Determining groundwater quality based on volcanic terrain: a case study from the Island of Tenerife, Spain

Abstract

This research analyses the water of 258 significant tunnels throughout the Island of Tenerife used to obtain groundwater and establishes a clear relationship between the qualities of the water and the volcanic lithologies of the island of Tenerife. Each water sample from each tunnel was taken to an approved laboratory for analysis, where the values of Ca2+, Mg+, Na2+, K+, HCO3 − , CO3 2− , Cl− , SO4 2− , NO3 − , H2PO4 − , SiO2 and F, as well as water quality parameters, namely electrical conductivity (EC), hardness, residual sodium carbonate (RSC) and adjusted sodium adsorption ratio (SARaj), were determined. The tunnels have been grouped according to the mineralogy present in the lithologies crossed by the water. The tunnels on the Northeast and the West of the island have the highest percentage of volcanic terrain lithologies, including basaltic lava and pyroclastic flows, where the main minerals are amphibole, olivine, augite, pyroxene plagioclase. However, the tunnels of the West cross lithologies with ignimbrites and epiclastic deposits and intramontane sediments, leading to an improvement in water quality compared to the Northeast cluster. This work shows that by drilling holes to search for fresh groundwater in volcanic terrain where surface lithologies can be identified, it is possible to estimate the water quality beforehand.