Abstract
An applied and adaptive field research work titled above and a series of shallow tube well (STW) pumping tests were carried out in the district of Tangail during January 2004 to June 2007 to develop a sustainable minor irrigation scheme management system. Based on the problems faced by the farmers in running several minor irrigation schemes this study was undertaken to find out their scope of development and way of solution. Accordingly, some technical aspects for the selected minor irrigation schemes have been assessed. The specific objectives were to identify the associated problems related to minor irrigation scheme management development with illustrated documents and assessment of the scope of its development. As such, an economically viable pumping system has been developed and formulated a method of suggesting a realistic and sustainable institutional infrastructure for rapid extension of the developed pumping system. In determining an economically viable pumping arrangement, a modified system of coupling with belt-pulley combination has been introduced. This facilitates reducing energy consumption per unit area-yield and hence to reduce pumping costs to a remarkable extent. The scope of enhancing production rate has also been explained by comparing the national and regional rates with that achieved through Sustainable Minor Irrigation Management System (SMIMS) as shown with photographic views as well as crop cut records. For HYV Boro, the average of the farmers' confessed yields (7.91 Mt/ha) under the SMIMS showed 190 percent increase in additional yields compared to the national average yield rate of 2.73 Mt/ha. From crop cut yields the average production rates were obtained as 6.43 Mt/ha at the DTW and an average of 6.29 Mt/ha for three STW irrigation schemes. The seasonal average energy requirements were calculated as 787 kWh/ha for the DTW and 771 kWh/ha for different directly coupled STWs. The generated average energy consumptions per unit area-yield were 122.5 kWh/ha-Mt for the DTW and 114.7 kWh/ha-Mt for the STWs. The relative discharge with respect to consumed energy in pumping for the DTW was calculated to be 3.83 Ips/kWh. The averages of that for the existing directly coupled system of operation for STWS and that for the developed Belt- Pulley System (BPS) of coupling were obtained as 6.96 and 10.68 lps/kWh, respectively. Thus, pumping with STWs by the two systems of coupling with respect to DTW operation yielded 82 and 179 per cent relative benefits. Though the existing system of coupling of STWs gave 82 percent relative benefit due to increased relative discharge with respect to DTW operation, yet the DTW yielded 8.39 percent benefit in consuming energy per unit area for its higher discharge. These findings supported the importance of pumping by larger stream sizes and development of inter- connected buried pipe system of distribution. The appropriately matched pumping sets in BPS produced about 62% of average benefit over the average of the STWs operated by the farmers with directly coupled system at field level. The danger of mishandling of the pulley combination sets has also been cautioned by calculating its adverse effects. The electricity: diesel equivalence ratio, found experimentally was 3.87 on an average. It designates that 3.87 kWh of electric energy are produced by one liter of diesel fuel. Based on different basis of calculations and the present costs of diesel (Tk.44/lit) and electricity (Tk.3.05/kWh) for irrigation with 20% rebate in energy consumption, the average of energy ratio (Electricity: Diesel) and that of cost ratio (D: E) become 3.43 and 5.26, respectively. To make a balance, justified prices of diesel and electricity have been recommended which can be considered for national policy planning purpose. For materializing the conceptually developed system of management, some policy guidelines regarding formulation of an irrigation act have also been suggested.