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Elevation of lower stability in the lower Weihe River Comprehensive Management

Abstract: In this paper, field data analysis and mathematical modeling methods such as reducing and stabilizing the riverbed elevation of the comprehensive management of the Lower Weihe River and other important issues were studied, obtained the following understanding: (1) Tongguan is the Sanmenxia reservoir area of natural card Weihe River mouth and the base level of erosion, from the reduction of siltation, to alleviate flood disasters and to improve eco and environmental considerations, the bed elevation is very necessary; (2) by adjusting the Sanmenxia reservoir, Tongguan elevation is lower, but a different water and sediment conditions, the degree of reduction is different, short-term goal could be identified as the decline in 1m, a combination of various measures after long-term goals can be identified as drop 2m; (3) Tongguan elevation reduced to a relatively stable state usually takes 4 to 8 years, which is water and sediment and reservoir operation model; (4) recommended the use of Sanmenxia Reservoir Recent open vent with flood water level, non-flood control 312 ~ 318m wide program, considering that the non-flood water level after the current control is better in the 315m; (5) governance of the Lower Weihe River to be taken, including the bed elevation, river regulation and dredging, dike reinforcement and heightening inter-basin water transfer and other comprehensive measures.
Keywords: Tongguan elevation reduced stability of the Sanmenxia Reservoir Weihe River Comprehensive measures

1 Elevation of change and its effects 1.1 Tongguan elevation changes in the history of Sanmenxia Reservoir construction ago, the Yellow River is the natural river Tongguan, the lack of measured data, the current changes in the history of Elevation of the existence of 3 different views: the first view is that Tongguan elevation in history is the sustained elevation and uplift rate of annual is relatively large; second view is that the history of Tongguan elevation is slowly rising, lifting the annual rate is very small; third view is that the history of Tongguan elevation is relatively stable. The above-mentioned three kinds of information cited in the main view has [1] : (1) 1966 iron bridge near the drilling 年 Tongguan information; (2) 1929 to 1960 measured 1000m 3 / s flow Tongguan water level; (3) using a small thickness of the North River deposition inferred from Tongguan elevation. Obtained from the drilling data analysis from the Three Kingdoms period to 1960, the average silt Tongguan elevation higher 0.006 ~ 0.008m, inferred from the small North River silt deposition Tongguan elevation average high 0.014 ~ 0.027m, shows that these two kinds of methods used by the Tongguan In higher elevation values vary greatly, with a small North River deposition inferred Tongguan elevation bias. The use of 1929 to 1960 measured data, the average silt Tongguan elevation obtained high 0.035 ~ 0.09m, also have expert analysis of the 1929 to 1960 measured data, that the deduction of one of the 1942 and 1947 years of missing data, while Tongguan elevation state of relative equilibrium [2] , we can see, even using the same data, will get very different results. This and various data processing methods use a great relationship, and this is the problem of sedimentation in Sanmenxia Reservoir in's characteristics. The author believes that: Historically, the Weihe River is a no underground river dike, the main river channel conveyance capacity at about 5000m 3 / s or so, had also a navigable channel capacity; In addition, Xi'an 1m riverside area the following cultural relics unearthed a large number of Qin, Hua county near the beach to the measured high deposition 3m, and the 1929 to 1960 measured data from 1942 to 1947, net of years of missing data, etc. to comprehensive analysis, that the history of Tongguan The average elevation is slowly rising, may in some periods because of different water and sediment will be substantially increased or decreased, but the general trend of a long period slowly rising, less likely to accumulate in history lift a few tens of meters.

