SARA-JADE GOVIA
In a small island state with a strong, successful history of oil and gas exploration, it is quite difficult to imagine a geologist doing anything else besides looking for oil and gas. If they are not doing that, then the next thing for a geologist to spend her/his time on is finding sand, clay, gravel, or limestone pockets in our aggregate-rich geological formations of our mountain ranges.
However, at the confluence of these two sectors (petroleum and aggregate) lie the geologists, the hydrogeologists, to be specific, who explore our islands’ complex geology for water.
Perhaps the first hydrogeological mission – the science of finding water using geology – in the country was inadvertently consolidated in a petroleum geoscience assignment, where geologists would often find freshwater in the shallower depths of the rock formations they drilled into. As geology would have it, freshwater pockets were found beneath oil reservoirs as the deepest well in the country, according to the Water Resources Agency (WRA), in Cap-de-Ville at a depth of 764 metres (2,507 feet) in the Erin Sands Formation.
Naturally, the valuable product at that time was not those freshwater lenses, or aquifers as hydrogeologists call them, but the deeper rock with hydrocarbon reserves. Nevertheless, these expeditions amassed substantially beneficial data and information that led to the development of water wells scattered around these oil and gas fields, where the harnessed water was first used for petroleum exploration operations and later, for community water supply.
The first water well in Trinidad, according to WASA, was drilled in the Diego Martin Valley in the 1890s. These wells, developed in the gravels of the Diego Martin Valley, were treated at the River Estate Waterworks and supplied west Port of Spain. In Tobago, WRA recorded the first exploration water wells, also drilled in sub-surface gravels, between 1911 and 1912 in Lowlands and Cove Estate.
Decades later, TT has developed multiple aquifers spanning the Northern Range, Central Range, the southwestern peninsula and the southeastern coast from Mayaro to Guayaguayare.
In Tobago, the aquifer systems are spread across the Main Ridge. The Main Ridge has historically been a protected site for not only flora and fauna, but for the substantial role the rainforest plays in safeguarding the island’s water resources. According to Unesco, the Tobago Main Ridge is one of the oldest legally protected forest reserves in the world, proclaimed since 1776. Since that time, the Main Ridge was recognised as having significant value in attracting rain and storing water to maintain the rich biosphere.
The value of the Main Ridge for water resources is evident today in the location of Tobago’s more prolific groundwater wells which are found tapping into the fractures of the mountain range bedrock. Between 20 and 25 per cent of the country’s water supply comes from aquifers, with the remainder sourced from surface water
