Reservoir ecological flow configuration method based on multi-section water transfer and multi-target fish collaborative protection

Abstract

The invention discloses a reservoir ecological flow configuration method based on multi-section water transfer and multi-target fish collaborative protection, which comprises the following steps: S1, determining a hydrological sensitive area and an ecological sensitive area based on water transfer influence constraint and fish resource distribution data, superposing the hydrological sensitive area and the ecological sensitive area to construct a habitat evaluation model, determining a typical fish key habitat, and constructing a reservoir ecological flow configuration model; determining a target spawning site; s2, integrating the two-dimensional hydrodynamic model and the fish habitat model, calculating habitat hydraulic power demands and flow pulse demands of different fishes in the spawning period, constructing an ecological water demand process in the spawning period, and calculating basic hydrological demands of ecological base flow for supplementing a non-spawning period; and S3, carrying out ecological water demand coupling on a plurality of spawning sites with overlapped spawning periods, and determining a reservoir ecological flow collaborative configuration scheme. According to the method, on the basis of the particularity of multi-section water transfer disturbance and multi-target collaborative protection of a water source area of western-line engineering, the ecological water demand of typical fishes is researched, and a reservoir ecological flow configuration scheme is determined.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir management, and in particular to a reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection. Background Art

[0002] Ecological water demand in a river usually refers to the amount of water that needs to be maintained in the river in order to exert the normal functions of the river ecosystem and maintain the biodiversity in the river. Ecological flow in a river generally refers to the minimum water requirement for the survival of aquatic and riparian organisms. In order to maintain the stability of the river ecosystem and achieve the goal of river water ecological protection, it is crucial to determine a scientific and reasonable ecological water demand process and formulate appropriate water resources management strategies. There are hundreds of methods and calculation models for ecological water demand research, which are mainly divided into hydrological method, hydraulic method, habitat simulation method and holistic method.

[0003] The adverse effects of water conservancy construction on fish are reflected in the weakening of longitudinal connectivity of rivers, river fragmentation, changes in topography and geomorphology, and changes in hydrological conditions. With the increasing requirements for the protection of fish habitats, the ecological response of fish habitats to changes in hydrological conditions has become a hot topic. Many scholars have conducted in-depth research on the ecological water demand of a single fish in a certain spawning ground, but there are few studies on the relationship between habitat quality responses among multiple sensitive habitats. Therefore, the identification and quantification of the relationship between hydrological and ecological characteristics between multiple target spawning grounds of typical fish and the coupling method system of the ecological water demand process of key habitats of multi-target fish still need to be discussed in depth.

[0004] The primary goal of ecological flow regulation is to meet the hydrological process required for the spawning and reproduction of key protected fish and promote the ecological protection of rivers in the water source area. Under the current climate, hydrological boundary conditions and changes in engineering plans, it is necessary to conduct a comprehensive analysis of ecological water demand in combination with the particularity of "multi-section water diversion disturbance and multi-target coordinated protection" in the Dadu River source area. By scientifically identifying the key fish habitats within the scope of the project, reasonably quantifying the connection between multiple fish habitats, and formulating the ecological flow process at the reservoir dam site, a scientific basis can be provided for the management of reservoir ecological flow. Summary of the invention

[0005] In order to solve the ecological water demand problem of typical fish, protect the hydrological process required for fish spawning and reproduction, and promote the ecological protection of rivers in water source areas, the present invention provides a reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection.

[0006] The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection provided by the present invention comprises the following steps:

[0007] S1. Determine the hydrologically sensitive areas based on the constraints of water diversion impacts, determine the ecologically sensitive areas based on fish resource distribution data, superimpose the hydrologically sensitive areas and the ecologically sensitive areas to construct a habitat assessment model, determine the key habitats of typical fish through habitat assessment, and determine the target spawning grounds.

[0008] The purpose of step S1 is to evaluate the flow recovery downstream of the dam site after water diversion through quantitative calculation and analysis, and to identify areas that are sensitive to changes in hydrological conditions, namely hydrologically sensitive areas, based on flow recovery constraints. At the same time, based on the distribution characteristics of fish resources, representative typical fish are selected as research objects, and the spatial distribution of these typical fish spawning grounds is carefully analyzed to clarify their ecologically sensitive areas. Finally, the hydrologically sensitive areas and ecologically sensitive areas are superimposed, key fish habitats are screened, and target spawning grounds are determined to provide scientific support and basis for subsequent research on fish ecological water demand. Specifically, it includes the following two steps:

[0009] S11. Determine the hydrologically sensitive area: In order to clarify the impact of water diversion on the river downstream of the reservoir dam site, the average annual water diversion volume of the reservoir is evenly distributed to each month, and the flow before and after water diversion is calculated and compared and analyzed. The degree of flow recovery after water diversion in the river downstream of the reservoir is expressed as a percentage. The calculation formula for the degree of flow recovery after water diversion, Q′, is as follows:

[0010]

[0011] Where: Q i调水后 Q is the flow rate of each section below the dam after the monthly water diversion volume is allocated; i调水前 is the flow rate of each section below the dam under natural conditions.

