water from irrigation areas have contributed to elevated groundwater levels along much of the River, and consequently, increased groundwater discharge to the River.
Clearing and replacing of deep rooted native trees and grasses with annual crops and pastures have meant that naturally occurring salts are brought to the land surface and as a result the watertable gradient drives groundwater towards the River.
<Back to Top...>
What will be the effect on urban users?
As salinity increases, its taste becomes detectable and water becomes harder, increasing the amount of soap and detergent required for washing. Also, saline water increases the rate at which pipes and fittings corrode, thus increasing maintenance costs.
<Back to Top...>
What are the predictions for increased salinity?
The Salinity Audit of the Murray-Darling Basin (released by the Murray-Darling Ministerial Council in October 1999) predicts that salinity at Morgan will increase by 95 EC units in 2015 if there is no further intervention. This figure includes 30 EC for potential future developments.
<Back to Top...>
If there is no further intervention to combat salinity, what will happen?
From the 1999 MDB Ministerial Council Salinity Audit, it was predicted that without radical changes to land and water management in the Murray-Darling Basin that:
- 3 to 5 million hectares will become salinised by 2100.
- Salinity in the lower Murray will increase by 50% by 2050 (exceed the 800 EC
threshold for desirable drinking water quality in the next 50-100 years).
- Average salinity at Murray Bridge will be 980 EC by 2100, a rise of 390 EC.
- Agricultural productivity decline and infrastructure losses in the Basin will be
costing $1 billion per year by 2100.
- Increase in economic impacts - the cost of one EC unit increase in river salinity
at Morgan lies in the range of $93,000 to $142, 000 per year.
- Increase in dryland salinity from the current 68,000 hectares to 116,000 hectares
by 2050.
- Floodplain salinity will increase from 25,000 hectares to 40,000 hectares
(mostly adjacent to highland irrigation areas).
<Back to Top...>
Why is increased salinity a problem?
It can impact on crops, reducing irrigated crop yields and can cause loss of orchard trees. Irrigators will bear the greatest individual economic loss from increasing salinity in the River.
<Back to Top...>
What is the cost of salinity?
- Economic
Salinity costs $47 million per year to the users of River Murray water.
Unchecked, salinity could have an annual cost of $1 billion within 100 years.
Agricultural losses
- Environmental
Changes in water quality in river
Continued decline of trees
Reduction in biodiversity, both water and land based
Habit changes
Loss of wetlands and floodplains
- Social
Rural communities economically affected through reduced productivity
Recreational activities threatened
Archaeological resources threatened
Loss of native flora, fauna
<Back to Top...>
What is dryland salinity?
Dryland salinity is when salty groundwater affects soils, causing plants to wither and die.
It has resulted from clearing native deep rooted plants and replacing them with shallow rooted annual crops and pastures. These shallow rooted crops are inefficient in their use of the annual rainfall, allowing much of it to escape beyond the root zone to the groundwater system below. This is in contrast to deep-rooted native vegetation that only allows small amounts of annual rainfall to escape past the root zone. This excess recharge of water below the root zone causes the typically saline ground water to rise bringing it in contact with roots of crops.
<Back to Top...>
What effects does salinity have on urban water users of piped River Murray water?
With increased salinity the taste becomes detectable and water becomes harder, increasing the amount of soap and detergents required for washing. Also, saline water increases the rate at which pipes and fittings corrode, thus increasing maintenance costs.
<Back to Top...>
What is being done?
South Australian River Murray Salinity Strategy Draft State, Department for Water Resources
Dryland Salinity Strategy, South Australia, Soil Conservation Council, 2000
Basin Salinity Management Strategy - Murray-Darling Basin Ministerial Council
<Back to Top...>
What can I do?
Assist with native tree propagation, so native trees can be planted in areas that have been cleared to reduce groundwater recharge. In urban areas, plant natives that require less water.
<Back to Top...> Salinity Information
Information sheets
From Murray-Darling Association
Salinity Audit Community Summary, Murray-Darling Basin (MDB) Ministerial Council, 1999
Draft Basin Salinity Management Strategy 2001 2015 Community Summary, MDB Ministerial Council, 2000
Whats What about Salinity and the River Murray, Fact Sheet 1, 1997 (this sheet
also available at www.murrayusers.sa.gov.au)
Dryland Salinity What are the impacts and how do you value them, National
Dryland Salinity Program. <Back to Top...> More information
|
