A method for determining compensation control threshold in river channel

Abstract

The present invention relates to a method for determining a compensation control threshold in a river channel, which includes selecting indicators to construct a river health evaluation system based on a near-natural concept; calculating a comprehensive weight of river health evaluation; selecting a plurality of methods to calculate the ecological flow process of a river control section; evaluating the ecological flow process, and comprehensively determining the compensation control threshold in the river channel; evaluating the river health level; establishing a response relationship between the river health grade and the compensation control threshold in the river channel according to the river health evaluation system based on a near-natural concept, and determining the compensation control threshold in the river channel of the river according to the response relationship; the present invention solves the problem of threshold judgment and identification of the coordination between river ecological flow and river health.

Description

Technical Field

[0001] The invention relates to the technical field of river ecological compensation control, and in particular to a method for determining a compensation control threshold in a river channel. Background Art

[0002] Rivers are the link between water, nature and human society, and have important ecological and social service functions. With the rapid development of social economy, the phenomenon of competitive water use between people and nature has become increasingly prominent in some areas. Excessive production and domestic water use outside the river has squeezed out ecological water use in the river, causing serious damage to the service functions of river water ecosystems and restricting the high-quality development of river basins and regions.

[0003] As a new type of water resources management, river basin ecological compensation is an important measure to alleviate the contradiction between river ecosystem and social and economic water supply and demand, and to promote the coordinated development of river basin ecological protection and social economy. In order for rivers to play their basic ecosystem service functions, they need to maintain a certain amount of ecological water. Excessive water withdrawal for production, life and ecology outside the river will damage the service functions of the river. The compensation control threshold within the river plays a coordinating role in river ecology and regional social and economic development, and is also a key control factor for ecological compensation.

[0004] Most existing studies use the minimum ecological flow of rivers as the compensation control threshold, lacking the threshold judgment and identification that considers the coordination between river ecological flow and river health, making it difficult to clarify the in-river compensation control threshold and its relationship between river health and river ecosystem function.

[0005] In the issue of ecological compensation caused by river ecological water deficit, how to evaluate the river's near-natural health level and determine the water compensation threshold in the river based on the river health level is the key to defining and quantifying the compensation control threshold in the river.

[0006] The present invention solves the problem of threshold judgment and identification of the coordination between river ecological flow and river health, which is conducive to improving the theoretical and methodological system of watershed ecological compensation, promoting the implementation of watershed ecological protection, and providing an important basis for the implementation of the ecological compensation system. Summary of the invention

[0007] In order to solve the problem of threshold judgment and identification of river ecological flow and river health coordination, the purpose of the present invention is to provide a method for determining the compensation control threshold in a river channel, comprising the following steps:

[0008] S1 Select indicators to construct a river health evaluation system based on the concept of near-nature and formulate river health grade evaluation standards, specifically:

[0009] S101 Construct the criteria layer of river health assessment system;

[0010] S102 constructs the indicator layer corresponding to the river health assessment system and the criterion layer;

[0011] S103 classifies the health level of the target layer rivers and establishes the range value of each indicator of the health level level;

[0012] S2 calculates the comprehensive weight of river health assessment, which is:

[0013] S201 subjective calculation weights are first fuzzy quantized through expert scoring to form a judgment matrix, which is then scored by experts to construct a comprehensive judgment matrix;

[0014] S202 calculates the eigenvector of the judgment matrix and performs consistency check;

[0015] S203 calculates the combined weight vector to synthesize the weights of each level;

[0016] S204 sorts the levels as a whole, and then obtains the importance ranking of each indicator, and records the weight W j ;

[0017] S205 Determination of objective weights First, the data is normalized and preprocessed;

[0018] S206 calculates the information entropy e according to the following formula j :

[0019]

[0020] Among them, e j is the entropy value of the jth indicator, p ij is the numerical weight of the jth indicator of the i-th project, Z ij is the value of the jth indicator of the ith project;

[0021] S207 calculates the variation index d according to the following formula j :

[0022] d j =1-e j ;

[0023] Among them, d j is the variation index of the jth indicator;

[0024] S208: Calculate the entropy weight v according to the following formula j :

[0025]

[0026] Among them, v j is the entropy weight of the jth indicator;

[0027] S209 combined with weight w jand weight v j , calculate the comprehensive weight of river health assessment

[0028] S3 calculates the ecological flow process of the river control section;

[0029] S301 collects the monthly average runoff data of the hydrological reference station and compares the runoff of the hydrological station to the design section;

[0030] S302 calculates the ecological flow process of the river control section according to the data.