Figure 1 Tongguan elevation difference change process
1.2 at different stages after the construction of the Sanmenxia Reservoir Elevation of change the construction of the Sanmenxia Reservoir, the water level at Tongguan experienced a sharp rise - fall - the basic stability - the gradual uplift of 4 stages [ ,1 ~ 4] , Figure 1 (a) and (b) for the year Tongguan elevation difference of the change process, the map shows: (1) in September 1960 to 1969 high flood water level of the end of reservoir operation, Tongguan elevation rapid elevation of 5.25m, 1969 年 ~ 1973 flood at the end the end of reservoir flood low water level, Tongguan elevation drop 2.01m, 1973 年 ~ 1985 flood at the end the end of reservoir to store flood water and releasing muddy clear, Tongguan elevation at a relatively basic stable since the end of 1985 flood, continuous inflow dried up, slow continuous uplift Tongguan elevation to the end of 2002 flood, Tongguan elevation rose to 328.78m, note the water level of reservoir operation and water and sediment have a major impact on Tongguan elevation; ( 2) the annual Xun Hou and many years before the flood season Tongguan elevation difference is negative, indicating changes in Elevation of the year is basically a flood washed down washed down some of the flood season and even 1.8m, non-flood elevation is siltation. Xunhou next year with a year Xunhou fluctuations Tongguan elevation difference is that non-flood water level control is essential Sanmenxia Reservoir, its movements are an important influence Tongguan elevation; (3), 2002 Xun Hou, Sanmenxia Reservoir The maximum water level control for non-flood season in 318.00m, from October 24, 2002 ~ June 30, 2003, the average dam level 315.59m, 2003 Reservoir in flood season is basically open vent and low water level, combined with the Weihe River in 2003 autumn floods 6 peak, Tongguan elevation in the October 19, 2003 decreased compared with pre-flood 0.88m, Xun Hou recovering somewhat. 1.3 Tongguan elevation down the role of Tongguan in the following confluence of the Yellow River and Weihe River is about 5000m, was the confluence of HUANG Wei-Sanmenxia reservoir area after the natural water flow into the bayonet. Elevation of direct effects on erosion and deposition of the Lower Weihe River, Weihe River is the base level of erosion.
<TD Width=\<TD Class=a6 width=\siltation 3.79 billion m 3 , the following deposition 2940000000 Tongguan m 3 , 2002 Xun Hou, Tongguan water level rose to 328.78m,[link widoczny dla zalogowanych], before the construction of lift than the 5.38m. As a base level of erosion of the Elevation of elevation, led to serious siltation downstream of Weihe River. 1960 to 2000 the total deposition in the Lower Weihe River reached 1.33 billion m 3 , Figure 2 for different periods of different sections of the Lower Weihe River unit length of the scour that increased with the Elevation of Weihe River The deposition intensity continues to move upwards, the more significant influence over the scope of section 26 Wei deposition (Lintong), so that the rivers will decline,[link widoczny dla zalogowanych], flooding capacity decreases [5] , Weihe River has become \hanging river \
Figure 2, the lower Weihe River unit length of scour
Jun. Huaxian station and flooding capacity of the river section before the construction of 4500 ~ 5000m 3 / s down to about 1999, 1500m 3 / s, 2003 Weihe River flood in emerging peak throughput, but the water level high, long duration, slow evolution, the formation of a large disaster situation in the Lower Weihe River is the inevitable result of heavy siltation. Sedimentation basin also makes the ecological environment worsening, not improving living standards along the river, to the Weihe River Plain region's economic development related serious adverse effect. Measured data analysis shows that the cumulative Lower Weihe River Sediments and water level are and Elevation Huaxian better correlation shown in Figure 3 and Figure 4, the map shows: Tongguan elevation lift high, aggregate deposit volume Weihe River to increase the water level will rise Huaxian. Therefore, to reduce siltation, to reduce the flood level,[link widoczny dla zalogowanych], to reduce flooding and improve the ecological environment, starting bed elevation is necessary.
<TD Width=\
<TD Width=\
Figure 3 Weihe River and the Elevation of total deposit volume relationship
Huaxian Figure 4 the relationship between water level and water level Tongguan
1.4 2003 of Weihe flood conditions 2003 年 8 月 since the 24th lasted two and a half months of the Lower Weihe River, although not peak, only once in every few years flood,[link widoczny dla zalogowanych], but flood volume, flood lasted longer, resulting in Weihe River burst a dam (Youmeng dike), 3 Nanshan tributary of the burst 10, which side mountains and rivers 5, Rib River 4, Shidi River 1. Flood losses is the largest ever Weihe River, Weihe River floods were caused by cross Xianyang, Xi'an, Weinan 3 city six counties inundated 46 towns, the affected population of 49 million, transfer of population 292 200, an area of 536.8 thousand hectares crops affected, 57,600 houses collapsed, 22 highway interrupted, damaged highways 512km, transmission lines 1388km,[link widoczny dla zalogowanych], communication line 951km, 20 township hospitals were flooded, 182 schools, 49,000 students out of school classes, the direct economic losses of about 2.9 billion . 2003 年 6 October, Xianyang Station to water 3.939 billion m 3 , to sediment 091 000 000 t; Lintong stations to water, 7.093 billion m 3 , and sediment volume 294 000 000 t; Huaxian stations to water, 7.525 billion m 3 , and sediment volume 298 000 000 t. 2003 before the flood season Tongguan elevation is 328.78m, 7 月 25 日 Tongguan water level had reached 329.10m, 8 Tongguan elevation for the last ten days before the flood 328.79m, Weihe 6 peak, the October 19 Tongguan elevation to 327.94m, compared with pre-flood reducing 0.85m. 2003, after the flood, higher than the lower Weihe River great changes took place before the flood season, beach widespread deposition, deposition thickness at about 0.4m, the maximum thickness of deposition for the Yang section office (Wei silt 16 (b)) of 1.5m; main channel erosion occurs, generally higher than pre-flood river channel broadening of 50 ~ 100m, the local river broadening the 100 ~ 200m, thalweg points down before the flood season generally higher than 0.5 ~ 1m, deep local reach 2m above, Figure 5 before and after the flood compared Huaxian stations measured cross section shows that the flood silt beach properties brush slot. Weihe River in 2003 (Wei-silt 37 - Wei bar 4) were washed sediment 0.1693 million m 3 , changes in the performance section for the red tank silt beach; along it was expressed as two red, the middle silt, such as Figure 6.

Figure 52 003 Love County, a large cross section through real changes of erosion
Figure 6 Lower Weihe River in 2003 and scour along the change
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