A method for monitoring benthic macroinvertebrates in different types of rivers

Abstract

The present invention belongs to the technical field of benthic animal monitoring, and in particular to a method for monitoring large benthic invertebrates in different types of wadable rivers. The method provides a method for monitoring large benthic invertebrates in wadable rivers through five main steps, namely, classifying rivers by type, laying out monitoring points, selecting sampling areas, sampling, and counting the types and numbers of large benthic invertebrates in samples. The method can effectively and practically monitor large benthic invertebrates in different types of wadable rivers, and provide a reference and reference for carrying out benthic animal monitoring in different types of rivers.

Description

Technical Field

[0001] The invention belongs to the technical field of benthic animal monitoring, in particular to a monitoring method for large benthic invertebrates capable of wading through different types of rivers. Background Art

[0002] Macrobenthic invertebrates are a key target for water ecological monitoring and assessment, and their monitoring data serve as foundational data for implementing river water ecological protection measures and policies. Given the diversity of macrobenthic invertebrates in different types of wadeable rivers, and the significant impact of human activities on their distribution, selecting appropriate methods for monitoring these macrobenthic invertebrates is crucial for comprehensively reflecting the overall status of the monitoring area. Currently, relevant technical guidelines and specifications for water ecological monitoring have been issued, such as the "Technical Guidelines for Biodiversity Observation: Freshwater Benthic Macroinvertebrates" (HJ710.8-2014) and the "Technical Guidelines for Water Ecological Monitoring: Monitoring and Assessment of River Aquatic Organisms (Trial Implementation)" (HJ1295-2023). These technical guidelines and specifications generally provide a method for monitoring river benthic invertebrates, without considering the environmental variations and habitat characteristics of different river types. This significantly impacts benthic invertebrate monitoring, making actual sampling difficult. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for monitoring macrobenthic invertebrates in different types of wadable rivers, which can effectively and practically monitor macrobenthic invertebrates in different types of wadable rivers.

[0004] To solve the above problems, the present invention adopts a technical solution: a method for monitoring macrobenthic invertebrates in different types of rivers, comprising the following steps:

[0005] S1. Classification of river types:

[0006] S11. Extract the water system grid based on the river mainstream vector data and digital elevation model of the target basin, and generate the basic water catchment unit using the terrain gradient and water system grid;

[0007] S12. Generate a buffer zone along the main river based on the river main stream vector data, and use the buffer zone as the basic unit for indicator calculation;

[0008] S13, obtaining terrain characteristic indicators of the buffer zone, the terrain characteristic indicators including altitude, terrain undulation, and slope;

[0009] S14. Use terrain characteristic indicators to classify rivers into mountainous rivers, hilly rivers, and plain rivers;

[0010] S2. Monitoring point layout: Monitoring points are laid out at equal intervals along the main stream of the river;

[0011] S3. Sampling area selection: The river section 100m upstream and downstream of the monitoring point center is used as the sampling area;

[0012] S4. Sampling: Collect samples from bottom to top according to the direction of water flow;

[0013] S5. Count the species and numbers of macrobenthic invertebrates in the samples.

[0014] Furthermore, in step S11, in the SWAT hydrological analysis module of ArcGIS software, the water network is extracted by using depression filling, flow direction analysis, and flow analysis.

[0015] Furthermore, in step S12, the vector data of the main river stream is imported into ArcGIS software, and the buffer distance is set using the Buffer tool to generate a buffer zone along the main river.

[0016] Furthermore, in step S13, the Slope tool of the ArcGIS software is used to calculate the slope in the buffer zone based on the digital elevation model; the Focal Statistics tool of the ArcGIS software is used to calculate the difference between the maximum elevation and the minimum elevation in the buffer zone, and the difference between the maximum elevation and the minimum elevation is used as the terrain relief; in the ArcGIS software, the raster pixel value of the elevation in the buffer zone is used as the altitude value.

[0017] Furthermore, step S14 includes:

[0018] S141. Determine the classification principle: The priority of terrain characteristic indicators is terrain relief > slope > altitude;

[0019] S142. Using the raster calculator in ArcGIS software, run a nested conditional function to generate a river type raster, where pixel values ​​are defined as follows: 1 for a mountainous river, 2 for a hilly river, and 3 for a plain river.

