Abstract:
Climate change is expected to inflict severe consequences on the hydrological cycle
and water resources of a catchment. With this backdrop, it is crucial to have better
insight into the functioning of current water resources systems along with future water
resources planning and management due to the fact that amidst growing populations
and ever-increasing resource use, competition among users, and more recently,
widespread ecosystem degradation and climate change impacts have exacerbated the
already grave situation. In order to assess this impact, a semi-distributed monthly
water balance model was adopted and developed to simulate and predict the
hydrological processes incorporating several predicted future climatic scenarios.
This study focuses on analyzing the long-term precipitation trends in the three distinct
climatic zones and climate change impacts on streamflow variability in Mahaweli
basin which extends over wet, dry and intermediate climatological zones. Monthly
precipitation data for a span of 30 years from 1988-2018 have been used for trend
analysis using Mann-Kendall and 15-year monthly rainfall and streamflow data set is
used for calibration and validation of “abcd” hydrological model to evaluate the
climate change impacts on streamflow for future water resources management at three
selected sub-watersheds in each zone of the basin. The changes in precipitation and
temperature during the study period were correlated differently with observed changes
in streamflow. The rainfall trends in the intermediate and dry zone parts of the basin
were identified to be positive while the trend in the wet zone part was found to be
decreasing, however, not statistically significant in both cases. Streamflow
precipitation elasticity was evaluated for sensitivity check.
The “abcd” hydrologic model can be recommended to use for streamflow simulations
and water resources investigations in monthly temporal resolution for the watersheds
which are having similar characteristics with parameter values in the ranges of a
(0.961-0.998), b (0-250), c (0.001-0.999) and d (0.01-0.999). The abcd model has
proven to be a valuable tool not only for assessing the hydrologic characteristics of
diverse watersheds but also for evaluating the hydrologic consequences of climate
change in selected basins which may also be helpful in both pre-disaster risk
management and post-disaster rehabilitation.
