Kabiri, Reza
(2014)
Assessment of climate change impact on runoff and peak flow: a case study on Klang watershed in West Malaysia.
PhD thesis, University of Nottingham.
Abstract
Climate change is a consequence of changing in climate on environment over the worldwide. The increase in developmental activities and Greenhouse Gases (GHGS) put a strain on environment, resulting in increased use of fuel resources. The consequence of such an emission to the atmosphere exacerbates climate pattern. There are numerous Climate Change Downscaling studies in coarse resolution, which have largely centred on employing the dynamic approaches, and in most of these investigations, the Regional Climate Model (RCM) has been reported to numerically predict the local climatic variables. The majority of previous investigations have failed to account for the spatial watershed scale, which could generate an average value of downscaled variables over the watershed scale.
To address shortcomings of previous investigations, the work undertaken in this project has two main objectives. The study first aims to implement a spatially distributed Statistical Downscaling Model (SDSM) to downscale the predictands, and second to evaluate the impact of climate changes on the future discharge and peak flow. It is conducted based on the IPCC Scenarios A2 (Medium–High Emission scenario) and B2 (Medium–Low Emission scenario). The main objectives of the study are as follows:
• To generate fine resolution climate change scenarios using Statistical Downscaling Model in the watershed scale,
• To project the variability in temperature, precipitation and evaporation for the three time slices, 2020s (2010 to 2039), 2050s (2040 to 2069) and 2080s (2070 to 2099), based on A2 and B2 scenarios,
• To calibrate and validate hydrological model using historical observed flow data to verify the performance of the hydrological model,
• To evaluate the impact of climate changes on the future discharge and future peak flow for three timeslices: 2020s (2010 to 2039), 2050s (2040 to 2069) and 2080s (2070 to 2099).
Thus, to meet the objectives of the study, projection of the future climate based on climate change scenarios from IPCC is carried out as the most important component in the research. The results of this research are presented as follows:
• The study indicates that there will be an increase of mean monthly precipitation but with an intensified decrease in the number of consecutive wet-days and can be concluded as a possibility of more precipitation amount in fewer days.
• The watershed is found to experience increased rainfall towards the end of the century. However, the analysis indicates that there will likely be a negative trend of mean precipitation in 2020s and with no difference in 2050s. The precipitation experiences a mean annual decrease by 7.9%, 0.6% in 2020s and 2050s and an increase by 12.4% in 2080s corresponding A2 scenario.
• The maximum and minimum temperatures are likely to be increased toward the end of the century by 2.7oC and 0.8oC respectively when compared to the current observed temperature (1975-2001) at the Subang temperature station.
• The average annual mean discharge is predicted to be decreasing by 9.4%, 4.9% and an increase of 3.4% for the A2 and a decrease of 17.3%, 13.6% and 5.1% for the B2 scenario, respectively in the 2020s, 2050s and 2080s.
• The average annual maximum discharge is projected to decrease by 7.7% in 2020s and an increase by 4.2% and 29% in A2 scenario for 2050s and 2080s, respectively. But there will most likely be a decrease in the maximum discharge for all the future under B2 scenario. It is projected a decrease of 32.3%, 19.5% and 2.3% for 2020s, 2050s and 2080s, respectively.
• The projected mean discharge indicates a decline in the months from January to April and also from July to August in all the three future periods for A2 and B2 scenarios. There is an increasing trend in the discharge of September and October in the 2020s according to the A2 and B2 scenarios.
• The highest increase in precipitation frequency occurs in 2080s under A2 scenario in which the increase in the magnitude of 100 Return Year is found to be 88% greater than the one of the maximum observed.
• The highest increase in flood frequency at Sulaiman streamflow station occurs in 2080s under A2 scenario. The increase in the magnitude of 100 Return Year is found to be 26.5% greater than the one of the maximum observed.
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