Hydrological impacts of climate change on rice cultivated riparian wetlands in the Upper Meghna River Basin (Bangladesh and India)

• Published in: Hydrological sciences journal Vol. 65; no. 1; pp. 33 - 56
• Main Authors: Rahman, Mohammed M., Thompson, Julian R., Flower, Roger J.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02.01.2020; Taylor & Francis Ltd
• Subjects: Agricultural resources; Annual rainfall; Bangladesh; Boro rice; Climate change; Climate models; Cultivation; Environmental risk; Evapotranspiration; Flood damage; Flood risk; Flooding; Floods; Floodwater; Food security; General circulation models; Grain cultivation; haor wetlands; Harvesting; Hydrology; Mapping; Mean annual precipitation; Rain; Rice; Ripening; River basins; River discharge; River flow; Rivers; Soil; Soil water; SWAT; Traditional foods; Wetlands; Bangladesh
• ISSN: 0262-6667; 2150-3435
• DOI: 10.1080/02626667.2019.1676427

Riparian depressional wetlands (haors) in the Upper Meghna River Basin of Bangladesh are invaluable agricultural resources. They are completely flooded between June and November and planted with Boro rice when floodwater recedes in December. However, early harvest period (April/May) floods frequently damage ripening rice. A calibrated/validated Soil and Water Assessment Tool for riparian wetland (SWATrw) model is perturbed with bias free (using an improved quantile mapping approach) climate projections from 17 general circulation models (GCMs) for the period 2031-2050. Projected mean annual rainfall increases (200-500 mm or 7-10%). However, during the harvest period lower rainfall (21-75%) and higher evapotranspiration (1-8%) reduces river discharge (5-18%) and wetland inundation (inundation fraction declines of 0.005-0.14). Flooding risk for Boro rice consequently declines (rationalized flood risk reductions of 0.02-0.12). However, the loss of cultivable land (15.3%) to increases in permanent haor inundation represents a major threat to regional food security.