River runoff is the discharge amount for its upstream, and it is the water inflow for its downstream. Therefore, the river runoff not only reflects the basic situation of water inflow and water consumption in the upstream, but also affects the downstream. Whether water for living, production, ecological use, etc. can be guaranteed will have a major impact. The amount of river discharge is affected by natural factors such as the amount of river water in the upstream area, the amount of groundwater overflow, and the amount of water lost in the river (the amount of water lost in the river is mainly seepage loss, and the amount of evaporation is small, which has little impact on the amount of discharge). It is also affected by the human-built Control of the amount of water diverted and stored by water conservancy projects such as water conservancy projects and reservoirs; in different river sections, due to the influence of natural and human factors and the degree of control, the amount of water discharged varies greatly. According to the water replenishment and water consumption characteristics of river runoff in the plain area of ??the main stream of the Heihe River, as well as the mutual replenishment and drainage relationship between river water and groundwater, the river channel is divided into three sections (i.e., Yingluo Gorge - Heihe Bridge - Zhengyi Gorge - Juyanhai) for river discharge. Analysis and study of quantities and their controlling factors.
4. 9. 1 Caotanzhuang and the amount of leakage from the bridge
The river water leaks above the bridge, and the groundwater under the bridge overflows. The bridge becomes the replenishment and drainage relationship between river water and groundwater in the plain area of ??the main stream of the Heihe River. turning point. The Caotanzhuang water conservancy project is built between Yingluo Gorge and the bridge. The channel water diversion is mainly concentrated in the section from Yingluo Gorge to Caotanzhuang. The river water leakage above Caotanzhuang is relatively stable, and the water leakage below Caotanzhuang changes due to the fluctuation of water discharge below Caotanzhuang. larger. Therefore, the discharge amount from Caotanzhuang is mainly controlled by the water inflow from Yingluo Gorge and the water diversion volume from the channel above Caotanzhuang, and is also affected by the artificial opening and closing of the Caotanzhuang floodgate; the discharge amount from the bridge is mainly controlled by the discharge amount from Caotanzhuang and The amount of water leakage from the river below Caotanzhuang.
The runoff of the Heihe River from the mountain is controlled by the Yingluoxia Hydrological Station, and its runoff basically represents the yield of the Qilian Mountains in the region. The annual runoff in Yingluoxia has been changing cyclically for many years, and is generally relatively stable with no obvious upward or downward trend. However, in the past 20 years, the runoff has been in the declining phase of long-term fluctuations. Affected by this, the discharge of Caotanzhuang and the bridge has also declined. trend, and the discharge volume of Caotanzhuang and Daqiao and the runoff of Yingluoxia all show synchronous changes (Figure 4.45, Figure 4.46); the monthly discharge of Caotanzhuang and Daqiao and the monthly water flow of Yingluoxia all show a trend of crossing the origin of the coordinates. Quadratic function relationship (Figure 4.47).
Figure 4. 45 The discharge volume from Caotanzhuang and the bridge and the water inflow from Yingluo Gorge and the water diversion volume curve of the East-West Main Canal
Figure 4. 46 The monthly water volume from Yingluo Gorge and Caotanzhuang and Caotanzhuang Monthly discharge volume of the bridge (1998-2000) Duration curve
The annual water diversion volume of the channel is not enough to have a significant impact on the annual discharge volume of the bridge, but the monthly water diversion volume changes greatly, and coupled with the control effect of the water conservancy project, it has a significant impact on the bridge's annual discharge volume. The monthly discharge has a great influence, especially in seasons with small water inflow and large water diversion (such as spring and autumn). Caotan Village often has no discharge flow or the discharge volume is small and all the water leaks along the way, causing the bridge river channel to be cut off. The current interruption can last for 2 to 5 months (Table 4.21).
The comprehensive impact of water inflow from Yingluoxia and channel water diversion on the discharge of the bridge can be reflected in the impact of water discharge from Caotanzhuang on it. There is a quadratic function statistical relationship between the monthly water release volume of the bridge and Caotanzhuang (Figure 4.48). When the monthly water release volume of Caotanzhuang is less than 0.13×108m3, all water is lost along the way. Only when it is greater than 0.13×108m3, the water will pass through the bridge river channel. Drainage.
