Axial flow pumps can reduce energy use and costs for low-lift surface water irrigation in Bangladesh

Abstract

With conventional centrifugal pumps (CEN), less than 50% of southern Bangladesh’s farmers invest in dry season irrigation, partly due to high and continually increasing diesel energy costs. Diesel pump efficiencies in Bangladesh are only 25% (compared to 35% for electric pumps) mainly due to techno-mechanical problems. New policies championed by the Government of Bangladesh prioritize sustainable crop intensification in Bangladesh’s delta. A key example is the Master Plan for Agricultural Development in the Southern Region of Bangladesh, which focuses strongly on the development of surface water irrigation to spur increased crop output within this impoverished region. However, this objective is unlikely to be achieved without fundamental changes in the energetics and cost of irrigation. Where surface water is available in the complex deltaic environment of Southern Bangladesh, axial flow pumps (AFPs) may comprise part of the solution to this problem. Through a partnership between the Bangladesh Agricultural Research Institute (BARI) and the International Maize and Wheat Improvement Center (CIMMYT) in the Cereal Systems Initiative for South Asia (CSISA) project, we conducted two experiments to help test this hypothesis. In our first experiment, we assessed pulley arrangements to arrive at optimal configurations for water discharge at 1-, 2- and 3-m heads for prototype AFPs manufactured in Bangladesh. The second experiment compared the hydraulic, energetic, and economic performance of AFPs and CENs. CENs produced less discharge than AFPs at all heads. Both CENs and AFPs showed an inverse relationship between discharge and increasing head, although AFPs showed considerably less flow as head increased. Importantly, as a measure of energy efficiency, discharge per unit of fuel was highest for AFPs (+51% and +21% at 1- and 2-m lifts), though this declined with rising head until convergence with CEN at 2.8- m. High AFP discharge reduced irrigation time requirements when simulated for Boro rice, wheat, and maize. Compared to CEN, AFPs can save between 5,444–2,955 BDT (70–38 USD) ha–1 season–1 for Boro rice at 1- and 3-m heads, respectively, and 1,167–622 BDT (15–8 USD), and 2,022–1,089 BDT(26–14 USD) ha–1 season–1 for wheat and maize. Fuel efficiency reductions above 2.8-m highlighted the importance of technology targeting to ensure AFP deployment in environments where the greatest efficiency gains are achievable.