[0031] S4 evaluates the ecological flow process and comprehensively determines the compensation control threshold in the river channel;

[0032] S401 quantitatively analyzes the correlation between monthly ecological flow series and average monthly runoff;

[0033] S402 selects the monthly average flow to analyze the ecological flow guarantee degree and determines the ecological flow satisfaction degree;

[0034] S403 calculates the percentage relationship between the monthly ecological flow and the average natural flow, and evaluates the ecological environment of the river under the ecological flow scenario;

[0035] S404 Comprehensively determine the inner edge line of ecological flow process control, the median line of ecological flow process control and the outer edge line of ecological flow process control of the river control section according to the evaluation results;

[0036] S5 evaluates the river health level, specifically:

[0037] S501 constructs a matter-element matrix R based on the river health evaluation system of the near-nature concept described in step S2:

[0038]

[0039] In the formula, R(N, C, V) is the matter-element matrix; the thing to be evaluated is recorded as N; c represents the n features of the evaluation matter-element, and v represents the value of the n features;

[0040] S502 constructs a river health evaluation system based on the near-nature concept described in step S2, and constructs a classic domain R j :

[0041]

[0042] Where N j represents the jth level of matter-element; V ji It represents the value range of the i-th evaluation index of the matter-element at this feature level;

[0043] S503 Based on the river health evaluation system of the near-nature concept described in step S2, construct a section R p :

[0044]

[0045] In the formula, v pi Represents matter-element with respect to feature c i The value range of

[0046] S504 performs comprehensive correlation calculation based on the river health evaluation system of the near-nature concept described in step S2:

[0047]

[0048] In the formula, is the combined weight determined in step 1.9, k j (v i ) is the correlation degree of the evaluation matter-element at the jth level and the i-th indicator;

[0049]

[0050] Among them, k j (v i ) represents the correlation degree of the i-th indicator at the j-th level; p ji (v xi , v ji ) represents the evaluation of matter-element to interval v ji The distance v pi represents the value range of the i-th index of the evaluation element; v ji represents the value range of the jth level and the ith indicator; v xi Indicates v ji The value range of a certain point in

[0051]

[0052] Where a represents v ji Lower limit, b represents v ji Upper limit;

[0053] S6 establishes a response relationship between the river health grade and the compensation control threshold in the river channel based on the river health evaluation system of the near-nature concept and the river health evaluation result of step S5, and determines the health status of the river and the compensation control threshold in the river channel.

[0054] Furthermore, the S101 constructs a river health assessment system, including four criteria layers: hydrological integrity, chemical integrity, morphological structural integrity, and biological integrity.

[0055] Furthermore, the S102 constructs a river health evaluation system, including 10 indicator layers corresponding to the quasi-measurement layers, specifically: water resource development and utilization rate C1, flow process variation degree C2 and minimum downstream ecological flow satisfaction degree C3 corresponding to hydrological integrity, water quality quality C4 and drinking water source water quality compliance status C5 corresponding to chemical integrity, longitudinal connectivity index C6, riverbank stability C7 and riverbank vegetation coverage C8 corresponding to morphological structural integrity, large benthic animal diversity index C9 and fish retention index C10 corresponding to biological integrity, see Table 1 for details.

[0056] Table 1 River health assessment system based on the concept of near-nature

[0057]

[0058] Furthermore, S103 classifies the target layer river health level, specifically, classifies the target layer river health level into 5 levels, namely, I, II, III, IV, and V, corresponding to 5 health levels, namely, very healthy, healthy, sub-healthy, unhealthy, and pathological.

[0059] Further, as shown in Table 2, S103 sets the range values ​​of each indicator of the health level grade:

[0060] Table 2 Range values ​​of various indicators at different levels

[0061]

[0062] Furthermore, the subjective calculation weights of step S201 are first scored by 3-5 experts according to a scale, where scale 1 indicates that two elements are equally important; 3 indicates that one element is slightly more important than the other; 5 indicates that one element is significantly more important than the other; 7 indicates that one element is strongly more important than the other; 9 indicates that one element is extremely more important than the other; 2, 4, 6, and 8 represent the middle values ​​of the above adjacent judgments. Each expert constructs his or her own judgment matrix according to the scale, and for each element in the judgment matrix, calculates its geometric mean to construct a comprehensive judgment matrix.

[0063] Preferably, the subjective weight calculation in step S201 is first scored by three experts according to a scale.

[0064] Furthermore, the S401 quantitatively analyzes the correlation between the monthly ecological flow sequence and the average monthly runoff. The Pearson correlation coefficient R ranges from -1 to 1. The closer its absolute value is to 1, the better the correlation is, that is, the better the hydrological rhythm evaluation is.

[0065] Furthermore, the above S402 selects the monthly average flow to analyze the degree of ecological flow guarantee, and the ratio of the time series length when the flow in the river channel is greater than the ecological flow to the total series time length is the ecological flow satisfaction degree.

[0066] Furthermore, S404 comprehensively determines the annual ecological flow process control inner edge line, ecological flow process control median line and ecological flow process control outer edge line of the river control section based on the evaluation results, wherein the ecological flow process control inner edge line corresponds to the minimum ecological flow process control line, the ecological flow process control median line corresponds to the appropriate ecological flow process control line, and the ecological flow process control outer edge line corresponds to the recommended ecological flow process control line.

