River flow and its controlling factors
4.9. 1 Caotan Village and Bridge Drainage
The river water on the bridge leaks and the groundwater under the bridge overflows. The bridge has become a turning point in the relationship between river water and groundwater recharge and drainage in Heihe Plain. Caotanzhuang water control project is built between Yingluo Gorge and the bridge, and the river diversion is mainly concentrated in the reach from Yingluo Gorge to Caotanzhuang. The leakage of the river above Caotanzhuang is relatively stable, but it changes greatly due to the fluctuation of Caotanzhuang flow. Therefore, the discharge of Caotanzhuang is mainly controlled by the inflow of Yingluo Gorge and the diversion of the river above Caotanzhuang, and it is also affected by the manual opening and closing of Caotanzhuang flood gate. The flow of the bridge is mainly controlled by the flow of Caotanzhuang and the leakage of the lower channel of Caotanzhuang.
The mountain runoff of Heihe River is controlled by Yingluoxia Hydrological Station, and its runoff basically represents the runoff of Qilian Mountain. The annual runoff of Yingluoxia has changed periodically for many years, and it is generally stable, with no obvious upward and downward trend. However, in the past 20 years, the runoff has been in a period of long-term fluctuation, and the discharge of Caotanzhuang and Bridge also shows a downward trend, and the discharge of Caotanzhuang and Bridge changes synchronously with the runoff of Yingluo Gorge (Figure 4. 45 and figure 4. 46). The monthly discharge of Caotanzhuang and Bridge and the monthly inflow of Yingluo Gorge are both quadratic functions of the coordinate origin (Figure 4. 47).
Figure 4. 45 Caotanzhuang, bridge flow curve, inflow from the inflow gorge, and diversion from the east-west main canal.
Figure 4. 46 Duration curve of monthly inflow of Yingluo Gorge and monthly discharge of Caotanzhuang and Bridge (1998 ~ 2000).
The annual intake of the canal is not enough to significantly affect the annual flow of the bridge, but the monthly intake changes greatly, and the control function of the water control project has a great influence on the monthly flow, especially in the season when the inflow is small and the intake is large (such as spring and autumn), which often makes Caotanzhuang have no or small water discharge, but all the water leaks along the way, resulting in the interruption of the river course of the bridge, which can last for 2-5 months (Table 4.
The comprehensive influence of Yingluo Gorge inflow and canal diversion on bridge discharge can be reflected in the influence of Caotanzhuang discharge. There is a quadratic statistical relationship between the monthly discharge of the bridge and the monthly discharge of Caotanzhuang (Figure 4. 48). When the monthly flow of Caotanzhuang is less than 0. 13× 108m3, all the water along the way will be lost, and only when it is greater than 0. 13× 108m3 water will be discharged through the bridge channel.
Figure 4. 47 Relationship curve between monthly discharge of Caotanzhuang, Bridge and Yingluo Gorge (1998 ~ 2000).
The inflow of Yingluo Gorge is 198 1 ~ 2000, with an average of 16. 48× 108m3/ a, and the flow of Caotanzhuang and Bridge is 7. 52 × 108, 5. 3 1× 65438 respectively. The inflow of the river between Yingluo Gorge and the bridge is 4. 50× 108m3/ a, and the water diversion capacity of the main canal is 6. 52× 108m3/ a, and the bridge flow is 5. 3 1× 108m3/ a, accounting for 27% and 40% of the total respectively.
Figure 4. Relationship curve of monthly discharge (1998 ~ 2000) between Bridge 48 and Caotanzhuang.
Table 4. Analysis Table of the Relationship between Yingluoxia Bridge and 4 1 River Water Consumption and Discharge
Note: The water diversion of main canal and the evaporation from Caotanzhuang to Da Qiao are the equilibrium calculation values.
