Subsurface drainage practices: From manual installation to large-scale implementation

Drainage of agricultural lands is an instrument for production growth, a safeguard for sustainable investment in irrigation, and a tool for conservation of land resources. Projections to meet the food and fibre needs of the world during the next 25 years shows that drainage of at least 10–15 million ha should be improved, which will require an investment of € 19 billion or about € 750 million annually. It is expected that one third of this area will be provided with subsurface drainage systems.Subsurface drainage has been practiced for thousands of years, however, the rapid introduction in Europe and North America only started around 1940, when the prevailing empirical knowledge of drainage and salinity control gained a solid theoretical foundation. Since then, the installation practices evolved from purely manual installation on individual farm plots to fully mechanized installation programmes covering thousands of hectares. To make this rapid change possible, practical tools for the implementation had to be developed, starting with the introduction of new types of installation equipment, i.e. trencher and trenchless drainage machines. To optimize the use of these machines, however, a number of problems had to be solved. New materials for drain pipes and envelopes had to be developed to reduce the high transportation and installation cost of the traditional materials and to improve quality of construction. Next, the traditional method of quality control proved to be inadequate because of the increased speed and method of mechanical installation. And last but not least, staff had to be trained in these modernised drainage machinery and installation techniques, as well as in the planning and organization of the implementation process. This paper discusses these developments in installation techniques, equipment and materials, and the corresponding institutional changes that were needed to keep up with these changing demands. These developments are still going on to meet the specific needs of installation in developing countries, under climatic, physical and social conditions that differ from the ones for which they have been designed. Furthermore, the specific needs of drainage are also changes, particularly with regards to the quality of drainage water, that require changes in the drain system design and corresponding installation practices.