Figure 4. 47 Relationship curve between Caotanzhuang and Daqiao monthly discharge and Yingluoxia monthly water supply (1998-2000)
The average water supply in Yingluoxia from 1981 to 2000 The discharge volume from Caotanzhuang and Daqiao is 7.52 × 108 and 5. 31×108m3/a respectively, accounting for 46% and 32% of the water inflow from Yingluoxia respectively. The infiltration volume of river water between Yingluoxia and the bridge is 4.50×108m3/a, the water diversion volume of the main canal is 6.52×108m3/a, and the discharge volume of the bridge is 5.31×108m3/a, accounting for 27% and 40% of the total volume respectively. % and 32%, that is, about 70% of the Heihe River water in this section is consumed by seepage and water diversion, and about 30% is discharged through the bridge (Table 4.41).
Figure 4. Relationship curve of monthly discharge between 48 Bridge and Caotanzhuang (1998-2000)
Table 4. Water inflow and consumption of the river between 41 Yingluoxia-Daqiao, Analysis table of relationship between discharge volume
Note: The water diversion volume of the main canal and the evaporation volume between Caotanzhuang and Daqiao are equilibrium calculated values.
4. 9. 2 Discharge of Zhengyi Gorge
Zhengyi Gorge is the landform boundary between the plains in the middle and lower reaches of the main stream of the Heihe River, and is also the connection point of water resources in the middle and lower reaches; due to groundwater All the water has been released in Zhengyi Gorge, so the runoff in Zhengyi Gorge can represent all the water resources in the main stream of the Heihe River from the middle reaches to the lower reaches. It is not only a symbol of water inflow and water consumption in the middle reaches, but also the basis for water release and water use in the lower reaches.
The amount of water released from Zhengyi Gorge is mainly controlled by the amount of water coming from Yingluo Gorge, the amount of water diverted from the irrigation area, and the amount of groundwater overflow. It is also affected by the amount of river water seepage. The annual discharge volume of Zhengyi Gorge is closely related to the inflow of the river section from Yingluo Gorge to Zhengyi Gorge (water inflow from Yingluo Gorge and groundwater overflow volume) (Figure 4.49). The interannual changes in the discharge volume of Zhengyi Gorge inherit the characteristics of Yingluo Gorge. The characteristics of water inflow from the gorge are approximately linear (Figure 4.50) and change almost simultaneously; however, due to the sharp attenuation of groundwater overflow since the 1980s, the discharge from Zhengyi Gorge has deviated from the water inflow from Yingluo Gorge. It has a stable trend and is developing simultaneously with the amount of groundwater overflow. It can also be seen from Figure 4.49 that the dry years for the water inflow from Yingluoxia coincide with the rich years for groundwater overflow. The regulating effect of groundwater overflow keeps the discharge from Zhengyi Gorge relatively stable during this period.
The monthly water release volume of Zhengyixia Gorge varies greatly. The peak section has a good correspondence with the monthly water release volume of the bridge. The valley area has a poor relationship due to the influence of water diversion (Figure 4. 51, Figure 4. 52).
The annual water release volume of Zhengyi Gorge is (5. 14 ~ 17. 55) × 108m3, the multi-year average annual water discharge volume is 10. 24 × 108 m3, and the multi-year average monthly water discharge volume is 0. 08 × 108 ~ 1. 22 × 108m3, annual flow interruption time is 1 to 2 months.
Figure 4. 49 The relationship curve between the discharge amount of Zhengyi Gorge and the water inflow and groundwater overflow from Yingluo Gorge
Figure 4. The annual discharge amount of 50 Zhengyi Gorge and the annual water volume of Yingluo Gorge ( 1950～2002) Relationship diagram
Figure 4. 51 Monthly discharge of Zhengyi Gorge and the bridge (1998～2000) Duration curve
Figure 4. 52 Monthly discharge of Zhengyi Gorge and the bridge Amount (1998～2000) Relationship Curve
4. 9. 3 Discharge of Zhengyi Gorge-Juyanhai River Channel
The entire line below Zhengyi Gorge is a section of river water seepage. The average seepage loss of river water from 1998 to 2000 was 3.66×108m3/a, of which the infiltration amount in the section above Shaomaying was 1.16×108m3/a, and the infiltration amount in the section between Shamaying and Langxinshan was 1.16×108m3/a. The amount of river water infiltration in the section below Langxin Mountain is 1. 45×108m3/a. Shaomaying is the boundary between Dingxin River Valley and Ejina Plain, and Langxin Mountain is the bifurcation of the Heihe River from a single channel to a double channel. To the south of Langxin Mountain, a single river channel receives water from the upstream. To the north, water is diverted from the east and west rivers to the lower reaches. There are many branches and distributary rivers along the way. As a result, the downstream river channel has not been abundant since the 1990s. The amount of discharged water has been difficult to flow into the Juyan Sea.
