A method for evaluating river longitudinal connectivity

Abstract

The present invention discloses a method for evaluating the longitudinal connectivity of a river, and belongs to the technical field of water resources. The specific steps of the method of the present invention include: obtaining barrier information that affects the longitudinal connectivity of the river; classifying the barrier information to obtain the barrier type and the distance between barriers, and further obtaining the comprehensive impact factor a of the natural barrier. i ; Set the barrier factor P i , and according to the barrier coefficient P i and natural barrier comprehensive impact factor a i , and obtain the river longitudinal connectivity index S; construct an evaluation standard for river longitudinal connectivity, and obtain the health evaluation result of river longitudinal connectivity in combination with the river longitudinal connectivity index S. The method of the present invention overcomes the defect that the existing river longitudinal connectivity evaluation method only evaluates artificial barriers such as river-blocking buildings or facilities, and achieves a more objective evaluation of the longitudinal connectivity of rivers in the evaluation area, and is suitable for wide promotion and application. It is also of great significance for the construction and demolition site selection of river-blocking buildings or facilities such as reservoirs and hydropower stations.

Description

Technical Field

[0001] The invention belongs to the technical field of water resources, and in particular relates to a method for evaluating the longitudinal connectivity of a river. Background Art

[0002] The evaluation of river longitudinal connectivity is of great significance for achieving river health and the construction and demolition site selection of river-blocking structures or facilities such as dams. The methods actually used in the existing technology for river health evaluation mainly use the barrier coefficient method to calculate the longitudinal connectivity index of the river to evaluate the longitudinal connectivity of the river. Among them, the longitudinal connectivity index is calculated based on the number, type and barrier coefficient of artificial barriers such as dams or facilities. Some studies consider the scale and location of artificial barriers.

[0003] Natural waterfalls and steep slopes hinder the upstream movement of fish, causing natural fragmentation of river habitats, which to some extent offset the blocking effect of river-blocking buildings or facilities such as reservoirs and hydropower stations in upstream and downstream sections. Relevant scholars occasionally involve natural waterfalls (such as waterfalls) in their research on the longitudinal connectivity of rivers, but the analysis methods are relatively complex and not intuitive enough, and cannot be directly applied to the improvement of technical standards, which is not conducive to the promotion of technical methods.

[0004] The river longitudinal connectivity indicators in the existing water conservancy industry technical standards "Guidelines for River and Lake Health Assessment (Trial)" and local standards "River, Lake (Reservoir) Health Assessment Specifications" (DB35 / T 2096-2022) and "Technical Specifications for River and Lake Health Assessment in Mountainous Areas" (DB 3311 / T 222-2022) are not suitable for mountain rivers or do not have the obvious characteristics of mountain rivers, and cannot avoid the impact of steep changes in natural terrain on the evaluation results of river longitudinal connectivity. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for evaluating the longitudinal connectivity of rivers, so as to solve the technical problem that the evaluation of the longitudinal connectivity of rivers in mountainous areas in the prior art is not objective and accurate enough.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide a method for evaluating the longitudinal connectivity of a river, comprising the following steps:

[0007] S1. Generalize the river system and obtain the barrier information that affects the longitudinal connectivity of the river;

[0008] S2. Classify the barrier information to obtain the barrier type and the distance between barriers; and obtain the comprehensive impact factor a of natural barriers based on the barrier type and the distance between barriers. i ;

[0009] S3. Set the barrier coefficient P i , and according to the barrier coefficient P iand natural barrier comprehensive impact factor a i , and obtain the river longitudinal connectivity index S;

[0010] S4. Construct an evaluation standard for the longitudinal connectivity of rivers, and obtain the health evaluation results of the longitudinal connectivity of rivers based on the river longitudinal connectivity index S and the evaluation standard.

[0011] On the basis of the above technical solution, the present invention can also be improved as follows:

[0012] Further, step S1 is specifically as follows: generalize the river system using high-resolution remote sensing data, use image objects as processing units, and adopt image object-oriented methods to classify remote sensing data and obtain information to obtain barrier information that affects the longitudinal connectivity of the river.

