An analytical model, based on unsaturated zone water and solute balanc
es, was developed to describe the uptake of saline groundwater by plan
ts 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 wat
er extraction; iii, the uptake of water concentrates solutes in the so
il solution until some threshold salinity is reached, above which plan
ts can no longer extract water due to osmotic effects; iv. uptake of t
he groundwater does not affect the water table level; and v. uptake of
groundwater is only limited by transmission of groundwater through th
e soil, Model predictions were compared with measurements of groundwat
er uptake made over 15 months at five sites in a Eucalyptus forest in
a semi-arid area, using independently measured model parameters. Depth
and salinity of groundwater, and soil type varied greatly between sit
es. Predicted groundwater uptake rates were close to measured values,
generally being within similar to 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 c
omplete salinisation of the soil profile within 4 to 30 yr at the site
s studied, unless salts were leached from the soil by rainfall or floo
d 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 ari
d and semi-arid areas.