[0067] Furthermore, the determination of the in-channel compensation control threshold of the river in S6 is specifically:

[0068] For rivers in the healthy and between healthy and very healthy levels, the inner edge of ecological flow process control is used as the compensation control threshold in the river channel;

[0069] For rivers in sub-health and between sub-health and health, the median line of ecological flow process control is used as the compensation control threshold in the river channel;

[0070] For rivers that are in a pathological state or between pathological and sub-healthy levels, the outer edge of the ecological flow process control line is used as the compensation control threshold within the river channel.

[0071] The beneficial effects of the present invention are:

[0072] 1. The method for determining the compensation control threshold in the river channel of the present invention introduces a near-natural concept, constructs a near-natural river health evaluation system, and improves the accuracy of river health evaluation.

[0073] 2. Aiming at the needs of river ecological protection, the river health evaluation system is coupled with a variety of hydrological ecological flow calculation methods, the flow control line is divided, and a method for determining the water compensation control threshold in the river channel is proposed, which solves the problem of threshold judgment and identification of the coordination between river ecological flow and river health. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a schematic diagram of the process of the present invention;

[0075] Figure 2 A schematic diagram of an ecological flow calculation process line calculated for a specific embodiment of the present invention;

[0076] Figure 3 A schematic diagram of the monthly satisfaction guarantee rate calculated for a specific implementation of the present invention;

[0077] Figure 4A schematic diagram of the ecological flow control line of the Maotai hydrological station section of the Chishui River calculated according to a specific embodiment of the present invention;

[0078] Figure 5 This is a schematic diagram of the compensation threshold in the river channel of the Maotai hydrological station section of the Chishui River calculated according to a specific implementation method of the present invention. DETAILED DESCRIPTION

[0079] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0080] This embodiment implements the present invention with the Maotai section of Chishui River as the object.

[0081] The Chishui River Basin is located on the south bank of the Sichuan River. The basin is located in the border area of ​​Yunnan, Guizhou and Sichuan provinces, at 104°4*′-106°5*′ east longitude and 27°1*′-28°5*′ north latitude. It flows through Maotai Town, Zunyi City, Guizhou Province, at 106°2*′ east longitude and 27°5*′ north latitude.

[0082] S1: Select indicators to construct a river health evaluation system based on the concept of near-nature and formulate river health grade evaluation standards, which specifically include the following steps:

[0083] S101: Construct a river health assessment system based on a near-nature concept, including four criteria: hydrological integrity, chemical integrity, morphological integrity, and biological integrity;

[0084] S102: Construct a river health evaluation system based on the concept of near-nature, including 10 indicator layers corresponding to 4 criterion layers, as shown in Table 3:

[0085] Table 3 River health assessment system based on the concept of near-nature

[0086]

[0087] S103: The target layer river health level is divided into five levels: I, II, III, IV, and V, which correspond to five health levels: very healthy, healthy, sub-healthy, unhealthy, and pathological. The range values ​​of each indicator of the health level are formulated:

[0088] Table 4 Range values ​​of various indicators at different levels

[0089]

[0090] S2: Calculate the comprehensive weight of river health assessment, including the following steps:

[0091] S201: Subjective calculation weights are first scored by three experts according to a scale, where 1 means that two elements are equally important; 3 means that one element is slightly more important than the other; 5 means that one element is significantly more important than the other; 7 means that one element is strongly more important than the other; 9 means that one element is extremely more important than the other; 2, 4, 6, and 8 represent the middle values ​​of the above adjacent judgments. Each expert constructs his or her own judgment matrix according to the scale.

[0092] For each element a in the judgment matrix ij , calculate its geometric mean

[0093] Construct a comprehensive judgment matrix. The indicator importance judgment matrix is ​​shown in Table 5;

[0094] S202: Calculate the eigenvector of the judgment matrix and perform a consistency test. The consistency test results are shown in Table 6. The calculation results show that the maximum eigenvalue is 10.755. According to the RI table, the corresponding RI value is 1.486. Therefore, CR = CI / RI = 0.056 < 0.1, and the consistency test is passed.