[0020] S143, using the table display zoning statistics tool in ArcGIS software, using the planar vector data of the basic unit of the catchment as the statistical unit, using the river type raster as the input data, setting the statistical field to MAJORITY, and outputting a statistical table;

[0021] S144. Connect the attribute field that records the river type pixel value in the statistical table to the attribute table of the watershed basic unit layer to complete the assignment of the river type pixel value; then perform a spatial intersection operation on the main stream vector data and the watershed basic unit layer to generate an intersection result layer.

[0022] Furthermore, in step S2, when the length of the river mainstream is less than 80 km, at least one monitoring point is set up every 20 km; when the length of the river mainstream is 80 km less than 120 km, at least one monitoring point is set up every 30 km; when the length of the river mainstream is greater than 120 km, at least one monitoring point is set up every 40 km.

[0023] Furthermore, in step S2, the layout of monitoring points for mountainous rivers is as follows: the sampling units are divided at intervals of 500m in altitude gradient, and at least one monitoring point is arranged in each sampling unit, and the monitoring point is located upstream of the sampling unit; when there are at least two tributary confluences in a basic water catchment unit, if the distance between the most upstream and most downstream tributary confluences is less than 5km, one monitoring point is arranged downstream of the most downstream tributary confluence; if the distance between the most upstream and most downstream tributary confluences in a basic water catchment unit is greater than 5km, at least two monitoring points are arranged, one of which is located downstream of the most upstream tributary confluence, and the other is located downstream of the most downstream tributary confluence, and the distance between the two adjacent monitoring points is greater than 5km. Km; when there is a dam blocking the main stream, a monitoring point is set up 3 km downstream of the dam; if there are both a tributary confluence and a dam within a sampling unit with an altitude gradient of 500 m, the monitoring points are set up in the order of decreasing priority of the dam, tributary confluence, and altitude gradient, and the distance between adjacent monitoring points is greater than 5 km;

[0024] The layout method of monitoring points for hilly rivers is as follows: when the winding degree of the river section is greater than 1.5, at least one monitoring point is arranged on the concave side of the bend; when there are independent land use types within 1 km of the vertical river bank, one monitoring point is arranged at the corresponding position of each land use type. If there are more than two complex land use types, only one monitoring point is arranged. Independent land use types include industrial parks, urban areas and concentrated farmland areas; when there are at least two tributary confluences in the basic watershed unit, if the distance between the upstream and downstream tributary confluences is less than 5 km, one monitoring point is arranged downstream of the downstream tributary confluence; if the distance between the upstream and downstream tributary confluences in the basic watershed unit is greater than 5 km, at least two monitoring points are arranged, one of which is located downstream of the upstream tributary confluence and the other is located downstream of the downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km. Km; when there is a dam blocking the main stream, a monitoring point is set up 3 km downstream of the dam; if there are two or more elements of the following at the same time: a sinuosity greater than 1.5, independent land use types, tributary confluences, and dams, the monitoring points are set up in the descending order of priority of the dam, sinuosity, land use types, and tributary confluences, and the distance between adjacent monitoring points is greater than 5 km; the calculation formula for sinuosity is:

[0025] K=L / l, K is the sinuosity, L is the actual length of the river section, and l is the straight length of the river section;

[0026] The layout of monitoring points for plain rivers is as follows: when there are independent land use types within 1 km of the vertical river bank, one monitoring point is arranged at the corresponding position of each land use type. If there are more than two complex land use types, only one monitoring point is arranged; when there are both natural river banks and non-natural river banks, one monitoring point is arranged on the natural river bank and the non-natural river bank respectively; when there are at least two tributary confluences in a basic watershed unit, if the distance between the most upstream and the most downstream tributary confluences is less than 5 km, one monitoring point is arranged downstream of the most downstream tributary confluence; if the distance between the most upstream and the most downstream tributary confluences in a basic watershed unit is greater than 5 km, at least two monitoring points are arranged, one of which is located downstream of the most upstream tributary confluence, and the other is located downstream of the most downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km. Km; if two or more of the following elements exist at the same time: independent land use type, tributary confluence, and coexistence of natural and non-natural river banks, the monitoring points shall be arranged in the descending order of priority of the coexistence of natural and non-natural river banks, independent land use type, and tributary confluence, and the distance between adjacent monitoring points shall be greater than 5 km.

[0027] Furthermore, in step S4, a multi-habitat comprehensive sampling method is used to select at least three habitat types in each sampling area for quadrat sampling.

