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

The Impacts of AMMA Radiosonde Data on the French Global Assimilation and Forecast System

Abstract The high vertical density soundings recorded during the 2006 African Monsoon Multidisciplinary Analysis (AMMA) campaign are assimilated into the French numerical weather prediction Action de Recherche Petite Echelle Grande Echelle (ARPEGE) four-dimensional variational data assimilation (4DVAR) system, with and without a bias correction for relative humidity. Four different experiments are carried out to assess the impacts of the added observations. The analyses and forecasts from these different scenarios are evaluated over western Africa. For the full experiment using all data together with a bias correction, the humidity analysis is in better agreement with surface observations and independent GPS observations than it was for the other experiments. AMMA data also improve the African easterly jet (AEJ) on its southeasterly side, and when they are used with an appropriate bias correction, the daily and monthly averaged precipitation results are in relatively good agreement with the satellite-based precipitation estimates. Forecast scores are computed with respect to surface observations, radiosondes, and analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF). The positive impacts of additional radiosonde observations (with a relevant bias correction) are found to propagate downstream with a positive impact over Europe at the 2–3-day forecast range