[0095] S203: Calculate the combined weight vector to synthesize the weights of each level. The analysis results are shown in Table 7;

[0096] Table 5 Index importance judgment matrix

[0097] index <![CDATA[C1]]> <![CDATA[C2]]> <![CDATA[C3]]> <![CDATA[C4]]> <![CDATA[C5]]> <![CDATA[C6]]> <![CDATA[C7]]> <![CDATA[C8]]> <![CDATA[C9]]> <![CDATA[C 10 ]]> <![CDATA[C1]]> 1 2 0.25 0.25 0.333 0.5 0.5 0.5 0.5 0.333 <![CDATA[C2]]> 0.5 1 0.2 0.2 0.5 0.333 0.5 0.4 0.4 0.333 <![CDATA[C3]]> 4 5 1 1 2 2 2 2.5 0.333 1 <![CDATA[C4]]> 4 5 1 1 2.5 2.5 1.667 2.5 1 1 <![CDATA[C5]]> 3 2 0.5 0.4 1 2 1.429 2 1 0.5 <![CDATA[C6]]> 2 3 0.5 0.4 0.5 1 1.25 1 0.5 0.077 <![CDATA[C7]]> 2 2 0.5 0.6 0.7 0.8 1 1 0.5 0.333 <![CDATA[C8]]> 2 2.5 0.4 0.4 0.5 1 1 1 0.5 0.333 <![CDATA[C9]]> 2 2.5 3 1 1 2 2 2 1 0.333 <![CDATA[C 10 ]]> 3 3 1 1 2 13 3 3 3 1

[0098] Table 6 Consistency test results

[0099] Maximum characteristic root CI value RI value CR value Consistency test results 10.755 0.084 1.486 0.056 pass

[0100] Table 7 Analysis results

[0101]

[0102] S204: Sort the levels as a whole, and then get the importance ranking of each indicator, record the weight W j , the weight calculation results show that the weight of indicator 1 is 4.212%, the weight of indicator 2 is 3.409%, the weight of indicator 3 is 14.149%, the weight of indicator 4 is 15.332%, the weight of indicator 5 is 9.284%, the weight of indicator 6 is 6.232%, the weight of indicator 7 is 6.611%, the weight of indicator 8 is 6.248%, the weight of indicator 9 is 13.072%, and the weight of indicator 10 is 21.451%.

[0103] S205: Determination of objective weights First, normalization preprocessing is performed on the data;

[0104] S206: Calculate information entropy e according to the following formula j :

[0105]

[0106]

[0107] Among them, e j is the entropy value of the jth indicator, p ij is the numerical weight of the jth indicator of the i-th project, z ij is the value of the jth indicator of the ith project;

[0108] S207: Calculate the variation index d according to the following formula j :

[0109] d j =1-e j ;

[0110] Among them, d j is the variation index of the jth indicator;

[0111] S208: Calculate the entropy weight v according to the following formula j , the calculation results are shown in Table 8.

[0112]

[0113] Among them, v j is the entropy weight of the jth indicator.

[0114] Table 8 Objective weight calculation results

[0115] project Information entropy value e Information utility value d Weight (%) Water resources development and utilization rate C1 0.896 0.104 10.949 Minimum downstream ecological flow satisfaction degree C3 0.938 0.062 6.545 Water quality level C4 0.876 0.124 12.967 Drinking water source water quality compliance status C5 0.916 0.084 8.809 Vertical connectivity index C6 0.923 0.077 8.09 Riverbank stability C7 0.893 0.107 11.265 Riparian vegetation coverage C8 0.908 0.092 9.606 Macrobenthic fauna diversity index C9 0.908 0.092 9.649 Fish Stock Index C10 0.873 0.127 13.336 Flow process variation degree C2 0.916 0.084 8.783

[0116] The calculation results show that the weight of water resources development and utilization rate C1 is 10.949%, the weight of minimum downstream ecological flow satisfaction degree C3 is 6.545%, the weight of water quality quality degree C4 is 12.967%, the weight of drinking water source water quality compliance status C5 is 8.809%, the weight of longitudinal connectivity index C6 is 8.09%, the weight of riverbank stability C7 is 11.265%, the weight of riparian vegetation coverage C8 is 9.606%, the weight of large benthic animal diversity index C9 is 9.649%, the weight of fish retention index C10 is 13.336%, and the weight of flow process variation degree C2 is 8.783%. The maximum weight of the indicator is fish retention index C10 (13.336%), and the minimum weight is minimum downstream ecological flow satisfaction degree C3 (6.545%).

[0117] S209: Combined weight w j and weight v j, the comprehensive weight of river health assessment is calculated by multiplication synthesis method

[0118]

[0119] The method of combining subjective and objective weights not only avoids excessive subjective influence, but also reduces the impact of sudden changes in indicator value data, making the calculated weights more convincing. The comprehensive weights obtained based on the above calculations are shown in Table 9.