[0028] Furthermore, in step S3, the sampling area selection process for mountainous rivers and hilly rivers is as follows: different water surface ripple types of rivers are selected as candidate sampling quadrat areas, and the water surface ripple types include dense, general, and sparse types, wherein the river flow velocity corresponding to the dense water surface ripple is greater than 1 m / s, the river flow velocity corresponding to the general water surface ripple is between 0.5 m / s and 1 m / s, and the river flow velocity corresponding to the sparse water surface ripple is less than 0.5 m / s; bottom sediment types, aquatic plants, and river islands are selected as candidate sampling quadrat areas, and the bottom sediment types include pebbles, gravel, bedrock, boulders, sand and gravel, soft mud, and clay, and the aquatic plants include dead branches and leaves, rotten wood, water plants, submerged plants, floating plants, floating-leaf plants, and emergent plants; and the actual sampling area is allocated in each sampling quadrat candidate area using the averaging method;

[0029] The sampling area selection process for plain rivers is as follows: bottom sediment types, aquatic plants and river islands are selected as candidate sampling quadrat areas, and the actual sampling area is allocated in each candidate sampling quadrat area using the averaging method.

[0030] Furthermore, in step S4, if the river width is less than 200m, the sampling frequency is at least 20 times, and the sampling area of ​​each time is 0.06~0.075m 2, the total sampling area is 1.2-1.5m 2 If the river width is greater than 200m, the sampling frequency shall be at least 40 times, and the sampling area shall be 0.05m each time. 2 , the total sampling area is 2m 2 ;

[0031] When collecting samples, for mountain rivers and hilly rivers, samples are collected alternately in the middle and at the edge of the river; for plain rivers, samples are collected at the edge of the river.

[0032] The beneficial effects of the present invention are as follows: the present invention mainly provides a method for monitoring large benthic invertebrates in different types of wadable rivers through five main steps: river type classification, monitoring point layout, sampling area selection, sampling, and statistics of the types and numbers of large benthic invertebrates in samples. The method can effectively and practically monitor large benthic invertebrates in different types of wadable rivers, providing reference and reference for carrying out benthic animal monitoring in different types of rivers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a flow chart of the present invention;

[0034] Figure 2 This is a schematic diagram of the layout of tributary monitoring points (the interval between tributaries is greater than 5 km);

[0035] Figure 3 This is a schematic diagram of the layout of tributary monitoring points (the tributary interval is less than 5km);

[0036] Figure 4 This is a schematic diagram of the layout of monitoring points at river meanders;

[0037] Figure 5 It is a schematic diagram of the layout of monitoring points for different land types (centralized farmland areas);

[0038] Figure 6 It is a schematic diagram of the layout of monitoring points for different land types (urban areas);

[0039] Figure 7 It is a schematic diagram of the layout of monitoring points for different land types (composite areas);

[0040] Figure 8 It is a schematic diagram of the sampling area of ​​the monitoring points;

[0041] Figure 9 This is a schematic diagram of the benthic sampling method for mountainous rivers and hilly rivers;

[0042] Figure 10 This is a schematic diagram of the benthic animal sampling method for plain rivers. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and examples.

[0044] The present invention provides a method for monitoring macrobenthic invertebrates in different types of rivers, such as Figure 1 As shown, the following steps are included:

[0045] S1. River Type Classification. The distribution of macrobenthic invertebrates varies in wadeable rivers with different topographical features, so appropriate monitoring plans need to be developed based on the characteristics of each river type.

[0046] S11. Extraction of basic watershed units: Extract the watershed grid based on the target basin's river mainstream vector data and digital elevation model (DEM). The river mainstream vector data and digital elevation model can be obtained from existing databases. Specifically, in the ArcGIS software's SWAT hydrological analysis module, techniques such as depression filling, flow direction analysis, and discharge analysis can be used to extract the watershed network. Basic watershed units are then generated using terrain gradients and the watershed grid. Terrain gradients can be obtained from the digital elevation model. The SWAT hydrological analysis module is a functional module in ArcGIS software, and techniques such as depression filling, flow direction analysis, and discharge analysis are functional units of the SWAT hydrological analysis module. This step can be directly implemented using the software.

[0047] S12. Buffer Settings: Generate buffer zones along the main river using the river mainstream vector data. Specifically, import the river mainstream vector data into ArcGIS and use the Buffer tool to set a buffer distance of 500 meters. Then, generate buffer zones along the main river, using the buffer zone as the basic unit for metric calculations. The Buffer tool is also a function module in ArcGIS and can be used directly.

