Abstract:
Enormous challenges associated with drinking water supply in Bangladesh are already present. Equally important is the climate change, which has the potential to escalate the current drinking water scarcity problems. The major dimensions of climate change for Bangladesh include more intensive precipitation events, increases in surface temperatures which will increase evaporation rates, prolonged dry periods, sea level rise with consequent salinity intrusion in the coastal areas of Bangladesh, expectations of greater turbulence in the atmosphere with more frequent extreme events like cyclones associated with storm surges. It is, therefore, essential to develop an analytical tool to comprehend the intimate relationship of climate change dimensions and future state of drinking water resources both in terms of water quantity and quality.
This thesis features the generation of future climate projections for Bangladesh on monthly and annual basis, for the period of 2011 to 2100, for selected parameters including precipitation, temperature and evaporation rate, using both Global and Regional Climate Models. Four selected IPCC ensemble GCMs and a RCM called PRECIS have been applied in this regard. From the multi-model average temperature change with respect to 1971-2000, it is evident that the winter months in Bangladesh will show relatively more warming in future. Also precipitation changes for Bangladesh indicate that the precipitation will continue to increase in all the months in future years. Percentage of precipitation increment is expected to be quite higher for dry and pre-monsoon months compared to the monsoon season, though such increase will be insufficient in absolute terms. The monsoon months like June and July are still going to have extensive precipitation events in future years. Also, the large scatters in the projected precipitation quantities are noted, indicating that there will be erratic rainfall pattern in future, with the variations representing significant fluctuations from average conditions. As for evaporation, the pre-monsoon months (March - May) show distinct increase in the amount of evaporation in future than the dry and monsoon months, which can be as high as 225 mm in a month.
Also a mathematical algorithm has been developed, on the basis of the ‘Hydrologic Water Balance’ principle, which quantifies the possible water quantity into a typical drinking water pond as well as a household rain water storage system in any of the year upto 2100 on monthly basis. The proposed model incorporates the projected changes in future hydro-meteorological climate variables along with increasing human consumption into the geometry of the particular systems. Trend of the model-simulated maximum monthly storage deficit in a particular pond clearly indicates a gradual deficit-amplification through time. Also, the proposed model has been applied in determination of critical design storage volume for the particular pond, sufficient enough to meet a range of consumption amount as well as variability of hydro-meteorological parameters due to climate change. As for the rain water storage system, through model simulation within an arbitrary designated service period of 15 years in future, it is found that net potential water available in a month can increase upto 1000 m3 whereas average monthly drinking water demand for a 6-person family is around 1.35 m3 only.