[0013] Further, step S2 is specifically as follows:

[0014] S201, classifying the barrier information to obtain the barrier type and the distance between the barriers;

[0015] S202. Obtain the comprehensive impact factor a of natural barriers based on the barrier type and distance between barriers. i :

[0016] When LT ij When <0.1, a ij =0;

[0017]

[0018] When LT ij ≥K ij When ij =1;

[0019]

[0020] Among them, a i is the comprehensive impact factor of natural barriers on artificial barriers; a ij is the natural barrier impact factor of natural barriers on artificial barriers; LT ij is the distance between natural barriers and artificial barriers, in km; K ij is the maximum impact range of natural barriers on the longitudinal connectivity of artificially blocked rivers, in km; n is the number of natural barriers; i is the serial number of artificial barriers; j is the serial number of natural barriers.

[0021] Further, step S3 is specifically as follows: according to the number and degree of influence of river-blocking structures or facilities affecting the longitudinal connectivity of the river within the unit river length, the longitudinal connectivity index S of the river is obtained:

[0022]

[0023] Where m is the number of artificial barriers that affect the longitudinal connectivity of the river; L is the length of the river in km.

[0024] The beneficial effects of the present invention are as follows: the method of the present invention overcomes the defect of existing river longitudinal connectivity evaluation methods that only evaluate artificial barriers such as river-blocking structures or facilities, reflects the terrain influence of natural barriers, and achieves a more objective evaluation of the longitudinal connectivity of rivers in the evaluation area. It is suitable for wide promotion and application, and is also of great significance for the site selection for the construction and demolition of river-blocking structures or facilities such as reservoirs and hydropower stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the method of the present invention;

[0026] Figure 2 A schematic diagram of the main stream of Tongzi River and the locations of artificial and natural barriers;

[0027] Figure 3 Schematic diagram of the impact range and influencing factors of natural barriers. DETAILED DESCRIPTION

[0028] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. If no specific conditions are specified in the embodiments, the embodiments are carried out under normal conditions. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0029] Example

[0030] This embodiment takes the main stream of Tongzi River in Guizhou Province as an example to illustrate the implementation process of the river longitudinal connectivity evaluation method of this application. The Tongzi River Basin is located in the slope zone where the Yunnan-Guizhou Plateau transitions to the southern Hunan hills and the Sichuan Basin. The terrain is high in the east and low in the west. The highest point is at the source, with an elevation (Yellow Sea base) of 1872m; the lowest point is at the estuary, with an elevation of 330m, a natural drop of 1542m, and an altitude of generally 800-1300m. The basin has a complex landform type, mainly mountainous terrain, with some hills and a small number of flat plains and river valley basins. The mountains in the Tongzi River Basin are all branches of the Dalou Mountains. The Dalou Mountains start from Bijie City in the west and extend to Sichuan Province in the northeast. They are northeast-southwest. They are both the watershed between the Wujiang River system and the Chishui River, and the boundary mountain between the Guizhou Plateau and the Sichuan Basin. The Tongzi River Basin is dominated by medium and low mountains, with high mountains and deep valleys, obvious vertical differences in mountains, and relatively scattered cultivated land.

[0031] The Tongzi River originates from Meizi Village, Mazong Township, Tongzi County. It is a first-level tributary on the right bank of the Chishui River. It flows into the Chishui River at Lianghekou, Xijiu Town, Xishui County. The river spans four counties (cities), namely Tongzi, Zunyi, Renhuai and Xishui, with a drainage area of ​​3,362 km 2 The main stream is 126 km long and has an average slope of 12.3‰.