[0048] S13. Obtain terrain characteristic indicators: Obtain the terrain characteristic indicators of the buffer zone, which include altitude, terrain relief, and slope. Altitude reflects the river's geographical location and climatic characteristics; terrain relief reflects the complexity and depth of the river's terrain; and slope reflects the angle between the river and the horizontal plane.

[0049] Specifically, the Slope tool of ArcGIS software was used to calculate the slope within the buffer zone based on the digital elevation model, with the output unit being degrees (°); the Focal Statistics tool of ArcGIS software was used to calculate the difference between the maximum and minimum elevations within the buffer zone, and the difference between the maximum and minimum elevations was used as the terrain relief, with the output unit being meters (m); in ArcGIS software, the raster pixel values ​​of the elevation within the buffer zone were used as the altitude values, with the output unit being meters (m).

[0050] S14. Use terrain characteristic indicators to classify rivers into mountainous rivers, hilly rivers, and plain rivers. Specifically, the following are included:

[0051] S141. Determine the division principle: The priority of terrain characteristic indicators is terrain relief > slope > altitude. That is, among the three indicators of terrain relief, slope and altitude, the division is based on terrain relief first. If the terrain relief indicator cannot be clearly divided, the slope and altitude are used as reference in turn.

[0052] The specific classification basis is shown in Table 1 below:

[0053] Table 1 Basis for classification of different river types

[0054]

[0055] S142. Calculation of river types based on raster data: Based on the above-mentioned river classification principles and basis, and using the nested conditional function (Con) in ArcGIS software, a classification formula is written. The nested conditional function (Con) is located in the raster calculator module in ArcGIS software. Altitude data, terrain undulation data, and slope data are input into the classification formula. Running the nested conditional function (Con) can generate a river type raster. The pixel values ​​of each terrain feature are defined as follows: 1 for mountainous rivers, 2 for hilly rivers, and 3 for plain rivers.

[0056] S143. Zoning statistics of basic watershed units: Use the "Display Zoning Statistics as Table" tool in ArcGIS software, use the surface vector data of the basic watershed units as the statistical unit, use the river type raster as the input data, set the statistical field to MAJORITY, and output the statistical table. Among them, "Display Zoning Statistics as Table" is a functional module in ArcGIS software and can be used directly. In this functional module, you can set the "Statistical Type". "MAJORITY" is an option that comes with "Statistical Type", which can be directly checked. The meaning of "MAJORITY" is: determine the most frequently occurring value among all pixels in the value grid that belong to the same area as the output pixel.

[0057] S144, River Type Attribute Assignment: Connect the attribute field containing the river type pixel values ​​in the statistical table to the attribute table of the catchment unit layer to complete the river type pixel value assignment. Then, perform a spatial intersect operation on the river mainstream vector data and the catchment unit layer to generate the intersection result layer. This operation assigns the river type attribute field of the catchment unit layer to the mainstream vector data, completing the river type classification.

[0058] S2. Monitoring point layout: Monitoring points are arranged at equal intervals along the main stream of the river.

[0059] Specifically, when the length of the river mainstream is less than 80km, at least one monitoring point shall be set up every 20km; when the length of the river mainstream is less than 80km and less than 120km, at least one monitoring point shall be set up every 30km; when the length of the river mainstream is greater than 120km, at least one monitoring point shall be set up every 40km.

[0060] The key considerations for the layout of monitoring points for different types of rivers are as follows:

[0061] For mountainous rivers, monitoring points are mainly arranged based on three factors: altitude gradient, tributary confluence and dam. The sampling points are divided into sampling units with an altitude gradient of 500m as interval, and at least one monitoring point is arranged in each sampling unit, and the monitoring point is located upstream of the sampling unit.

[0062] When there is only one tributary confluence, the impact of the tributary confluence is not considered. The confluence of two tributaries will have a certain impact on the benthic animals in the main stream, so it is necessary to consider setting up monitoring points downstream of the tributary confluence. Specifically, when there are at least two tributary confluences in a basic water unit, if the distance between the most upstream and most downstream tributary confluences is less than 5km, then a monitoring point should be set up 100m downstream of the most downstream tributary confluence, such as Figure 3 If the distance between the upstream and downstream tributaries in a basic unit of water catchment is greater than 5 km, at least two monitoring points should be set up, one of which is located 100 m downstream of the upstream tributary confluence, and the other is located 100 m downstream of the downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km, as shown in the following example: Figure 2 shown.

