International Journal of Scientific and Research Publications, Volume 8, Issue 9, September 2018 725 ISSN 2250-3153 Variation of Annual and Seasonal Rainfall Patterns in Kandy District of Sri Lanka U.S. Meegahakotuwa* and K.W.G. Rekha Nianthi** * Kandy/Mulgama Maha Vidyalaya, Gampola Education Zone, Central Province, Sri Lanka ** Department of Geography, University of Peradeniya, Peradeniya, Sri Lanka DOI: 10.29322/IJSRP.8.9.2018.p8195 http://dx.doi.org/10.29322/IJSRP.8.9.2018.p8195 Abstract- Rainfall variability over space and time must be significant rainfall trend, but the SWM season rainfall shows a regarded as the most significant aspect of the monsoon climate statistically significant decreasing trend. The drop in the SWM over Sri Lanka. The main objective of this study was to identify season rainfall is 2.4 mm per year. the spatial distribution of annual and seasonal rainfall in Kandy District (2005-2014) and long term annual and seasonal rainfall Index Terms - Leeward side, Rainfall, Trend, Variation, trends in Kandy (1875-2014). The monthly rainfall data have Windward side. been collected from 19 rainfall stations in Kandy District. The data was obtained from the Department of Meteorology and I. INTRODUCTION other relevant institutions. Spatial interpolation was applied to The Kandy District is situated in the Central Highland of Sri prepare the isohyet maps for Kandy District using Radial Basis Lanka. It extends in latitude from 60 26’ to 70 29’ North and from Functions Method in ArcGIS 10.4. The rainfall trends over the 800 26’ to 800 59’ East longitudes. The District is bounded North 140-years period were estimated using the Linear Regression by Ukuwela, Rattota, Laggala, Pallegama and Wilgamuwa model. The Mann-Kendall statistical method was used to identify Divisional Secretary Divisions (DSD) of Matale District, East by the significant or non-significant monotonic tendencies. Mahiyangana DSD of Badulla District and Walapane, According to the analysis the highest annual average rainfall Hanguranketha, Kothmale, Nuwaraeliya and Ambagamuwa (5,660 mm) has been recorded at Galamuduna Estate in Korale DSDs of Nuwaraeliya District and West by Aranayake, Dolosbage, and the lowest is recorded at Kundasale (1,594 mm) Bulathkohupitiya, Mawanella and Rambukkana DSDs of Kegalle during the study period from 2005 to 2014. According to the District and Mawathagama and Rideegama DSDs of Kurunegala seasonal rainfall, during the FIM period (March-April) the District. Kandy District has an area of 1,940 square kilometers. rainfall varies from 700 mm (Craighead Estate) to 241 mm (Minipe). Rainfall during SWM period (May to September) The Kandy District has extended from 100 m to 1600 m in height varied from 3,436 mm at Galamuduna to 174 mm at Minipe. The from the sea level. Its Eastern side is bounded to Mahaweli Southwestern windward side received the highest rainfall while River. The annual average rainfall is 1840 mm for the Kandy the Eastern leeward side received the lowest rainfall during District. The Minipe DSD in the Eastern region of the District is SWM season. The Galamuduna Estate (1053 m) is situated in consisting with mountains features and Low-Country Dry Zone highest rainfall region of Wet Zone Up-Country of Sri Lanka. landscapes. The average temperature of the areas of; Delthota, The SIM period (October to November) showed most evenly Pasbage Korale, Ganga Ihala Korale, Udadumbara and Panwila distributed rainfall over the Kandy District. During the NEM shows a low temperature than other areas of the District but the period (December-February), the highest rainfall was recorded in Minipe shows a higher temperature. the Eastern side of the Kandy District. The highest rainfall (700 mm–1,000 mm) is recorded in and around Minipe station during The Mahaweli River is the main river which flows across the this season. Kandy Plateau area received a lower rainfall in the Kandy District and it covers 110 km (total of 335 km) within NEM season. The study revealed that the annual and seasonal Kandy District. In addition to that, the stream of water of distribution of rainfall over Kandy District has considerable Deduru-Oya begins in the Poojapitiya DSD and Ma-Oya begins variations. Based on the annual average rainfall, the wettest place in the Ganga Ihala Korale DSD. The Southern part of Knuckles of the Kandy District was the Galamuduna Estate and the driest mountain range situated in Kandy District is a unique ecological places were the Kundasale and Minipe. The month of June was zone. This zone is the main catchment area of Mahaweli and recorded as the wettest month (777 mm) in Galamuduna and the Aban Ganga. Hantana, Ambuluwawa, Balana range, Alagalla, same month, Minipe (5 mm) was observed as the driest month Hunnasgiriya and Dolosbage mountains are located in Kandy during the study period. The complex topographical features and District. The waterfalls like; Asupini Ella, Galaboda Ella, and orographic barriers highly affected for the seasonal rainfall Kadiyanhela are also situated in the Kandy district. variations