Dimensionnement du drainage des sols lourds de la plaine du Gharb, Maroc

In Morocco agricultural drainage is an important development factor in the same way as other agricultural water management facilities. 30% of the irrigable area require drainage. The major part of this area is in the Gharb plain. Due to the urgent need for developing the Gharb plain, drainage system design was derived from investigations carried out in other countries while that a field experiment under Morocco's conditions be implemented. Drainage systems have been operated and managed since more than two decades in the Gharb plain. The Gharb Regions Agricultural Reclaimation Agency (ORMVAG) is now facing several problems related to surface drainage network maintenance and to monitoring irrigated soil evolution. To cope with this situation, ORMVAG plans to : increase credits allocated to operation and maintenance ; make farmers and managers aware of the situation ; set up an experimental station ; test other drainage system types, for example, singular drainage systems. / Au Maroc, le drainage agricole constitue une opération d'aménagement importante à l'instar des autres équipements hydro-agricoles. En effet, 30 % de la superficie irrigable nécessite un drainage. La plus grande partie se trouve dans la plaine du Gharb. L'urgence de l'aménagement de la plaine du Gharb a fait que la conception du système de drainage a été inspirée des études élaborées dans d'autres pays en attendant qu'une expérimentation à l'échelle du Maroc soit menée. Après plus de deux décennies de fonctionnement et de gestion des réseaux de drainage dans la plaine du Gharb, l'ORMVAG (Office régional de Mise en Valeur Agricole du Gharb) se trouve, actuellement, confronté à plusieurs problèmes relevant de l'entretien des réseaux de drainage superficiel et du suivi de l'évolution des sols sous irrigation. Pour remédier à cette situation, l'ORMVAG envisage : d'augmenter les crédits alloués à l'exploitation et l'entretien ; de sensibiliser les agriculteurs et les gestionnaires ; d'installer une station expérimentale ; d'essayer d'autres types de réseaux de drainage, par exemple les systèmes de drainage direct

Effects of prior hydrogenation on the structure and properties of thermally nanocrystallized silicon layers

Nanocrystalline silicon layers have been obtained by thermal annealing of films sputtered in various hydrogen partial pressures. The as-deposited and crystallized films were investigated by infrared, Raman, x-ray diffraction, electron microscopy, and optical absorption techniques. The obtained data show evidence of a close correlation between the microstructure and properties of the processed material, and the hydrogen content in the as-grown deposit. The minimum stress deduced from Raman was found to correspond to the widest band gap and to a maximum hydrogen content in the basic unannealed sample. Such a structure relaxation seems to originate from the so-called "chemical annealing" thought to be due to Si-H2 species, as identified by infrared spectroscopy. The variation of the band gap has been interpreted in terms of the changes in the band tails associated with the disorder which would be induced by stress. Finally, the layers originally deposited with the highest hydrogen pressure show a lowest stress-which does not correlate with the hydrogen content and the optical band gap¿and some texturing. These features are likely related to the presence in these layers of a significant crystalline fraction already before annealing