Performance evaluation of different modes of minor irrigation in lower meghna river floodplain

Abstract

A study was undertaken to evaluate the performance of different modes of minor irrigation (STW, DTW and LLP) in Narsingdi and Brahmonbaria districts under Lower Meghna River Floodplain (AEZ No. 17).For this purpose 48 irrigation schemes and 48 farmers’ fields were selected to collect relevant data and information. Irrigation schemes were classified on the basis of modes of irrigation system like pricing, source of energy, lined or earthen cannel systems.The performances of selected schemes and selected farmers’ fields were based on seven indicators, which can be broadly classified in terms of engineering, agronomic and social performances. Indicatorswere command area ratio/ irrigated area performance, production performance, profitability of farmers, financial self-sufficiency, relative water supply, conveyance efficiency and water use.Another objective of the study was compared the change in performance indicators during the last decades (a study was conducted in Rajbari district, AEZ-1). Performance evaluation using the selected indicators was done both qualitatively and quantitatively and based on both primary and secondary data. Primary data were collected mainly through direct field measurements, field observation and field level discussions with farmers, pump owners and local people. Secondary information was collected from published and unpublished documents obtained from different sources. In this study, the average command area ratio or irrigated area performancevalues are 0.77 for STWs, 0.76 for LLPs and 0.81 for DTWs. Theaverage production performance values are 1.02 in STWs, 0.98 in LLPs and 0.97 in DTWs. It was observed that command area ratio and production performance are higher than previous study.The average profitability of farmers values are 2.88 in STWs, 2.92 in LLPs and 3.47 in DTWs, higher than previous study. The area based pricing system is more profitable than time based irrigation system to farmers. Financial self-sufficiency indicator was calculated in terms of both ‘with family labor’ and ‘without family labor’. Including and excluding family labor, the financial self-sufficiency values for LLPs are 1.46 and 1.72; for STWs 1.35 and 1.65; and for DTWs 1.40 and 1.59, respectively.The average relative water supply are 1.10 for STWs, 1.11 for LLPs and 1.32 for DTWs. Among STWs, DTWs and LLPs, farmers of DTWs are using more water than STWs and LLPs. As all DTWs are lined so the on-farm supply is high compared to STWs and LLPs. It was observed from the calculated data that the average relative water supply of the study area is very high compared to the previous data. The conveyance efficiency in lined and earthen canal systems of STWs and LLPs are0.93 and 0.70; 0.78 and 0.69, respectively. The conveyance efficiency of lined canals is 0.90.As expected, all the lined irrigation canal schemes show better efficiency than the schemes with earthen-canal.The average water use or water productivity for the time based and area based STWs are 2198l/kg and 2485 l/kg, for LLPs are 2390l/kg and 2633l/kg for DTWs are 2830l/kg and 3003l/kg, respectively. As expected, all the lined irrigation canal schemes show higher water use than the schemes with earthen-canal. The average conveyance loss found in the present study is much improved compared to those of the past studies. Although area based pricing is popular with the farmers because of high rate of hourly water supply, the time based irrigation pricing system is popular to the pump owners. If the government sets a ceiling on the pricing system that would make the time based pricing system profitable to both the pump owners and the farmers, then the time based pricing would be acceptable to the farmers. To make the time based pricing system acceptable to the farmers, the prices may be set at 61.5%, 41.5% and 55% lower than the present prices for STWs, DTWs and LLPs, respectively. This study shows that the command area, yield and profitability indicators are higher compared to the previous studybut at the same time the farmers are now using more water (higher RWS).