Research Article

Plant and Soil

, Volume 175, Issue 1, pp 1-11

First online:

Uptake of saline groundwater by plants: An analytical model for semi-arid and arid areas

  • Peter J. ThorburnAffiliated withQueensland Department of Primary Industries, Resource Management InstituteCentre for Groundwater Studies
  • , Glen R. WalkerAffiliated withCSIRO Division of Water ResourcesCentre for Groundwater Studies
  • , Ian D. JollyAffiliated withCSIRO Division of Water ResourcesCentre for Groundwater Studies

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An analytical model, based on unsaturated zone water and solute balances, was developed to describe the uptake of saline groundwater by plants in dry regions. It was assumed that: i. initially, the profile had low water and salt contents to some depth; ii. both water and solutes move upwards from the water table by piston flow due only to plant water extraction; iii. the uptake of water concentrates solutes in the soil solution until some threshold salinity is reached, above which plants can no longer extract water due to osmotic effects; iv. uptake of the groundwater does not affect the water table level; and v. uptake of groundwater is only limited by transmission of groundwater through the soil. Model predictions were compared with measurements of groundwater uptake made over 15 months at five sites in aEucalyptus forest in a semi-arid area, using independently measured model parameters. Depth and salinity of groundwater, and soil type varied greatly between sites. Predicted groundwater uptake rates were close to measured values, generally being within ∼ 0.1 mm day-1. Sensitivity analysis showed that groundwater depth and salinity were the main controls on uptake of groundwater, while soil properties appeared to have a lesser effect. The model showed that uptake of groundwater would result in complete salinisation of the soil profile within 4 to 30 yr at the sites studied, unless salts were leached from the soil by rainfall or flood waters. However, a relatively small amount of annual leaching may be sufficient to allow groundwater uptake to continue. Thus groundwaters, even when saline, may be important sources of water to plants in arid and semi-arid areas.

Key words

Eucalyptus floodplain groundwater salinity transpiration water table