[0063] When there is a dam blocking the main stream, a monitoring point is set up 3 km downstream of the dam.

[0064] If there are both tributary confluences and dams within a sampling unit with an altitude gradient of 500m, the monitoring points shall be arranged in the order of decreasing priority of dam, tributary confluence, and altitude gradient, and the distance between adjacent monitoring points shall be greater than 5km.

[0065] For hilly rivers, the four main factors to be considered are meandering, land use type, tributary confluence, and dam. The layout of monitoring points is as follows: when the meandering of a river section is greater than 1.5, at least one monitoring point is laid out on the concave side of the bend. Figure 4 As shown in the figure, in river bends, the convex side is more strongly eroded by the river, which is not conducive to the survival of benthic animals. Therefore, monitoring points are placed on the concave side to collect more benthic animal samples. When multiple monitoring points are set up, the distance between two adjacent monitoring points should be greater than 5 km.

[0066] When there are independent land use types within 1 km of the vertical river bank, one monitoring point is set up at the corresponding position of each land use type, such as Figure 5 and Figure 6 If there are more than two composite land use types, only one monitoring point is set up, such as Figure 7 The independent land use types include industrial parks, urban areas and concentrated farmland areas.

[0067] When there is only one tributary confluence, the influence of the tributary confluence is not considered. When there are at least two tributary confluences in a basic water catchment unit, if the distance between the most upstream and most downstream tributary confluences is less than 5 km, a monitoring point is set 100 m downstream of the most downstream tributary confluence, such as Figure 3 If the distance between the upstream and downstream tributaries in a basic unit of water catchment is greater than 5 km, at least two monitoring points should be set up, one of which is located 100 m downstream of the upstream tributary confluence, and the other is located 100 m downstream of the downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km, as shown in the following example: Figure 2 shown.

[0068] When there is a dam blocking the main stream, a monitoring point is set up 3 km downstream of the dam.

[0069] If there are two or more elements among the following: winding degree greater than 1.5, independent land use type, tributary confluence, and dam, the monitoring points shall be arranged in the order of decreasing priority of dam, winding degree, land use type, and tributary confluence, and the distance between adjacent monitoring points shall be greater than 5 km.

[0070] The calculation formula of the winding degree is:

[0071] K=L / l, K is the winding degree, L is the actual length of the river section, and l is the straight length of the river section.

[0072] For plain rivers, the three main factors to be considered are land use type, natural and non-natural river bank types, and tributary confluence. The monitoring point layout method is: when there are independent land use types within 1 km of the vertical river bank, one monitoring point is arranged at the corresponding position of each land use type, such as Figure 5 and Figure 6 If there are more than two composite land use types, only one monitoring point is set up, such as Figure 7 shown.

[0073] When both natural and unnatural riverbanks exist, one monitoring point is set up on each. Unnatural riverbanks are artificially treated riverbanks, usually hardened riverbanks; natural riverbanks are natural, untouched riverbanks.

[0074] When there is only one tributary confluence, the influence of the tributary confluence is not considered. When there are at least two tributary confluences in a basic water catchment unit, if the distance between the most upstream and most downstream tributary confluences is less than 5 km, a monitoring point is set 100 m downstream of the most downstream tributary confluence, such as Figure 3 If the distance between the upstream and downstream tributaries in a basic unit of water catchment is greater than 5 km, at least two monitoring points should be set up, one of which is located 100 m downstream of the upstream tributary confluence, and the other is located 100 m downstream of the downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km, as shown in the following example: Figure 2 shown.

[0075] If two or more of the following elements exist at the same time: independent land use types, tributary confluences, and coexistence of natural and non-natural river banks, the monitoring points shall be arranged in the order of decreasing priority of the coexistence of natural and non-natural river banks, independent land use types, and tributary confluences, and the distance between adjacent monitoring points shall be greater than 5 km.

[0076] S3. Sampling area selection: The sampling area is the river section within 100m upstream and downstream of the monitoring point center, such as Figure 8 shown.

[0077] In order to fully consider the spatial heterogeneity of river habitats, a multi-habitat comprehensive sampling method was used to select at least three habitat types for sample plot sampling in each sampling area. The multi-habitat comprehensive sampling method is to select three or more habitat types for sampling in the candidate sampling area according to the habitat priority order, and the sampling area of ​​each candidate sampling area is evenly distributed.

