|FAO Irrigation and Drainage Paper 40 Organization, operation and manintenance of irrigation schemes (1986)|
|Part II - The services of a water management organization|
|6. Maintenance service|
|6.3 Maintenance activities|
The retention in good working order of open drains includes the following operations:
- light deforestation
- weed control in the canal section
- seeding grass in the canal section
- maintenance of flow gauges and other measuring devices
- removal of silt
- maintenance of pumping stations where water cannot be evacuated by gravity.
For practical purposes, the maintenance of open drains is very similar to that of earth irrigation canals. However, all too often drainage networks receive much less attention than the irrigation ones. The result is that during heavy rain, when they are much needed, they do not work as they should.
Drainage maintenance should always be programmed from downstream to upstream, and as far as possible completed within an irrigation season. The intervals in regular maintenance should not exceed periods of 2-3 years between two consecutive cleanings.
Tile drains are subject to two main problems: (a) obstruction due to silting and plant roots, and (b) mineral deposits. The most common is the first. Mineral deposits of iron and manganese occur quite frequently in some irrigation schemes and the time necessary for such depositions varies widely from a few months to 30-40 years, depending on the mineral composition of the soil.
Methods for cleaning the drains are discussed later in this publication.