Trends of Rainfall in Sri Lanka over the Last Century

Abstract

Utilizing over 100 years of rainfall records in 15 meteorology stations, an analysis was carried out to extract the trends of annual rainfall depth in Sri Lanka over the last century. A statistically significant increasing trend of rate 3.15 mm/year was observed at Colombo and decreasing trends were observed at Nuwara Eliya and Kandy with rates of 4.87 mm/year and 2.88 mm/year respectively. Since no coherent increase or decrease of rainfall in any group of stations in the wet or dry zones was observed, the possibility of large scale change over the past century was ruled out. However, more recent data records (1949 onwards), revealed a decreasing trends in 13 of the 15 stations. Thus, traces of a temporal change seem to be apparent in the rainfall records over the last half century. In general, the downward trends in recent decades are steeper than the long term variations. For the recent data records, the largest downward trend of 11.16 mm/year was observed at Batticaloa. 9 data records maintained by the Department of Meteorology, Sri Lanka [2]. They have applied the necessary quality control checks on the data and estimated missing values using difference and ratio methods suggested by Thom [3]. The recent data records were obtained from the IRI monthly climatic data (IRI/LDEO Climate data Library) and Statistical abstracts from the Department of Meteorology as well as through direct purchase. Table 1 shows a summary of the selected rainfall stations used in this work.

Changes in Rainfall in Sri Lanka during 1966 – 2015

“…[1] while for the period 1966-2015, the decreasing trend is 2.35 mm/yr. That is, the rate of decrease has reduced.…”

“…Rainfall trends in Sri Lanka in the 100 years leading upto 1998 have been studied based on the monthly rainfall data recorded at 15 gauging stations [1]. In this study, MannKendall statistic, Spearman statistic and leastsquare regression method have been chosen to detect the trends in the rainfall time series.…”

Wet and dry spell analysis for decision making in agricultural water management in the eastern part of Ethiopia, West Haraghe

“…The fish productivity from fresh water is likely to be stricken by longer dry spells. Longer dry spells also interrupt generating electricity using hydroelectric power (Jayawardene, 2005). Therefore, the effects of dry spells in various sectors as described above ultimately have a direct impact on the economy of a country.…”

Water Resource Management in Dry Zonal Paddy Cultivation in Mahaweli River Basin, Sri Lanka: An Analysis of Spatial and Temporal Climate Change Impacts and Traditional Knowledge

“…The rainfall in the period from October to December intensifies, and further reduces in the period from January to March and July to August. Also, in the western hill slopes, including the upper catchment area in the basin, the intensification of rainfall in the period from October to December impacts stream flow, which causes inundation in downstream areas [41,42]. Furthermore, low pressure disturbances in the southwest Bay of Bengal and Southeast Arabian Sea generate tropical cyclones [43].…”