The Central Groundwater Board defines the Lakshadweep aquifer as that which occurs under phreatic conditions in the coral sandy aquifer with the fresh water, floating as a lens over the brackish water underlain by saline water. The calcareous sands overlying these islands are highly porous and bulk of the rainfall infiltrates the aquifer displacing the saline water and creates a freshwater lens due to the density difference and the hydraulic continuity of groundwater with seawater. Beneath a thin layer of vegetal humus there is fine coral sand extending over the surface of all the islands in Lakshadweep which is underlain by oolitic limestone with embedded bits of shell and then by another layer of fine sand. Groundwater is found at a depth of about 2 m from the surface and it is the traditional source of water for many of the islands. Since the elevation and topography of islands are very important in determining the thickness and geometry of the freshwater lens – islands show a high magnitude of temporal and spatial variations in thickness, shape as well as the groundwater quality of their lenses. The exact geometry of these lenses, chemical quality, behaviour under various stresses and their potential are of great significance for planning and effective management of the freshwater resources in Lakshadweep.
As per the records of the Public Works Department of Lakshadweep Administration, to cater to the water requirements of the present population (2011 Census) more than 27 lakhs litre per day is needed. However, the present availability of water per day is 5.45 lakh litre only, creating a deficit of 21.55 lakh litre per day for this intensely populated region. Also, as per the Department, there is 2884 rain water harvesting structures installed in the Islands apart from three desalination plants at Kavaratti, Minicoy and Agatti. The Department has also set up nine water quality testing plants.
Effective management options are necessary to sustainably use the island aquifer especially in the wake of local inhabitants installing motorised pumps and associated sanitary fittings to withdraw and distribute water from shallow wells. Also, Lakshadweep governmental records show that there is no centralised sewage disposal system and most households construct soak pits for disposal of latrine waste close to the open wells, making water unsafe for use. Moreover, many islands are experiencing large scale construction of buildings, roads, pavements, sports and other infrastructure. The Public Works Department claims to have constructed all weather roads over nearly 0.2 per cent of the island area with Kavaratti, being the headquarters, topping the charts. All of these hinder the natural groundwater recharge mechanism. The prevailing strategy of the people to meet the increasing freshwater demand is by rain water harvesting, desalination plants and even by transporting potable water from mainland. Although the requirements of the population could be met through these means, long term sustenance of biodiversity dependant on such regimes would be difficult. Therefore, imposition of groundwater management plans is essential for protecting the vulnerable and rare ecosystems from further exacerbated anthropogenic pressure. Environment-friendly technological interventions along with best management practices of watershed conservation and also intensive awareness programmes for the local people are necessary for ensuring sustained long term protection of the islands.