Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydr

Water in Celtic Countries: Quantity, Quality and Climate Variability (Proceedings of the Fourth InterCeltic Colloquium on Hydrology and Management of Water Resources, Guimarães, Portugal, July 2005). IAHS Publ. 310, 2007, 172-180.

Assessing aquifer vulnerability to seawater intrusion using GALDIT method: Part 2—GALDIT Indicators Description

A. G. CHACHADI¹&JOÃO PAULO LOBO FERREIRA²

1 Goa University, Dept. of Earth Science, Goa University, Goa – 403 206, India

chachadi1@rediffmail.com

2 Laboratório Nacional de Engenharia Civil (LNEC), Hydraulics and Environment Department (DHA), Groundwater Division (NAS), Av. do Brasil, 101, 1700-066 Lisboa, Portugal

Abstract This paper is Part 2 of a paper submitted to the 4th InterCeltic Colloquium as Lobo-Ferreira et al. (2007). In this second part of the paper the method for assessing GALDIT index parameters is fully explained. The original development of the GALDIT index was done in the framework of the EU-India INCO-DEV COASTIN project, aimed at the assessment of aquifer vulnerability to seawater 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 seawater 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 found to include the basic requirements needed to assess the general seawater intrusion potential of each hydrogeological 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 hydrogeological settings has been devised using GALDIT factors. 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. In this part we also present the first applications of the method developed for the Bardez aquifer in Goa, India.

Key words aquifer vulnerability; groundwater protection; modelling; seawater intrusion