Due to the poor condition of the head works (bund and associated structures) of the Iranamadu reservoir, water is not being fully stored during monsoon seasons for the past 10 years (usually 4-5 ft below Full Supply Level, by opening spill gates during heavy rains), and as a result, availability of water for irrigation purposes is limited. An ADB/AFD funded Headwork improvement component 36 has been initiated which will increase the capacity of the tank by 16.3 million m3 to 148.1 million m3 by strengthening and raising the bunds to 31.40 m msl. Part of the incremental volume will be diverted to Jaffna for drinking water supply.

The proposed IFAD Project would be used for the rehabilitation of the downstream canal
system which provides irrigation water to 8 455 ha. The Irrigation rehabilitation sub-component would include the following activities.

The Iranamadu tank has a left bank and a right bank main channel of a total length of 30 km. Due to the poor or lack of maintenance for a long time, the channel system has badly deteriorated. The channel bund tops are below the designed level and are full of depressions and scours. Most of the structures are badly damaged. Many of these need reconstruction and the rest extensive repairs and improvements. In addition both canals need to be desilted and cleared of trees, debris and weed growths which obstructs the flow. Typical activities37 to improve the main canal include secondary growth clearing; compacted earth fill on channel bund to design profile and level; desilting in the channel bed; strip turfing of newly filled slopes; construction of retaining walls at badly scoured sections; repairs of regulators; repairs of turn out structures, installation of measurement devices; and construction of drainages under crossings. The Project will support all of these activities.

Currently the Provincial Irrigation Department (PID) is undertaking some repair work on one regulator which controls the water issue to distribution canals (D3) of the left bank area. There are five more structures which need rehabilitation in the left bank main canal. In the right bank main canal there are 11 structures which need rehabilitation for proper control of water. Out of that, two structures are being constructed at the cost of LKR 10 million. PID is also now in the process of rehabilitating the right bank canal roads.

The total length of branch and distribution canals is about 135 km. The condition of the branch and distributory canals is same as that of the main canals. PID is now in the process of rehabilitating one of the D3 commencing from left bank main canal. Rehabilitation of three drop structures and three regulators along D3 canals is now in progress. Rehabilitation works that the Project will support are similar to those for the main canals. Further measurement devices will be installed at all (repaired) turn out structures.

The total length of field channels in the scheme is 123 km. Most of the bunds of the field canals have been washed away. There are not many water control structures and water is issued to the field by cutting an opening in the canal bund. All the field channels needs to be provided with pipe outlets for individual farms. There is also a need to introduce canal roads as access to individual farms. The project will support such structures.

Repair and improvement of farm roads in the command area is required. Works would include gravelling, repairs of causeways, bridges, construction of pedestrian crossing etc and the Project will finance such work.

Drainage in the scheme above the coastal belt is poor and during heavy rains the farm lands are flooded causing severe crop damage particularly during harvest time. The main drainage canals are heavily silted up and overgrown with scrub and trees, and are choked with tree stumps and weeds. Some of the riverine reservation areas allocated for canal bank protections in medium and minor drainage are also being gradually encroached by adjoining riparian farmers for cultivation. Drainage improvement in areas prone to salinity development is therefore required and will be supported by the Project. Main activities include bush clearance, desilting, compacted earth fill on Kanagarajan Aru flood bund, and vegetative strengthening of canal slopes for which planting material will be provided with project funds.