IRRIGATION SCHEDULING IN A CANAL COMMAND AREA A CASE STUDY

Abstract

'Irrigation is important for agricultural production, specifically in arid and semi arid regions where rainfall is inadequate to sustain crop growth. Nov a day, it has become essential for increasing and stabilizing the production to feed the ever increasing world population. The world has experienced a large investment in irrigation sector, more particularly in the past few decades, and irrigated areas almost doubled. Since the water resources have become increasingly scarce, more water is likely .to be diverted from agriculture to meet human and urban consumption requirements in near future. The frequent water shortages, farmers often facing deficiencies in water deliveries due to poor management of available water have resulted in reduced yields and incomes. Both at the system and farm levels, there exist a range of problems that abate reduce the benefits of irrigation investments significantly. On the other hand, the excessive use of water has also led to a range of environmental problems such as,waterlogging, leaching of agro-chemical, and consequent groundwater pollution. Irrigation scheduling is a basic tool to improve water use efficiency, and enhance yields, and to maintain the quality of soils and ground water as well. The research results over the past decade have led to enhanced knowledge on plant-water relations useful for judicious irrigation management and, in turn, the improved water use efficiency. This study is primarily aimed at to determine crop water requirements and irrigation water requirements to suggest a suitable cropping pattern for command area of Way Sekampung Irrigation Project, an agricultural improvement scheme. To this end, the available CROPWAT program which is a decision support system developed by the land and water development Division of FAO was employed. This program is able to compute reference evapotranspiration, crop water requirement, and crop irrigation requirement; to develop irrigation schedules under various management conditions and scheme water supply; and to evaluate rainfed production and drought effects and efficiency of irrigation practices. The present analysis however attempted to study the effect of various iii ABSTRACT governing factors, such as stipulated irrigation efficiency, staggering of planting date, irrigation scheduling option, maximum infiltration to soil, maximum rooting depth, on field water supply (FWS). The last three factors were found to have insignificant influence on the computed field water supply. The sensitivity analysis showed FWS to decrease with increase in irrigation efficiency. The rate of decay of FWS increased significantly as the date of plantation shifted from November 15 to. October 15. Since both the factors equally affected the FWS, the judicious consideration of either or both of these can lead to enhancement of irrigation output with reduced water supply.