Abstract:
It is crucial to assess the impacts due to climate change on the hydrological cycle for the
characterization of basin hydrology and water resource management. Climate elasticity can be
used as an indicator to quantify the sensitivity of streamflow to climate change. This
study estimates the climate elasticity of runoff concerning precipitation and evaporation, in
the Kalu river and Kelani river basins in the wet zone of Sri Lanka. The Ellagawa subbasin of
the Kalu river and the Hanwella subbasin of the Kelani river were selected for the assessment.
The non- parametric estimator was selected based on the simplicity to assess the climate
elasticity of runoff in the selected wet zone basins under current climate scenarios. At the
same time, the climate elasticity under synthetic climate change scenarios was assessed using
a hydrological model. The HEC-HMS rainfall-runoff model was selected based on the
accessibility, flexibility, reliability, and data requirements to simulate streamflow. The
rainfall elasticity and evaporation elasticity were estimated for prevailing climate
conditions. According to the results, the increase in runoff due to the increase in
precipitation under current climate scenarios is small compared to the reduction of runoff
due to increased evaporation as a result of increased temperature, whereas according to
the model results, climate change results in causing -41% to 31% change in runoff in the
Kalu river basin and -49% to 23% change in runoff in the Kelani river basin based on two
scenarios, respectively, under synthetic climate change scenarios that were developed for
the period of 2016-2035 considering the predicted precipitation and evaporation changes
comparative to the baseline period of 1986-2005. According to the results, these crucial
river basins are vulnerable to water scarcity and/or a surplus of water as well in the future.
Therefore, the findings of this research are very important to plan proactive solutions in
advance to manage the basin water resources efficiently.
