Abstract:
Information related to hydraulic and hydro-meteorological parameters and their
chronological trends is a prime requirement for city planners and policymakers to manage
water resources in urban settings. Jaffna city faces various problems related to the quantity
and quality of water resources and water-related hazards. Lack of information on
hydraulic parameters is a hindrance in alleviation of these problems. The town depends
solely on the availability of groundwater for drinking, domestic and livelihood needs, in
the absence of surface waters. However, groundwater is saline in most of the areas within
the city. Water scarcity is high in coastal Jaffna due to its high population (population
density of 22,579 per km2
). Jaffna town has low surface elevations above the msl ranging
from 0.1 m on the coast to 5.49 m inland. It is underlain by brown or grey calcareous
sands. Aquifers in the said formations are unconfined in nature with shallow water tables
ranging from 1-15 meters from the ground surface. Salinisation of groundwaters in Jaffna
is believed to be a consequence of natural and anthropogenic activities such as leaching
from calcareous sands and evaporation returns, mixing of saline waters, sea salt sprays
and water table fluctuations. As a result, the majority of the areas in Jaffna city require
freshwater supplies and water pricing has become a dominant scenario. The present study
aims to analyse groundwater salinity levels against groundwater table elevations (msl). A
systematic approach was adopted using a 0.25 km2 grid covering the entire town (20.2
km2) and one sampling locality was selected from each grid. Depth to the groundwater
table, Electrical Conductivity (EC) and Total Dissolved Solids (TDS) were determined
using a digital portable EC meter in 285 dug wells. Water table elevations (msl) against
water salinity were mapped with the aid of Arc Map 10.3. Groundwater table elevations
(msl) vary from -3.1 m to 2.9 m in Jaffna, whereas groundwater salinity is found along
the South, Southeast and Western coasts exemplifying a strong correlation with lower
water table elevations. High groundwater salinisation however matches with that of water
in the presence of calcareous sands in selected locations but no strong patterns were found.
Groundwater salinisation in Jaffna town was probably due to fluctuations of water tables
due to natural loss of groundwater discharge, over-extraction, leaching of salts from
calcareous formations and needs to be monitored to arrive at better decisions with regard
to urban supplies of water.