The Prototype Testing Study of Sanmenxia Reservoir doc15.doc

此文档收集于网络，如有侵权，请联系网站删除The Prototype Testing Study of Sanmenxia ReservoirLi Xingjin, Ji Li, Wang Gui e, LiuJunAbstract: This article through collecting the data of prototype testing on Sanmenxia reservoir in 2003 to 2007, summarizes the character of erosion-deposition in Sanmenxia reservoir area and the change of Tongguan elevation, and analyses the effect on erosion-deposition of Xiaolangdi reservoir area, which caused by operation of Sanmenxia reservoir in flood season.Key words: Sanmenxia reservoir Sediment Tongguan elevationForewordSanmenxia reservoir locates at the end part of the middle Yellow River, and it is the first large size controlling multi-purpose project building on Yellow River. The main function of the reservoir was flood control, and it had some other functions such as ice flood control, irrigation, water supply, power supply and so on. The first construction of Sanmenxia dam was founded in Apr 1957, impounded in Sep 1960. The reservoir began its operation after main structure finished in Apr 1961, from then on, it had been rebuild two times in order to increase discharge capacity and lessen the deposition in reservoir area. Now it has 12 bottom holes, 12 deep holes, 2 tunnels and 1 pipe, total has 27 holes for flood and sediment discharge, the discharge capacity of reservoir is 9701m3/s when water level at 315m(not include generator discharge capacity). The hydroelectric power station of Sanmenxia reservoir has seven generators; total installed capacity is 410 MW. 1 The reason of the Prototype Testing Tongguan elevation means the water level of Tongguan section when 1000 m3/s flow pass through. Tongguan elevation can be used as a signal of channel deposition at join section of Yellow River and Wei River, the change of Tongguan elevation can reflect the change of erosion and deposition at the lower Wei River and Xiaobeiganliu reach of Yellow River a certain extent. Sanmenxia dam is on the downstream of Tongguan section for 113.5km. At beginning of reservoir operation, the reservoir area occurred severe deposition for discharge capacity absence and some other reasons, and Tongguan elevation had a rapid rise. After that, with discharge capacity enlarged and operation mode remodeled of the reservoir, Tongguan elevation dropped and kept stable state. (See chapter 3.3 )From the mid-1980s, the annual flow of Tongguan station which now is the inflow station of Sanmenxia reservoir, especially flood season flow, had great decrease (See table 1), and Tongguan elevation had a durative rise. For the sake of controlling and reducing Tongguan elevation, many measures have been adopted, and the prototype testing on Sanmenxia reservoir is one of them.1.1 Fig.1 The Schematic Diagram of Sanmenxia Reservoir AreaThe prototype testing on Sanmenxia reservoir began from 2003, now it is still keeping. Compared with former operation mode, the highest operation water level of Sanmenxia reservoir was decreased from 324m to 318m, and in flood time of flood season, discharge with max discharge capacity instead of discharge with water level controlled.2 Water-sediment characteristics and operation of reservoir in testing period1.2 2.1 Water and sediment volume of inflow of the reservoirDuring the 5 years, the average annual flow is 23.15 billon m3, sediment volume is 0.35 billon tone, respectively reduce 42.3% and 66.6% compare with the long term average water and sediment volume of 1974 to 1985, and respectively reduce 6.9% and 50.5% compare with 1986 to 2002, belong to low water and sediment series (see table 1). Form the ratio of water and sediment of flood season to a water year, the water volume in flood season accounts for 48.9%, the sediment volume in flood season accounts for 77.9%, these ratios are nearly with ratios in 1986 to 2002. Table 1 Monthly water and sediment volumes in flood season of 2003 to 2007 TimeJul AugSepOctJulOctYearWater volume（108m3）2003200715.9626.0536.4234.72113.2231.51974198544.4263.3568.4360.1236.3400.91986200225.7636.9329.4518.42110.6248.5Compare with 19741985（%）-64.1-58.9-46.8-42.2-52.1-42.3Compare with 19862002（%）-38.0-29.523.788.52.4-6.9Sediment