Abstract
Sandbar development would stop the water and sediment exchange between main river and tributary and even influence the normal reservoir opeartion. From the surveyed data of reservoir built many years ago, it shows that when there is a bar in tributary mouth, the tributary volume below the bar will become nullification during the period of flood control or water and sediment regulation of reservoir. There are more tributaries in Xiaolangdi reservoir than the others that it occupies 41.3% of the total initial volume of tributary volume. Obviously, the effective use of tributary volume has been important influenced by comprehensive utilization efficiency of reservoir scheduling, such as flood control, sedimentation reduction and comprehensive utilization. Results of Xiaolangdi Reservoir mobile-bed physical model experiments show that tributary is equivalent to lateral extension of river bed, the tributary intrusion deposition process have strongly relations with the factors, such as original topography, river bed deposition shape and its regime, process with input discharge and input sediment, and method of reservoir regulation. The variation trends of main river and tributary terrain forecasted by model test are basically in accordance with field surveyed data. The results could be used for research, design, and forecasting of reservoirs in sediment-laden river.
Highlights
Tributary sandbar often occurs at the mouth of tributary which lie in a disadvantageous site.With reservoir operation,if there are little possibility for tributary flood and poor water and sediment input match from main river,large scale sandbar forms at the mouth of tributary with interrupting the water and sediment exchange between main river and tributary and influencing the reservoir operation precision.For example,sandbar development in the mouth of Guishui river in Danjiangkou reservoir,stops the water supply from the reservoir
With the help of field surveyed data from built reservoirs are analyzed in analogy,the research results of sandbar variation in long series model tests in the first stage of late retainning sediment period of xiaolangdi reservoir is condensed.The results could be technically refered by the sediment-laden river planed,designed and operated
Tributary amounts to the horizontal extend of the main river bed.the backward flow process on the tributary bed including deposition quantity and formation is closely related to the factors including the tributary natural landform conditions,main river deposition landform,main river regime,water and sediment input process and reservoir operation etc
Summary
Tributary sandbar often occurs at the mouth of tributary which lie in a disadvantageous site.With reservoir operation,if there are little possibility for tributary flood and poor water and sediment input match from main river,large scale sandbar forms at the mouth of tributary with interrupting the water and sediment exchange between main river and tributary and influencing the reservoir operation precision.For example,sandbar development in the mouth of Guishui river in Danjiangkou reservoir,stops the water supply from the reservoir. Sandbar development in the mouth of Yuan river and Longmen river brings many problems.From the bulit reservoirs with long term practical operation,sandbar stops the water and sediment exchange between main river and tributary ,and reservoir capacity of tributary can not be used effiency.Even the reservoir general utilization benefit would be heavily hindered.,water and sediment movement law have not been controled and modeled.From the study on the physical model of Xiaolangdi reservoir by Zhangjunhua[9,10,11,12,13,14],the deposition in tributary which is mainly induced by turbidity current had been found with further study on the backward flow between main river and tributary. With the help of field surveyed data from built reservoirs are analyzed in analogy,the research results of sandbar variation in long series model tests in the first stage of late retainning sediment period of xiaolangdi reservoir is condensed.The results could be technically refered by the sediment-laden river planed,designed and operated
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