CLIMATE EXTREMES AND PRECIPITATION TRENDS IN KELANI RIVER BASIN, SRI LANKA AND IMPACTS ON STREAMFLOW VARIABILITY UNDER CLIMATE CHANGE

Climate change is increasingly sensed by nations vulnerable to water-related disasters, and governments are acting to mitigate disasters and achieve sustainable development. Uncertainties in General Circulation Models’ (GCM) rainfall projections and seamless long-term hydrological simulations incorporating warming effects are major scientific challenges in assessing climate change impacts at the basin scale. Therefore, the Data Integration and Analysis System (DIAS) of Japan and the Water Energy Budget-based Rainfall-Runoff-Inundation model (WEB-RRI) were utilized to develop an integrated approach, which was then applied to the Mahaweli River Basin (MRB) in Sri Lanka to investigate climate change impacts on its hydro-meteorological characteristics. The results for the Representative Concentration Pathway (RCP8.5) scenario from four selected GCMs showed that, with an average temperature increase of 1.1 °C over the 20 years in future (2026 to 2045), the basin will experience more extreme rainfall (increase ranging 204 to 476 mm/year) and intense flood disasters and receive sufficient water in the future climate (inflow increases will range between 11 m3/s to 57 m3/s). The socio-economic damage due to flood inundation will also increase in the future climate. However, qualitatively, the overall trend of model responses showed an increasing pattern in future meteorological droughts whereas there is uncertainty in hydrological droughts. Policymakers can utilize these results and react to implementing soft or hard countermeasures for future policymaking. The approach can be implemented for climate change impact assessment of hydro-meteorology in any other river basin worldwide.

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Agritourism as a sustainable adaptation option for climate change

Open Agriculture ◽

10.1515/opag-2019-0074 ◽

2019 ◽

Vol 4 (1) ◽

pp. 737-742

Author(s):

R.P. Mahaliyanaarachchi ◽

M.S. Elapata ◽

M. Esham ◽

B.C.H. Madhuwanthi

Keyword(s):

Climate Change ◽

Sri Lanka ◽

Crop Production ◽

Management Practices ◽

Global Climate ◽

Climate Extremes ◽

Farming Systems ◽

Adaptation Option ◽

Climatic Effects ◽

Cropping Patterns

AbstractThe global climate change has become one of the imperative issue for the smallholder dominated agriculture and tourism sectors in Sri Lanka. This study investigated the perception of farmers on climate change and the potential of agritourism as a sustainable adaptation option to mitigate the negative impacts of climate change in both tourism and agricultural sectors. The study was carried out in the low country dry zone (LCDZ) and the upcountry wet zone (UPWZ) of Sri Lanka. A survey strategy followed by structured and unstructured interviews were undertaken to collect the data. The sample was composed of 100 farmers each from the UPWZ and LCDZ respectively. The study revealed that there had been climate extremes in both climatic zones in terms of high rainfall and longer dry spells. Thus, it was important for the farmers to have necessary knowledge and skills on different diversification techniques related to crop-production, integrated farming systems and climate resilient production which are economical and mitigate the adverse climatic effects. However, the results revealed that the farmers have altered the cropping patterns and crop management practices rather than adopting entrepreneurial activities like agritourism. Lack of awareness of agritourism within the farming community is the main reason for farmers not contemplating this important diversification option. The results indicate that a significant number of farmers showed interest in considering agritourism as an option to mitigate climate change. It is important to educate farmers on diversification options.

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Flood inundations and risk mapping in a tidal river: a case study for the Kelani River basin, Sri Lanka

10.21203/rs.3.rs-161788/v1 ◽

2021 ◽

Author(s):

Jayanaga Thanuka Samarasinghe ◽

Eranda Perera ◽

Fang Yenn Teo ◽

Andy Chan ◽

Surajit Ghosh

Keyword(s):

Sri Lanka ◽

River Basin ◽

Hydrodynamic Model ◽

Hydrological Model ◽

Tidal River ◽

Return Periods ◽

Coefficient Of Correlation ◽

Pearson Coefficient ◽

Inundation Extent ◽

Kelani River

Abstract The downstream low-lying regions of the Kelani River, including some areas in the Districts of Colombo and Gampaha, Sri Lanka, frequently face severe inundations due to extreme rainfalls in the upper basin. In the present study, 1-D and 2-D hydrodynamic models in HEC-RAS have been used to examine the flood inundations in the tidal influenced Kelani River with ground observations and remote sensing. The HEC-RAS model has been used to produce a flood hazard map for hazard assessment in the lower Kelani River basin under different return periods. Furthermore, expected discharges for different return periods have been estimated using the hydrological model HEC–HMS with the updated intensity depth frequency curves for the Kelani River basin. Sentinel 1 imagery and field survey results are used to validate the simulated flood inundation extent; hydrodynamic model results validated against observed stage measurements; hydrological model validated against discharge measurements. Further, the validated hydrodynamic model showed the high capability to capture flow processes (Nash-Sutcliffe coefficient = 0.90 and Pearson coefficient of correlation = 0.95) along with inundation extent (Success Index = 0.90) of selected historical extreme events. Then the hydrological model is used to predict the flows of the Kelani River basin with a good agreement (Nash-Sutcliffe coefficient = 0.91 and the Pearson coefficient of correlation = 0.93). Finally, flood risk zoning for different return periods are developed based on the present model which would be a useful benchmark to design and implement flood control and mitigation measures for the river basin.

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