|Native name||කළු ගඟ (Kalu Ganga)|
|• elevation||2,400 m (7,874 ft)|
|Length||129 km (80 mi)|
|Basin size||2,766 km2 (1,068 sq mi)|
|• left||Kukule River|
Kalu Ganga (Sinhala : කළු ගඟ; literally: Black River) is a river in Sri Lanka. Measuring 129 km (80 mi) in length, the river originates from Sri Padhaya and reach the sea at Kalutara. The Black River flows through the Ratnapura and the Kalutara District and pass the city Ratnapura. The mountainous forests in the Central Province and the Sinharaja Forest Reserve are the main sources of water for the river.
Kalu Ganga basin is one of the most important river basins in Sri Lanka which receives very high rainfalls and has higher discharges. Due to its hydrological and topographical characteristics, the lower flood plain suffers from frequent floods and it affects socio-economic profile greatly. During the past several years, many researchers have investigated climatic changes of the main river basins of the country, but no studies have been done on climatic changes in the Kalu Ganga basin. Therefore, the objective of this study was to investigate precipitation trends in Kalu Ganga basin. Annual and monthly precipitation trends were detected with Mann-Kendall statistical test. Negative trends of annual precipitation were found in all the analyzed rainfall gauging stations. As an average, -0.98 trend with the annual rainfall reduction of 12.03 mm/year was found. April and August were observed to have strong decreasing trends. July and November displayed strong increasing trends. In conclusion, the Kalu Ganga basin has a decreasing trend of annual precipitation and it is clear that slight climatic changes may have affected the magnitude and timing of the precipitation within the study area.
Kalu Ganga basin is the second largest river basin in Sri Lanka covering 2766 km2 and much of the catchment is located in the highest rainfall area of the country, which reflects the high annual rainfall. The annual rainfall in the basin is averaged to 4000 mm and leads to 4000 million m3 of annual flow. The Kalu Ganga originates from the central hills of wet zone at an altitude of 2250 m and garners rainfall on the western slopes and falls out to the sea at Kalutara after traversing about 129 km. The basin has steep gradients in upper part and mild gradients in lower part. Due to these hydrological and topographical characteristics of the river basin, its lower flood plain suffers from frequent floods during the Southwest monsoon season. Therefore, the damages to the socio-economic profile are significantly high since the lower flood plain of Kalu Ganga is densely populated and it is a potential area for rice production. During the past several years,[ which? ] attention has been paid to study on precipitation changes of main river basins of Sri Lanka. El Niño-southern oscillation influences on stream flow in Kelani River. In studied 2005 hydrology and environmental flows in the Walawe River basin. However, we[ who? ] could not find any academic literature regarding climatic changes in Kalu Ganga basin, which is one of the four main rivers in Sri Lanka. The major possible effects of climate change may include variability in water resources, increase desertification, loss of biodiversity and changes in agricultural productivity. One of the most significant consequences resulting from climate change may be the alteration of regional hydrological cycles and subsequent changes in stream flow regimes. Studies of general circulation model reveals that increased global temperature could lead to increase the amount and intensity of regional precipitation. Precipitation is a good indication of the impacts from climate change on water resources. Changes in precipitation patterns are very important for water resources managers to deal with the water resources planning and management. Variations in precipitation over daily, seasonal, annual, and decadal timescales influence water resource systems. In addition to the studies on short-term variability of precipitation, long-term detection of precipitation is essential for understanding the potential impacts on water resources resulting from climate change. Therefore, the objective of this study was to investigate long-term precipitation trends, which is one of the crucial parameters in climatic change in the Kalu Ganga basin.
Hydrology is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is called a hydrologist. Hydrologists are scientists studying earth or environmental science, civil or environmental engineering, and physical geography. Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as environmental preservation, natural disasters, and water management.
Sri Lanka, formerly called "Ceylon", is an island nation in the Indian Ocean, southeast of the Indian subcontinent, in a strategic location near major Indian Ocean sea lanes. The nation has a total area of 65,612 km2, with 62,707 km2 of land and 2,905 km2 of water. Its coastline is 1,340 km (830 mi) long. The main island of Sri Lanka has an area of 65,268 km2; it is the twenty-fifth largest island of the world by area. Dozens of offshore islands account for the remaining 342 km2 area. The largest offshore island, Mannar Island, leads to Adam's Bridge.
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Ratnapura is a major city in Sri Lanka. It is the capital city of Sabaragamuwa Province, as well as the Ratnapura District, and is a traditional centre for the Sri Lankan gem trade. It is located on the Kalu Ganga in south-central Sri Lanka, some 101 km (63 mi) southeast of the country's capital, Colombo. Ratnapura is also spelled as Rathnapura.
Galle is a district in Southern Province, Sri Lanka. It is one of 25 districts of Sri Lanka, the second level administrative division of the country. The district is administered by a District Secretariat headed by a District Secretary appointed by the central government of Sri Lanka.
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2018 Sri Lanka floods and landslides caused from an annual heavy southwest monsoon beginning around 19 May. As of 26 May 2018; the monsoon floods affected in about 19 districts, killed at least 21 people, about 150, 000 people were affected and further left approximately 23 people missing. The death casualties were reported from 22 May onwards in the provinces including South, Northwest, North and East. About 4 people were reported dead due to lightning, 5 people were killed due to floods and lightning, 8 people died due to drowning and further left 4 people dead resulting from fallen trees. The DMC report claimed about 400, 000 people have been displaced to safer locations. About 105 houses were reported to have fully damaged and over 4832 houses have been partially damaged.
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The 2019 floods and landslides in Sri Lanka were the floods which were caused from heavy torrential rainfalls during September 2019. As of 26 September 2019; the monsoon floods affected in about 13 districts, killing at least 2 persons, injuring 6 people and about 116, 000 people are affected. One casualty was reported in the Galle District and the other one was reported in Kolonnawa, where a teenager drowned in the flood water. About 282 houses were reported to have been damaged mainly in Galle and Matara while 22 houses out of 150 houses were completely destroyed in the two districts.