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Lowered watertable

Impact

The watertable represents the upper level of  the body of groundwater.  A watertable is lowered when water leaves the system – i.e. when the rate of discharge and/or extraction exceeds the amount of water entering the system (recharge).  The level of the watertable is influenced both by natural processes and human activity.  Recharge is said to be reduced when there is less water perculating through the soil to groundwater levels.  This can result from a variety of factors including: increased plant water uptake, reduced water infiltration due to soil compaction by stock or cultivation, installation of sub-surface drainage or construction of impervious surfaces, i.e. pavements and buildings.  Extraction can be increased by increasing deep-rooted vegetation or by increasing the amount of water drawn from the resource for purposes such as irrigation and domestic use.  The impacts of a lowered watertable can be negative or positive depending on groundwater quality, soil properties and location within the catchment landscape.

Suggested indicator: Depth to groundwater
A reduced watertable level may be associated with the positive impacts of:
Potential associated impacts Suggested indicators
Reduced potential and realised salinity and sodicity problems
  • Saline land*
  • Soil salinity*
  • Soil chemistry*
Reduced soil waterlogging
  • Plant available water content*
Increased plant growth and productivity
A reduced watertable level may be associated with the negative impacts of:
Potential associated impacts Suggested indicators

Reduced quantity of water available, reduced base flows to streams and possibly permanent loss of groundwater storage capacity
  •  Water flow*
In coastal basins, salt water intrusion can occur
  • Salinity of water*
Reduced groundwater pressure leading to subsidence – as the watertable declines, water pressure is reduced causing the fine particles that held the water to become compacted and the land above can sink damaging buildings and agricultural lands.  
Destruction of groundwater dependent ecosystems, i.e. plants and animals that live in groundwater systems or rely, sometimes exclusively, on groundwater for survival including: some terrestrial vegetation, river base flow systems (rivers fed by groundwater), aquifer and cave ecosystems, wetlands, terrestrial fauna and estuarine and near-shore marine ecosystems
  • Native vegetation area
  • Vegetation desity*
  • Impacts on native vegetation*
  • Ground cover
  • Shrub cover*
  • Tree canopy cover & health*
  • Weed cover*
  • Organic litter*
  • Native plant richness*
  • Weed species*
  • Pasture species*
  • Soil life*
  • Impacts on native fauna*
  • Native land fauna*
  • Fauna behaviour*
  • Exotic pest fauna*
  • Fish*
  • River & wetland fauna*
  • Aquatic macro-invertebrates*
  • Microalgae in water*
  • In-stream habitat*
  • Wetland areas*
  • Impacts on wetlands*

* Yet to be developed

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