Ground water flow modelling of the Malta mean sea level aquifer : development of a simulator programme

Abstract

For most coastal islands, groundwater is the major source of domestic freshwater. In Malta, half of the domestic water supply is derived from groundwater. It is therefore desirable that some form of reliable groundwater assessment can be carried out. The dissertation involves groundwater quantity modelling. Hence, aspects of groundwater pollution are not considered. In quantity modelling, flow directions and changes in storage are considered. In this way, the problem of saltwater intrusion can also be assessed. The aquifer considered is the mean sea level aquifer of the island of Malta. The first part of the dissertation consists of software development in order to be able to compute infiltration values from potential evapotranspiration, rainfall and runoff data. The algorithm, has been based on a lumped reservoir conceptual model. The input data consisting of potential evapotranspiration, rainfall and runoff has been processed on a monthly basis such that annual infiltration values were obtained. A finite difference groundwater flow model has also been developed and verified for the freshwater-lens type of aquifer. Both steady state and unsteady state conditions have been implemented. Suitable graphical interfaces have been developed for data entry, and results display facilities. The simulator has been run to obtain results for the 20-year period covering 1975-1995, using a 1-year time-step. Extrapolation has also been included in order to cover a time span of up to the year 2004. In this process, existing field piezometric data have been used to calibrate the aquifer parameters.