[0012] When a large tributary flows into the main stream, the flow in the river channel will be fully restored. The hydrologically sensitive area can be determined by constraining the flow recovery degree Q' after water diversion. In the present invention, the river section with a flow recovery degree Q'≤70% is defined as the hydrologically sensitive area.

[0013] S12. Method for determining ecologically sensitive areas: Based on the distribution characteristics of fish resources, select representative typical fish as research objects, investigate the distribution of spawning grounds of typical fish, and analyze the spatial distribution of these typical fish spawning grounds in detail to clarify their ecologically sensitive areas.

[0014] S13. Superimpose hydrologically sensitive areas and ecologically sensitive areas, and construct a habitat assessment model in accordance with the principle of "upstream priority and comprehensive assessment". The specific methods are as follows:

[0015] (1) Construct an index system. Based on the impact of water conservancy projects and the distribution of spawning grounds, an index system is constructed to measure the priority protection order of spawning grounds from two aspects: the degree of project response and the characteristics of spawning grounds:

[0016]

[0017] In the formula, x′ is the normalized result of each indicator; min(x) is the minimum value of each indicator; max(x) is the maximum value of each indicator;

[0018] (2) The entropy weight method is used to determine the indicator weight. The calculation formula is as follows:

[0019]

[0020] d j =1-E j

[0021]

[0022] Where: p(x ij ) is the standardized value of each indicator; E j is the information entropy of the jth item; d j is the difference coefficient of the j-th indicator, w j is the indicator weight.

[0023] (3) Using the values ​​and weights of the indicators determined in steps (1) and (2), the priority protection comprehensive assessment value V of each spawning ground is obtained by weighted summation method. 综 , the calculation formula is as follows:

[0024] V 综 =∑C i ω i ,i=1,2,…,n

[0025] Where: C i is the normalized result of each index; ω i is the indicator weight, and n is the number of indicators.

[0026] S2. Divide the fish life cycle into different parts, integrate the two-dimensional hydrodynamic model and the fish habitat model, use the IFIM method to calculate the habitat hydraulic demand and flow pulse demand of different fish during the spawning period, construct the ecological water demand process of fish during the spawning period, and calculate the ecological base flow to supplement the basic hydrological demand during the non-spawning period; the specific steps are as follows:

[0027] S21. A hydrodynamic model is established for the identified typical key fish habitats to perform numerical simulations, and the hydrodynamic parameters under different flow conditions are obtained. The WUA is calculated by combining the fish habitat model and the velocity and depth suitability curves. The WUA is defined as the product of the unit habitat suitability index and the unit area. The WUA calculation formula is as follows:

[0028]

[0029] Where: n is the number of units; A iis the area of ​​the calculation unit, m 2 ;HSI i SI is the comprehensive habitat suitability index of the calculation unit; vi SI is the flow rate suitability index, ranging from 0 to 1; di SI is the water depth suitability index, ranging from 0 to 1; ci It is the river suitability index (including bottom quality and cover conditions), and its value range is 0 to 1.

[0030] The velocity and water depth suitability curve is obtained by collecting and selecting typical fish characteristic data.

[0031] A one-dimensional HEC-RAS hydrodynamic model was established from the upper boundary of the spawning ground to the downstream hydrological station. The one-dimensional hydrodynamic model was first calibrated and verified to ensure the accuracy and reliability of the model. Then the one-dimensional hydrodynamic data of the spawning ground were extracted and used for the calibration and verification of the two-dimensional hydrodynamic model.

[0032] S22, obtaining the flow-WUA relationship of different fish species in the spawning grounds, determining the optimal flow, optimal interval and suitable interval of ecological water demand during the spawning period of fish, and introducing eco-hydrological indicators to construct the ecological water demand process during the spawning period of fish. Preferably, the flow corresponding to 80% and 60% of the WUA peak is set as the optimal interval and suitable interval, respectively.

[0033] Fish have different requirements for hydraulic conditions in different life cycles. For the spawning period, in addition to ensuring the flow required for a suitable spawning habitat, it is also necessary to shape a flow pulse process that stimulates fish spawning, provide signals for fish spawning, and stimulate fish gonadal development. Flow pulse is defined as a fluctuation process in which the flow rises from a minimum to a maximum, and then falls back to the next local minimum, with a total duration of no less than three days. Since broodstock need about two days of stimulation to spawn, the flow pulse process is further set as a flow pulse process in which the water level rises for more than two days.

[0034] S23. For fish in the non-spawning period, the hydrological method is used to calculate the ecological base flow to supplement the basic hydrological demand in the non-spawning period; to ensure that the habitat of fish can still maintain the necessary ecological water volume during the non-breeding stage, thereby ensuring the survival and reproduction of fish. The hydrological method used can be one of the Tennant method, 7Q10 method, Qp method and Texas method.

[0035] S3. Couple ecological water demand for multiple spawning grounds downstream of multiple reservoirs with hydrological connections and overlapping spawning periods, and determine the coordinated configuration plan for reservoir ecological flow.

[0036] Purpose of step S3: The reservoir ecological flow process formulated based on the needs of a single fish may cause potential conflicts in actual operations due to the differences in flow requirements of different fish, which in turn affects the scientific management and effective allocation of ecological flow. There are hydrological connections between the spawning grounds in the downstream river section of the reservoir, and this hydrological connection associates the WUA between different spawning grounds. If the spawning periods are independent of each other, the ecological water demands of different spawning grounds during the spawning period will not affect each other; on the contrary, when the spawning periods overlap, it is very likely that the ecological water demands of the upstream and downstream spawning grounds will not be met at the same time. At this time, it is necessary to couple the ecological water demands of these spawning grounds to reasonably allocate the ecological flow of the reservoir.

