Modelling variable density groundwater flow

Highly saline groundwater may be found at depth. Large variations in salini ty can have considerable effect on the groundwater flow. The effects may ne ed to be addressed in modelling groundwater flow for an assessment of the p erformance of an underground repository for radioactive waste. Issues relat ing to the modelling of variable-density groundwater flow are discussed. It is shown that the position as well as the width of transition zones betwee n fresh and saline groundwaters may depend on the transverse dispersion. Th erefore, accurate modelling requires the use of numerical methods that do n ot introduce excessive dispersion. The equations that characterise variable density flow with large variations in salinity are highly non-linear, and it is shown that they may have multiple, steady-state solutions in cases of practical interest. (C) 2001 Elsevier Science Ltd. All rights reserved.