Geographic Information Systems (GIS) has become an important tool for hydrology and groundwater expert witnesses. An especially useful application of GIS concerns water quality in groundwater. In the case of groundwater contamination and the need for subsequent containment and cleanup of the contaminant, an existing framework of the groundwater system would be valuable in planning remediation measures.
An example concerning the use of GIS addresses a common problem associated with groundwater pumping and land subsidence or intrusion in coastal areas. Areas that have been overpumped of groundwater can subside, and when near the sea, this may invite flooding. Also, overpumping of groundwater in coastal regions may bring a different problem, such as the case in California where salt-water intrusion has compromised the aquifer. Generally, a salt water interface inland of the coast extends below the land surface dependent on the distance from the coast. Overpumping can bring the salt water interface to a higher position and contaminate an aquifer.