Can Crop Production Intensification Through Irrigation Be Sustainable? An Ex-Ante Impact Study of the Coastal Zone of Bangladesh

Abstract

South-central coastal zone of Bangladesh, has potential to intensify crop production by growing dry winter season ‘Boro’ rice, maize, wheat, pulses and oilseeds using irrigation from southward flowing freshwater rivers. The impacts of surface water withdrawal for irrigation and its consequences are unclear. Field measurements and model simulation was used to investigate the effects of irrigation water withdrawal for Boro rice. Under the baseline conditions of 2015, about 250,000 ha could potentially be irrigated with river water (salinity levels < 2 dS/m). The impact on river water salinity would be minimal. Similarly, a minor change in water flow and salinity was simulated for the moderate climate change scenario (RCP 4.5) that forecasts a sea level rise of 22 cm in 2050. Only under the extreme climate change scenario (RCP 8.5), resulting in a sea level rise of 43 cm by 2050, and low flow conditions that are exceeded in 90 percent of the cases, the 2 dS/m isohaline would move landward by 64 to 105 km in March and April for the Tentulia and Buriswar Rivers. This would expose an additional 36.6% of potentially irrigable cropland to salinity levels of 2 to 4 dS/m. However, Boro rice is already well established by that time and can tolerate greater levels. There is considerable scope to expand irrigated crop production without negatively exposing the cropland.

Keywords: water flow, salinity, Water withdrawal, Ecosystem services, Sustainable intensification, climate change