Assessment of irrigation efficiency and techno-socio-economic opportunities for its improvement in minor irrigation

Abstract

In Bangladesh, about 63% of the arable land is now irrigated and there is immense pressure to bring more areas under irrigation. But the expansion of irrigation has been thwarted due to reduced transboundary flow, unplanned and unregulated withdrawal of groundwater and inefficient management. Improvement of irrigation efficiency (IE) and efficient management would have a dominant role in enhancing the development of irrigation. In this context, this study was taken up with the objectives of estimating the present level of IE and water productivity (WP), determining the parameters that affect the IE, and assessing the techno-socio-economic potentials for improving the IE. The study was carried out in 7 districts of 5 agro-ecological zones. In total, 85 irrigation schemes were selected in such a way that they represent all the major variables of irrigation performance namely, type of pumping technology (STW, DTW and LLP), source of water (surface and groundwater), management system (public and private), pricing system (area based, time based and crop share based), water distribution system (buried pipe, lined and earthen canal) and source of energy (diesel and electricity). In addition, field experiments were also carried out to study the impact of improved on- farm water management (alternate wetting and drying: AWD) technology over the traditional practice of continuous flooding. Field data on pump discharge (Q), total hours of pump operation (H), total irrigated area (A), crop yield, and rainfall data were collected, and evapotranspiration (ETo) were estimated during the 2008 and 2009 irrigation seasons. Participatory rural appraisal tools like, FGD and test of farmers' knowledge were conducted in 5 upazilas in order to find out the reasons of using excess irrigation water and their probable solutions, areas of farmers’ knowledge gap, acceptability of different technologies, etc. From the analysis of field data on water requirement and supply and crop yield, the present average IE and WP of the country were estimated as 34% and 0.498 kg/ m3(2006 lit/kg), respectively. It was also found that the source of energy and types of irrigation equipment have no significant impact on IE. The opportunity of improving the IE by implementing time based water pricing system over area based system is 3.85%, that of lined canal system over earthen canal is 3.37% and that of AWD technology is about 6.28%. The improvement of IE due to management system i.e. public-private-partnership (PPP) over privately managed scheme is about 2.65%. Buried pipe system and crop shared method increased the IE by 6.38% and 1.63%, respectively over earthen-area based system. From mathematical calculation and regression analyses, the combined contribution of water pricing system (time based), water distribution system (buried pipe), management system (PPP) and AWD, in increasing the IE from the base condition of earthen-area based-private system varied from 17.55% to 18.84%. From the farmers’ survey, it was found that the knowledge gap of farmers about on- farm water management technology is the highest among all the four important agricultural inputs and services. Besides, the four selected indicators are also found to be techno-socio-economically viable and sustainable, if these are implemented in integrated manner. Creation of awareness among different stakeholders through training and demonstration for rapid dissemination of AWD technology and introduction of demand based water marketing system instead of supply based system can be achieved with minimum financial implication. Replacement of earthen canal by construction of lined canal and buried pipe may be done in phases but would require active participation of all the concerned stakeholders and introduction of PPP approach for participatory irrigation water management. Considering the food security, economic development, poverty reduction and protection of natural environment, the government should take the opportunity of the abovementioned variables in an integrated manner for increasing IE from 34% to close to its potential value of 50%.