Special Issue: Irrigation Management in Asia
IRRIGATION FOR POVERTY ALLEVIATION (pp. 383-391)
M.A. Chitale, Secretary General, ICID, New Delhi, India
Abstract: Compared with rainfed farming, irrigation has been accepted as a more powerful tool of agricultural and economic growth. However, seasonal irrigation alone on small farms for producing grains does not provide adequate income to the farmer to move above the poverty line. Special provisions are necessary to help the weaker sections of society, such as the small farmers and landless labourers, to draw the full advantage of the new situation after irrigation is introduced. Irrigation projects should be planned as area development measures and should fulfil social criteria in addition to the techno-economic criteria. Liberal concessional international financial assistance should flow to the projects that specifically provide for poverty alleviation measures.
IMPROVED OPERATION OF LARGE IRRIGATION CANAL SYSTEMS IN SOUTHEAST ASIA (pp. 393-415)
Rainer Loofa, Bitanjaya Dasb and Guna N. Paudyalc
aAssociate Professor, School of Civil Engineering, IREM Program, Asian Institute of Technology, Thailand; bLecturer, Water and Land Management Institute, India; cResident Manager, Danish Hydraulic Institute, Dhaka, Bangladesh
Abstract: Poor performance of the irrigation systems in Southeast Asian countries is a cause for concern considering the increasing water scarcity. Lack of adequate knowledge and systematic ignorance of main system management has been identified as one of the primary factors for the resulting poor performance of these systems. In this study a model has been developed for operating the main canal of these systems by integrating hydraulics of the flow and decision-making technique. The model developed was applied to the main canal of the Phitsanulok Irrigation Project in Northern Thailand. The results of this application approved the concept and envisaged substantial improvement in the operation of the main canal. The model can in general be applied to similar irrigation systems in the developing countries.
RESEARCH AND DEVELOPMENT FOR SUSTAINABLE IRRIGATION MANAGEMENT (pp. 417-424)
Roberto Lenton, Director General, International Irrigation Management Institute, Colombo, Sri Lanka
Abstract: This paper seeks to provide guidelines to governments planning to undertake research and development programmes aimed at finding ways to manage irrigation systems in a sustainable way. After describing the challenges affecting irrigated agriculture at the present time, the paper presents two examples of action-orientated research projects, from which some preliminary principles for effective irrigation management research and development are derived.
CHARACTERISTICS OF RICE FIELD IRRIGATION: THE JAPANESE EXPERIENCE (pp. 425-430)
Yutaka Takahasi, Department of Civil Engineering, Shibaura Institute of Technology, Tokyo, Japan
Abstract: Paddy irrigation management is now facing a turning point in Japan. After the Second World War the irrigation systems in Japan achieved so-called modernization including reorganization of the cultivated land and concrete lining of irrigation channels, etc. As a result of modernization, economical and technological efficiency rose while labour and other conditions improved. However, new problems are arising centring on farm life and several environmental conditions, especially changes to the ecosystem which had reached a state of equilibrium before modernization and the accompanying changes to the hydrological cycle.
EQUITY ASPECTS OF IRRIGATION DEVELOPMENT: EVIDENCE FROM TWO SYSTEMS IN THE HILLS OF NEPAL (pp. 431-443)
Rabi K. Maskeya, Karl E. Weberb and Rainer Loofc
aResearch Associate; bProfessor and Dean; cAssociate Professor, Asian Institute of Technology, Bangkok, Thailand
Abstract: Equity is of great relevance to developing irrigation. Its two dimensions-horizontal in regard to water distribution to farmland and vertical in terms of productivity differences between farm categories-are studied in two irrigation systems, an old farmer-managed and a new government-agency-managed system. Equity in the distribution of irrigation water differed between abundant and scarce water supply conditions. Paddy grown during the monsoon season when water is available in abundant quantity shows that there was a reasonable degree of fairness in its distribution between head and tail reach farmland. However, wheat grown in the dry season with limited supply of water rendered evidence of unfair distribution demanding better management of irrigation water. The analysis of vertical equity shows that small farms are more efficient than large ones in increasing productivity through the use of irrigation facilities.
