Impact of Sea Level Rise on Agriculture Using Groundwater in Bangladesh

Bangladesh, located on the northern littoral of the Bay of Bengal, is one of the most vulnerable countries to the impacts of climate change and sea level rise. Agriculture is the prime economic activity in the densely populated coastal areas of the country. During the dry season of the year (November to April), when rainfall is low, the irrigation is done by extracting groundwater. Over the years this continuous groundwater pumping causes the depletion of groundwater table. Due to the proximity to the sea, the lowering of groundwater initiates saltwater intrusion into the coastal aquifers and this affects the crop production significantly. The objective of this project was to establish generic models to evaluate the inter-relationships among different cropping patterns, irrigation requirements, groundwater recharge and saltwater intrusion in the south-west coastal region of Bangladesh. The models were initially used to analyze the current situation and then future predictions were also made by considering climate change and sea level rise in the future. Crop Irrigation models were established in CROPWAT by using CLIMWAT climate data for two meteorological stations in the area (i.e. Khulna and Barisal). Two cropping patterns were considered, i.e. rice cultivation throughout the year and mixed cultivation of rice and vegetables. Crop water requirements (CWR), Irrigation required (IR) and groundwater recharge were calculated. Groundwater modelling was done in MODFLOW and the changes of groundwater head were observed. The distance of landward saltwater intrusion from the shoreline for pumping groundwater was determined by particle tracking method and the safe distance of wells from the sea was calculated for present condition. Future predictions for these were also made by considering climate change and sea level rise. The analysis showed that mixed cultivation of rice and vegetables increase the groundwater recharge. This cropping pattern also reduces the extent of saltwater intrusion inland. As a result the loss of cultivable land due to groundwater salinity problem is less. For future scenarios, as a consequence of climate change, the analysis reveled that groundwater recharge will be higher in the future due to increase of total annual rainfall. However, if the farmers cultivate rice and vegetables jointly, there is a possibility that in the future the recharge will be so high that it may elevate the groundwater table very close to the ground surface. This will initiate the problem of water logging in the lands. It was also found from the analysis that in Barisal, the safe distance of irrigation wells from the sea to avoid saltwater intrusion will be same in present time as well as in the year 2100. However, for Khulna, this distance will not remain the same.Coastal and Marine Engineering and Management (CoMEM)Hydraulic EngineeringCivil Engineering and Geoscience