volume（108t）200320070.45681.0870.65020.53582.7303.503197419852.4693.5741.8660.9628.87110.48198620021.7662.4560.78990.2265.2387.071Compare with 19741985（%）-81.5-69.6-65.2-44.3-69.2-66.6Compare with 19862002（%）-74.1-55.7-17.7137.1-47.9-50.5Analyzing the source composing of water and sediment, the average water and sediment volume of Longmeng station account for total volumes of four stations (Longmeng, Huaxian, Hejin, Nanronghua station) respectively 73.2% and 52.3%, average sediment concentration is 9.8 kg/m3. The average volume of water and sediment of Huaxian station account for total volume of four stations respectively 23% and 44.6%, the average sediment concentration is 26.6 kg/m3.(See table 2)Table 2 The statistics of water and sediment volume of Sanmenxia reservoir area stations in 2003 to 2007ItemsLongmengHuaxianHejinNanronghuaSummationTongguanWater volume（108m3）Average in 5 year177.655.674.4214.813242.5231.5Account for total(%)73.223.01.82.0100Sediment volume(108t)Average in 5 year 1.7371.4830.0050.0963.3213.503Account for total(%)52.344.60.22.9100Average sediment concentration（kg/m3）9.826.61.1319.913.6915.131.3 2.2 Statement of reservoir inflow floodDuring testing period, the average reservoir annual inflow flood peak is 3174 m3/s, only occupy 46.6% of long-term average (6805 m3/s). Especially, the annual flood peak in 2004, 2006, 2007 does not get 3000 m3/s even, and both volume of water and sediment in flood are small.(See table 3)Table 3 The statistics of water and sediment volume in flood time in 2003 to 2007YearFlood timem.ddm.ddPeak volumeWater volume（108m3）Sediment volume（108t）Flow（m3/s）Sediment concentration（kg/m3）20038.18.4211081.83.9040.21928.259462.2959.1910.19422043.068.871.77120048.218.2522903666.4351.06420058.148.24219058.613.510.40459.3010.11448036.826.140.588620068.269.8260058.817.370.52039.129.25240050.316.790.250320077.248.4212085.214.050.38398.98.15213053.57.8590.271710.710.26228031.424.810.2861Remark：flood means the flow which peak flow more than 2000 m3/s at Tongguan stationAnalyzing the inflow distribution of water and sediment volume at different flow grade in flood season in 2003 to 2007, the most volumes of water or sediment occur at 10001500m3/s flow grade, the least is at more than 4000m3/s flow level (Fig. 2). From the figure, we also can find, the average sediment concentration is small when inflow less than 1500 m3/s, because these range flow is the basic flow of upper river. Most flow that more than 1500m3/s are caused by storm water, so that, the average sediment concentration have a notable increase, and the highest average sediment concentration happens on 25003000m3/s flow grade.1.4 Fig.2 The inflow distributing of average water and sediment volume at different flow grade in flood season in 2003 to 20071.5 2.3 Reservoir operation in testing period2.3.1 Reservoir operation in non-flood seasonDuring the testing period, the control level of reservoir have notable different with in 1973 to 2002. The reservoir has two tasks in 1973 to 2002, ice-flood control in winter and irrigation in spring. For these two tasks, the reservoir water level are in some occasions higher than 318m, there is 97 days in one non-flood season in those year normally, occupy 39.6% of non-flood season days. In past 5 years, have no water level higher than 318m, the mainly control level concentrated on 315 to 318m, is occupies 87.2% of non-flood season days.2.3.2 Reservoir operation in flood seasonBefore 2003, especially before Xiaolangdi reservoir impounded, in order to avoid down river channel deposition that caused by low flow with high sediment concentration, the reservoir always maintain water level at 298 to 300m when discharge in flood time. In flood time of testing period, reservoir operation mode is “emptying the reservoir and discharge completely”, that means, before flood coming to the dam, open all floodgates and decrease reservoir water level until empty. During past 5 years, the lowest water level arrived at 284m that dropped 14 to 16m compared with before. The complete discharge operated 19 times during the 5 years, and the total operation time is 74 days.3 Result analysis of reservoir prototype testing 1.6 3.1 The change of erosion and deposition in reservoir areaThe reservoir area has formed