Performance evaluation of irrigation water delivery system of Ganges - Kobadak (G-K) project

Abstract

The study was conducted at Ganges - Kobadak Irrigation Project during the season Kharif-I and Kharif-II, 1999. The main objectives of the study were to critically review the different indicators developed and proposed by different authors for performance evaluation of irrigation project and to assess the performance of the system in terms of adequacy, efficiency, equity and dependability. Performance evaluation was carried out using indicators suggested by Bos et al. (1993). Eight tertiary units of three secondary canals were selected for this purpose. Data were collected through field measurement and from project officials. A large number of performance indicators for irrigation project performance evaluation are discussed and many of the indicators are not applicable due to nonavailability of data. Performance standards for the different indicators are required to compare the results and that the performance can be quantified accordingly. The rotational Relative Water Supply (RWS) to the selected tertiary units varied from 0.29 to 5.26 during Kharif-I season and 0.04 to 8.16 during Kharif-II season. This wide variation of RWS was mainly due to lack of control of flow. The secondary canal near the head of the system always received more water than the tail end canals. The average seasonal irrigation efficiency of the selected tertiary units varied from 11% to 59% during Kharif-I season and 13% to 77% during Kharif-II season. The low irrigation efficiency was mainly due to misuse of irrigation water and poor water control. Lack of proper maintenance and interference of farmers in water distribution in the upper reaches of the system were also responsible for low irrigation efficiency. The coefficient of variation of relative water supply to different selected tertiary units varied from 0.01 to 0.68 during Kharif-I and 0.01 to 1.22 during Kharif-II season. Ratio of actual to planned duration of water supply to the selected tertiary units varied from 0.79 to 1.43 during Kharif-I and 0.45 to 1.61 during Kharif-II. This reflects the fact that actual delivery did not follow the schedule and most of the selected tertiary units received water for greater number of days than programmed. Overall, the system performed poorly in terms of efficiency and equity but it performed well in terms of adequacy and dependability of supply. Adequacy of the system was 2.31 and 1.7 for Kharif-I and Kharif-II seasons respectively but irrigation efficiency was poor (0.56 and 0.60 for Kharif-I and Kharif-II respectively). Equity in water delivery also found to be poor (0.63 and 0.76 for Kharif-I and Kharif-II respectively). Dependability of supply i.e. the ratio of actual to planned duration of water delivery was 1.20 and 1.06 for Kharif-I and Kharif-II seasons respectably. Irrigated area performance (1.00) and production performance (0.89) were quite good during the Kharif-II season but these were not satisfactory (0.67 and 0.78) during the Kharif-I season. During the Kharif-I season the water delivery could not be made to a substantial portion of the targeted area due to inadequate head. Yield performance was satisfactory (0.89) during the Kharif-I season but it was not satisfactory (0.72) during Kharif-II. During the Kharif-II season supplementary irrigation could not be provided to the tail end of some secondary canal due to poor condition of canals. Cropping intensity performance was found to be satisfactory (0.995). Economic performance such as total financial viability (0.55), financial self-sufficiency (0.002) and fee collection performance (0.008) was very poor. To keep the irrigation system functioning O&M allocation must be increased and at the same time emphasis must be given on increasing water tax collection. Without adequate recovery of operation cost, the future of the project will be uncertain.