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A platform for research: civil engineering, architecture and urbanism
Verification of drainage design criteria in the Nile Delta, Egypt
Abstract A monitoring programme to verify the design criteria of subsurface drainage systems was conducted in a pilot area in the Nile Delta in Egypt. The programme, which covered a 9-year period, included the monitoring of the cropping pattern, crop yield, soil salinity, watertable, discharge and salinity of the drainage water and overpressure in the subsurface drainage system. The results showed that the yield of all crops (wheat, berseem, maize, rice and cotton) increased significantly after the installation of the subsurface drainage system. Optimum growing conditions for the combination of crops that are cultivated in rotation in the area required that the watertable midway between the drains had a average depth of 0.80 m. A corresponding drain discharge of 0.4 mm/d was sufficient to cope with the prevailing percolation losses of irrigation water and to maintain favourable soil-salinity levels. The additional natural drainage rate in the area was estimated at 0.5 mm/d. The most effective way to attain these favourable drainage conditions is to install drains at a depth between 1.20 to 1.40 m. For drain-pipe capacity the Manning equation can be used with a design rate of 1.2 mm/d, for collector drains this rate should be increased to 1.8 mm/d to compensate for the higher discharge rates from rice fields. These rates should be used in combination with a roughness coefficient (n) of 0.028 to take sedimentation and irregularities in the alignment into account. When this value of the roughness coefficient is used, no additional safety has to be incorporated in the other design factors (e.g. the design rate).
Verification of drainage design criteria in the Nile Delta, Egypt
Abstract A monitoring programme to verify the design criteria of subsurface drainage systems was conducted in a pilot area in the Nile Delta in Egypt. The programme, which covered a 9-year period, included the monitoring of the cropping pattern, crop yield, soil salinity, watertable, discharge and salinity of the drainage water and overpressure in the subsurface drainage system. The results showed that the yield of all crops (wheat, berseem, maize, rice and cotton) increased significantly after the installation of the subsurface drainage system. Optimum growing conditions for the combination of crops that are cultivated in rotation in the area required that the watertable midway between the drains had a average depth of 0.80 m. A corresponding drain discharge of 0.4 mm/d was sufficient to cope with the prevailing percolation losses of irrigation water and to maintain favourable soil-salinity levels. The additional natural drainage rate in the area was estimated at 0.5 mm/d. The most effective way to attain these favourable drainage conditions is to install drains at a depth between 1.20 to 1.40 m. For drain-pipe capacity the Manning equation can be used with a design rate of 1.2 mm/d, for collector drains this rate should be increased to 1.8 mm/d to compensate for the higher discharge rates from rice fields. These rates should be used in combination with a roughness coefficient (n) of 0.028 to take sedimentation and irregularities in the alignment into account. When this value of the roughness coefficient is used, no additional safety has to be incorporated in the other design factors (e.g. the design rate).
Verification of drainage design criteria in the Nile Delta, Egypt
Abdel-Dayem, Safwat (author) / Ritzema, H. P. (author)
1990
Article (Journal)
English
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