CONSIDERATIONS FOR SUSTAINABLE IRRIGATION DEVELOPMENT IN ASIA (pp. 445-455)
Asit K. Biswas, Chairman, Middle East Water Commission, Oxford, England
Abstract: The Asian population is expected to increase from 3103 million in 1990 to 5811 million in 2050 and to 6817 million in 2150. Such rises will invariably augment demands for all water uses. Water availability is unlikely to increase to accommodate all the expected demand growth. This will escalate the conflict between various water uses. Irrigation, which is now the most significant user of water, is likely to be the main loser. Its percentage share of total water used will decline steadily in the future. This will mean that the irrigation sector will have to do more with less water by increasing its efficiency significantly. The Asian countries will also have to take a balanced approach between irrigation development and environmental protection.
GROUNDWATER MANAGEMENT MODELS FOR ASIAN DEVELOPING COUNTRIES (pp. 457-474)
Ashim Das Gupta and Pushpa R. Onta, Water Resources Engineering Program, Asian Institute of Technology, Thailand
Abstract: This paper provides an overview of groundwater management modelling, with particular reference to the situations prevalent in the developing countries of Asia. A state-of-the-art review of mathematical models, developed primarily in the advanced countries is first made. Different approaches and techniques of systems analysis are considered. Due to their increasing importance, water quality aspects are included and emphasized. Key issues and problems including important research needs for the future are highlighted. Some recommendations are made on appropriate modelling strategies for groundwater management in Asian developing countries.
MANAGING MOUNTAIN WATERSHEDS IN NEPAL: ISSUES AND POLICIES (pp. 475-495)
Gopal B. Thapa and Karl E. Weber, School of Environment, Resources and Development, Asian Institute of Technology, Thailand
Abstract: In view of the ongoing watershed degradation and its adverse impacts on the biophysical and socio-economic environment in the Hills of Nepal, this paper analyses its causal nexus and assesses the status of common and private properties based on afield survey in the Upper Pokhara Valley. Contributing fresh evidence of cause and intensity to the debate, the findings indicate that the mountain watersheds are undergoing degradation caused primarily by the mounting population pressure on forest and land resources, almost exclusive dependency of the hill people on agriculture as the source of livelihood, and changing national policies regulating the ownership of common properties. To address this problem, some broad policy measures are outlined within the framework of an integrated watershed management strategy.
RAINFALL NETWORK DESIGN USING THE KRIGING TECHNIQUE: A CASE STUDY OF KARNALI RIVER BASIN, NEPAL (pp. 497-513)
Rainer Loofa, Peder Hjorthb and Om Bahadur Rautc
aAsian Institute of Technology, Thailand; bDepartment of Water Resources Engineering, Lund Institute of Science and Technology, Sweden; cNepal Electricity Authority, Design Department, Durbar Marg, Kathmandu, Nepal
Abstract: Spatial variation structure of monthly and annual mean precipitation in the Karnali river basin, Nepal has been analysed by using kriging. The physiographic and climatological features of the basin are presented in sufficient detail to better understand the spatial and temporal variation pattern of the precipitation within the basin. The concept of ‘regionalized variables’ and the theory of kriging have been introduced. Based on the spatial variability of the precipitation obtained by kriging, a methodology has been developed for selecting the best locations for a given number of rain gauges planned to be added in a network. It has been demonstrated that kriging can be of valuable use in identifying the optimal locations for a set of additional rain gauges using kriging standard deviation as an indicator. The results obtained from kriging are realistic to the extent that the stationarity assumptions are true. Quantification of error nevertheless makes it possible to select locations of rain gauges in such a way that the estimation error is kept to a minimum.