Lockyer Salinity Fact Sheet 2: Managing for salinity
Why managed salinity?
Salinity can potentially impact on agricultural land, infrastructure, water quality and the environment. The table below summarises some impacts.
|Agricultural Production||Plants use more energy to extract water from salt affected soil, resulting in reduced yields or even plant death depending on the salt tolerance of the plant.|
|Soil Erosion||Reduced plant yields can result in reduced surface cover and lead to more of the ground surface being exposed to erosive processes. Salt affected areas are often subject to periods of waterlogging, increasing the vulnerability of soils to erosion.|
|Water Quality||Water with high salinity levels affects the taste of drinking water, the cost of treatment and the suitability for stock use and irrigation.|
|Freshwater ecology||Increased salt levels in streams affects the organisms that live in these environments and can change the composition and diversity of these habitats and impact on the foodweb.|
|Terrestrial biodiversity||Loss of, and changes in, native vegetation in salt affected areas can result in loss of natural habitat and fragmentation of wildlife corridors.|
|Infrastructure||Salinity can result in road damage and instability and corrosion of concrete affecting the life span of bridges and houses.|
Salinity impacts vary in response to the balance of inputs (rainfall, irrigation and water storages) and outputs (evaporation, stream flow, plant transpiration and down-valley groundwater
flow). The extent to which this balance is altered, determines the area of salt affected land and associated salinity impacts.
Tree clearing can cause watertables to rise and increase the area of land affected by salinity.
Increased salinity levels in water affect its suitability for drinking, irrigation, stock use (Figure 1) and supporting aquatic life.
Actions to manage salinity
Dealing with salinity involves balancing the volume of water entering the ground-water system (recharge), with the volume of water leaving the groundwater system (discharge), thereby managing the depth of the water table below the ground surface (Figure 2). A landscape approach using a range of options, such as the ones outlined below, is required to maintain the water table more than 1.5m below ground level:
- Plant, regenerate and maintain native vegetation in recharge, transmission and discharge zones;
- Encourage and promote the growth of deep rooted tree species;
- Install bores upslope of discharge areas if flow rates are acceptable and water is of suitable quality (Figure 1) for alternative uses;
- Increase groundwater use in recharge areas by pumping water from bores and using drainage systems to redirect water to other storages;
- Install sub surface drainage where groundwater quality is acceptable (Figure 1);
- Seek advice on best irrigation practices for managing salinity;
- Maximise cropping opportunities and avoid leaving land in fallow over summer rainfall season;
- Avoid building dams at sites where the water table is high;
- Build roads along ridges where disruption to water tables will be minimal;
- Build houses (and wastewater disposal systems) well away from areas with high water tables;
- Distribute water evenly over large on-site disposal areas;
- Maintain a high percentage of grass cover (Figure 3) by managing grazing pressure;
- Mow your grass no shorter than 75mm in wet or effected areas to increase water use and minimise evaporative concentration;
- Minimise tracks and avoid bare areas; and