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Human activities

Changes in land use have altered the way water moves through the landscape and may contribute to salinity problems.

• The broad scale clearing of native vegetation for agricultural and urban development can upset the natural water balance and contribute to rising groundwater and salt mobilisation.
• Clearing, overgrazing, drought or fire can remove vegetation, leaving the soil bare and prone to erosion. Erosion of the topsoil can expose saline or sodic sub-soils resulting in the formation of a hard soil crust, increased saline run-off and poor soil structure.
• Compaction of soil during road construction and across drainage lines reduces soil permeability and water through flow resulting in shallow groundwater ponding, evaporation and salt accumulation.
• Effluent from towns, intensive agriculture and industry can contain high levels of salt.
• Current farming systems contribute to salinity because even under best management practices the leakage for most agricultural land still exceeds the capacity of the landscape to shed the excess water.

Water use patterns also have a direct impact on salinity.

• The volume, timing, seasonality and location of river flows all impact on salinity.
• The amount, timing and technique of adding irrigation water to land greatly influences the impact of irrigation salinity.
• Extractions of river water can reduce the flow and result in increased salt concentrations.
• The amount of salt stored in some groundwater systems is enormous (some aquifers are saltier than seawater).
• Salt can also be added into rivers and streams from industrial processes, such as mining.
• Over watering gardens and leakage from pipes and drains can elevate groundwater levels in urban areas.