Location and Area
Jaffna District is located in the Northern Province of Srilanka, about 410 km away from Colombo. It consists of the peninsula and seven inhabited Island. North, East and west boundaries of the District are Indian Ocean, South is Jaffna Lagoon and Kilinochchi District. The total land area including Island waters is 1,012.01 Sq.km. Jaffna District is divided into four Sub divisions. They are Islands, Valikamam,Thenmaradchi andVadamaradchi. The Land in Jaffna District could be characterized as flat with less than 5% slop. There are 1084 ponds and 2,433 ditches scattered all over the District with connected channels to conserve rain water. Excess water easily drained into the sea/lagoon. The levels are Point Pedro 15.24m, Myliddy 10.8m., Chankanai 3.04 m and Kokuvil 6.09m above the Sea level.
Jaffna District falls under dry zone. Peak rainfall is during the months of October to December during North East Monsoon and the Scattered during April to May. The inter Monsoon rain is uncertain. The District received 1,470.7 mm of rain during theyear 2011. The average temperature during the year fluctuated between 25.14 and 31.22 centigrade with an annual average of 28.18 centigrade.
The soil and water resource of the Jaffna Peninsula are both related to the lime stone geology of the land. The soils are formed on the marine deposits and sendiments under the influence of seawaves and winds on lime stones.Tile lime stone being a porous rock is the source of groundwater for the Peninsula.Well drained and high productive calcic Red Yellow latasol andRed Yellow latasol soil types are found in central areas (60,000Ha). Alkalin saline soil and Regasol are found in costal areas(26000Ha) andAlluvial soil is inValukaiAru area (10000Ha). In certain areas coral lime stone is available. This different soil types offer scope for cultivation of exotic as well as local crops.Tile depth of soil varies from 90cm- 150cm.
Jaffna peninsula has a source of Ground Water store in the Subterrain layer of limestone.The limestone is the main aquifer. This a quifer has several isolated caves and caveins capable of storing ground water without evaporation losses. It is a excellent aquifer. The entire g round water is generated from percolated rainfall and it forms a freshwater lens beneath the peninsula. It is found that the fresh water lens do not extend below the base of the lime stone. The fresh water lens is sustained by the buoyancy of fresh water in relation to sea water. Difference in density, (1.0,1.025) giving a ratio of 40:1. That is every meter of fresh water above the sea level requires a depth of fresh water lens of 40m when no mixing between fresh and seawater takes place.There is no sharp interface between fresh and seawater.