4.9.2 Discharge of Justice Gorge
Zhengyixia is the geomorphological boundary line in the middle and lower reaches of Heihe River, and it is also the connection point of water resources in the middle and lower reaches. Because the groundwater in Zhengyixia has been completely drained, the runoff of Zhengyixia can represent all the water resources from the middle reaches to the lower reaches of Heihe River, which is not only the sign of water inflow and water consumption in the middle reaches, but also the support of water inflow and water consumption in the lower reaches.
The discharge of Zhengyi Gorge is mainly controlled by the incoming water from Yingluo Gorge, water diversion from irrigation area and groundwater overflow, and is also affected by river water leakage. The annual runoff of Zhengyixia is closely related to the inflow of Yingluoxia-Zhengyixia reach (Yingluoxia inflow and groundwater overflow) (Figure 4. 49), the interannual variation of the discharge of Zhengyi Gorge inherits the characteristics of Yingluo Gorge, which is approximately linear (Figure 4. 50) and change almost synchronously. However, since the 1980s, due to the sharp decline of groundwater overflow, the discharge of Zhengyi Gorge deviated from the stable trend of inflow of Yingluo Gorge, and developed synchronously with groundwater overflow. From fig. 4. 49. It can also be seen that the low water year of Yingluo Gorge is just the high water year of groundwater overflow, and the regulation of groundwater overflow keeps the inflow of Zhengyi Gorge relatively stable during this period.
The monthly discharge of Zhengyi Gorge changes greatly, and the corresponding relationship between peak and bridge monthly discharge is good, but the relationship between valley area and water diversion is poor (Figure 4.5438+0, Figure 4. 52).
The annual discharge of Justice Gorge is (5. 14 ~17.55) × 108m3, annual average emission10. 24× 108m3, with an average monthly emission of 0. 08 × 108.
Figure 4. 49 Relationship curve of Zhengyi Gorge discharge, Liuying Gorge inflow and groundwater overflow.
Figure 4. 50 The relationship between the annual runoff of Zhengyixia and Liuyingxia (1950 ~ 2002).
Figure 4. Monthly discharge duration curve of Zhengyixia Bridge (1998 ~ 2000)5 1.
Figure 4. 52 monthly discharge relation curve of Zhengyixia Bridge (1998 ~ 2000)
4.9.3 Zhengyixia-Juyanhai Flow
The whole line below Zhengyixia is the river leakage reach, and the average river leakage from 1998 to 2000 is 3. 66× 108m3/ a, in which the leakage of the upper reaches of Shaomaying River is 1. 16× 108m3/ a, Shaomaying to Langlang. Shaomaying is the dividing line between Ding Xin Valley and Ejina Plain, and Langxin Mountain is the bifurcation of Heihe River from single channel to double channel. Langxin Shan Zhinan receives the upstream water from a single channel, and its north side discharges from the East and West Rivers to the downstream. There are many branches along the way to divert the river water, which makes it difficult for the water discharged from the downstream channel to flow into Juyan Sea since the 1990s.
4.9.3. 1 Shaomaying-Langxinshan Flow
The discharge under Shaomaying and Langxin Mountain is mainly controlled by the discharge under Zhengyi Gorge, the water diversion in Ding Xin Irrigation District and the water consumption in Dongfeng Field, and is also affected by seepage. In recent 20 years, the annual discharge of Zhengyixia has been decreasing, which makes the annual discharge of Shaomaying and Langxinshan decrease as a whole, and both of them increase and decrease synchronously, and the difference is stable for many years, which is the leakage and water consumption of diversion irrigation (Figure 4. 53). The relationship between the discharge of Shaomaying and Langxinshan and the discharge of Zhengyixia, whether annual runoff or monthly average discharge, is approximately a quadratic curve change (Figure 4. 54 and figure 4. 55), which shows that the discharge of Shaomaying and Langxin Mountain decreases with the increase of the discharge of Zhengyi Gorge, which conforms to the law of runoff growth and leakage rate decline, and shows that the annual or monthly discharge of Shaomaying and Langxin Mountain is obviously affected by river leakage. The relationship curve between the monthly discharge of Shaomaying and Langxinshanhe River and the monthly discharge of Zhengyi Gorge is scattered at small discharge points, but relatively concentrated at large discharge points, which shows that the river diversion has a great influence on the small discharge of the river, making the cutoff time of Shaomaying and Langxinshanhe River obviously longer than that of Zhengyi Gorge, and the further downstream, the longer the river cutoff time.