[0032] The longitudinal connectivity of the Tongzi River was evaluated using the method of the present invention. Figure 1 As shown, the following steps are included:

[0033] S1. Generalize the river system and obtain the barrier information that affects the longitudinal connectivity of the river;

[0034] In the process of obtaining barrier information that affects the longitudinal connectivity of rivers, high-resolution remote sensing data is used to generalize the river system, and image objects are used as processing units. Image-oriented methods are used to classify remote sensing data and obtain information. Through remote sensing image analysis and interpretation, preliminary information on artificial and natural barriers in the mainstream of Tongzi River is extracted. In combination with relevant water conservancy and hydropower project planning and statistical data, Tongzi River's "one river, one policy" plan and other materials, as well as field surveys, the barrier information is reviewed to obtain the barrier information of the longitudinal connectivity of the mainstream of Tongzi River. Specifically:

[0035] S101, multi-scale image segmentation

[0036] The natural or artificial barriers in the image are segmented, and the segmentation results are obtained by setting different segmentation scales, color and shape factor weights. The larger the segmentation scale and shape factor weights are, the more complete the object is; conversely, the more "fragmented" the object is; then spectral difference segmentation is used for auxiliary segmentation to optimize the "over-segmented" image.

[0037] Image segmentation is the process of generating image objects, which provides a basis for subsequent image classification. In the process of generating image object layers, the multi-scale image segmentation method divides the ground objects into meaningful objects with the premise of minimizing information loss.

[0038] S102, Standard nearest neighbor function classification

[0039] S1021, determine the barrier category: the image is first transformed by standard false color, and then the barrier category is defined by visual judgment and the spectral characteristics and texture characteristics of the main barriers in the evaluation area to identify natural barriers or artificial barriers in the river channel;

[0040] S1022, define and optimize feature space: first select multiple feature spaces for classification through remote sensing interpretation software, and obtain the result of feature optimization through testing; then select feature values ​​through experiments, such as average brightness value, spectral characteristics of three bands, and maximized difference, etc.;

[0041] S1023, selecting samples: selecting samples for each type of blockage in the image object based on the segmentation results, and analyzing the characteristics of the samples through the remote sensing interpretation software system;

[0042] S1024, classification: select the standard nearest neighbor classification method to classify the image objects, and finally identify and extract the barrier information that affects the longitudinal connectivity of the river.

[0043] S103, Blocking Information Review

[0044] To ensure the accuracy of river barrier information interpreted from remote sensing data, for rivers where longitudinal connectivity evaluation is planned, comprehensive information such as river basin comprehensive planning, river-related water conservancy and hydropower project planning, “one river, one policy” plans, river health evaluation reports, etc. from the water conservancy and hydropower departments are collected to review information such as the type, quantity, and location of barriers that affect the longitudinal connectivity of rivers. When insufficient data is collected, additional field surveys are conducted to review and confirm information on artificial and natural barriers along the river.

[0045] S2. Classify the barrier information to obtain the barrier type and the distance between barriers; and obtain the comprehensive impact factor a of natural barriers based on the barrier type and the distance between barriers. i ; Specifically:

[0046] S201, classify the barrier information to obtain natural barrier type, artificial barrier type ( Figure 2 ) and the distance between the barrier;

[0047] Artificial barriers: There are 14 artificial barriers in the main stream of Tongzi River, including: 2 reservoir dams, namely Tianmenhe Reservoir and Xinqiao Reservoir; 8 barrage-type hydropower stations, namely Daijiagou Power Station, Baijiapo Power Station, Guantang Power Station, Entan Power Station, Qixin Power Station, Yuanmanguan Power Station, Yangjiayuan Power Station, Jinyang Power Station; 4 overflow dams;

[0048] Natural barriers: There are 3 natural barriers in the main stream of Tongzi River, including 2 waterfalls and 1 open and dark river alternation. The natural waterfalls are Daijiagou waterfall and Guantang waterfall. Daijiagou waterfall is located 172m upstream of Daijiagou Hydropower Station, with a waterfall height of 85m; Guantang waterfall is located 1km downstream of Guantang Hydropower Station, with a waterfall height of 7m; the open and dark river alternation is located about 245m upstream of Daijiagou Hydropower Station.

[0049] S202. Obtain the comprehensive impact factor a of natural barriers based on the barrier type and distance between barriers. i :

[0050] According to the height of water drop and the strength of the barrier to fish upstream movement, natural barriers are divided into three categories:

[0051] (1) Waterfall

[0052] For a single drop with a large drop (a drop greater than 1m), fish cannot swim upstream. When there is a waterfall near the upstream and downstream of the artificial barrier, the barrier will have a reduced impact on the health of the river.