[0120] Table 9 Index weight calculation results

[0121] index subjective objective Comprehensive weight Indicator properties <![CDATA[C1]]> 0.042 0.099 0.040 + <![CDATA[C2]]> 0.034 0.088 0.029 <![CDATA[C3]]> 0.141 0.065 0.089 + <![CDATA[C4]]> 0.153 0.110 0.162 + <![CDATA[C5]]> 0.093 0.088 0.079 + <![CDATA[C6]]> 0.062 0.081 0.049 + <![CDATA[C7]]> 0.066 0.113 0.072 + <![CDATA[C8]]> 0.062 0.116 0.070 + <![CDATA[C9]]> 0.131 0.106 0.134 + <![CDATA[C 10 ]]> 0.215 0.133 0.276 +

[0122] S3: Select multiple methods to calculate the ecological flow process of the river control section, which includes the following steps:

[0123] S301: Select the monthly average runoff measured data of Maotai Hydrological Station from 1958 to 2021;

[0124] S302: Six schemes are used to calculate the ecological flow process of the river control section. The calculation results of ecological flow of each method are shown in Table 10:

[0125] (1) Option 1: Based on the long series of natural monthly average flow, monthly average water level or runoff of the control section for 30 years or more, a series of frequencies composed of the driest monthly average flow of each year are used to select the driest monthly average flow, monthly average water level or runoff at different frequencies as the ecological flow of the river control section. The frequency is generally 90%.

[0126] (2) Option 2: Based on the monthly average flow data, in order to avoid the impact of data from extremely dry and abundant years, data with a frequency below 5% and above 95% are eliminated, and the ratio of the sum of the minimum flow of each month to the sum of the monthly average flow is calculated. The product of this ratio and the average flow of each month is the ecological flow of each month.

[0127] (3) Option 3: Based on the precipitation and runoff characteristics of the basin, the year is divided into four seasons: spring, summer, autumn and winter. The ratio of the flow value corresponding to the 95% runoff frequency in each month of each season to the seasonal monthly average is defined as the frequency coefficient; finally, the frequency coefficient is multiplied by the median flow of each month to obtain the ecological flow of that month.

[0128] (4) Option 4: Considering the seasonal variation of the river, the monthly average flow of a certain frequency is used to express the required ecological flow. The previous research results and the biological characteristics of fish in the Chishui River Basin are comprehensively analyzed, and the specific percentage is taken as 30%.

[0129] (5) Option 5: divide the long series into wet years, normal years, and dry years, and take the monthly average flow corresponding to the 90% guarantee rate of the normal year group as the ecological flow.

[0130] (6) Scheme 6: Use observational data to correct the input parameter distribution through the likelihood function, and use random sampling to converge it to the Bayesian posterior distribution. The samples obtained by statistical sampling can be used to calculate the posterior distribution of the parameters. According to the posterior distribution of the parameters, the ecological flow is calculated based on the monthly frequency method based on the P-III distribution.

[0131] Table 10 Ecological flow calculation results of each scheme

[0132] month Solution 1 Solution 2 Option 3 Option 4 Option 5 Option 6 1 23.8 11.8 26.3 22.1 31.1 28.3 2 23.8 13.2 28.5 23.9 36.4 31.3 3 23.8 13.4 19.8 24.0 30.5 26.2 4 23.8 17.8 22.3 27.0 37.8 21.5 5 23.8 28.3 36.9 44.6 50.5 38.6 6 23.8 51.4 88.3 84.5 106.4 86.6 7 23.8 58.2 101.3 97.0 115.8 90.4 8 23.8 46.0 79.9 76.5 66.8 46.7 9 23.8 33.7 47.9 56.0 59.0 37.9 10 23.8 25.3 36.6 42.8 48.0 37.6 11 23.8 16.9 23.2 27.1 42.8 29.3 12 23.8 12.7 27.1 22.7 36.4 28.7

[0133] S4: Comprehensive determination of the compensation control threshold in the river channel specifically includes the following steps:

[0134] S401: Quantitative analysis of the correlation between the monthly ecological flow series and the multi-year average monthly runoff. The Pearson correlation coefficient R ranges from -1 to 1. The closer its absolute value is to 1, the better the correlation is, that is, the better the hydrological rhythm evaluation is. Combined with Table 11 and Figure 2-3 It can be seen that the results of the ecological flow calculated by Scheme 1 are consistent in each month, which fails to reflect the seasonal variation characteristics of the annual runoff, so its results are not correlated with the hydrological rhythm. Except for Scheme 1, the other five schemes are significantly correlated at the P≤0.01 level (two-tailed), and the correlation coefficients are all above 0.9, and the hydrological rhythm fitting is good. Among them, the ecological flow process calculated by Scheme 2 has the best fitting effect with the actual runoff, with a correlation coefficient of 0.999. The second is Scheme 4, with a correlation coefficient of 0.999. Among the other five methods, Scheme 6 has a relatively poor fitting effect with the hydrological rhythm, with a correlation coefficient of 0.922.

[0135] Table 11 Correlation between ecological flow calculated by each scheme and multi-year average flow

[0136] plan Correlation coefficient Solution 1 0 Solution 1 0.999** Option 3 0.976** Option 4 0.998** Option 5 0.966** Option 6 0.922**

[0137] Note: **Significant correlation at P≤0.01 level (two-tailed).

