A MODIFIED LAYOUT OF THE SUBSURFACE DRAINAGE SYSTEM FOR RICE AREAS IN THE NILE DELTA, EGYPT

In the Nile Delta in Egypt, rice is cultivated in rotation with "dry-foot" crops. To reduce water losses from areas cultivated with rice without restricting drainage from other areas, a modified layout of the subsurface drainage system has been developed. The principles of the modified layout have been investigated in experimental fields under fully controlled conditions as well as in farmers' controlled fields. In addition, the performance of the modified layout was monitored in two areas of around 2000 ha each. The introduction of the modified layout will save approximately 25% of the irrigation water supplied to rice fields, which would otherwise be lost through the subsurface drainage system. The restricted outflow has no adverse effect on soil salinity or crop yield. Furthermore, the introduction of the modified layout will reduce the maintenance costs of the subsurface drainage systems because the farmers are no longer forced to adopt improper practices to restrict the drainage.