[0037] Based on the ecological water demand process of single target fish during the spawning period and the ecological base flow at the dam site during the non-spawning period, the reservoir outflow process is formulated. The reservoir outflow process gives priority to the ecological water demand during the spawning period, and the outflow during the non-spawning period is supplemented by the results of hydrological methods.

[0038] In order to maximize the utilization of fish habitats, the ecological water demands of different fish species during the overlapping spawning periods upstream and downstream are coupled, and the single fish water demand is converted into multi-target water demand. This allows the spawning grounds of different fish species and different river sections with hydrological linkages to maximize their ecological functions and achieve optimal configuration of reservoir flow.

[0039] The method of coupling ecological water demand for multiple spawning sites is as follows:

[0040] Based on the flow-WUA relationship of each spawning ground calculated according to the ecological water demand during the spawning period, the interval confluence Q between the upstream and downstream spawning grounds 区 As a link, connecting multiple spawning grounds, the hydrological relationship between the upstream and downstream spawning grounds is Q 上 +Q 区 =Q 下 , using the above hydrological relationship to establish WUA 上 with WUA 下 relationship; joint Q 上 ~WUA 上 , Q 下 ~WUA 下 and Q 上 +Q 区 =Q 下 Establishment of WUA 上 ~WUA 下 relationship and in WUA 上 ~WUA 下 The optimal ecological flow combination pattern for the coordination of multiple spawning grounds is sought in the relationship between the two.

[0041] In order to facilitate the comparison of the WUA of fish in multiple spawning grounds with hydrological connections under different flow combinations, each spawning ground was normalized, and the formula is as follows:

[0042]

[0043] Where WUA i ′ is the normalized WUA, ranging from 0 to 1; WUA i is the WUA of fish at different flow rates in the spawning grounds, in m 2 ;Max(WUA i ) is the maximum value, unit is m 2 ;ω i is the weight of each spawning ground, which is determined according to different target requirements; C WUA It is the comprehensive result of normalized WUA of multiple spawning grounds, ranging from 0 to 1.

[0044] Strictly speaking, different spawning grounds should be given different weights due to the importance of the spawning grounds and the differences in hydrological responses, but due to insufficient information, this study considered that the weights of each factor were equal.

[0045] The evaluation method of the coupling results is as follows:

[0046] (1) For a single spawning site, when WUA is 80% or more of the peak value, the habitat quality is considered excellent; when WUA is between 60% and 80% of the peak value, the habitat quality is considered good; when WUA is less than 60% of the peak value, the habitat quality is considered poor;

[0047] (2) For n spawning grounds, when the habitat quality of all spawning grounds is excellent, the comprehensive evaluation result is considered excellent; when the habitat quality of all spawning grounds is good or above, and no less than n / 2 of them are excellent, the comprehensive evaluation result is considered good; when the habitat quality of all spawning grounds is good or above, and the number of excellent ones is less than n / 2, the comprehensive evaluation result is considered medium; all other cases are poor.

[0048] Finally, based on the optimal flow combination pattern of ecological water demand, the optimized reservoir annual flow process is constructed.

[0049] Compared with the prior art, the present invention is beneficial in that:

[0050] Based on the particularity of "multi-section water regulation disturbance and multi-target coordinated protection" in the water source area of ​​the West Line Project, this invention conducts in-depth research on the ecological water demand of typical fish to determine the reservoir ecological flow configuration plan, which can provide a scientific basis for reservoir ecological flow management.

[0051] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The present invention is a flow chart of the reservoir ecological flow configuration method.

[0053] Figure 2 The target spawning ground location is identified by constructing a key habitat model in an embodiment of the present invention.

[0054] Figure 3 This is the relationship curve between the flow rate and WUA of the Sichuan-Shaanxi Taihu spawning ground studied in the embodiments of the present invention.

[0055] Figure 4 This is the flow process line of Sichuan-Shaanxi Taimen during the spawning period calculated in the embodiment of the present invention.

[0056] Figure 5 This is the annual flow process of the Huona Dam Reservoir before the implementation of the embodiment of the present invention.

[0057] Figure 6 This is the annual flow process of the Keke Dam Reservoir before the implementation of the embodiment of the present invention.

[0058] Figure 7 This is a position relationship diagram of the spawning ground according to an embodiment of the present invention.

[0059] Figure 8 Schematic diagram of the coupling mode of ecological water demand of spawning grounds according to an embodiment of the present invention.

[0060] Fig. 9 This is the coupling process of the ecological water requirements of the three spawning grounds in the embodiment of the present invention.

[0061] Fig.10 This is an optimized ecological flow configuration scheme for the Huona Reservoir according to an embodiment of the present invention.

