IMPROVEMENTS IN HYDROLOGIC PLANNING OF AN IRRIGATION PROJECT -A CASE STUDY

Abstract

The main objective of this study was to investigate possible improvements in irrigation planning particularly with regard to crop water and irrigation water requirement/demand, water distribution planning (irrigation scheduling) and analysis of cropping pattern based irrigation development scenarios. To meet this objective, conventional practices in India and Indonesia have been critically examined and analysis of Pandanduri Irrigation Project in Indonesia has been carried out. There is empiricalism and gross simplification in conventional approach for irrigation planning. With availability of computer technology and analytical tools it is possible to simulate long term behavior and analyze several alternatives (options) under variety of conditions such as variation in cropping pattern, variation in irrigation demand, consideration of group system of irrigation, irrigation scheduling option etc. Some important guidelines on requirement of hydrologic data and for simulation study are reviewed and highlighted Too ambitious or too pessimistic cropping pattern may cause several errors in sizing of an irrigation project. In planning stage a design-cropping pattern is evolved and assumed to be constant over the years. Design and actual cropping pattern could be significantly different depending on several factors as seen in project command areas in India. Irrigation scheduling at field level and water distribution planning for the command area should form part of irrigation planning at project preparation stage itself. Computer software's such as CROPWAT and others can be used for water distribution planning on more scientific basis as illustrated in chapter 5. Case study of Pandanduri Irrigation Project has been carried out as an exercise to illustrate (i) proper analysis of climatic data (rainfall, radiation), (ii) use iii tgrmibtoimme41114, i tr alyetscilvgio, g'itztvraser et/are tf-vvigceitivor. SPaoje.74-a. verde .44efly of standard Penman-Monteith Method for estimation of crop water requirement, (iii) application of golongan (group) concept in crop calendar and estimation of peak diversion requirement, (iv) analysis of different cropping patterns and (v) analysis of irrigation scheduling options. This study has been limited to water planning only. Economic financial environmental and social aspects of irrigation project planning have not been covered in this study. It is hoped that such type of study will lead to -further work in bringing further improvements in conventional planning procedures.