[0078] Specifically, the sampling area selection process for mountainous rivers and hilly rivers is as follows: different water surface ripple types of rivers are selected as candidate sampling plots, and the water surface ripple types include dense, general and sparse types. Among them, the river flow velocity corresponding to dense water surface ripples is greater than 1m / s, the river flow velocity corresponding to general water surface ripples is between 0.5m / s and 1m / s, and the river flow velocity corresponding to sparse water surface ripples is less than 0.5m / s; bottom sediment types, aquatic plants and river islands are selected as candidate sampling plots, and bottom sediment types include pebbles, gravel, bedrock, boulders, sand and gravel, soft mud and clay. Aquatic plants include dead branches and leaves, rotten wood, water grasses, submerged plants, floating plants, floating-leaf plants and emergent plants.

[0079] The above process can screen out multiple candidate sampling areas. Among these candidate sampling areas, at least three candidate sampling areas are selected for sampling. The selection priority order of each candidate sampling area is shown in Table 2 below:

[0080] Table 2 Priority order of habitat selection in candidate sampling areas

[0081]

[0082] The actual sampling area is allocated within each candidate sampling quadrat region using an averaging method. The averaging method divides the total sampling area by the number of selected candidate sampling quadrat regions to obtain the sampling area for each candidate sampling quadrat region. The sampling area for each candidate sampling quadrat region is the same. The total sampling area is described in step S4 below.

[0083] The sampling area selection process for plain rivers is as follows: bottom sediment types, aquatic plants and river islands are selected as candidate sampling quadrat areas, and the actual sampling area is allocated in each candidate sampling quadrat area using the averaging method.

[0084] S4. Sampling: To avoid interference of upstream samples on downstream samples, sample collection shall be carried out from bottom to top according to the direction of water flow.

[0085] Specifically, if the river width is less than 200m, the sampling frequency should be at least 20 times, with each sampling area of ​​0.06~0.075m 2 , the total sampling area is 1.2-1.5m 2 If the river width is greater than 200m, the sampling frequency shall be at least 40 times, and the sampling area shall be 0.05m each time. 2 , the total sampling area is 2m 2 When conducting semi-quantitative sampling of macrobenthic animals, 3-m-long plots were collected within a 10-m-long sampling area along the riverbank.

[0086] When collecting samples, for mountainous and hilly rivers, the large undulating topography will cause changes in factors such as the flow, bottom sediment and depth of the river. Changes in factors such as flow, bottom sediment and depth will significantly affect the distribution of benthic animals, resulting in uneven distribution of benthic animals at the edge and middle of the river, showing a clustered or patchy distribution. "Z"-shaped sampling can cover a larger sampling range, reduce sampling bias caused by over-concentration of sampling locations, and make the sampling results more accurately reflect the average conditions of the entire study area. Therefore, sampling is carried out alternately at the deepest wading location and the edge of the river, that is, sampling is carried out according to the "Z"-shaped method, such as Figure 9 As shown in the figure, the D-type hand-held net (with a bottom frame side length of 0.3 m) is preferred as a sampling tool for mountainous and hilly rivers.

[0087] For plain rivers, the distribution of benthic animals at the deepest part of the river and at the river edge is relatively small. Sampling is done at the river edge, i.e., according to the "one" method, such as Figure 10 As shown, the preferred sampling tool is a Soper net (the frame side can be 0.3m × 0.3m), followed by a D-type hand net (the bottom frame side can be 0.3m). When collecting quantitative and semi-quantitative samples, mutual interference should be avoided.

[0088] S5. Count the species and number of macrobenthic invertebrates in the samples to obtain the distribution of macrobenthic invertebrates in different areas.

