Geological and hydrogeological reconstruction of the main aquifers of the Maltese islands

Geological and hydrogeological conceptualizations of the five main aquifers of Malta were performed by means of characterization of the groundwater bodies’ geometries to assess their hydraulic properties. The starting point was 23 new geological cross-sections, intended to intercept all the main structural features of the Maltese archipelago at once. This conceptual analysis constitutes a fundamental phase in the development of groundwater models, and in turn influences the assessment of transmissivity and the numerical models’ structure, calibration and related uncertainties. Besides the construction of the geological sections, a crucial step in building a coherent geological conceptual model involved data homogenization and use of different tuning scales, with respect to both geometric and hydraulic aquifer features. Cross-section quality was spatially assessed by the fit on both a high-resolution digital terrain model and the surface geological data, and the information was subsequently merged with previously determined inconsistencies within borehole stratigraphic data collected from various sources. The geological boundaries data (contact lines and point data) and the dense fault system of the Maltese islands (horst and graben structure) were interpolated by means of the “spline with barriers” algorithm. The resulting surfaces of the main geological formation beds constitute the new detailed geological conceptual model of the whole Maltese archipelago, needed for a more reliable assessment of hydrogeological parameters. The achieved hydrogeological conceptual models of the main Maltese groundwater bodies constitute the basis for groundwater numerical modelling to better understand and quantify the groundwater resources available within the hydrological reservoirs.