Sedimentation Trend and Behavior of Turbid Water in the Reservoir
摘要
A half of the water demand for agriculture and urban water supply is covered by surface water resources even in arid land, however the capacity of the reservoirs is gradually degraded due to sedimentation. Therefore, sedimentation control in reservoirs is an important issue in the sense of sustainable surface water resource management. In the case of North African countries, due to the clear precipitation difference between rainy season in winter and dry season in summer, the flood water in rainy season is stored for irrigation and potable use in the dry season. This longer retention time than humid area causes more rapid sedimentation. In this study, the detailed behavior of turbid water which is discharged from upper catchment in rainy winter season is discussed with a numerical simulation model applied to a reservoir in northern Tunisia. Because of the low solar irradiance, thermal stratification was not found in the water body in winter and turbid water flowed along the bottom of the reservoir as a density flow. Understanding the speed and thickness of this density flow is very important for proper management of reservoirs, whether the turbid flood water can be removed by opening the spill way or other measures. The numerical simulation was carried out with some different cases of density of inflow and intake rate at the dam, which define the thickness and speed of the bottom flow.