regulation of erosion and deposition gradually that silting in non-flood season and scour in flood season after using operation mode of “Xuqingpaihun” mode after the end of flood season in 1973 (Xuqingpaihun operation mode is that storing clear water at normal time under the profitable or limited water level and releasing muddy water in flood time). With various water-sediment conditions and different operation modes, the volume and distribution of erosion-deposition had biggest change too.During the testing period, the major area of sedimentation is on the down reach of the Huangyu 30th section, the volume of sedimentation of the major area is 93.2% of total deposition volume. Compared with testing before, the main sedimentation area move down 26km (See Fig. 3), and close to the dam. The reach between Tongguan and Guduo, changed from deposition to erosion. Calculated with the testing data, and validated by the simple Saint-Venant equations, the farthest backwater effect approach to the Huangyu 33rd section, that is 33km apart from the sixth of Tongguan section. Up from the Huangyu 33rd section, the channel has become the natural river channel instead of reservoir character. At common conditions, the backwater distance is under the Huangyu 31st sections, between the Huangyu 31 to 33 sections, this reach belong to the variable backwater region. The farthest backwater effect in flood season approach the Huangyu 24th section, the channel upwards of this section belong to natural river channel.Fig. 3 Schematic diagram of the sections in reservoir areaTable 4 Distribution statistic of alluvial volume at different period in non-flood seasonReachTime ItemDam pointHuangyu section 12 Huangyu section 1222Huangyu section 2230Huangyu section 3036Huangyusection 3641（3rd）Total alluvial volume（108m3）1974-1985Alluvial volume（108m3）1.272.984.086.121.4115.86Ratio to total alluvial volume（%）8.0 18.825.738.68.91986-1995Alluvial volume（108m3）0.463.535.213.130.5212.85Ratio to total alluvial volume（%）3.627.540.424.44.11996-2002Alluvial volume（108m3）0.0291.6724.4582.4440.0928.695Ratio to total alluvial volume（%）0.319.251.3 28.1 1.12003-2007Alluvial volume（108m3）0.56141.4661.7680.3243-0.04984.07Ratio to total alluvial volume（%）13.836.043.4 8.0-1.2During the testing period, under Tongguan section, the sediment erosion volumes of each part of reservoir area are bigger than the volume deposited at same parts. The accumulative net scour volume of sediment is 0.125 billion m3. The main reach of scour below at Dayudu section, occupy 98% of total scour volume in flood season (See table 5), the scour parts in flood season correspond with the silting parts in non-flood season. Table 5 Distribution statistic of alluvial volume at different period in flood seasonReachTime ItemDam pointHuangyu section 12 Huangyu section 1222Huangyu section 2230Huangyu section 3036Huangyu section 3641（3rd）Total alluvial volume（108m3）Total scour volume（108m3）1974-1985Alluvial volume（108m3）-1.1-2.37-3.99-6.28-1.53-15.270.59Ratio to total alluvial volume（%）7.215.526.141.1101986-1995Alluvial volume（108m3）-0.12-3.42-4.96-2.68-0.11-11.291.56Ratio to total alluvial volume（%）1.130.343.923.71.01996-2002Alluvial volume（108m3）0.016-1.456-4.311-2.1990.028-7.920.773Ratio to total alluvial volume（%）-0.218.454.427.8-0.42003-2007Alluvial volume（108m3）-0.8205-1.719-2.035-0.6385-0.1086-5.32-1.25Ratio to total alluvial volume（%）15.432.338.312.02.01.7 3.2 Characters of sediment discharge of reservoir As character of Yellow River, the sediment comes into reservoir with flood that formed by storm water. Discharge completely when flood flow in, with kinetic energy of flood and the water level dropped down, can occur alongshore erosion and backward erosion, so that , the discharge in flood time of flood season not only can release the sediment holding by inflow, but also can move silting sediment out, and get high sediment discharge efficient. During past 5 years, except three times water and sediment regulations of Yellow River, the annual average day which discharge completely is 12.8 days in a water year, occupy 10.4% of days in flood season. The average sediment volume out of reservoir during the complete discharge period is 0.283 billion tons, it