A thesissubmitted in partial fulfillment of the requirements for the degree of Master of Engineering in Water Engineering and Management

Thesis (M. Eng.) - Asian Institute of Technology, 2013

The increase of population and climate change has placed additional burden on water supply systems which is already under stress. Under that circumstance, rainwater harvesting, a sustainable water source, is increasingly drawn attention as vitalsources inprovision of water. Effects of climate change on hydrological cycle and precipitation distribution will ultimately impact on performance of the system, which must be taken into account for necessary adaptation measuresin design and applications.Firstly, two non-parametric test namely Mann-Kendall and Sen{u2019}s slope were applied for investigation on historical trend of temperature and precipitation. The study showed significant increasing trend of max and minimum temperature is recorded over all stations with approximately rate of 0.3 degree per decade. Although trend of precipitation is not significant throughout the region, two among nine studied stations show significant increasing trend, by contrast there is one station with significant decreasing trend. Secondly, through employment of bias correction techniques on PRECIS Regional Climate Model, it is expected that there is a2-5%increase of total annual rainfall during the period of 2021-2040 & 2041-2060 compared to those of the observation. A decrease on average annual number of strong and heavy day is presented. However, there is significant increase on maximum dry spell from 30-45 days average, which equivalents to an increase of 50-100%of maximum dry durationofthe observation period. Performance of rainwater harvesting is simulated using behavior model underthree different climatic conditions. Development of demand-storage-reliability relationshipreveals that 100% annual reliability can be achieved in humid climate cities. Analysis on future performance of rainwater harvesting shows a reduction of 5-8 % of annual reliability of the system, which should be considered in planning of future rainwater harvesting. Analysis on change of tank storageand/orroof area so as to maintain the system{u2019}s reliability over time was conducted. The result showedthat an increase of 10% roofarea will not only considerably reduce the necessary adjustment of tank storage compared to those of changing tank or roof area only, but also reduce from 15-60% of storage requirement to the observation period.