Bangladesh Integrated Water Resources Assessment supplementary report: land use, crop production, and irrigation demand

[摘要] In this report, we describe the current trend in land use, crop area, crop production and irrigation based on the recent historical data, estimate net irrigation requirements of the major crops for historical and climate change conditions, and analyse regional irrigation water demand considering different scenarios. The study has been conducted as part of the Bangladesh Integrated Water Resources Assessment Project funded by the DFAT- CSIRO Research for Development Alliance.The data used in trend analysis are sourced from the Statistical Yearbook of Bangladesh published every year by the Bangladesh Bureau of Statistics (BBS) and the National Minor Irrigation Survey Report published by the Bangladesh Agricultural Development Corporation (BADC). We have used a daily soil water balance model to estimates net irrigation requirements of different crops. The climatic data used in the model are collected from the Bangladesh Meteorological Department (BMD). The analysis suggests that net cropped area is decreasing rapidly at a rate of 30,000 ha per year according to the data available from the Bangladesh Bureau of Statistics though some literature suggest a much faster rate recently. Cropping intensity is gradually increasing and recently there are areas where even 4 crops are grown within a year. Aus, Aman and Boro rice together covers about 80% of the total crop area of the country in a year. Wheat and other minor cereals cover about 4% of the total cropped area. 70% of the net cropped area is under Aman cultivation. For Boro and Aus, this is about 60 and 13%, respectively. Boro area at the country level appears to have reached the pick as there is no growth in area over the last few years. The area of Aus is gradually declining and the area of Aman is more or less steady. There is significant growth in the area of maize, potato and tomato in the northwest region. The area of other crops at the country level declined due to rise in Boro cultivation.There is linear growth in the yield of Aus, Aman and Boro rice. The average yield of Boro rice is nearly twice the yield of Aman and more than twice the yield of Aus. The growth in average yield of rice is 76 kg/ha/year. There is significant spatial variation in the yield of Aus, Aman, and Boro rice. Boro covers 42% of the total rice area and produces 57% of the total production. Aman contributes 38% to total rice production from 50% of the total rice area. The contribution of Aus to total production is about 5% from 9% of the total area.There has been phenomenal growth in irrigation over the last 2 decades. This appears to be slowing down in recent years. So the physical growth in irrigation may have reached to the potential under the current bio-physical and infrastructure conditions. Irrigation is heavily dominated by groundwater; about 80% of the total area is irrigated by groundwater.Irrigation demand analysis shows that despite huge rainfall during the Aman season, the crop still needs supplementary irrigation for full yield potential. Irrigation requirements vary due to the variation in planting date. For Boro rice, transplanting from January onwards would be the most suitable. Due to climate change net irrigation requirements of Boro rice may increase by maximum of about 3% for 2050 dry climate condition.95% of the total irrigation demand is for Boro rice. The total irrigation demand is not expected to increase much from the current condition as there is no growth in Boro cultivation area in recent years. There is no appreciable impact of climate change on irrigation water demand. Irrigation demand can be reduced significantly by replacing some Boro area with wheat and other non-rice crops such as maize and potato.Further studies are required to understand the impact of reduced irrigation water pumping on the groundwater resources in the context of the regional water balance.

[发布机构] CSIRO

[学科分类] 地球科学(综合)