Groundwater Exploration Study in the Medigama- Ahangama, Sri Lanka

The present research study was conducted in the Medigama fruit farm area to identify the groundwater recharg ing areas and how the levels of the groundwater correlate different other environmental parameters. The study area is located within the 80° 22´ longitudes and 5° 90´ latitudes in the Southern coastal area of Sri Lanka. The area receives about 1900mm of mean annual rainfall while owing to mean annual temperature of about 25°C. The dug wells available in the farm and surrounding area were used to explore the groundwater. Within this context, favourable areas for groundwater resources were determined by observing the dug wells and measuring geomor phologic characteristics like the elevation, morphological valleys and aquifers. The analysis of these parameters indicated the South-east region where the dug wells are located, as the most favourable area for groundwater recharge. An unconfined aquifer was distributed in the study area which is consisted with sandy clay and laterite. Therefore it is permeable and the recovery rate too is high in the dug wells. As the atmospheric precipi tation has a great impact on the groundwater level, it was monitored for a period of 22 months and the results were plotted in hydrographs. The results revealed that the groundwater level is not descended below 3.5m for 3 months continuing drought in the dug well 3 area and during the atmospheric precipitation period water level is stabilized in 1.00m below ground level.Pumping test was conducted in dug wells to identify the aquifer characteristics and ideal pumping rates. It was discovered that if the pumping test continues nearly 3.7 hours at a rate of 49.7 litres/ minute and ground water level 2.54m from ground level and withdrawn water quantity is 11033.9 litres. Moreover, groundwater quality in the wells outside the farm area and the water samples collected during the pumping test were analysed and found out that the physical and chemical parameters are under WHO and Sri Lankan standards