A primary requirement for sustainable agriculture is the maintenance of a satisfactory balance of water, air and salt in the rootzone favourable for plant growth. This balance can be achieved by adequate drainage.
Drainage can be either natural or artificial. Most land has some natural surface and subsurface drainage. When natural drainage is inadequate, artificial drainage is required to increase the drainage capacity.
Artificial drainage is essential to sustain irrigated agriculture. Often, subsurface drainage is needed in irrigation schemes to control the rising water table and avoid waterlogging and salinization. Conventional subsurface drainage systems are of two types, vertical (tubewells) and horizontal (drainpipe) systems. When properly designed, installed and maintained, these systems are efficient in lowering the water table and preventing salinization of irrigated lands. However, they have two drawbacks, namely, they are costly and they generate drainage effluents, which will have to be either carefully reused or safely disposed of.
An option is biodrainage, which can be less costly and more environmentally friendly. It is a combined drainage-cum-disposal system. Biodrainage relies on vegetation, rather than mechanical means, to remove excess water. The driving force behind the biodrainage concept is the consumptive water use of plants. Biodrainage is economically attractive because it requires only an initial investment for planting the vegetation, and when established, the system could produce economic returns by means of fodder, wood or fibre harvested.
There is consensus that biodrainage, when properly implemented, can lower the water table. It could solve problems associated with waterlogged areas and canal seepage. What is not clear is the ability of the biodrainage system to maintain a salt-balance.
This publication is a compilation of existing information, both formally published and unpublished literature. It aims to inform water professionals in general and drainage experts in particular of current knowledge of biodrainage and further research needs.
The biodrainage system can lower water tables adequately and enough information exists for pilot applications. It is hoped that this publication will induce further research, debate, discussions and pilot testing and hence contribute to sustainable agricultural development.
Tom Brabben
Acting Officer-in-Charge
IPTRID