[0089] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for monitoring macrobenthic invertebrates in different types of rivers, characterized by: The following steps are involved: S1. Classification of river types: S11. Extract the water system grid based on the river mainstream vector data and digital elevation model of the target basin, and generate the basic water catchment unit using the terrain gradient and water system grid; S12. Generate a buffer zone along the main river based on the river main stream vector data, and use the buffer zone as the basic unit for indicator calculation; S13, obtaining terrain characteristic indicators of the buffer zone, the terrain characteristic indicators including altitude, terrain undulation, and slope; S14. Use terrain characteristic indicators to classify rivers into mountainous rivers, hilly rivers, and plain rivers; S2. Monitoring point layout: Monitoring points should be laid out at equal intervals along the main stream of the river. For mountainous rivers, monitoring points should be laid out based on three factors: altitude gradient, tributary confluence, and dams. For hilly rivers, monitoring points should be laid out based on four factors: sinuosity, land use type, tributary confluence, and dams. For plain rivers, monitoring points should be laid out based on three factors: land use type, natural and unnatural riverbank types, and tributary confluence. S3. Sampling area selection: The sampling area is the river section 100m upstream and downstream of the monitoring point center; The sampling area selection process for mountainous and hilly rivers is as follows: different types of river surface ripples are selected as candidate sampling quadrat areas. The types of water surface ripples include dense, general, and sparse types. The bottom type, aquatic plants, and river islands are selected as candidate sampling quadrat areas. The actual sampling area is allocated in each candidate sampling quadrat area using the averaging method. The sampling area selection process for plain rivers is as follows: selecting bottom sediment types, aquatic plants and river islands as candidate sampling quadrat areas, and using the averaging method to allocate actual sampling areas in each candidate sampling quadrat area; S4. Sampling: Collect samples from bottom to top according to the direction of water flow; S5. Count the species and numbers of macrobenthic invertebrates in the samples.

2. A method for monitoring macrobenthic invertebrates in wading rivers of different types as claimed in claim 1, characterized in that: In step S11, in the SWAT hydrological analysis module of ArcGIS software, the water network is extracted by using depression filling, flow direction analysis, and flow analysis.

3. The method for monitoring macrobenthic invertebrates in wading rivers of different types according to claim 1, characterized in that: In step S12, the river main stream vector data is imported into ArcGIS software, and the buffer distance is set using the Buffer tool to generate a buffer zone along the main river.

4. The method for monitoring macrobenthic invertebrates in wading rivers of different types according to claim 1, wherein: In step S13, the slope tool of ArcGIS software is used to calculate the slope in the buffer zone based on the digital elevation model; the Focal Statistics tool of ArcGIS software is used to calculate the difference between the maximum elevation and the minimum elevation in the buffer zone, and the difference between the maximum elevation and the minimum elevation is used as the terrain relief; in ArcGIS software, the grid pixel value of the elevation in the buffer zone is used as the altitude value.

5. The method for monitoring macrobenthic invertebrates in wading rivers of different types according to claim 1, characterized in that: Step S14 includes: S141. Determine the classification principle: The priority of terrain characteristic indicators is terrain relief > slope > altitude; S142. Using the raster calculator in ArcGIS software, run a nested conditional function to generate a river type raster, where pixel values ​​are defined as follows: 1 for a mountainous river, 2 for a hilly river, and 3 for a plain river. S143, using the table display zoning statistics tool in ArcGIS software, using the planar vector data of the basic unit of the catchment as the statistical unit, using the river type raster as the input data, setting the statistical field to MAJORITY, and outputting a statistical table; S144. Connect the attribute field that records the river type pixel value in the statistical table to the attribute table of the watershed basic unit layer to complete the assignment of the river type pixel value; then perform a spatial intersection operation on the main stream vector data and the watershed basic unit layer to generate an intersection result layer.

6. The method for monitoring macrobenthic invertebrates in wading rivers of different types according to claim 1, characterized in that: In step S2, when the length of the river mainstream is less than 80km, at least one monitoring point is set up every 20km; when the length of the river mainstream is 80km less than the length of the river mainstream and less than 120km, at least one monitoring point is set up every 30km; when the length of the river mainstream is greater than 120km, at least one monitoring point is set up every 40km.

