Trends in extreme events of rainfall in low country wet zone of Sri Lanka

Abstract

It has been reported that growth and production of crops are severally affected by the changing climate. Thus, climate changes may have significant impact on a country like Sri Lanka which has an agriculture based economy.  Plantation sector contributes more to export agriculture, which is mainly confined in the wet zone of the Island. Most of the management practices of plantation crops such as tea, rubber and coconut are linked with weather pattern; especially with the rainfall pattern. Evidence for change in the amount and the distribution of rainfall in Sri Lanka are not very apparent. However, trends in the occurrence of extreme events of rainfall may be apparent and there by the crop production may be affected. A study was carried out to identify trends in extreme events of rainfall in low country wet zone where most of rubber plantations and low grown tea plantations are found.  Daily rainfall data from eight agro ecological stations in the Wet zone Low country (WL) of the Island for the period from 1941 to 2010 were used in the study. Boundary line techniques, parametric and non parametric regression techniques were used to identify trends in extreme events of rainfall. It was found that significant changes in total precipitation were not apparent while there were very clear evidences for changing incidences of extreme events with respect to rainfall.  In some areas under investigation, trends of occurring low annual rainfalls in time was apparent. There were significant evidences for declining trends in annual rainy days in some areas of low country wet zone of the country, which may be favorable for operations like exploitation of rubber latex. However, there was a tendency for increasing incidences of lengthy dry spells in some areas in the low country wet zone. This may bring adverse impacts on some operations such as crop establishment and fertilizer application and crop yield of tea and rubber.