Temporal Changes in Drought Pattern of Different Agro-Ecological Regions in Sri Lanka

Abstract

Protracted period of deficient precipitation is called as a drought which affects the environment, economy and social status of human beings. Rainfall data is the main factor to analyze and identify drought pattern in a particular area. Due to climate changes, it is possible that drought patterns have gradually changed. According to annual variation in the rainfall, climate in Sri Lanka categorized into four seasons, viz.:first inter monsoon, Southwest monsoon, second inter monsoon and Northeast monsoon. Sri Lankans are affected by several natural disasters such as floods, droughts, landslides etc. To find out feasible and possible solutions, it is very important to analyze the changes of rainfall patterns and drought patterns. The objective of this study was to study the changes in the rainfall pattern in 3 selected meteorological stations (Anuradhapura, Hambanthota and Nuwara Eliya) from 1901 to 1930 and 1971 to 2000 (two 30 year periods of time of at the beginning and end of twentieth century). Monthly rainfall data of these two time periods were collected from meteorological department of Sri Lanka. Rainfall trend was analyzed using Microsoft Excel and frequency analysis was done by using Minitab statistical package. Standard Precipitation Index (SPI) was used to identify and analyze strength of drought months during considered two 30 year periods, which was done by monthly and seasonally for selected stations. The SPI analysis revealed the severity of droughts and illustrated the changes of drought patterns in selected areas with time. The results indicated that trend of rainfall was decreased during 1971-2000 period compared to 19 0 1 -1 9 3 0 period in all three stations. The highest total rainfall has occurred during 1901-1930. Number of droughts occurred during the two 30 year time periods were very much similar and it was statistically proven by the Wilcoxon signed rank test. The number of droughts occurred seasonally was comparatively differed in first and last three decades in the twentieth century.