The role of drainage of sustainable agriculture

摘要

Due to persistent neglect by the public sector, the need for land drainage has developed for 10-15 million hectares in arid and semi-arid countries, as well as in the humid tropics. Data on land with high salinity levels, land removed from production, yield depressions, and waterlogged and flooded land indicate the immense need for investment and improvement of drainage management. While change has been impressive in improving irrigation performance by transferring the management of irrigation systems to farmers organizations, this option can be applied to drainage only under very restrictive conditions. Drainage is a more difficult task for transfer because of its publicgoods characteristics, production aspects and the externalities associated. There is no one institutional solution, but instead a wide range of options moving along a continuum, - from government department, parastatal, service and management-contracting, cooperative and communal arrangements etc. However, the authors argue thatthe state has to play a prominent role in investment and in the setting of an institutional framework. Although difficult, a review of effective practices that some countries have experimented shows that drainage pays if suitable models are applied: drainage protects the resource base for food production; it sustains and increases yields and rural incomes, protects irrigation investment; it serves rural and urban residents and protects human lives and assets against flooding and high groundwater levels,and, finally, improves health conditions - success stories that are rarely recognized. Issues of particular concern are the reuse of drainage water for irrigation, and the relation and effects of drainage on natural areas and habitat (wetlands) which requires approaches both technical and institutional in nature that serve for the mitigation and balance of negative aspects.