[0138] S402: Select the monthly average flow to analyze the degree of ecological flow guarantee. The ratio of the time series length when the flow in the river is greater than the ecological flow to the total series time length is the ecological flow satisfaction. The ecological flow process lines calculated by each scheme are as follows: Figure 2 From the monthly scale analysis, the ecological flow results calculated by the six schemes in the dry season are roughly the same, but the results calculated by various schemes in the flood season are quite different, among which the ecological flow process results calculated by scheme 5 are larger than those of other schemes.

[0139] From the perspective of ecological flow satisfaction, Scheme 1 and Scheme 2 have a high degree of satisfaction throughout the year, with a satisfaction degree of more than 95% in each period, which is also easy to achieve in dry years. Scheme 6 is second only to the above two schemes in terms of satisfaction in each period, with a satisfaction degree of only 89.1% in March, May and October, and a satisfaction degree of more than 90% in the remaining months, which better meets the needs of river water ecology; Scheme 3, Scheme 4 and Scheme 5 have a low degree of satisfaction in the flood season, reaching only about 75% in some months, and there may be competition for water use with outside the river during the flood season in normal water years and dry years.

[0140] S403: Based on the percentage relationship between the ecological flow in the river and the multi-year average natural flow, the ecological environment of the river under the ecological flow scenario is evaluated. For example, when the ecological flow is 10% of the natural flow, it means that the current ecological flow can maintain the survival of the river biological habitat at the minimum; 30% means that a suitable habitat ecosystem can be maintained; 60% to 100% means that the natural ecosystem of the river is basically achieved. The calculation results of the above schemes are compared and evaluated as shown in Table 12.

[0141] Table 12 Ecological flow evaluation results of each scheme

[0142]

[0143] S404: Based on the evaluation results of S401-S403, comprehensively determine the inner edge line of the ecological flow process control, the median line of the ecological flow process control, and the outer edge line of the ecological flow process control of the river control section, and use the three ecological flow process control lines as the basis for the compensation control threshold in the river channel. The section above the Chishui River where the Maotai hydrological station is located involves the Chishui River Yunnan-Guizhou-Sichuan buffer zone and the rare and unique fish nature reserve in the upper reaches of the Yangtze River (Chishui River Guizhou section). The minimum discharge flow of the Maotai hydrological station section is 23.0m 3 / s. The minimum discharge flow of the Maotai hydrological station section is 23.8m / s after the hydrological data is extended to 2021 and the first scheme is used to calculate 3 / s, the result is close to the minimum downstream flow rate recorded in the data.

[0144] In the fish spawning period (May to October), the percentage of ecological flow to natural flow in Scheme 1 is less than 30%, which cannot meet the suitable conditions for the habitat of most aquatic organisms. Therefore, Scheme 1 is not applicable to the Chishui River. During the fish spawning period (May to October), excessive ecological water use in the river may lead to prominent competitive water use inside and outside the river, resulting in insufficient water use for other industries, thereby aggravating the contradiction of "three life water use". Therefore, the results of Schemes 3, 4 and 5 are not applicable to the Chishui River during the fish spawning period (May to October).

[0145] The minimum downstream flow of rivers mainly guarantees the basic species health and benign cycle of river water ecosystems, but the ecological water volume of rivers also needs to maintain the multi-dimensional service functions of water ecosystems. For the long-term development of ecosystems, there should be a certain reserved space for ecological flow. In the fish spawning period (May to October), schemes 2 and 6 with evaluation levels of "medium" to "very good" are coupled, and their outer envelope is taken as the outer edge line of the ecological flow process control in the flood season, and their inner envelope is taken as the median line of the ecological flow process control in the flood season. In the dry season (November to April), scheme 1 is used as the dry season ecological flow process control line.

[0146] S5: Evaluate the health level of the river;

[0147] Furthermore, the step S5 of evaluating the river health level specifically includes the following steps:

[0148] S501: Based on the river health evaluation system of the near-nature concept described in step S2, construct a matter-element matrix R:

[0149]

[0150] Where R(N, C, V) is the matter-element matrix; the thing to be evaluated is recorded as N; c represents the n features of the evaluated matter-element; and v represents the value of the n features.

[0151] S502: Based on the river health evaluation system of the near-nature concept described in step S2, a classic domain R is constructed. j :

[0152]

[0153] Where N j represents the jth level of matter-element; v ji It represents the value range of the i-th evaluation index of the matter-element at this feature level;

[0154] S503: Based on the river health evaluation system of the near-nature concept described in step S2, construct a section R p :

[0155]

[0156] In the formula, v pi Represents matter-element with respect to feature c i The value range of

[0157] S504: Based on the river health evaluation system of the near-nature concept described in step S2, a comprehensive correlation degree calculation is performed:

[0158]

[0159] In the formula, is the combined weight determined in step 1.9, k j (v i ) is the correlation degree of the evaluation matter-element at the jth level and the i-th indicator;

[0160]

[0161] Among them, k j (v i ) represents the correlation degree of the i-th indicator at the j-th level; p ji (v xi , v ji ) represents the evaluation of matter-element to interval v ji The distance v pi represents the value range of the i-th index of the evaluation element; v ji represents the value range of the jth level and the ith indicator; v xi Indicates v ji The value range of a certain point in

[0162]

[0163] Where a represents v ji Lower limit, b represents v ji Upper limit.

