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Title: Modelling climate change impacts on the water regimes of the river-wetland systems in the data-scarce transboundary Upper Meghna River Basin (Bangladesh and India)
Author: Rahman, M. M.
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2017
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Many regions are likely to be increasingly exposed to water related problems due to climate change-driven modifications to the hydrological cycle. Flooding is the major long-term problem in the haor wetlands of the transboundary (Bangladesh and India) Upper Meghna River Basin (UMRB). Past studies of haor wetlands and changes due to climate change have provided conflicting results. Many studies either ignore the role of haors on local hydrology or do not correctly represent haor hydraulics. In order to address the above issues, this study first develops a modified version of the Soil and Water Assessment Tool (SWAT) for riparian wetlands (SWATrw). This model better represents bidirectional hydraulic interactions between wetlands, rivers and aquifers. A case study for the comparatively data rich Hakaluki haor shows that SWATrw outperforms the original SWAT in the simulation of haor hydrology including flash flooding from adjacent rivers and the persistence of water through the dry season haor which is sustained by aquifers. A SWATrw model for the entire UMRB is developed and manually calibrated and validated against 21 years (1990-2010) of observed streamflow and river stage at 18 gauging stations. The model is forced with projections from four CMIP5 GCMs for the RCP4.5 scenario. An improved Quantile Mapping (QM) based approach is developed to remove biases from raw GCM data as well as adjusting dry day (coldest day for temperature) frequency. Compared to the baseline (1981-2000), monsoonal streamflows are projected to increase by up to 12% for 2021-2040 and 42% for 2061-2080. Dry season low flows decrease by as much as 58%. The average flooding risk in haors in April is likely to decrease which will likely benefit Boro rice cultivation. However, flooding risk in May is considerably higher compared to the baseline.
Supervisor: Thompson, J. R. ; Flower, R. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available