is 76% of total annual average sediment volume out of reservoir in flood season. (See table 6)Table 6 Statistic of sediment discharge volume in flood season in 2003 to 2007YearComplete discharge period（108t）Flood season（108t）Ratio of complete discharge to flood season（%）Flow inDischargeNet outFlow inDischargeNet outOutNet out20033.357 6.4823.1255.3277.756 2.429 83.6 129 20041.050 2.0691.0192.3162.724 0.408 76.0 250 20051.430 3.1271.6972.4773.611 1.134 86.6 150 20060.281 1.1560.8751.6972.075 0.378 55.7 231 20070.33361.3150.98141.8312.482 0.651 53.0 151 200320071.290 2.8301.5392.730 3.730 1.000 75.9 154 In one flood event, the scour efficiency by complete discharge has the rule that it will be attenuation with discharge time detains. Ordinarily, the intensity scour happens in the beginning of complete discharge 3 to 5 days, along with discharge time last, the scour action weakened rapidly, and then the outflow sediment concentration is similar with inflow even if the scour flow rate increase than before.1.8 3.3 Change of Tongguan elevation From long time information of history, the riverbed of Tongguan reach had slight rise with time. The geological drilling data indicated, in the past 1800 years, which from three kingdoms period to 1960, Tongguan riverbed had raised 16.5m, the annual average rise is 0.009m. From 1929 the year which Tongguan station have initial hydrology records, to 1960 the year dam was built, Tongguan elevation increased 1.98m, the annual average rise is 0.07m.At the beginning of Sanmenxia reservoir impoundment, because the discharge capacity was not enough and the mode of reservoir was unsuitable, the backwater effect even passed over the Tongguan station, the reservoir area was silted heavily, Tongguan elevation had a rapid rise. From 1973, the added and rebuilt discharge conduits were completed and begun to use in operation, the operation mode of reservoir changed to “Xuqingpaihun” mode, the rise of Tongguan elevation had been controlled. From 1973 to 1985, the Tongguan elevation, although there were undulations in one water year or several water years sometimes, get 326.64m in the end of flood season in 1985, and have the same volume with 1973s. After 1986, because of beginning operation of Longyangxia reservoir, which on the upper reaches of Yellow River and with operation mode that storing water in flood season and discharge water in non-flood season, and because of the decrease of runoff, Tongguan elevation grew fast. Since 1996, workings of dredging at Tongguan reach begun, and in that way, the rise of Tongguan elevation was kept within limits. However, Tongguan elevation had durative increase again for durative dry year, at end of flood season of 2002, the Tongguan elevation became 328.78m.Since the end of flood season of 2002, the prototype testing on Sanmenxia reservoir was started, at non-flood season, the highest reservoir water level was controlled lower than 318m. At the same time, water and sediment regulation on the Yellow River was hold for 5 years and several other methods were been operated to decreasing deposition, including cutoff at Dongluwan bend, warping tests in Lianbotan of Xiaobeiganliu reach of Yellow River, reduction Tongguan elevation test by using peach floods, watercourse coordination. With the effects of these comprehensive measures, Tongguan elevation dropped 1.05m until the end of flood season of 2007 upon lessened water-sediment conditions from upper reach, the annual average decrease volume is 0.21m.Table 7 Statistic of Tongguan elevation changing (at end of flood season)YearLast periodTongguan elevation（m）Changing range(m）StatementScopeAnnual averageThree kingdoms period19601800321.1416.50.009Geological profile information1929195930323.452.310.07Hydrology data1960196910328.655.200.52Reservoir impounded, flood detaintion mode197019734326.64-2.01-0.502Dam rebuilt1974198512326.6400Xuqingpaihun mode1986199510328.281.640.164Longyangxia reservoir impounded199620027328.780.500.071Durative dry year with lower water and sediment200320075327.73-1.05-0.21Prototype testing on Sanmenxia reservoir,water and sediment regulation on Yellow River4 Impacts on erosion and deposition of Xiaoliangdi reservoir areaSanmenxia reservoir loc