[0062] Fig.11 This is the optimized ecological flow configuration scheme of the Keke Reservoir according to the embodiment of the present invention. DETAILED DESCRIPTION

[0063] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0064] like Figure 1 As shown, the reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection provided by the present invention comprises the following steps:

[0065] Step S1, determine the hydrologically sensitive areas based on the water diversion impact constraints, determine the ecologically sensitive areas based on the fish resource distribution data, superimpose the hydrologically sensitive areas and the ecologically sensitive areas to construct a habitat assessment model, determine the typical fish key habitats through habitat assessment, and determine the target spawning grounds.

[0066] In this embodiment, daily flow data of the Dadu River source area for nearly 50 years were collected, organized and analyzed, frequency calculations were performed and three typical years, namely, wet years, normal water years and dry years, were scientifically selected. The impact of water diversion on the Dadu River source area after the total amount of water diversion was evenly distributed to each month under the hydrological conditions of the West Line Project in different years was systematically analyzed. The focus was on studying the flow recovery downstream of the dam site in the driest month of the dry year, and typical fish and their key habitats were screened.

[0067] Determination of hydrological sensitive areas: According to the flow changes of each month in the wet year, normal year and dry year at the hydrological station after the water diversion of the West Line Project, it can be known that February in the dry year is most affected by the water diversion, and this month is also the driest month in the dry year. It is taken as a typical operating condition to analyze the changes in water volume along the river downstream of the reservoir after the water diversion. The driest month in the dry year is selected as the typical operating condition to analyze the flow recovery downstream of the dam site. After the confluence of the Mako River and the Ako River at the Zumuzu River, the flow recovered to 66% of the natural condition. After the confluence of the Zumuzu River and the Chuosijia River, the flow at Shuangjiangkou recovered to 77% of the natural condition. At the Dajin hydrological station, the flow recovered to 78%. The river sections where flow recovery is less than 70% are set as hydrologically sensitive areas, which include the river section about 181km below Zhuanda Reservoir, the Mako River section about 182km downstream of Huona Reservoir, the Ako River section about 124km downstream of Keke Reservoir, and the river section 55km below the confluence of Mako River and Ako River.

[0068] Determination of ecologically sensitive areas: According to the distribution of fish resources in the survey area, combined with the changes in fish resource quantity and the importance of fish, typical fish are selected from the 12 fish species in the source area of ​​the Dadu River of the West Route Project. In this embodiment, Sichuan-Shaanxi Taimen is a national first-class protected fish and is listed in the Red List of Endangered Species in China. Historically, Sichuan-Shaanxi Taimen has been distributed throughout the Dadu River. It is currently in a critically endangered state and is only distributed above the confluence of the Chabao River in the upper reaches of the Dadu River; the heavy-mouthed schizothorax is a national second-class protected fish and a provincial-level protected fish in Sichuan Province; the Qikou schizothorax is a species endemic to China and a fish endemic to the upper reaches of the Yangtze River. The existing distributed fish in the upper reaches of the Dadu River are dominated by Qikou schizothorax and heavy-mouthed schizothorax, so the above three fish species are selected as typical fish, and the distribution of spawning grounds of typical fish is investigated to determine the ecologically sensitive areas where the spawning grounds are located.

[0069] The hydrologically sensitive areas and ecologically sensitive areas are superimposed, and a habitat assessment model is constructed according to the principle of "upstream priority, comprehensive assessment". In this embodiment, the spawning site assessment results are shown in Table 1, and the basic conditions of the key habitats selected according to the principle of "upstream priority, comprehensive assessment" are shown in Table 2.

[0070] Table 1 Spawning ground assessment

[0071]

[0072] Table 2 Basic information of key habitats selected according to the principle of “upstream priority, comprehensive assessment”

[0073]

[0074] Based on the above method, four typical key habitats were identified, namely Dageniang (spawning site A) and Rong'an Township (spawning site B) for the spawning of Sichuan-Shaanxi Tailer, Lianghe Primary School (spawning site C) and Ribubalang (spawning site D) for the spawning of schizothorax. Spawning sites A and B are located in the Mako River and Ako River, tributaries of the Zumuzu River, respectively, with the source reservoirs Huona and Keke upstream. Spawning site D is located in the main stream of the Zumuzu River. The spatial locations of the three are upstream and downstream, and have hydrological connections. The key habitats of specific typical fish are as follows: Figure 2 shown.

[0075] Step S2, divide the fish into different life cycles, integrate the two-dimensional hydrodynamic model and the fish habitat model, use the IFIM method to calculate the habitat hydraulic demand and flow pulse demand of different fish during the spawning period, construct the ecological water demand process line during the spawning period, and calculate the ecological base flow to supplement the basic hydrological demand during the non-spawning period.

[0076] This embodiment investigates the living habits of typical fish, mainly the flow velocity and water depth suitability curve, to provide support for the subsequent calculation of ecological water demand during the spawning period. The spawning period of the heavy-mouthed schizothorax is from August to September, the schizothorax is from March to June, and the taimen is from March to April. The research on schizothorax is relatively mature, while the relevant research on taimen is relatively rare. The spawning research of taimen in the past 30 years has been analyzed and summarized to obtain the flow velocity and water depth suitability curve of taimen. The suitable flow velocity for reproduction is 0.38-0.9m / s, and the water depth is 0.15-1m.