[0164] After formulating the corresponding indicators for each level, each indicator is standardized to obtain the classic domain and section domain of the indicator. The correlation between the indicator layer, criterion layer and river health level for each level is calculated according to the correlation calculation method. The classic domain and section domain of the evaluation indicator are shown in Table 13. Chishui River (above Maotai section)

[0165] The correlation between the near-natural river health assessment levels from 2017 to 2021 is shown in Table 14.

[0166] Table 13 Evaluation indicators in classic domain and section domain

[0167]

[0168] Table 14 Correlation of the health assessment level of the Chishui River (above the Maotai section) from 2017 to 2021

[0169]

[0170] From the perspective of different criterion layer types, the hydrological integrity of the Chishui River (above the Maotai section) reached a very healthy level from 2017 to 2021, and the chemical integrity, morphological structure integrity and biological integrity all reached a healthy level. From the perspective of different indicator types, the indicators with a large weight and relatively low current health level are water quality C4 and fish retention index C10. In order to maintain the healthy status of the river, it is necessary to ensure that sewage is discharged in compliance with standards, strictly control the approval of sewage outlets into the river, gradually promote the control of non-point source pollution in the basin, and develop a regional water pollution prevention and control system.

[0171] S6: Based on the river health evaluation system of the near-nature concept and the river health evaluation results of step S5, a response relationship between the river health level and the compensation control threshold in the river channel is established to determine the health status of the river and the compensation control threshold in the river channel, specifically:

[0172] For rivers in the healthy and between healthy and very healthy levels, the inner edge of ecological flow process control is used as the compensation control threshold in the river channel;

[0173] For rivers in sub-health and between sub-health and health, the median line of ecological flow process control is used as the compensation control threshold in the river channel;

[0174] For rivers in the pathological state and between the pathological state and sub-healthy state, the outer edge of ecological flow process control is used as the compensation control threshold in the river channel;

[0175] like Figure 4-Figure 5 As shown, the inner edge line of the ecological flow process control corresponds to the minimum ecological flow process control line, the median line of the ecological flow process control corresponds to the appropriate ecological flow process control line, and the outer edge line of the ecological flow process control corresponds to the recommended ecological flow process control line. According to the river health evaluation results of the near-nature concept in step S5, the health status of the river and the compensation control threshold in the river channel are determined. According to the judgment principle of the compensation control threshold in the river channel: the Chishui River (above the Maotai section) is at the "healthy" level, and the inner edge line of the ecological flow process control is implemented as the compensation control threshold in the river channel. Overall, the river health status evaluation level of the Chishui River (above the Maotai section) is in a healthy state.

[0176] At present, the minimum ecological flow of the Maotai section of the Chishui River is calculated using Scheme 1, which has no correlation with the hydrological rhythm and fails to reflect the seasonal variation characteristics of the annual runoff. In addition, the percentage of ecological flow to natural flow in Scheme 1 during the fish spawning period (May to October) is less than 30%, which cannot meet the suitable conditions for most aquatic organisms. Once the river health level shows a downward trend, the compensation control threshold in the river channel must be implemented in time according to the ecological flow control process line corresponding to the river health level.

