Título:

Assessing aquifer vulnerability to seawater intrusion using GALDIT method: Part 1 – Application to the Portuguese Aquifer of Monte Gordo

Resumo:

This paper is divided in two parts. Part 1 presents the first application in Europe of an index developed in the framework of the EU-India INCO-DEV COASTIN project aiming the assessment of aquifer vulnerability to sea-water intrusion in coastal aquifers. The most important factors controlling seawater intrusion were found to be the following: Groundwater occurrence (aquifer type; unconfined, confined and leaky confined); Aquifer hydraulic conductivity; Depth to groundwater Level above the sea; Distance from the shore (distance inland perpendicular from shoreline); Impact of existing status of sea water intrusion in the area; and Thickness of the aquifer, which is being mapped. The acronym GALDIT is formed from the highlighted letters of the parameters for ease of reference. These factors, in combination, are determined to include the basic requirements needed to assess the general seawater intrusion potential of each hydrogeologic setting. GALDIT factors represent measurable parameters for which data are generally available from a variety of sources without detailed examination. A numerical ranking system to assess seawater intrusion potential in hydrogeologic settings has been devised using GALDIT factors. The application of the method is exemplified in the paper for the assessment of aquifer vulnerability to seawater intrusion in Portugal (Monte Gordo aquifer in the Portuguese Southern Algarve region). The system contains three significant parts: weights, ranges, and ratings. Each GALDIT factor has been evaluated with respect to the other to determine the relative importance of each factor. Part 2 of the paper is available in the Proceedings of this 4th Interceltic Colloquium as CHACHADI and LOBO-FERREIRA (2005). In the second part of the paper the method for assessing GALDIT index parameters is fully explained and an application to a costal aquifer located in Goa, not only for today’s conditions but also considering a 0.5 m sea level rise are presented.

Autores:

J. P. Lobo Ferreira, Catarina Diamantino, A. G. Chachadi, M. J. Henriques