| Because of its special geographical location,the Inner Mongolia section of rthe\Yellow River often suffers from severe ice block and ice dam disasters during the ice flood season.Since Liujiaxia reservoir and Longyangxia reservoir has implemented the ice prevention,and also followed the principle "head of large,medium in the middle,small end",by controlling discharge volume to reduce the melting ice flood disaster in the Inner Mongolia reach,but this method only consider water scheduling mode,whether or not impact fluvial process of ice flood season in Inner Mongolia reach,this paper will analyze temporal and spatial variation of water-sediment and fluvial process in ice flood season,it thinks that the reservoir operation for ice prevention has impacted fluvial process in Inner Mongolia reach,and obatain some conclusions:(1)The variation of water and sediment amount in each period was analyzed,according to the division of ice-flowing period,freeze up period and break-up period.With the operation of the reservoir,compared with the natural runoff,the river flow in Inner Mongolia increased,and the river flow in Inner Mongolia increased by 25%on average during the whole ice flood season.During the ice-flowing period,the sediment transport rate of Bayangaole increased sharply.The section with the highest sediment transport rate during the freeze up period was the Shizuishan section.During the break-up period,the sediment transport rate of Bayangaole increased mostly.Compared with water,the increase of sand is more obvious.(2)With the operation of reservoir,it can be seen from the cross-sectional shape of the channel in ice flood season,that the channel of Bayangaole and Sanhuhekou in the Inner Mongolia reach has shrunk seriously.Under the same flow area,the width of the Shizuishan channel is basically balanced,and the Bayangaole channel is in the state of erosion.Sanhuhekou channel and Toudaoguai channel is balanceable but perfer to erosion.The river slope of ShiBa reach remain the same,and the hydrodynamic force in favor of sediment transport is reduced,the SanTou section becomes steeper,which is favorable to transport sediment.(3)The Contrast between the natural condition and the j oint operation of the two reservoirs,the change of scour and silt amount of the whole sediment is as following:the silt amount of the ShiBa reach changes from 4.4 million t to the scour 4.32 million t;The BaSan reach has been scoured 2.14 million t and silted 5.1 million t.The SanTou reach has been scoured 1.22 million t and slightly silted 290,000 t.The change of scour and silt amount of the bed load scour and deposition is as the following:the silt of ShiBa reach changed from 70,000 t to the scoured 6400 t;The BaSan reach changed siltation 49,000 t.SanTou reach silts 1100 t turns into erosion of 5200 t.(4)It can be seen from the change of water and sediment,riverbed morphology and the amount of scouring and silting between river sections in the Inner Mongolia reach of the Yellow River during the ice flood season,that the reservoir operation changed the riverbed evolution during the ice flood season.The reasons for the change of riverb ed evolution are analyzed.During the break-up period,the water temperature was 2.74 ?,after joint scheduling,the water temperature is 5.59 ?,that makes the sediment eff-iciency reduced in a low temperature,it is less favor of the river sediment;In the break-up period of Santou reach,the flood volume increases and the flood duration increases,which is beneficial to sediment transport.After Ice scheduling,Bayangaole's incoming sediment coefficient increases,water and sand are not harmonious,sediment loads is abundant during ice-flowing period in Bayangaole hydrological station,In addition,during the break-up period,the reservoir reduce the discharge,that is not conducive to the sediment transport,and the erosion capacity of the reach is weakened,as a result,more and more serious silting in the BaSan reach of the Yellow River,and SanTou reach has a micro-silting trend. |
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