According to the river flow data during the centralized water transfer in Heihe River (July ~165438+1October, 2002), the daily flow of Langxin Mountain lags behind Zhengyi Gorge for about 3 days, and the changes of peak and valley values are basically the same (Figure 4. 56). The daily discharge of Langxin Mountain and Zhengyixia is roughly cubic polynomial, and the distribution of points is scattered, which is related to the lag effect of runoff. According to the daily flow scatter chart drawn with a delay of 3 days, the daily flow of Langxin Mountain and Zhengyixia presents a linear relationship through the coordinate origin, with an increase rate of about 52%, that is, the average runoff dissipation is 48% (Figure 4. 57).
Figure 4. 53 Annual Runoff Duration Curve of Yingluo Gorge, Zhengyi Gorge, Shaomaying and Langxin Mountain.
Figure 4. 54 curve of annual discharge of Shaomaying, Langxinshan and Zhengyixia.
The average annual flow of Shaomaying from 1998 to 2000 was 5. 57× 108m3, and the annual cutoff time is generally 2-5 months. From 1988 to 2000, the average annual flow of Langxin Mountain was 3. 8 1× 108m3, and the annual cutoff time is generally 4-6 months.
The discharge of centralized water transfer in 4.9.3.2 and its inflow into the lake
The East and West Juyan Seas shrink until they are exhausted, which is the result of the continuous decrease of the flow in Zhengyi Gorge and the increase of the water consumption in the lower reaches.
In order to curb the further deterioration of the ecological environment in the downstream areas and improve the prominent contradiction of water use, water transfer was organized in 2000, and Heihe water has entered Dongjuyanhai for many times (Table 4. 42). The water was transferred from August to June in 2000, all of which flowed through Shaomaying, and was replenished to Ding Xin Irrigation District and Dongfeng Reservoir successively. In September of 13, Langxin Mountain flowed, and after water division, it was discharged along the east and west rivers, reaching 30km of Xihe River and 30km of Donghe River 130km below Langxin Mountain, which realized inter-provincial water transfer for the first time and created the unification of Heihe resources. During the water transfer from May 38, 2006 to August-June, the water discharge under Zhengyixia and Langxin Mountain was 2. 3× 108m3 and 0. 76× 108m3, with interval leakage of 67%. /kloc-In September of 0/7, the water flowed to the town of Dalaikubu, but it never happened. From July to June, 2002, water was transferred three times. The total displacement of Zhengyi Gorge and Langxin Mountain is 4. 4× 108m3 and 3. 08× 108m3, and the interval leakage loss is 30%. All the water was sent to the East Giant Rock Sea for three times, and the seawater volume of the East Giant Rock reached 0. 49 times in September. In July 2003, the water was transferred from 10 to 20, and the discharge of Zhengyixia and Langxinshan was 0. 48 × 108m3 and 0. 08× 108m3, with interval leakage of 83%. The water head 19 reaches Langxin Mountain, and the current is still 650 from Dongjuyanhai on the 23rd.
Figure 4. Relationship curve of monthly discharge of Shaomaying, Langxinshan and Zhengyixia.
Figure 4. 56 Duration curve of daily flow in Langxin Mountain and Zhengyixia (July 2002 ~165438+1October).
Figure 4. 57 Relationship curve of daily discharge between Langxinshan and Zhengyixia during critical dispatching period.