4. 9. 3. 1 Shaomaying-Langxin Mountain Discharge
The water discharge from Shaomaying and Langxin Mountain is mainly affected by the discharge from Zhengyi Gorge and the water diversion volume from Dingxin Irrigation District. , The control of water consumption in the Dongfeng farm area is also affected by the amount of river water seepage loss. In the past 20 years, the annual discharge of Zhengyi Gorge has continued to decrease, causing the annual discharge of Shaomaying and Langxinshan to show an overall decreasing trend. The two have increased and decreased simultaneously. The difference has been relatively stable for many years. This is due to the leakage and diversion of irrigation in their intervals. Water consumption (Figure 4.53).
The relationship between the discharge volume of Shaomaying and Langxinshan and the discharge volume of Zhengyi Gorge, whether it is annual runoff or monthly average flow, is approximately a quadratic curve change (Figure 4.54, Figure 4.55), indicating that Shaomaying The discharge rate of Langxinshan Mountain decreases with the increase of discharge volume of Zhengyi Gorge, which is in line with the law of increase in runoff volume and decrease of seepage rate. It shows that the annual or monthly discharge volume of Shaomaying and Langxinshan Mountain is obviously affected by the seepage loss of the river. The relationship curve between the monthly discharge of Shaomaying and Langxinshan and the monthly discharge of Zhengyi Gorge shows that the points in the small flow section are scattered and the points in the large flow section are relatively concentrated, indicating that channel water diversion has a greater impact on the small flow of the river. This influence As a result, the drying time of Shaomaying and Langxinshan rivers is significantly longer than that of Zhengyi Gorge, and the further downstream, the longer the drying time of the rivers.
According to the river flow data during the centralized water diversion period of the Heihe River (July to November 2002), the daily flow of Langxin Mountain lags behind the daily flow of Zhengyi Gorge by about 3 days, and its peak and valley changes are basically the same. (Figure 4.56). The daily flow rate of Langxin Mountain and Zhengyi Gorge is roughly related to a cubic polynomial, and the point distribution is scattered, which is related to the lag effect of runoff. Drawing a scatter plot of daily flow rate with a lag of 3 days, the daily flow rate of Langxin Mountain and Zhengyi Gorge shows a coordinate The straight-line relationship between the origin and the growth rate is about 52%, that is, there is an average of 48% runoff dissipation (Figure 4.57).
Figure 4. 53 Diachronic curves of annual runoff in Yingluo Gorge, Zhengyi Gorge, Shaomaying and Langxin Mountain
Figure 4. 54 Shaomaying, Langxin Mountain and Zhengyi Relationship curve of annual water discharge in the gorge
The average annual water discharge in Shaomaying from 1998 to 2000 was 5.57×108m3, and the annual outflow time was generally 2 to 5 months; the average annual water discharge in Langxinshan from 1988 to 2000 The discharge volume is 3.81×108m3, and the annual flow cutoff time is generally 4 to 6 months.
4. 9. 3. 2 Centralized adjustment of water discharge and amount into the lake
The shrinkage and exhaustion of Juyanhai in the east and west is the result of the continuous decline of water discharge from Zhengyi Gorge over the years. This is the result of impacts such as reduced water use and increased water use in downstream basins.
In order to curb the further deterioration of the ecological environment in the downstream areas and improve the prominent water conflicts, organized water diversion began in 2000, and the Heihe River water has been realized many times entering the Dongjuyan Sea (Table 4 . 42). From August to October 2000, water was transferred. The water flow passed through Shaomaying, and replenished water for Dingxin Irrigation District and Dongfeng Reservoir. On September 13, the water passed through Langxin Mountain. After the water was diverted, it was released along the east and west rivers, and the water reached Langxin Mountain. The 30km of West River and 130km of East River below Xinshan Mountain were inter-provincial water diversion for the first time, pioneering the unified management of water resources in the Heihe River. During the water diversion from August to October 2001, the water release volume under Zhengyi Gorge and Langxin Mountain was 2.3 respectively. ×108m3 and 0.76×108m3, the interval seepage loss was 67%. On September 17, the water flowed to Dalaikubu Town, but never entered the East Juyan Sea; from July to October 2002, water was transferred in three times, Zhengyi The total amount of water released under the Xiaxia and Langxin Mountains was 4.4×108m3 and 3.08×108m3 respectively, with a seepage loss of 30% in the interval. The three water diversions all sent water into the Dongjuyan Sea. The volume of the Dongjuyan Sea in September was Reaching 0. 49 × 108m3, the water surface area is 23. 6km2, and the maximum water depth is 0. 6m, but it dried up on May 21, 2003; from July 10 to 20, 2003, water was transferred, and the water released under Zhengyi Gorge and Langxin Mountain was respectively 0. 48 × 108m3 and 0. 08 × 108m3, with a seepage loss of 83% in the interval. The water head reached Langxin Mountain on the 19th, and the water flow was still 130km away from the East Juyan Sea on the 23rd.
