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Improvement of operational methods for the assessment of the water reservoir useful storage capacity using geoinformation systems. Case study of the Akdarya Reservoir, Samarqand Province, Uzbekistan.

Amélioration des méthodes opérationnelles pour l'évaluation de la capacité utile de stockage des barrages à l'aide d'outils de géo-information. Etude du barrage d'Akdarya, Province de Samarkand, Ouzbékistan.

Abstract : Sedimentation processes in man-made water reservoirs reduce their main asset: the volume storage capacity. This raises engineering, environmental and economic issues for the communities around the world and in particular for the areas affected by strong water deficit. Because of Uzbekistan's arid climatic conditions and uneven spatial and temporal water resources distribution, responsive and innovative water availability assessment surveys of all major water reservoirs are required. Bathymetric survey is a traditional method that is carried out for the estimation of reservoir volumes and surface areas for the corresponding reservoir stages in order to assess the water availability. Volume and surface area differences derived from multiple surveys of a reservoir provide storage loss estimates over time due to sedimentation. However, two main factors such as intensive field data measurement and post data-processing often limit the frequency of these surveys. Alternatively, innovative depth measurement technologies coupled with contouring and surface mapping programs provide automated reservoir volume and surface area calculations. This significantly reduces time, work load and financial burdens for reservoir sedimentation projects. This study deals with the use of a geostatistical approach to assess the reservoir sedimentation in the Akdarya reservoir in Uzbekistan. Geostatistical approach includes (semi-) variogram analysis and interpolation (kriging and simulations (turning bands)) techniques predicting values at unsampled locations for generating digital bathymetric surface models of reservoir bottom conditions in order to calculate volume and surface area at given water elevation. Simulation enables to have range of reservoir volumes and surface areas with the same probability in comparison to the kriging and traditional methods. This gives a real estimation of the water resource availability for operators and managers to sustainably manage natural resources and hydraulic infrastructure.