7. A method for monitoring macrobenthic invertebrates in wading rivers of different types as claimed in claim 6, characterized in that: In step S2, the layout of monitoring points for mountainous rivers is as follows: the sampling units are divided into intervals of 500m in altitude gradient, and at least one monitoring point is arranged in each sampling unit, and the monitoring point is located upstream of the sampling unit; when there are at least two tributary confluences in a basic water catchment unit, if the distance between the most upstream and the most downstream tributary confluences is less than 5km, one monitoring point is arranged downstream of the most downstream tributary confluence; if the distance between the most upstream and the most downstream tributary confluences in a basic water catchment unit is greater than 5km, at least one monitoring point is arranged downstream of the most downstream tributary confluence. Two monitoring points are set up, one of which is located downstream of the confluence of the most upstream tributary, and the other is located downstream of the confluence of the most downstream tributary. The distance between the two adjacent monitoring points is greater than 5 km. When there is a dam blocking the main stream, one monitoring point is set up 3 km downstream of the dam. If there is both a tributary confluence and a dam within a sampling unit with an altitude gradient of 500 m, the monitoring points are set up in the order of decreasing priority of the dam, tributary confluence, and altitude gradient. The distance between adjacent monitoring points is greater than 5 km. The layout method of monitoring points for hilly rivers is as follows: when the winding degree of the river section is greater than 1.5, at least one monitoring point is arranged on the concave side of the bend; when there are independent land use types within 1 km of the vertical river bank, one monitoring point is arranged at the corresponding position of each land use type. If there are more than two complex land use types, only one monitoring point is arranged. Independent land use types include industrial parks, urban areas and concentrated farmland areas; when there are at least two tributary confluences in the basic watershed unit, if the distance between the upstream and downstream tributary confluences is less than 5 km, one monitoring point is arranged downstream of the downstream tributary confluence; if the distance between the upstream and downstream tributary confluences in the basic watershed unit is greater than 5 km, at least two monitoring points are arranged, one of which is located downstream of the upstream tributary confluence and the other is located downstream of the downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km. Km; when there is a dam blocking the main stream, a monitoring point is set up 3 km downstream of the dam; if there are two or more elements of the following at the same time: a sinuosity greater than 1.5, independent land use types, tributary confluences, and dams, the monitoring points are set up in the descending order of priority of the dam, sinuosity, land use types, and tributary confluences, and the distance between adjacent monitoring points is greater than 5 km; the calculation formula for sinuosity is: K=L / l, K is the sinuosity, L is the actual length of the river section, and l is the straight length of the river section; The layout of monitoring points for plain rivers is as follows: when there are independent land use types within 1 km of the vertical river bank, one monitoring point is arranged at the corresponding position of each land use type. If there are more than two complex land use types, only one monitoring point is arranged; when there are both natural river banks and non-natural river banks, one monitoring point is arranged on the natural river bank and the non-natural river bank respectively; when there are at least two tributary confluences in a basic watershed unit, if the distance between the most upstream and the most downstream tributary confluences is less than 5 km, one monitoring point is arranged downstream of the most downstream tributary confluence; if the distance between the most upstream and the most downstream tributary confluences in a basic watershed unit is greater than 5 km, at least two monitoring points are arranged, one of which is located downstream of the most upstream tributary confluence, and the other is located downstream of the most downstream tributary confluence. The distance between two adjacent monitoring points is greater than 5 km. Km; if two or more of the following elements exist at the same time: independent land use type, tributary confluence, and coexistence of natural and non-natural river banks, the monitoring points shall be arranged in the descending order of priority of the coexistence of natural and non-natural river banks, independent land use type, and tributary confluence, and the distance between adjacent monitoring points shall be greater than 5 km.

8. The method for monitoring macrobenthic invertebrates in wading rivers of different types according to claim 1, characterized in that: In step S4, a multi-habitat comprehensive sampling method is used to select at least three habitat types in each sampling area for quadrat sampling.

9. A method for monitoring macrobenthic invertebrates in wading rivers of different types as claimed in claim 8, characterized in that: In step S3, the river flow velocity corresponding to the dense water surface ripples is greater than 1m / s, the river flow velocity corresponding to the general water surface ripples is between 0.5m / s and 1m / s, and the river flow velocity corresponding to the sparse water surface ripples is less than 0.5m / s; the bottom types include pebbles, gravel, bedrock, boulders, sand and gravel, mud and clay, and the aquatic plants include dead branches and leaves, rotten wood, water grasses, submerged plants, floating plants, floating-leaf plants, and emergent plants.

10. The method for monitoring macrobenthic invertebrates in wading rivers of different types according to claim 1, characterized in that: In step S4, if the river width is less than 200m, the sampling frequency is at least 20 times, and the sampling area of ​​each time is 0.06~0.075m 2 , the total sampling area is 1.2-1.5m 2 If the river width is greater than 200m, the sampling frequency shall be at least 40 times, and the sampling area shall be 0.05m each time. 2 , the total sampling area is 2m 2 ; When collecting samples, for mountain rivers and hilly rivers, samples are collected alternately in the middle and at the edge of the river; for plain rivers, samples are collected at the edge of the river.

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