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close this bookDesign and Operation of Smallholder Irrigation in South Asia (WB, 1995, 134 p.)
close this folderChapter 11 - Construction and maintenance problems of drainage works
View the documentDrainage and the cultivator
View the documentFormal and informal tertiary drainage systems
View the documentSubsurface field drainage
View the documentPrimary and secondary drainage

Drainage and the cultivator

Drainage channels are designed to remove surface water from fields and in some situations to lower the watertable by extraction of groundwater. While these are very desirable functions drainage channels can pose severe maintenance problems. Difficulties in maintenance of unlined canals previously discussed, including weed growth and encroachment by phreatophyte plants, are aggravated in the case of drainage channels as ground conditions are usually wet year-round and vegetative growth can be prolific. Secondary and tertiary drains have an added problem. While cultivators reluctantly accept the disruption of access caused by the presence of irrigation channels, they are much less favorably disposed to secondary and tertiary drains. Tertiary drains, in particular, commonly exist on paper only, or are cultivated over within a year or two of construction. Secondary drainage channels, although nominally under Departmental jurisdiction, are often partially filled in by cultivators to provide crossings to fields or dwellings, or to provide ponds for small fish culture, such ponds usually being filled with water hyacinth and village debris.

The conclusion is that drainage channels should be limited to those which are essential, and that these should be adequately maintained and defended against encroachment. Provision of crossings, each with adequate culvert capacity, is essential, or obstruction by informal cultivator constructed crossings will inevitably result.