in the Kandy District. According to long term rainfall data series (1875-2014), the results clearly show that there is a Out of total land of the Kandy District, 41,521 hectare (21%) is statistically significant decrease in annual rainfall (2.6 mm/year) covered with forest. A large number of the animal community in Kandy station. The FIM, SIM and NEM seasons do not show a live in the forest belongs to the District. Among them Elephant, http://dx.doi.org/10.29322/IJSRP.8.9.2018.p8195 www.ijsrp.org International Journal of Scientific and Research Publications, Volume 8, Issue 9, September 2018 726 ISSN 2250-3153 Leopard Monkey, Wild Boar, Kola Diviya, Deer, Barking Deer They concluded that some stations in Central Highlands are prominent. Wild elephants can be seen in the areas such as demonstrate a decrease in the SWM, but no statistically Udadumbara, Minipe, Randenigala sanctuary and Meemure. significant upward or downward trend exists for the NEM. During the FIM and SIM the only statistically significant trend in Rainfall of Sri Lanka is of multiple origins, including monsoonal, the Central Highlands was the decreasing trend observed in convectional and depression activities. In the rainfall calendar of Nuwaraeliya. Sri Lanka, there are four distinctive periods have been recognized. They are, Wickramagamage (2015) examined the daily rainfall variations i. First Inter Monsoon (FIM): March to April for the period from 1981 to 2010. Out of 48 stations, 39 ii. South West Monsoon (SWM): May to September displayed negative trends during SWM period. The strongest iii. Second Inter Monsoon (SIM): October to November negative trends are found in the Central Highlands and iv. North East Monsoon (NEM): December to February surrounding areas. SWM is the dominant rainfall season in the Southwestern lowlands as well as the Highland Wet Zone of Sri Variability of rainfall over space and time must be regarded as Lanka. It is clearly shown that almost the entire island the most significant aspect of the monsoon climate over Sri experiences a reduction of rainfall during SWM. This decrease is Lanka. The Central Highland contains many complex negatively influenced to the irrigation and agriculture, domestic topographical features such as valleys, plains, ridges, peaks, water supply, industrial water supply and power generation in the plateaus, basin and escarpments. These topographical features country. strongly affect the spatial patterns of winds, seasonal rainfall, temperature, relative humidity and other climatic elements, II. METERIALS AND METHODS particularly during the monsoon seasons. The main objectives of this study are to examine; (i) the spatial and temporal variations of annual and seasonal rainfall patterns The Central Highlands is an important catchment area for the in Kandy District, (ii) the long term annual and seasonal rainfall river systems of Sri Lanka. Hence, the rainfall changes of the trends of Kandy station. The monthly rainfall data have been Central Hills of Sri Lanka have been studied widely. Madduma collected from 19 rainfall stations (Figure 1 and Table 1) in Bandara and Kuruppuarachchi (1988) found that the annual Kandy District for the period from 2005 to 2014. The data was precipitation at Nuwaraeliya in the Central Highlands has obtained from the relevant institutions like: decreased during the last century where land use has undergone i. Department of Meteorology, Colombo. significant changes. For example, between 1956 and 1981, area ii. Natural Resource Management Centre (NRMC). under tea and forests decreased from 61% to 39% and from 17% iii. Mid Country Tea Research Institute, Hantana. to 15%, respectively. On the other hand, the homestead and iv. Peradeniya Botanical Garden. croplands increased from 7% to 17% and from 7% to 15%, v. Tea Estate Offices in the Kandy District. respectively. Kayane et al. (1995) have shown that rainfall during the SWM Season has decreased in the Central Highland since the 1870’s. They also suggested that a significant decline in rainfall in the plateau could be related to global warming and the rise of the Sea Surface Temperatures (SST) in the surrounding Indian Ocean. Further, they have pointed out that the increased SST over the Indian Ocean will intensify the Indian Monsoon circulations, which in turn may increase the coastal windward rainfall with a comparative decrease of rainfall in the leeward areas of Sri Lanka. Rekha and Punyawardena (2003) have found that negative anomalies of rainfall are evident in the western slopes of the Central Highland where SWM is the dominant rainfall governing mechanism. The analyses clearly show that increased variability is the most dominant feature of the rainfall regime in the Central Highlands during recent time than that of any other trend. Madduma Bandara and Wickramagamage (2004) have found a significant decrease in annual rainfall in the upper watershed Figure 1: Geographical Distribution of the Rain Gauge Stations areas, over the last 100 years, reflecting at least a 20% decline at in the Kandy District.