Rice, the region's most important food crop, requires a great deal of water, since most of it is grown under flooded conditions. Water for irrigation has now become now a major limiting factor in rice production. The irrigated area has been expanding, while at the same time there has been a growing demand for water for industrial and residential uses. This decrease in the supply of available water has sharpened concerns over the allocation and optimum use of available water.
There is a need to enhance the efficiency of water use, through various approaches such as water-saving technologies and improved cropping systems. Aside from technological advances, innovative participatory approaches are needed in irrigation management to provide support at the community level. There is also a need to consider policy issues related to the valuation of water resources. This Workshop aimed at drawing on the experience of a range of Asian countries in water resource use efficiency as applied to irrigated rice-based diversified cropping systems.
The development of irrigation in Southeast Asia can be divided into four phases: community irrigation, river diversion schemes, the construction of large dams, and finally, the use of wells and pumps.
Irrigation efficiency is measured by the amount of water used by the crop, divided by the amount of water diverted. Irrigation efficiency in the Asian and Pacific region is fairly low, at only 30%. More than 60% of the world's irrigated area is in Asia, two thirds of it in India and China. From the early 1960s to the end of the 1990s, the irrigated area doubled in size.
The issues shaping the development of agriculture today are: water scarcity, the decline in cereal grain prices, the decline in large dam construction, more intensive exploitation of groundwater, increasingly severe environmental problems, and a decline in the contribution from agriculture to rural incomes. The need to produce more food and other agricultural products with less water is becoming a global concern.
As the era of globalization unfolds, major changes in technologies and policies will occur. Some areas will experience a shortage of water, while others may face the problem of draining away excess water. The challenge ahead lies in developing institutions that can integrate management of ground and surface water irrigation; integrate management of irrigation at a farm, system, and basin level; allocate water equitably among competing uses and users, including environmental services; and address the problems of irrigation development, including the impact of using wastewater on the environment and human health.
Different Asian countries are carrying out a range of programs to improve their use of irrigation water. Below is a selection of successful projects now in operation.
In Korea, fertigation is practiced as a method of enhancing the efficiency of water use and fertilizer application. Irrigation efficiency through fertigation is measured using hardware and software management tools. The recently developed Korean auto-irrigation system covers a number of plots, and can irrigate several plots at the same time. It uses an electronic tensiometer to measure the level of soil moisture, and an electric flow meter as a watering gauge. This system provides accurate and uniform applications of water and fertilizer at a low labor cost.
Japan taps its biggest river in Kyushu island, the Chikugo river, for irrigating diversified cropping systems through water re-use and recycling. This is made possible through the canal-reservoir network systems that can be found in the river's downstream portion. In these lowland areas, water demand for irrigation is higher than the potential water supply because of the river's relatively small basin.
Farmers practice the Ao-intake method as a means of maximizing the amount of stored water. During high tide, water pours in through the intake gate. Use of available water is maximized by a massive system of pipelines and pumps, as well as open canals. The main pipeline and pump systems are managed by the Japan Water Agency. Newly organized Land Improvement Districts and the Local Government Units manage the operation of creeks, lateral canals and drainage systems. Coupled with these developments is the transformation from rice-based farming to multiple cropping. The area planted in soybean and wheat is expanding, in contrast with the area planted in rice.
The National Irrigation Administration (NIA) in the Philippines has implemented a number of projects to enhance irrigation efficiency. The focus is on the establishment and capability development of Irrigators Associations (IAs). Improvements in the performance of irrigation systems can be attributed, not only to improved infrastructure and facilities, but also to the involvement of farmer-beneficiaries, from project planning to operation and maintenance of irrigation facilities. To effectively tap farmers' participation, pilot learning laboratories have been established. It has been a policy of NIA to help farmers organize into IA.
A common practice now in the Philippines is the pressurized irrigation system (PIS), which uses drip and sprinkler systems. More than 21,600 hectares are now irrigated in this way, mainly in Mindanao, much of which is planted in high-value crops such as banana and mango. PIS reduces non-beneficial evaporation, applies water uniformly to crops, reduces stress in plants, and helps increase the economic productivity of water. PIS is appropriate in high-value production and other intensive cultivation.
Irrigation systems for rice paddies depend party on the scale of production. Paddy farms in Taiwan, Korea, and Japan are fairly small. However, irrigation and drainage practices are sophisticated, and considerable labor is needed to control the gate operations. This becomes economically inefficient when labor costs are high. Rather than independent management of irrigation water by farmers, the focus now is on rotational block irrigation, with ditches to recycle the overflow. This system helps reduce labor costs, and promotes the use of mechanization.
