Changed deep drainage

Impact

Deep drainage refers to the water that moves through the soil to below the root zone of plants.  Deep drainage is an important part of the water cycle and the natural process that recharges groundwater sources and springs that may flow into creeks and rivers.  The amount of deep drainage may increase when deep-rooted perennial vegetation is cleared or water in excess of crop or pasture needs is applied by irrigation.  The affect of changed deep drainage depends on many factors including soil type, depth of watertable and land use.

Suggested indicator: Depth to groundwater
Increased deep drainage may be associated with:
Potential associated impacts Suggested indicators+
Mobilisation of salts, nutrients and pesticides from the soil leading to increased concentrations of these substances in groundwater
  • Salinity of water
  • Phosphates in water
  • Nitrates in water
  • Farm chemicals in water

A rise in watertable levels may contribute to:

  • land and surface water salinity problems and soil sodicity problems and subsequent decreased vegetation viability
  • Salinity of water
  • Soil salinity
  • Saline land
  • Soil chemistry
  • Vegetation density
  • Native vegetation area
  • Native plant richness 
  • Weed species 
  • Pasture species
  • Weed cover
  • Shrub cover
  • Tree canopy cover & health
  • Ground cover
 

Development of spring flows in other parts of the landscape where waterlogging may occur

Reduced deep drainage may be associated with:

Potential associated impacts Suggested indicators

Reduced groundwater recharge dropping watertable levels and leading to:

  • reduced risk of soil salinity/sodicity 
  • Soil chemistry
  • Salinity of water
  • Soil salinity
  • Saline land
 

Increased soil waterlogging

 

+ Descriptions of indicators (PDF, 76K)* provides a brief description of each indicator including techniques and purpose.

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Last updated 7 September 2010

Land Manager's Monitoring Guide