[0177] Although the present invention has been described in detail above by general explanation and specific implementation methods, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for determining a compensation control threshold in a river channel, characterized in that: The following steps are involved: S1 Select indicators to construct a river health evaluation system based on the concept of near-nature and formulate river health grade evaluation standards, specifically: S101 Construct the criteria layer of river health assessment system; S102 constructs the indicator layer corresponding to the river health assessment system and the criterion layer; S103 classifies the health level of the target layer rivers and establishes the range value of each indicator of the health level level; S2 calculates the comprehensive weight of river health assessment, which is: S201 subjective calculation weights are first fuzzy quantized through expert scoring to form a judgment matrix, which is then scored by experts to construct a comprehensive judgment matrix; S202 calculates the eigenvector of the judgment matrix and performs consistency check; S203 calculates the combined weight vector to synthesize the weights of each level; S204 sorts the levels as a whole, and then obtains the importance ranking of each indicator, and records the weight W j ; S205 Determination of objective weights First, the data is normalized and preprocessed; S206 calculates the information entropy e according to the following formula j : Among them, e j is the entropy value of the jth indicator, p ij is the numerical weight of the jth indicator of the i-th project, z ij is the value of the jth indicator of the ith project; S207 calculates the variation index d according to the following formula j : d j =1-e j ; Among them, d j is the variation index of the jth indicator; S208: Calculate the entropy weight v according to the following formula j : Among them, v j is the entropy weight of the jth indicator; S209 combined with weight w j and weight v j , calculate the comprehensive weight of river health assessment S3 calculates the ecological flow process of the river control section; S301 collects the monthly average runoff data of the hydrological reference station and compares the runoff of the hydrological station to the design section; S302 calculates the ecological flow process of the river control section according to the data; S4 determines the compensation control threshold in the river channel; S401 quantitatively analyzes the correlation between monthly ecological flow series and average monthly runoff; S402 selects the monthly average flow to analyze the ecological flow guarantee degree and determines the ecological flow satisfaction degree; S403 calculates the percentage relationship between the monthly ecological flow and the average natural flow, and evaluates the ecological environment of the river under the ecological flow scenario; S404 Based on the evaluation results, comprehensively determine the annual ecological flow process control inner edge line, ecological flow process control median line and ecological flow process control outer edge line of the river control section, and use the three ecological flow process control lines as the basis for the compensation control threshold in the river channel; S5 evaluates the river health level, specifically: S501 constructs a matter-element matrix R based on the river health evaluation system of the near-nature concept described in step S2: In the formula, R(N, C, V) is the matter-element matrix; the thing to be evaluated is recorded as N; c represents the n features of the evaluation matter-element, and v represents the value of the n features; S502 constructs a river health evaluation system based on the near-nature concept described in step S2, and constructs a classic domain R j : Where N j represents the jth level of matter-element; v ji It represents the value range of the i-th evaluation index of the matter-element at this feature level; S503 Based on the river health evaluation system of the near-nature concept described in step S2, construct a section R p : In the formula, v pi Represents matter-element with respect to feature c i The value range of S504 performs comprehensive correlation calculation based on the river health evaluation system of the near-nature concept described in step S2: In the formula, is the combined weight determined in step 1.9, k j (v i ) is the correlation degree of the evaluation matter-element at the jth level and the i-th indicator; Among them, k j (v i ) represents the correlation degree of the i-th indicator at the j-th level; p ji (v xi , v ji ) represents the evaluation of matter-element to interval v ji The distance v pi represents the value range of the i-th index of the evaluation element; v ji represents the value range of the jth level and the ith indicator; v xi Indicates V ji The value range of a certain point in Where a represents V ji Lower limit, b represents V ji Upper limit; S6 establishes a response relationship between the river health grade and the compensation control threshold in the river channel based on the river health evaluation system of the near-nature concept and the river health evaluation result of step S5, and determines the health status of the river and the compensation control threshold in the river channel.

2. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: The S101 constructs a river health assessment system that includes four criteria layers: hydrological integrity, chemical integrity, morphological structural integrity, and biological integrity.

3. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: The S102 constructs a river health evaluation system, including 10 indicator layers corresponding to the quasi-measurement layers, specifically: water resource development and utilization rate C1, flow process variation degree C2 and minimum downstream ecological flow satisfaction degree C3 corresponding to hydrological integrity; water quality quality C4 and drinking water source water quality compliance status C5 corresponding to chemical integrity; longitudinal connectivity index C6, riverbank stability C7 and riparian vegetation coverage C8 corresponding to morphological and structural integrity; large benthic animal diversity index C9 and fish retention index C10 corresponding to biological integrity.

4. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: S103 classifies the health grade of the target layer river, specifically, the health grade of the target layer river is divided into 5 grades, namely, I, II, III, IV, and V, which correspond to 5 health levels, namely, very healthy, healthy, sub-healthy, unhealthy, and pathological.

5. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: S103 Establish the range values ​​of each indicator of health level, specifically:

6. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: The S401 quantitatively analyzes the correlation between the monthly ecological flow sequence and the average monthly runoff. The Pearson correlation coefficient R ranges from -1 to 1. The closer its absolute value is to 1, the better the correlation is, that is, the better the hydrological rhythm evaluation is.

7. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: The S402 selects the monthly average flow to analyze the degree of ecological flow guarantee, and the ratio of the time series length when the flow in the river channel is greater than the ecological flow to the total series time length is the ecological flow satisfaction.

8. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: The subjective calculation weights in S201 are first fuzzily quantized through expert scoring to form a judgment matrix, which is scored by experts. Each expert constructs his own judgment matrix according to the scale. For each element in the judgment matrix, its geometric mean is calculated to construct a comprehensive judgment matrix.

9. The method for determining the compensation control threshold in a river channel according to claim 1, characterized in that: S6 determines the in-channel compensation control threshold of the river, specifically: For rivers in the healthy and between healthy and very healthy levels, the inner edge of ecological flow process control is used as the compensation control threshold in the river channel; For rivers in sub-health and between sub-health and health, the median line of ecological flow process control is used as the compensation control threshold in the river channel; For rivers that are in a pathological state or between pathological and sub-healthy levels, the outer edge of the ecological flow process control line is used as the compensation control threshold within the river channel.

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