An important concept is deep-water irrigation cultivation technique. This means providing the rice crop with surplus irrigation water when precipitation is plentiful. With this practice, fewer irrigations are needed and irrigation efficiency is improved. The water depth is increased gradually to 25 cm in keeping with the growth of the crop. The paddy field becomes a natural reservoir which helps to recharge groundwater and continuously return water to the system.
At the Workshop, the International Rice Research Institute (IRRI) presented the results of a two-year project on "Technology Transfer for Water Savings." The study aimed at developing a mechanism to bring water-saving technology to farmers. This involved selecting a pilot site, and assessing the needs and opportunities. A public seminar was then held to discuss water-saving technologies, and appropriate technology was selected. Demonstration farms were set up, where two years of validation was carried out. This included regular collection and analysis of data, not only about the soils and crops, but also the economic returns and other socio-economic aspects.
Regular discussion took place with farmers, and the technology was adapted according to feedback from farmers. Regular field days were held for farmers, to teach them about the technology. Finally, the technology was applied on a larger scale, and extension materials were developed.
The study area was in Central Luzon, among farmers who were using shallow tube wells as well as deep well systems. Among the water-saving technologies that were introduced to the area were controlled irrigation, in which standing water does not remain in fields continuously. Instead, fields alternate between submerged and non-submerged conditions. Research on controlled irrigation showed that it has good potential for reducing water needs. Yields can remain high without continuous flooding.
Moreover, results of the first season's trials indicated that controlled irrigation is a viable way of improving water productivity in both deepwell and shallow tubewell irrigation systems. Significant water savings of about 20% were attained in deepwell systems, and 11-15% in tubewells. There was no significant reduction in rice yield.
The farmers' role development is crucial in enhancing water use efficiency. One example that exemplifies this is the San Benito Irrigators' Association in Victoria, Laguna, Philippines. Farmers in this area organized themselves through the assistance of the local office of the National Irrigation Administration. A continuous education program made members conversant with the operations and management of the irrigation service. Farmers were able to adopt new technologies and increase their productivity. All members were given access to postharvest facilities.
A core project was the rehabilitation of old irrigation facilities. A participatory approach was followed. Farmers were given training, and were involved in the project from planning and conceptualizing programs and projects, up to implementation. To increase production income and maximize land use, farmers are practicing crop diversification (rice-watermelon). One policy of the irrigation association was that no water was supplied to farmers who did not have an official irrigation service fee receipt.
The problems identified during the presentations and discussions can be categorized into technical, economic, institutional, social and political, and environmental.
Some technologies that have been developed are not acceptable under local conditions. This is because of several factors, including a lack of funds for large infrastructure projects, a lack of technical skills to automate irrigation systems, and lack of adequate rainfall as one source of irrigation water. In developed countries, where funding is less of a problem, the issues related to the costs and benefits of large infrastructure projects are still under discussion. When governments make a large capital investment, there may be less concern to assess its cost effectiveness.
Common among developing countries with small farms is the problem of collecting irrigation service fees. Most, if not all, experience a low rate of payment of fees. This low rate of collection leads to another problem, of poor infrastructure and irrigation facilities due to lack of funds. This in turn reduces the productivity of farms.
The impact of intensive agriculture on the environment was another concern for almost all countries represented at the workshop. The growing public awareness of the deteriorating water quality and widespread water pollution makes it imperative to develop a more holistic approach to water resources management.
It seems that the key success factors in irrigation management are related and intertwined. The absence or weakness of one factor leads to the inability of the whole system to perform at its best. Among these factors are: availability and appropriateness of technologies; management approaches and systems; facilities and infrastructure development; government and policy support; provision of incentives and availability of financial support; and improvements in the institutional and organizational structures, functions, and operations.
Where there is an integrated, holistic approach to irrigation management, the impacts are positive. Water use efficiency involves a wide range of factors such as farm size, soil conditions, cropping patterns, agronomic crops, as well as the interplay of socio-political and economic aspects of allocation, management, and utilization of water.
In this Workshop, farmers' participation in the planning, implementation, monitoring, and evaluation of irrigation projects was given emphasis. Also, a well-organized water users' group or irrigation association must be in place to enable members to undertake operations and maintenance.
Held at Los Baños, Laguna, Philippines, on December 1- 5.
Countries represented: 9 (Japan, Korea, Lao PDR Malaysia, Philippines, Sri Lanka, Taiwan ROC, Thailand, Vietnam)
Papers presented: 17 (8 resource papers, 9 country papers)
Co-sponsors: Agricultural Resources Management Research Division, PCARRD-DOST
International Water Management Institute, Regional Office for Southeast Asia
Figure 1 Irrigated Rice Seedlings. More Than 60% of the World's Irrigated Area Is in Asia, but Irrigation Efficiency Is Fairly Low, at around 30%.
Figure 2 Irrigation Canal in Rice-Growing Area