[0053] (2) Steep slope (small waterfall or small cascade waterfall)

[0054] The height difference is small, and the water depth is shallow during normal water season, so only small fish can swim upstream. However, it does not pose an obstacle to fish migration during flood season. Such natural barriers will not block the genetic exchange of fish and will not produce significant habitat fragmentation. When there are small waterfalls near the upstream and downstream of artificial barriers, the barrier effect will weaken the impact on river health.

[0055] (3) Alternation of light and dark rivers

[0056] After the open river becomes a dark river, and the dark river becomes an open river, the water level and flow of the dark river are unstable. The difference in flow between the dry season and the rainy season can reach 10 times or more than 100 times. Some dark rivers have fast-flowing water, waterfalls, and even cascades. Some can form underground lakes. When there are alternations between open and dark rivers near the upstream and downstream of artificial barriers, the barrier effect on the health of the river is reduced.

[0057] The effect of natural waterfalls in weakening the blocking effect of artificial barriers is more obvious than that of natural steep banks, and the effect of natural steep banks in weakening the blocking effect of artificial barriers is more obvious than that of alternating open and dark rivers.

[0058] like Figure 3 As shown in the figure, the closer the natural barrier is to the artificial barrier, the more obvious the effect of weakening the barrier effect of the artificial barrier is. If the artificial barrier is built at or very close to the natural barrier, its impact on the longitudinal connectivity of the river may overlap with the impact of the natural barrier on the longitudinal connectivity of the river, and the impact of the artificial barrier on the longitudinal connectivity of the river can be offset and regarded as negligible;

[0059] If an artificial barrier is built near a natural barrier, the natural barrier will have a significant weakening effect on the barrier effect of the artificial barrier; the farther the artificial barrier is from the natural barrier, the smaller the weakening effect of the natural barrier on the barrier effect of the artificial barrier;

[0060] If there is a natural barrier within a certain range near an artificial barrier, and the natural barrier is within 0.1 km of the artificial barrier, its impact factor on the artificial barrier is set to 0; when the natural barrier is far away from the artificial barrier and exceeds the impact range of the natural barrier on the longitudinal connectivity of the artificial barrier river, the natural barrier is deemed to have no impact on the artificial barrier.

[0061] Natural barrier comprehensive impact factor a i The calculation formula is as follows:

[0062] When LT ij When <0.1, a ij =0;

[0063]

[0064] When LT ij ≥K ij When ij =1;

[0065]

[0066] Among them, a i is the comprehensive impact factor of natural barriers on artificial barriers; a ij is the natural barrier impact factor of natural barriers on artificial barriers; LT ij is the distance between natural barriers and artificial barriers, in km; K ij is the maximum impact range of natural barriers on the longitudinal connectivity of artificial barrier rivers, in km; n is the number of natural barriers; i is the serial number of artificial barriers; j is the serial number of natural barriers; the maximum impact range of natural barriers on the longitudinal connectivity of artificial barrier rivers is shown in Table 1.

[0067] Table 1 Maximum impact range of natural barriers on the longitudinal connectivity of artificially blocked rivers

[0068]

[0069] S3. Set the barrier coefficient P i , and according to the barrier coefficient P i and natural barrier comprehensive impact factor a i , and obtain the river longitudinal connectivity index S;

[0070] Set the barrier coefficient P according to the barrier type i ; Evaluate the impact of the number and type of obstacles such as dams in the region on the migration of fish and other organisms, energy and nutrient transfer in the overall spatial structure of the region, and set the barrier coefficient P of different types of artificial barriers from the perspective of river health. i ,The specific settings are shown in Table 2. Natural barriers are the background components of the river ecosystem. Natural barriers themselves have no impact on river health, and the barrier coefficient of natural barriers is 0;

[0071] Table 2 River longitudinal connectivity barrier coefficient P i set up

[0072]

[0073]

[0074] The total length of the Tongzi River is 126 km, with 14 artificial barriers and 3 natural barriers. According to the type of artificial barrier project, the barrier coefficient P of each artificial barrier such as reservoir, river-blocking hydropower station, and overflow dam is selected in combination with Table 2. i According to the type of each natural barrier and its relative position to the artificial barrier, the influence factor of natural barriers on artificial barriers is analyzed and calculated. Daijiagou Hydropower Station and Baijiapo Hydropower Station are affected by two natural barriers near the upstream and downstream at the same time. The minimum value of the influence factors of the two natural barriers is taken as the comprehensive influence factor of natural barriers. The calculation results are shown in Table 3.

