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Climate change risk profile of the mountain region in Sri Lanka (May 2022)

Sri Lanka
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Executive Summary

Mountains of the world occupy about 24% of the global land surface (Sayre et al. 2018) and significantly influence the regulation of environmental services and sustainability of livelihoods in most parts of the world. Mountain ecosystems are also considered highly vulnerable to current climatic conditions and projected climate scenarios. The mountainous region in the central part of Sri Lanka impacts the surrounding lowland areas. Yet, the country has no broadly relevant definition or boundary for the mountain region apart from a few subject-specific definitions.

This study developed a definition of the mountain region in Sri Lanka. The definition considers the physical, environmental, and socioeconomic factors unique to the mountain region. The present definition is not restricted to a specific discipline but is widely applicable to diverse disciplines, such as for developing legal policies or multidisciplinary tasks. The study compiled a basic resource profile for the mountain region by using available information on geographical and geological features. Rainfall, hydrology, and land use with major agricultural activities were also incorporated.

The climate change risk assessment was conducted by using multi-ensemble rainfall projections developed by the Department of Meteorology (DOM) in Sri Lanka. The study used RCP 8.5 for the period 2040–2060 as the climate change projection emission scenario with reference to the baseline period 1975–2005.

The projected data shows a marked change of annual average rainfall, with significantly high rainfall seasonality and considerable reduction during the first inter-monsoon (FIM) and northeast monsoon (NEM).

The analysis of landslide triggers due to excessive rainfall for the period 2040–2060 shows high risk in the Grama Niladhari Divisions (GNDs) in Ratnapura, Kegalle, and Nuwara Eliya Districts. Kandy District shows a high number of GNDs having high- and low-risk landslide potential, while Badulla District shows a higher number of GNDs with low-risk landslide potential.

Due to fluctuations in projected extreme seasonal rainfall, the river basins of Attanagalu Oya to Nilwala Ganga may be prone to heavy seasonal floods. Maha Oya, Walawe Ganga, and Kirama Ara river basins may experience moderate floods during the southwest monsoon and second inter-monsoon. The significant reduction of rainfall during the FIM and NEM in most river basins in the north, east, and southeast parts of the mountain region will cause severe water shortages affecting a large extent of the Mahaweli River.

Incorporating other climate parameters such as temperature and atmospheric water vapor would facilitate a more complete analysis. Using the newly developed shared socioeconomic pathway projections is expected to provide a more comparable analysis.

The findings of the study are beneficial for crucial resource identification, effective resource administration and management, and policy development in the mountain region in Sri Lanka.

Asian Development Bank: © Asian Development Bank