[0077] According to the IFIM method, by integrating the hydrodynamic model and the fish habitat suitability model, the relationship between different flow fields and the WUA of target fish is established. WUA is defined as the product of the unit habitat suitability index and the unit area. It is currently the most widely used habitat quality evaluation indicator. It can be used to determine the response of fish spawning habitats to the hydrological situation under reservoir regulation and evaluate the habitat suitability. The calculation formula is:

[0078]

[0079] Where: n is the number of units; A i is the area of ​​the calculation unit, m 2 ;HSI i SI is the comprehensive habitat suitability index of the calculation unit; vi SI is the flow rate suitability index, ranging from 0 to 1; di SI is the water depth suitability index, ranging from 0 to 1; ciis the river suitability index (including bottom and cover conditions), with a value range of 0 to 1. The bottom of the river section in the study area is gravel, which meets the spawning requirements of three typical fish species, so the river suitability index SI is calculated. ci Set to 1.

[0080] Furthermore, a HEC-RAS one-dimensional hydrodynamic model from the upper boundary of the spawning ground to the downstream hydrological station was established. The one-dimensional hydrodynamic model was first calibrated and verified to ensure the accuracy and reliability of the model. Then, the one-dimensional hydrodynamic data of the spawning ground location were extracted and used for the calibration and verification of the two-dimensional hydrodynamic model.

[0081] The flow rates corresponding to 80% and 60% of the WUA peak are set as the optimal interval and the appropriate interval.

[0082] In this example, the optimal flow rate for ecological water demand of Sichuan-Shaanxi Tailings in spawning grounds A and B is 70m 3 / s and 21m 3 / s; the optimal flow rate of ecological water demand of heavy-mouthed schizothorax in spawning sites C and D is 170m 3 / s and 150m 3 / s; the optimal flow rate of ecological water demand of Schizothorax chinensis in spawning sites C and D is 140m 3 / s and 150m 3 / s.

[0083] Then, calculate the ecological water demand of the spawning ground:

[0084] The flow corresponding to the maximum WUA is usually considered to be the most suitable ecological flow for fish reproduction. However, in actual practice, this flow cannot be guaranteed to exist for a long time. The flow above 80% of the WUA peak is defined as the optimal habitat, and the flow above 60% of the WUA peak is defined as the suitable habitat. The flow range corresponding to the optimal habitat is the optimal ecological water demand interval. When the flow of the spawning ground is between the optimal ecological water demand interval, it indicates that the WUA of the spawning ground can reach more than 80% of the WUA peak, and the habitat at this time is very beneficial to fish reproduction. The flow range corresponding to the suitable habitat is the suitable ecological water demand interval. When the actual flow of the spawning ground is within the suitable ecological water demand interval, the WUA of the spawning ground can reach more than 60% of the peak value, ensuring the reproduction needs of fish. On the contrary, when the flow of the spawning ground is not within the suitable ecological water demand interval, the suitable habitat of the spawning ground will lose 60% or more, which is extremely unfavorable for the reproduction and growth of fish. During the spawning period, the flow of the fish spawning ground should be guaranteed to be within the suitable ecological water demand interval as much as possible. Figure 3 This is the flow-WUA relationship curve of the spawning ground of Sichuan-Shaanxi Taimen in this embodiment. According to the analysis of the ecological hydrological indicators of the spawning ground, the flow pulse process is established to obtain the ecological water demand flow process line during the spawning period. Table 3 is the ecological water demand plan for the spawning period of Sichuan-Shaanxi Taimen. Figure 4 This is the flow process line of Sichuan-Shaanxi Taimen during the spawning period.

[0085] Table 3 Ecological water demand plan for Sichuan and Shaanxi Taimen spawning period

[0086]

[0087] Supplement the ecological rapids during the non-spawning period: Based on the collected hydrological data, combined with the maximum values ​​and specification requirements of the monthly results calculated by the four hydrological methods, namely the Tennant method, 7Q10 method, Qp method and Texas method, the ecological base flows of Zhuanda, Hona and Keke during the non-spawning period were determined.

[0088] Step S3: Conduct ecological water demand coupling research on multiple spawning grounds with hydrological connections and overlapping spawning periods downstream of multiple reservoirs, and propose a coordinated configuration plan for reservoir ecological flow, which provides a scientific basis and reference for reservoir ecological flow management.

[0089] Based on the ecological water demand process of single target fish during the spawning period and the ecological base flow at the dam site during the non-spawning period, the reservoir outflow process is formulated. The reservoir outflow process gives priority to the ecological water demand during the spawning period, and the outflow during the non-spawning period is supplemented by the results of hydrological methods.

[0090] Figure 5 and Figure 6 The annual flow processes at the Hona and Keke dam sites are shown respectively.

