Modeling Steady Sea Water Intrusion with Single-Density Groundwater Codes
Article first published online: 20 JUN 2012
© 2012, The Author(s). Ground Water © 2012, National Ground Water Association
Volume 51, Issue 1, pages 135–144, January/February 2013
How to Cite
Bakker, M. and Schaars, F. (2013), Modeling Steady Sea Water Intrusion with Single-Density Groundwater Codes. Ground Water, 51: 135–144. doi: 10.1111/j.1745-6584.2012.00955.x
- Issue published online: 2 JAN 2013
- Article first published online: 20 JUN 2012
- Received November 2011, accepted May 2012.
Steady interface flow in heterogeneous aquifer systems is simulated with single-density groundwater codes by using transformed values for the hydraulic conductivity and thickness of the aquifers and aquitards. For example, unconfined interface flow may be simulated with a transformed model by setting the base of the aquifer to sea level and by multiplying the hydraulic conductivity with 41 (for sea water density of 1025 kg/m3). Similar transformations are derived for unconfined interface flow with a finite aquifer base and for confined multi-aquifer interface flow. The head and flow distribution are identical in the transformed and original model domains. The location of the interface is obtained through application of the Ghyben-Herzberg formula. The transformed problem may be solved with a single-density code that is able to simulate unconfined flow where the saturated thickness is a linear function of the head and, depending on the boundary conditions, the code needs to be able to simulate dry cells where the saturated thickness is zero. For multi-aquifer interface flow, an additional requirement is that the code must be able to handle vertical leakage in situations where flow in an aquifer is unconfined while there is also flow in the aquifer directly above it. Specific examples and limitations are discussed for the application of the approach with MODFLOW. Comparisons between exact interface flow solutions and MODFLOW solutions of the transformed model domain show good agreement. The presented approach is an efficient alternative to running transient sea water intrusion models until steady state is reached.