Figure 4. 55 Monthly discharge relationship curve of Shaomaying, Langxin Mountain and Zhengyi Gorge
Figure 4. 56 Daily discharge of Langxin Mountain and Zhengyi Gorge (July 2002~ November) Duration curve
Figure 4. 57 Daily flow relationship curve between Langxinshan and Zhengyi Gorge during the key dispatch period
The centralized water diversion from July 8 to 28, 2002 is This was the largest water diversion in history. The water diversion period coincided with continuous rainfall in the upper reaches of the Heihe River, causing the Yingluoxia section to experience three flood peaks during the closure period.
The peak water head was released from Yingluo Gorge at 15:00 on the 10th, and reached the Zhengyi Gorge at 2:48 on the 11th. At 0:00 on the 13th, it flowed through Langxin Mountain and was divided into the East and West Rivers and was transported downward. At 9:00 on the 14th, the water head of the Xihe River reached the Caici Aobao Sluice , at 9:33, the head of the East River flows to Dalaikubu Town, the hinterland of Ejina Oasis. Due to the large amount of water, the first, second and seventh rivers of the East River have all flowed through. At 17:00 on the 17th, the first river The water heads of Hehe and Erdaohe rivers reach Dongjuyan Sea; the distances between Yingluo Gorge-Zhengyi Gorge-Langxin Mountain-Dongjuyan Sea are 185km, 164km, and 169km, and their average water head propagation speeds are 2.77km/h respectively. , 3. 63km/h, 1. 50km/h (Table 4.43). About 20 hours after the water head entered the East Juyan Sea, the average propulsion speed of the water head was 30m/h; at 17:30 on the 18th, the lake water surface was about 5km wide, the water surface area was 13km2, the flow into the lake was 50m3/s, and the water volume into the lake was 400×104m3; on the 28th At 17:30, the water surface area was 18. 5km2, the flow into the lake was about 4m3/s, and the water volume into the lake was 1100×104m3 (Table 4.44).
Table 4. 42 Statistical table of water discharge during the centralized water diversion period from 2000 to 2003
The above measurement data of the system during the centralized water diversion period are used to study the water discharge and discharge in the lower reaches of the Heihe River. The rules of entering the lake provide an important basis. The lower reaches of the Heihe River have a long seepage path and a large seepage loss, but the seepage rate and runoff still conform to the law of large runoff and small seepage rate (Figure 4.17). The runoff of Zhengyi Gorge (0. 4 ~ 4. 4) It is even slower below Ejina Banner. For example, in July 2002, the water diversion process from Langxin Mountain to Laikubu Town was 130km, and the water head discharge experienced 33. 5 hours, while the 39km from Dalaikubu Town to Dongju Yanhai took 79. 5 hours; Zhengyi Gorge During the period when the amount of water released is small, the water will not flow into Juyanhai due to leakage along the way, or even reach Langxin Mountain. Therefore, if water is to be sent into the lake, there must be enough water released; the evaporation in the lake area is as high as 3700mm, and a certain amount must be maintained. The volume of lake water must be sufficient to balance the loss of water such as evaporation and leakage. The second inflow of Dongju Yanhai in 2002 brought the water area to 23. 8km2. However, due to the subsequent lack of water replenishment, by 2003 On May 21, 2011, the Dongjuyan Sea dried up again.
The transfer of water from the Heihe River to Ejina has effectively alleviated further deterioration of the downstream ecological environment. In the normal or dry years from 1995 to 1999, the Langxin Mountain in the lower reaches of the Heihe River was cut off for about 230 to 250 days; after the implementation of unified water diversion, the flow was cut off for 212 days in 2000, 203 days in 2001, and 176 days in 2002. , the number of outage days has been reduced by 40 to 70 days. When water was brought into the lake in 2002, groups of rare animals such as white swans, gray geese, yellow ducks and other water birds migrated to the lake area. Groups of camels hurried towards the water from different directions. The scene was spectacular and exciting. However, how to transfer water scientifically and effectively, how to reasonably allocate the amount of water transferred to the downstream, whether to maintain the water volume in the lake area and whether and how much can be maintained are all issues that need to be studied and solved urgently.
Table 4. 43 Statistical table of river flow and velocity during the centralized water diversion period in July 2002
Table 4. 44 Dongjuyan Sea area and flow rate during the centralized water diversion period in July 2002 Water volume statistics table