Salinisation
Salinisation
Salinisation is a major issue that poses a threat to both freshwater resources and soil. The changes in natural salinaty levels in both water resources and soil surfaces can severly impact land use and function as well as negatively impact the overall health of an ecosystem. This is an issue that is seen throughout the world, however, the issue becomes even greater in regions of water scarcity such as arid and semi-arid regions that are heavily reliant on groundwater resources in order to sustain themselves. There are three main types of salinisation that can occur they being:
Natural salinisation - Disolution of minerals from bedrock as well as the accumulation of salts from rainfall accumulating over time.
Dry land salinisation - Rising water levels that increase salinity as they bring salts to the surface.
Irrigation salinisation - The evaporation of surface water from irrigation leading to the accumulation of salts on the surface which then leach into groundwater resources during precipitation events.
Salinisation is a major cause for concern in regions that recieve minimal rainfall while evapotranspiration remains high, leading to a deficit in water resources. As the evaporation of water resources occur the minerals and salts within the water remain as such there is an increase in the salinity level of the surface which can then leach into water resources causing the salinisation of freshwater.
Cause
Natural Salinisation
The process of natural salinisation occurs as a result of the erosion of minerals from bedrock within groundwater resources as well as the accumulation of salts in the subsurface as a result of precipitation. The natural process of natural salinisation occurs over long timeframes ranging from thousands to millions of years slowly changing the salinity of the soil surface and groundwater resources.
Dry land Salinisation
Dry land salinisation occurs in regions that are arid and semi-arid and is occurs as a result of increasing water table levels. This often occurs as a result of the removal of deep-rooted vegitation that is replaced by shallow-rooted grasses and crops that raise the water table bringing the salts to the surface. This process leads to an increase in the concentration of salts on the surface as when the surface dries out the salt remains behind.
Irrigation Salinisation
Occurs as a result of excessive irrigation practices in regions that have low precipitation levels but high levels of evapotranspiration. As a result of repeated irrigation and evaporation occur salts accumulate. The accumulated salts then leach into groundwater resources during precipitation events that naturally recharge groundwater resources, this increases the concentration of salts within the groundwater making it more saline.
Environmental Impact
Salinisation is an issue that not only impacts the environmental health of ecosystems across the globe but also threatens humans with the reduction in freshwater resources that are used throughout domestic and industrial processes. The imposing threat of salinisation on groundwater resources is extremly problematic in semi-arid and arid regions that rely on groundwater resources for drinking water, agriculture and other needs.
The major environmental impacts that are seen as a result of salinisation are:
Loss of groundcover/ landuse changes
Salt deposits on surface
Increased soil erosion
Increased salt concentration
Biodiversity loss
Reductions in freshwater resources
Mitigation
As salinisation is a natural process the mitigation of this issue is quite hard to achieve as such the type of salinisation that is occuring must first be identified before any efforts can be implemented. As natural and dry land salinisation occur as a result of natural processes it extremly difficult to achieve mitigative efforts, however, in relation to irrigation salinisation it is possible to mitigate the impacts of salinisation. This mitigation is achievable through the implementation of stricter controls on the ammount of irrigation that occurs as well as the implimentation of irrigation channels and capturing and treating saline water.
Reducing the abstraction of freshwater from groundwater resources allows for the recharge of these aquifers, the recharge of the aquifers reduces the concentrations of salt within the water reducing the environmental impact of salinisation.