A STUDY ON SUITABLE MEASURES FOR CONTROLLING SEEPAGE LOSSES FROM IRRIGATION DISTRIBUTION NET WORK

Abstract

Irrigation is an essential limiting factor for the production of food grains and other agricultural products necessary to sustain the life as well as to overcome the deficiencies in rainfall for stabilizing the agricultural production in arid and semi-arid regions. At present one sixth of agricultural land in the world has received the irrigation facilities and produces more than one third of the global food production. The requirements of food for the ever-growing world population need the higher agricultural production in which a large share comes from the irrigated lands. As the availability of water resources for irrigation has been increasingly difficult, the water, the cost of water resource development and management thus has also become a limiting factor for enhancing the irrigated agriculture in many of the irrigation projects. Extensive engineering development works have been undertaken worldwide to make available the adequate amount of water required for irrigation as well as for other purposes such as domestic, urban and industrial use. The growing competition of water demand between agricultural and non-agricultural sectors has increased the concern for the sustainability of irrigated agricultural system. At present approximately 75-80 % of the world available fresh water supply is used for agricultural and food production. The demand for good quality of water has been increasing tremendously since last few decades. Though the irrigation systems are constructed with high degree of quality control using best knowledge of the modern techniques available, the functional output is not acquired at a desired level. The irrigation systems thus created physically revealed very appreciable but the efficiencies shown is quite disappointing. The percentage of water effectively used in irrigation is around 40 — 60 % in an irrigation system in general. The remaining water is lost in the system, in the farm and on the field through evaporation, seepage and percolation into the ground water or runoff to the drainage system. Part of the lost water can be recovered but additional cost would be incurred. The water, used in whatsoever field is concerned, has multidimensional aspects such as agricultural, social, environmental, political, ecological and so on. Such complex and multi-dimensional resources in nature have to be thought properly for its sustainable use. iii Water losses in irrigation are caused due to various reasons. The physical, managerial and the social aspects of irrigation should work in harmony to have an efficient output. The physical system with best planning, proper alignment, good design and excellent construction can prove its existence for better service but certainly needs proper maintenance and operation for sustainability. The involvement of the users and their cooperation in each phase of development is very essential. Managerial sector, which is lagging behind in most of the developing countries has proved the loss of investment in proportion to the beneficial returns from the irrigation projects. Poor management of irrigation water is one of the principal reasons for the low water use efficiency in irrigation. The inadequate and often unreliable water deliveries in the main system cause farmers to face regular shortage in water supply resulting in reduced yields and incomes as well as much lesser command on area than planned originally. At farm level in appropriate field channels layout, insufficient or poor drainage and mismanagement of delivered water are responsible for seepage losses and reduced yields. Inefficient or ineffective water use is associated with a range of environmental problems such as water logging, Teaching of over used agro-chemicals causing ground water pollution. The soil and ground water salinization due inappropriate use of water are the most burning problems faced in recent years in many countries. The operation of the system, on the other hand, has the most effective role in acquiring maximum production. The water, if applied adequately in appropriate time and frequency in combination with other agricultural inputs results the crops yields to a higher range. The deciding factor is the irrigation scheduling as when to irrigate the crop and how much to apply. Scheduling is the key means for optimizing the agricultural production and for conserving water as well as improving performance and sustainability of the irrigation system, which requires good knowledge of crops water requirements and soil water characteristics that determine when to irrigate, while the adoption of the irrigation method determines the extent of water quantity to apply. The end users, however, are the farmers who advocate for the systems' success or failure. The whole attempt is to provide a good serviceable irrigation system to the iv beneficiaries for their social upliftment but quite often their existence and effectiveness towards the project is either neglected or overlooked. In past decades, the irrigation projects usually came into existence through top-down processes. In the project evolution period, the would be beneficiaries were much neglected in most of the developing countries whereas after completion and at serviceable phase their co-operation and involvement was found very essential for overall well functioning of the system as well as its look after. Their social, cultural and attitudinal behavior has to be synchronized with the need of the project, which, however, would be a long process. The ways and means for developing a notion of feeling of ownness about the project is to be sought for. The beneficiaries should be treated with a status as a co-partner with open mind by the agency with due weight and response to their grievances and pointed shortcomings of the system. This will motivate the beneficiaries to come forward with commitments and eager for the betterment of the system. The process and procedures of system (at the level they are assigned to) construction, maintenance, operation and utilization should be known to them by enhancing their present knowledge through trainings, observation tours, field demonstrations, media advertisement or other suitable procedures making them capable of using the physical, managerial, agricultural aspects of the system in a proper manner for best agricultural production without soil and land degradation for ever. The creation of technically sound, hydraulically efficient and operationally easy system is the basic need The system design, water allocation and distribution procedures are always made with certain assumptions and approximations which sometimes may not hold good in prevailing field conditions or in implementations which may be reflected by the functioning of the system. The feedbacks from the users, therefore, should get due weightage for discussions and interactions and those found suitable should be incorporated in the system on a real-time basis by the agency. The social need based water supply would primarily be the most important aspect to be considered by the system managers. A good linkage of communication, co-ordination, motivation and co-operation should be established between the users and the agency in all phases of the system development process for the successfulness of the project.