[0091] according to Figure 7 As shown in the reservoir-spawning site location relationship, the spawning sites A and B of the Sichuan-Shaanxi Taimen are located on the Mako River and the Ako River, tributaries of the Zumuzu River, respectively. The upstream is the Huona Reservoir and the Keke Reservoir, and they serve different fish species from the spawning site of the schizothorax D on the main stream of the Zumuzu River. The spawning sites A and B of the Sichuan-Shaanxi Taimen are the habitats of the Sichuan-Shaanxi Taimen, and the spawning period is from March to April; the spawning site of the schizothorax D is the habitat of the heavy-mouthed schizothorax and the light-mouthed schizothorax, and the spawning periods of the two are from August to September and March to June, respectively. It can be seen that the spawning periods of the Sichuan-Shaanxi Taimen and the light-mouthed schizothorax overlap (March to April). The ecological water demand flow of the Sichuan-Shaanxi Taimen during the spawning period is small, and the flow corresponding to the maximum WUA of the spawning site A is 70m 3 / s, the maximum WUA flow rate at spawning site B is 21m 3 / s, while the ecological water flow required by Schizothorax chinensis during the spawning period is relatively large, and the flow corresponding to the maximum WUA of the spawning site D is 150m 3 / s.

[0092] Depend on Figure 5 and Figure 6It can be seen that for March and April when the spawning period overlaps, there are differences in the flow processes at the two dam sites. The flow process based on the spawning needs of Sichuan-Shaanxi Taimen is smaller, and the flow process based on the spawning needs of Qikou Schizothorax is larger. When there are multiple ecological flow results, the usual practice is to use the outer envelope method to take the maximum value. Assuming that the maximum value of the optimal flow during the spawning period of different fish species at the Huona and Keke dam sites is the discharge flow process for the spawning needs of Qikou Schizothorax, the peak flows in March and April are 28m 3 / s and 17m 3 / s. Based on the catchment area, the flow rates of Sichuan-Shaanxi Taimen spawning grounds A and B are 63m 3 / s and 55m 3 / s. By Figure 3 It can be seen that the WUA corresponding to spawning ground A and spawning ground B is 1100m 2 and 827m 2 , the WUA normalized results were 0.97 and 0.5, respectively. Combined with the WUA of the spawning ground of Schizothorax chinensis D i ′ is 1, and the comprehensive result is 0.79. Table 4 shows that the maximum discharge volume of the reservoir according to the optimal flow rate of different fish spawning periods can still maintain a high WUA for spawning grounds A and D, but for spawning ground B, it cannot reach the suitable spawning habitat of Sichuan-Shaanxi Taimen (WUA is lower than 60% of the peak value at this time), so the discharge flow process cannot be directly discharged according to the maximum value.

[0093] Table 4 Spawning ground conditions of Huona and Keke reservoirs during the discharge process according to the maximum spawning demand of different fish species

[0094] Spawning Grounds Sichuan-Shaanxi Taimen A spawning ground Sichuan-Shaanxi Taimen B spawning ground Spawning grounds of Schizothorax chinensis D <![CDATA[Flow rate (m 3 / s)]]> 63 55 150 <![CDATA[WUA(m 2 )]]> 1100 827 21376 <![CDATA[WUA ′ ]]> 0.97 0.5 1

[0095] When the discharge flow at the dam site is small, it is conducive to the reproduction of Sichuan-Shaanxi Taimen that prefers slow-flow habitats upstream, but it will lead to insufficient ecological water flow for the Schizothorax that prefers rapids habitats downstream, which is not enough to stimulate its spawning and reproduction; conversely, if the discharge flow at the dam site is large, although it is conducive to the spawning of Schizothorax in the downstream spawning grounds, it is not suitable for the spawning and reproduction of Sichuan-Shaanxi Taimen upstream.

[0096] In order to maximize the utilization of fish habitats, the ecological water demands of different fish species during the overlapping spawning periods upstream and downstream are coupled, and the single fish water demand is converted into multi-target water demand. This allows the spawning grounds of different fish species and different river sections with hydrological linkages to maximize their ecological functions and achieve optimal configuration of reservoir flow.

[0097] The coupling method for key habitats is:

[0098] For multiple spawning grounds distributed in the cross-river network and with hydrological connections, the ecological water demand coupling of multiple spawning grounds was studied based on the principle of multi-field coordinated optimization. According to the flow-WUA relationship of each spawning ground calculated according to the ecological water demand during the spawning period, the interval confluence Q between the upstream and downstream spawning grounds 区 As a link, connecting multiple spawning grounds, the hydrological relationship between the upstream and downstream spawning grounds is Q 上 +Q 区 =Q 下 , using hydrological relationships to establish WUA 上 with WUA 下 The relationship between Figure 8 As shown. Joint Q 上 ~WUA 上 , Q 下 ~WUA 下 and Q 上 +Q 区 =Q 下 Establishment of WUA 上 ~WUA 下 relationship and in WUA 上 ~WUA 下 The optimal ecological flow combination pattern for the coordination of multiple spawning grounds is sought in the relationship between the two.

[0099] In order to more clearly and conveniently compare the WUA of fish in multiple spawning grounds with hydrological connections under different flow combinations, each spawning ground was normalized.

[0100] In this example, the ecological water demand of the three spawning grounds of Sichuan-Shaanxi Tailer A and B and the spawning ground of Qikou Schizothorax D was coupled to study the flow-WUA relationship of the three spawning grounds and the hydrological relationship Q A +Q B +Q 区 =Q D , the WUA relationship between the three spawning grounds can be obtained, and the impact of the flow of the two upstream Sichuan-Shaanxi Tailer spawning grounds A and B on the WUA of the downstream schizothorax D spawning ground can be determined. The WUA relationship results between the three spawning grounds are shown in Fig. 9 .