[0075] Table 3 Barrier coefficient P of artificial barrier i Calculation and analysis results of factors affecting natural barriers

[0076]

[0077]

[0078] The river longitudinal connectivity index S is obtained based on the number and degree of influence of river-blocking structures or facilities that affect the longitudinal connectivity of the river within a unit river length.

[0079] Taking into account the impact of natural terrain barriers in rivers, those with fish-passing facilities or those that do not affect fish migration are not included in the statistics;

[0080]

[0081] Where m is the number of artificial barriers that affect the longitudinal connectivity of the river; P i is the barrier coefficient of artificial barriers; L is the length of the river, in km;

[0082] S4. Construct the evaluation criteria for river longitudinal connectivity (Table 4). According to the river longitudinal connectivity index S and the evaluation criteria, obtain the health evaluation results of river longitudinal connectivity.

[0083] Table 4 Evaluation criteria for river longitudinal connectivity

[0084]

[0085]

[0086] If the influence of natural barriers on the longitudinal connectivity of the river is not considered, the barrier coefficient P of the artificial barriers in the mainstream of Tongzi River is i The total is 11, and the river longitudinal connectivity index S is 8.73 / 100km. According to Table 4, the health assessment result of the longitudinal connectivity of the mainstream river of Tongzi River is unhealthy.

[0087] According to the method of the present invention, after considering the topographic influence of natural barriers, the barrier coefficient P of the artificial barrier of the main stream of Tongzi River is calculated. i The total is 6.2, so the river longitudinal connectivity index S is 4.92 / 100km. According to Table 4, the health assessment result of the longitudinal connectivity of the mainstream river of Tongzi River is basically healthy, which is more in line with the actual situation and characteristics of mountain rivers.

Claims

1. A method for evaluating the longitudinal connectivity of a river, characterized in that: The following steps are involved: S1. Generalize the river system and obtain the barrier information that affects the longitudinal connectivity of the river; S2. Classify the barrier information to obtain the barrier type and the distance between barriers; and obtain the comprehensive impact factor a of natural barriers based on the barrier type and the distance between barriers. i ; Specifically: S201, classifying the barrier information to obtain the barrier type and the distance between the barriers; S202. Obtain the comprehensive impact factor a of natural barriers based on the barrier type and distance between barriers. i : When LT ij When <0.1, a ij =0; When 0.1≤LT ij <K ij hour, When LT ij ≥K ij When ij =1; Among them, a i is the comprehensive impact factor of natural barriers on artificial barriers; a ij is the natural barrier impact factor of natural barriers on artificial barriers; LT ij is the distance between natural barriers and artificial barriers; K ij is the maximum impact range of natural barriers on the longitudinal connectivity of artificially blocked rivers; n is the number of natural barriers; i is the serial number of artificial barriers; j is the serial number of natural barriers; S3. Set the barrier coefficient P i , and according to the barrier coefficient P i and natural barrier comprehensive impact factor a i , we get the river longitudinal connectivity index S; specifically: according to the number and degree of influence of river-blocking structures or facilities that affect the longitudinal connectivity of the river within a unit river length, we get the river longitudinal connectivity index S: Where m is the number of artificial barriers that affect the longitudinal connectivity of the river; L is the length of the river; S4. Construct an evaluation standard for the longitudinal connectivity of rivers, and obtain the health evaluation results of the longitudinal connectivity of rivers based on the river longitudinal connectivity index S and the evaluation standard.

2. The method for evaluating river longitudinal connectivity according to claim 1, characterized in that: The step S1 specifically includes: using high-resolution remote sensing data to generalize the river system, using image objects as processing units, and adopting image object-oriented methods to classify remote sensing data and obtain information, so as to obtain barrier information that affects the longitudinal connectivity of the river.

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