Sri Lanka Atomic Energy Board

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නිතර අසන පැණ විමසීම්

Identification of Isotopic Variation of Rain Water in Wet and Semi Arid Zones of Sri Lanka

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Location2Southwestern part of Sri Lanka receives rain from southwest monsoon rain and convectional rains during inter-monsoon seasons. They contribute surface water runoff and groundwater recharge in wet zone. Semi-arid zone receives rain from convectional process and due to depression in limited time period of the year. Isotopic (18O and 2H) composition of the rain vary with altitude, latitude and distance from the coast, etc due to fractionation of isotopes during evaporation, condensation and diffusion of water vapor. Surface water runoff and groundwater recharge are solely depend on the rainfall. Therefore understanding the rain process and its variation are important to see the rainfall variation and their impact on groundwater bodies. In this context, isotope technique in hydrology plays an important role to study the above processes. Therefore collection of isotopic data of rain in wet zone and semi-arid region as baseline information is important for the future groundwater and climatic investigations in Sri Lanka.

Isotope Hydrology Section of Sri Lanka Atomic Energy Board has initiated a project on collection of isotopic data as a baseline survey in wet zone and semi-arid zone. Objectives of this study are to collect isotopic composition of rain in above zones and to identify any correlation between isotopic composition with altitude as well as different distances from the coast. Twenty six locations have been identified in wet zone and semi-arid regions considering the distance from the coast and altitude of the locations. These locations are shown in the map.

Under this project installation of rainwater collectors is done in three stages. First stage was successfully carried out during 26th -28th April 2017 and eight rain water collectors were installed in Mathugama, Deniyaya, Sooriyakanda, Udawalawe, Katharagama, Hambanthota, Tangalle and Galle. In second stage, rain collectors were installed in Rathnapura, Beragala, Buttala, Siyabanduwa, Panama, Iginiyagala, MahaOya and Bibile during the 5th – 8th June 2017. In final stage, it is planned to install rainwater collectors in Chillaw, Wariapola, Kuliyapitiya, Kegalle, Hasalaka, Piduruthalagala and Hatton. This exercises will be continued for 2 years period.


අවසන් යාවත්කාලීන කිරීම 2017 ජූනි 13 වෙනි අඟහරුවාදා, 15:48