[0101] Fig. 9The heat map shows the WUA of the spawning ground of Schizothorax chinensis D, which is determined by the flow through the spawning grounds A and B and the interval confluence (interval confluence is calculated according to the catchment area). The two line graphs represent the flow-WUA relationship of spawning grounds A and B, respectively. The darker the color of the heat map, the greater the WUA of the Schizothorax chinensis at spawning ground D, and vice versa, the lighter the color, the smaller the WUA. It can be seen that the flow combination of spawning grounds A and B (including interval flow) can make the WUA of the Schizothorax chinensis at spawning ground D larger when it is within a certain flow range. When the flow of spawning ground A decreases, the flow of spawning ground B needs to increase to maintain the WUA of spawning ground D in a higher range, and when the flow of spawning ground B decreases, the flow of spawning ground A needs to increase to maintain a larger WUA of the Schizothorax chinensis.

[0102] Fig. 9 The red box in the middle represents the optimal ecological water demand range of spawning site A, 48 to 119 m 3 / s, the green box represents the optimal ecological water demand range of Rong'an Township, which is 10-31m 3 / s, the black slash part indicates that the WUA of the two spawning grounds has reached 80% of their respective WUA peaks. The darker flow combination in the heat map of the slash area can keep the WUA of the three spawning grounds at a high level.

[0103] The evaluation method of the coupling results is detailed in Table 5, specifically:

[0104] a. Combined with the requirements of habitat suitability interval and habitat optimal interval in the previous article: 60% of WUA peak and 80% of WUA peak, set rules to evaluate the coupling results. For a single spawning ground, when WUA is at 80% or above of the peak, the habitat quality is considered to be excellent; when WUA is at 60% or above of the peak, the habitat quality is considered to be good; below 60%, the habitat quality is considered to be poor.

[0105] b. For n spawning grounds, when the habitat quality of all spawning grounds is excellent, the comprehensive evaluation result is considered to be excellent; when the habitat quality of all spawning grounds is good or above, and no less than n / 2 of them are excellent, the comprehensive evaluation result is considered to be good; when the habitat quality of all spawning grounds is good or above, the comprehensive evaluation result is considered to be medium; all other cases are poor.

[0106] Table 5 Coupling result evaluation rules

[0107]

[0108] The normalized comprehensive results of WUA for the spawning grounds A and B of Sichuan-Shaanxi Taimen and the spawning ground D of Chikou schizothorax are shown in Fig. 9 The flow combination corresponding to the highest value is the optimal flow combination mode. The optimal flow combination mode and the habitat quality of the spawning ground are shown in Table 6. When the flow of the spawning ground A is 107m 3 / s, the flow rate of spawning site B is 21m 3 / s, WUA comprehensive result C WUA The best value is 0.97. At this time, the WUA of spawning sites A, B and D are 1048m 2 、1654m 2 and 20867m 2 The corresponding normalized results were 0.93, 1.00, and 0.98, respectively, that is, the WUA of the three spawning grounds were all above 80% of the WUA peak, and the WUA of the three spawning grounds were all at a high level.

[0109] Table 6 Coupling effect comparison

[0110]

[0111] Finally, based on the optimal flow combination pattern of ecological water demand, the optimized reservoir annual flow process is constructed.

[0112] According to WUA comprehensive results C WUA The optimal flow combination mode corresponding to the maximum is: the flow of spawning site A is 107m 3 / s, the flow rate of spawning site B is 21m 3 / s, at this time C WUA The peak flow rate of the Huona Reservoir was 47.0 m3 / s in March and April. 3 / s flow pulse process, with 5 peak flows of 37.3m / s from May to June 3 / s flow pulse process, with three peak flows of 37.3m / s from August to September 3 / s flow pulse process, in fact, the ecological base flow is discharged according to the hydrological method. Keke Reservoir creates three peak flows of 6.4m / s from March to April. 3 / s flow pulse process, with 5 peak flows of 14.2m / s from May to June 3 / s flow pulse process, with three peak flows of 14.2m / s from August to September 3 / s flow pulse process, and the ecological base flow is discharged according to the results calculated by hydrological method during the rest of the period.

[0113] According to the optimal flow combination model, the annual flow process optimization configuration of Huona Reservoir and Keke Reservoir is established. Fig.10 and Fig.11 .

