Abstract:
Upper Mahaweli basin is the origination of the main water source of Sri Lanka which is the Mahaweli
River. Therefore it is a timely requirement to identify the future climate trends on the basin, to take suitable
adaptation strategies. Statistical Downscaling model (SDSM) was used to predict future rainfall patterns of the
study area. Observed point rainfall data of ten gauging stations within the study area and Global Climate Model
(GCM) data of Hadley Centre Coupled Model, Version 3 (HadCM3) were used for model calibration and validation
processes. A representative data set for the study area was generated using Thiessen polygon method from the
observed rainfall data of selected gauging stations. Quality of the input data was checked prior to the model
calibration. Daily rainfall was forecasted from 1961 to 2099 under A2 (high emission scenario) & B2 (low emission
scenario) defined by Intergovernmental Panel on Climate Change (IPCC). Under A2 scenario the total annual
rainfall, maximum annual rainfall and annual averaged daily rainfall show an increasing trends and under B2
scenario all the above mentioned parameters show decreasing trends. But the recorded decreasing trends are
insignificant.