The centralized water transfer from July 8 to 28, 2002 was the largest of all previous water transfers. The water transfer period coincided with the continuous rainfall in the upper reaches of Heihe River, resulting in three flood peaks in Yingluoxia section during the closed period. The flood crest at 10 discharges from Yingluo Gorge at 15, reaches Zhengyi Gorge at 2: 48 at 13, and flows downstream in the east-west direction at 0: 00 at13. /kloc-at 9: 00 on October 4th, the head of Xihe River reached Aobaozha, and at 9: 33, the head of Donghe River flowed to Ejina Oasis. Due to the large inflow, the first, second and seventh rivers of Donghe River have all passed through the water, and the first and second rivers reach Dongju Salt Sea 17. The distances between Yingluo Gorge, Zhengyi Gorge, Langxin Mountain and Dongju Salt Sea are 185km, 164km and 169km respectively. 77 km/h, 3. 63km/h and 1. 50 kilometers per hour. About 20 hours after the head enters the East Juyan Sea, the average propulsion speed of the head is 30 m/h; 18 17:30, the width of the lake is about 5km, the water surface area is 13km2, the inflow is 50m3/ s, and the inflow is 400×104m3; 28th 17: 30, water surface area 18. 5km2, the inflow into the lake is about 4m3/ s, and the inflow into the lake is1100×104m3 (Table 4. 44).
Table 4. 42 Statistics of displacement during centralized water transfer from 2000 to 2003
The measured data of the above-mentioned centralized water transfer periodic system provide an important basis for studying the underwater flow and the law of entering the lake in the lower reaches of Heihe River. The lower reaches of Heihe River have a long leakage path and a large amount of leakage, but the leakage rate and runoff still conform to the law of large runoff and small leakage rate (Figure 4. 17). The runoff of Zhengyi Gorge is (0.4 ~ 4.4) × 108m3, and the leakage rate is 83% ~ 30%. From Zhengyi Gorge to Langxinshan River, the river head travels faster along the river, but below Langxinshan Mountain, due to the influence of diversion and seepage, the river head travels slower along the river, especially below Ejina Banner. For example, in July 2002, it took 33.5 hours for the water head to drain from Langxin Mountain to Laikubu Town at 130km, while it took 79.5 hours for Dalekubu Town to reach Dongju Salt Sea at 39km. In the period of small discharge of Zhengyi Gorge, the influence of seepage along the way can't make water flow into Juyan Sea or even reach Langxin Mountain, so if you want to send water into the lake, you must have enough discharge. The evaporation in the lake area is as high as 3 700 mm In order to maintain a certain lake capacity, it is necessary to have enough inflow to balance the loss of water such as evaporation and leakage. In 2002, the second inflow of the East Giant Salt Sea made the water area reach 23. 8km2, but it dried up again on May 265,438+0, 2003 due to the lack of follow-up water supply.
Renovating Heihe River to supply water for the people will effectively alleviate the further deterioration of the downstream ecological environment. During 1995 ~ 1999, the Langxin Mountain in the lower reaches of Heihe River was cut off for about 230 ~ 250 days. After the implementation of unified water transfer, the water supply was stopped for 2 12 days in 2000, 203 days in 2006, 5438+0 days, and 2002 176 days, and the water supply days were reduced by 40 ~ 70 days. In 2002, water was sent into the lake, and groups of rare animals, such as white swan, grey goose and yellow duck, migrated to the lake area. Droves of camels galloped from different directions to the water's edge, which was very spectacular and exciting. However, how to transfer water scientifically and effectively, how to rationally allocate the amount of water transferred to the downstream, whether to maintain the amount of water in the lake area, and how much can be maintained are all problems that need to be studied and solved urgently.
Table 4.43 Statistical Table of River Flow and Velocity during Centralized Water Transfer in July 2002
Table 4. 44 Statistical Table of East Juyan Sea Area and Water Quantity during Centralized Water Transfer in July 2002