[0114] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection, characterized in that: The following steps are involved: S1. Determine the hydrologically sensitive areas based on the constraints of water transfer impacts, determine the ecologically sensitive areas based on fish resource distribution data, superimpose the hydrologically sensitive areas and ecologically sensitive areas to construct a habitat assessment model, determine the key habitats of typical fish through habitat assessment, and determine the target spawning grounds; Among them, the river section where the flow recovery degree Q′ after water diversion is ≤70% is determined as the hydrological sensitive area; the calculation formula of the flow recovery degree Q′ after water diversion is as follows: Where: Q i调水后 Q is the flow rate of each section below the dam after the monthly water diversion volume is allocated; i调水前 is the flow rate of each section below the dam under natural conditions; S2. Construct the ecological water demand process of fish spawning period, and calculate the ecological base flow to supplement the basic hydrological demand in the non-spawning period; the specific steps are as follows: S21. A hydrodynamic model is established for the identified typical key fish habitats to conduct numerical simulations, and the hydrodynamic parameters under different flow conditions are obtained. The WUA is calculated by combining the fish habitat model and the velocity and depth suitability curves; WUA is defined as the product of the unit habitat suitability index and the unit area; S22. Obtain the flow-WUA relationship of different fish species in the spawning grounds, determine the optimal flow, optimal interval and suitable interval of ecological water demand during the spawning period of fish, and introduce eco-hydrological indicators to construct the ecological water demand process during the spawning period of fish; S23. For fish species in the non-spawning period, calculate the ecological base flow to supplement the basic hydrological demand in the non-spawning period; S3. Couple ecological water demand for multiple spawning sites downstream of multiple reservoirs with hydrological connections and overlapping spawning periods, and determine the coordinated configuration plan for reservoir ecological flow. The method for coupling ecological water demand for multiple spawning sites is as follows: Based on the flow-WUA relationship of each spawning ground calculated according to the ecological water demand during the spawning period, the interval confluence Q between the upstream and downstream spawning grounds 区 As a link, connecting multiple spawning grounds, the hydrological relationship between the upstream and downstream spawning grounds is Q 上 +Q 区 =Q 下 , using the above hydrological relationship to establish WUA 上 with WUA 下 Relationship; Joint Q 上 ~WUA 上 , Q 下 ~WUA 下 and Q 上 +Q 区 =Q 下 Establishment of WUA 上 ~WUA 下 relationship and in WUA 上 ~WUA 下 The optimal ecological flow combination pattern for the coordination of multiple spawning grounds is sought in the relationship between the two.

2. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection as claimed in claim 1 is characterized in that: In step S1, the method for determining the ecologically sensitive areas is: based on the distribution characteristics of fish resources, typical fish with representative characteristics are selected as research objects, and the spatial distribution of the spawning grounds of these typical fish is carefully analyzed to clarify the ecologically sensitive areas.

3. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection as claimed in claim 1 is characterized in that: In step S1, the hydrologically sensitive area and the ecologically sensitive area are superimposed to construct a habitat assessment model. The specific method is as follows: (1) Construct an index system to measure the priority order of spawning ground protection from two aspects: engineering response degree and spawning ground characteristics: In the formula, x′ is the normalized result of each index; min(x) is the minimum value of each indicator; max(x) is the maximum value of each indicator; (2) The entropy weight method is used to determine the indicator weight. The calculation formula is as follows: d j =1-E j Where: p(x ij ) is the standardized value of each indicator; E j is the information entropy of the jth item; d j is the difference coefficient of the j-th indicator, w j is the indicator weight; (3) Using the values ​​and weights of the indicators determined in steps (1) and (2), the priority protection comprehensive assessment value V of each spawning ground is obtained by weighted summation method. 综 , the calculation formula is as follows: V 综 =∑C i ω i ,i=1,2,…,n Where: C i is the normalized result of each index; ω i is the indicator weight, and n is the number of indicators.

4. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection according to claim 1 is characterized in that: In step S21, the WUA calculation formula is as follows: Where: n is the number of units; A i is the area of ​​the calculation unit, m 2 ; HSI i SI is the comprehensive habitat suitability index of the calculation unit; vi SI is the flow rate suitability index, ranging from 0 to 1; di SI is the water depth suitability index, ranging from 0 to 1; ci It is the river suitability index, ranging from 0 to 1.

5. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection as claimed in claim 1 is characterized in that: In step S22, the flow rates corresponding to 80% and 60% of the WUA peak are set as the optimal interval and the appropriate interval, respectively.

6. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection as claimed in claim 1 is characterized in that: In step S3, in the ecological water demand coupling method for multiple spawning grounds, in order to facilitate the comparison of the fish WUA of multiple spawning grounds with hydrological connections under different flow combinations, each spawning ground is normalized, and the formula is as follows: Where WUA i ′ is the normalized WUA, ranging from 0 to 1; WUA i is the WUA of fish at different flow rates in the spawning grounds, in m 2 ;Max(WUA i ) is the maximum value, unit is m 2 ; ω i is the weight of each spawning ground, which is determined according to different target requirements; C WUA It is the comprehensive result of normalized WUA of multiple spawning grounds, ranging from 0 to 1.

7. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection as claimed in claim 1 is characterized in that: In step S3, the evaluation method of the ecological water demand coupling results of multiple spawning sites is as follows: (1) For a single spawning site, when WUA is 80% or more of the peak value, the habitat quality is considered excellent; when WUA is between 60% and 80% of the peak value, the habitat quality is considered good; when WUA is less than 60% of the peak value, the habitat quality is considered poor; (2) For n spawning grounds, when the habitat quality of all spawning grounds is excellent, the comprehensive evaluation result is considered excellent; when the habitat quality of all spawning grounds is good or above, and no less than n / 2 of them are excellent, the comprehensive evaluation result is considered good; when the habitat quality of all spawning grounds is good or above, and the number of excellent ones is less than n / 2, the comprehensive evaluation result is considered medium; The rest are poor.

8. The reservoir ecological flow configuration method based on multi-section water diversion and multi-target fish coordinated protection as claimed in claim 7 is characterized in that: Based on the optimal flow combination pattern of ecological water demand, the optimized reservoir annual flow process is constructed.

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