INTEGRATED APPROACH FOR IRRIGATION SC-HEDULING IN A COMMAND AREA

Abstract

The success of an irrigation system depends on efficient water management. The scarcity of available land and water resources, which is outcome of the growing population, has necessitated its proper planning and management. Inadequate and uneven distribution of available water resources results in frequent crop failures and shortage of fodder and drinking water. Hydrologists have made attempts to make predictions of water availability to overcome the problems created due to temporal and spatial variations in precipitations. Irrigation scheduling is defined as the process of determining when to irrigate and how much water to apply. Irrigation scheduling is a systematic method by which a producer can decide when to irrigate and how much water to apply with goal to supply sufficient water to the plants with minimum loss to deep percolation or runoff. With smart irrigation scheduling, crops yields will not be limited by water stress from drought, and the waste of water and energy. The amount of water applied is determined by using a criterion to determine irrigation need and a strategy to prescribe how much water to apply in any situation. Through proper Irrigation scheduling, it should be possible to apply only the water which the crop needs in addition to unavoidable seepage and runoff losses and leaching requirements. , Irrigation management requires huge volume of data pertaining to hydrological, hydro-geological, meteorological, soil, agronomic and cropping pattern parameters. Regular monitoring and performance evaluation of command areas is needed to improve water management practices and achieve an increase in overall efficiency. With the availability of remote sensing and GIS tools, it is now possible to gather instant observations over large areas and to integrate and manage multi-disciplinary data. This study primarily is carried out for assessment of crop acreage, crop water requirements and irrigation need for carrying out irrigation scheduling in the Left Bank Canal (LBC) command area of Ghatprabha project, Karnataka state in southern India. In this study IRS IC/1D LISS III multi-temporal digital remote sensing data has been used iii to find the actual cropping pattern in the command area. The data of Rabi season has been used, as the satellite data of Kharif season was not available. Geographical Information System (GIS) has been used to store, analyse, and retrieve multidisciplinary data. Crop coefficients (Kc) for the major crops in the LBC along with potential evapotranspiration, estimated from point meteorological observations, are used to find the actual evapotranspiration. CROPWAT software, a decision support system developed by Food and Agricultural Organisation (FAO) was employed to compute reference evapotranspiration using Penman-Monteith method; crop water requirement and irrigation need to develop irrigation schedules under various management and water supply schemes. Results indicated that reference evapotranspiration is higher during the months of March, April and May. The crop water requirement is 427.97 mm for Wheat, Maize, Sorghum, 434.08 mm for Fodder/Pulses and it is 1175.15 mm for sugarcane The total net irrigation water requirement is 96454.03 ha-m in the Ghataprabha Left Bank Canal command. A sensitivity analysis has been conducted upon to study the effect of the most effective factors namely irrigation efficiency and the shift of planting date on the field water supply. These governing factors were found to have significant influence on the computed field water supply, the judicious consideration of either or both of them can lead to augmentation of irrigation output with reduced water supply.