The Canal Supply system. The water supply is not adequate to provide sufficient water for percolation. An intensive tertiary canal system with ample shallow field ditches will be a solution for good water supply. The more intensive the lay-out of the canal system, the larger the extent of the potential areas for good water supply will be. This water supply system is based on irrigation at high tide. Irrigation for wetland rice requires that land levels should not be higher than 20 cm above mean high tide level during springtide during periods of dry spells. Further the distance of the rice field to the adjoining tertiary canal should preferable not be more than 100 m. to reduce the distances for the on-farm water supply system.

The On-farm Water Management system. In most cases an intensive field ditch system for supply and drainage does not exists. This has two negative effects. Insufficient water reaches the fields and insufficient drainage occurs for leaching of the toxic components in the groundwater. Drainage of excess rain & tidal water occurs often only in the upper 20 cm of the soil, because of a ditch-wall effect in the tertiary canals and field ditches. (ditch wall effect= clogging of holes and cracks on the walls of the ditches, causing extreme low permeability). This prevents the leaching of the deeper subsoil and is a main cause of the extreme high toxicity's, often found in the fields. A subsurface drainage system will improve percolation considerably (there are no ditch wall effects ) and will reduce the workload for farmers to maintain the water management system.

The Operation of the Control gates. Training of Water User's Associations and gate operators is required and by means of the Model Areas the farmer's should be convinced the system based on leaching/percolation is working. This needs time for implementation. At present farmers tend still to operate the system for water retention as much as possible as soon there is high rainfall. This planting season there is ample prove that farmers who planted early with high rainfall and lots of leaching/percolation found much better yields than farmers who planted later with even higher rainfall but with mainly water retention in their fields during early growth of the rice plant.

Water supply and drainage system. This is the most critical part for good water management and high yields. Often the water supply is experienced as the most critical part of the water management system. As a cure for the insufficient water supply the control structures are closed. However this will work counter-productive, because it will decrease percolation and consequently increases the toxicity levels in the field. The system should aim at increasing both water supply and improving drainage.

Soil/water management and operation system. A proper operation of the irrigation/drainage system should benefit the yield levels and the potentials for crop diversification. The soil/water management should aim to promote the ripening of the soft soils by permitting the drying of the surface layers during the dry season. Deep plowing followed by intensive puddling for land preparation will benefit the yields. The water levels in the field should not drop below 30 cm below the surface during the growth period of the rice. For that reason ample water supply is crucial.

Institutional development system. The traditional developed areas usually have a well organized institutional infrastructure. It are usually the more difficult to operate areas where there are problems. Lack of understanding to apply the proper Soil and Water Management system and the lack of Operation & Maintenance budget and facilities are the key limitations for improvement.

For more information see Web page Institutions.