A capstone project report submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Engineering Civil and Infrastructure Engineering, School of Engineering and Technology

Capstone Project (B.Sc.)-Asian Institute of Technology, 2017

Climate change is now considered as real. It is affecting various sectors, including agriculture. Changes in crop water requirements (CWR) and hence irrigation water requirement (IR) is the primary pathways by which the climate change impacts the agriculture sector. Climate changes impacts are more sever in the tropical countries like Sri Lanka. Approximately 72% of paddy produced in Sri Lanka may alter substantially by climate changes. The Kelani River Basin is one of the most vulnerable one for floods in Sri Lanka. It results in losses of many paddy productions within a year. This study aims o understand how projected future climate is likely to impact on IR with a case of Thalangama Irrigation Project in the Kelani River Basin, Sri Lanka. This study used CROPWAT8.0 model to estimate CWR and IR under current and future conditions. Meteorological and other data were collected from local source. Future rainfall and temperature were taken from two regional circulation models (RCMs) under two scenarios (RCP4.5 and RCP8.5). Mid-future or the 2050s was considered as the future time of interest. Results showed that both temperature and precipitation is projected to increase. As a con sequence, CWR in the mid-future is projected to increase by 2.1% and 3.4% from baseline (2006-2015) under RCP4.5 and RCP8.5 scenarios, respectively. With the increase in effective rainfall, IR is projected to decrease by 38.8% and 12.9% in the mid-future under the two scenarios under consideration.