Groundwater favourable infiltration zones on granitic areas (Central Portugal)

Abstract

The Infiltration Potential Index (IPI) was used at Castelo Novo (Fundão, Central Portugal) to delineate favourable infiltration zones. The Infiltration Potential Index is a valuable tool to include in integrated water resources management in crystalline fractured rocks. An integrated approach combining hydrogeomorphology and GIS was developed applying multiple layers of information (tectonic lineaments, hydrogeological units, slope, drainage, land use, and precipitation). Different ranks were assigned to thematic layers and different weights were given to classes according to their contribution for groundwater using the Analytical Hierarchical Process (AHP) methodology. Almost 80% of the area is covered by slightly to moderately weathered (W1-2-W3) granite, having slopes of 5-15° and 15-25°, tectonic lineaments densities of 6-12 km/km2 and 12-18 km/km2 and drainage densities of 6-9 km/km2 and >9 km/km2. Scrub and/or herbaceous vegetation associations and bare rocks dominate. A moderate to high Infiltration Potential Index (IPI) is dominant in the area.