A method for calculating ecologically suitable flow in alpine canyon streams

Abstract

The present invention discloses a method for calculating the suitable ecological flow of alpine canyon streams. First, the basic data such as the multi-year average runoff, topography, vegetation, soil and climate of the stream are comprehensively collected, and the infiltration coefficient is determined according to the topography and vegetation soil, and the natural base flow is calculated. Then, the water demand parameters are determined for ecologically sensitive targets such as fish spawning and reproduction, maintenance of aquatic habitats, and growth of riparian vegetation, and the suitable ecological flow of each target is calculated using a multi-parameter comprehensive evaluation method and a time series analysis. Finally, the maximum value of each target flow is integrated to determine the final suitable ecological flow, and a data monitoring and evaluation system and a flow adjustment mechanism are established. Accurate calculation and dynamic adjustment are achieved by comprehensively considering multiple factors, ensuring the stability of the stream ecosystem and the rational use of water resources, and providing a scientific and effective flow calculation solution for the ecological protection of alpine canyon streams.

Description

Technical Field

[0001] The invention relates to the field related to water environment indicators of alpine canyon streams, and specifically to a method for calculating suitable ecological flow of alpine canyon streams. Background Art

[0002] Alpine canyon streams play an extremely important role in the ecosystem. They are not only the habitats of many aquatic organisms, but also play a key role in maintaining the ecological balance, material circulation and energy flow of the entire basin. However, with the continuous expansion of human activities, such as hydropower development, agricultural irrigation, industrial water use, etc., alpine canyon streams are facing increasingly severe flow change problems.

[0003] Traditional stream flow calculation methods often focus on meeting a single water demand, such as only considering the water demand for hydropower generation or simple irrigation water demand, while ignoring the complexity and diversity of stream ecosystems. For alpine canyon streams, their special topography, such as steep river slopes, complex geological structures, and changeable climate conditions, make the water flow process highly dynamic and uncertain. Ordinary flow calculation methods are difficult to accurately reflect the impact of these special factors on ecological flow, resulting in frequent damage to stream ecosystems during the development and utilization of water resources, threats to the survival of many rare aquatic organisms, degradation of riparian vegetation due to water shortage, reduced self-purification capacity of streams, deterioration of water quality, and a series of ecological and environmental problems.

[0004] In addition, most of the previous ecological flow calculation methods lack systematicity and comprehensiveness, and do not fully consider the differentiated flow requirements of different ecologically sensitive targets at different time and space scales. For example, fish spawning and reproduction may require appropriate flow under specific water temperature and flow rate conditions, while the maintenance of aquatic habitats requires flow to ensure a certain water depth and water quality. The growth of riparian vegetation is closely related to soil moisture content. These different needs are interrelated and mutually restricted. Traditional methods are difficult to effectively integrate and weigh them, and cannot provide a scientific and reasonable suitable ecological flow calculation solution for alpine canyon streams. Summary of the invention

[0005] The object of the present invention is to provide a method for calculating the suitable ecological flow of alpine canyon streams to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for calculating suitable ecological flow of alpine canyon streams, comprising the following steps:

[0007] Step 1: Collect basic data of alpine canyon streams, including the multi-year average runoff of the streams, the topographic data of the basin where the streams are located, the vegetation coverage type and coverage data in the basin, the soil type data in the basin, and the climate data in the basin, where the climate data includes the multi-year average precipitation, multi-year average temperature, and multi-year average evaporation;

[0008] Step 2: Determine the river slope of the stream and the river width and water depth of different river sections based on the collected topographic data, and determine the infiltration coefficient of the basin based on the vegetation coverage type and coverage data and soil type data; let the infiltration coefficient be α, and the infiltration amount calculation formula is: F = α × P, where P is the average precipitation over many years;

[0009] Step 3: Based on the multi-year average precipitation, multi-year average evaporation and infiltration coefficient, the natural base flow of the stream is calculated using the water balance equation, which is: Q b =PEF, where Q b is the natural base flow, P is the average precipitation over many years, E is the average evaporation over many years, and F is the infiltration;

[0010] Step 4: Based on the natural base flow and in combination with the ecologically sensitive targets of the watershed where the stream is located, determine the water demand parameters corresponding to the ecologically sensitive targets, wherein the ecologically sensitive targets include fish spawning and reproduction, maintenance of aquatic habitats, and growth requirements of riparian vegetation, wherein the water demand parameters for fish spawning and reproduction include the flow corresponding to the suitable water temperature range during the spawning period and the flow corresponding to the suitable flow velocity range, the water demand parameters for maintaining aquatic habitats include the flow corresponding to the suitable living water depths of different aquatic organisms and the flow required for maintaining suitable water quality, and the water demand parameters for riparian vegetation growth include the minimum flow required for saturation of soil water in the root layer of vegetation;

[0011] Step 5: According to the water demand parameters corresponding to different ecological sensitive targets, calculate the appropriate ecological flow of each ecological sensitive target respectively. The calculation method is as follows:

[0012] For fish spawning and reproduction, if there are multiple water demand parameters, the multi-parameter comprehensive evaluation method is used to calculate the appropriate ecological flow. The flow corresponding to the appropriate water temperature range during the spawning period is Q 1 , with weight β 1 The flow rate corresponding to the suitable flow rate range is Q 2 , with weight β 2 , the calculation formula for suitable ecological flow is: Q f =β 1 ×Q 1 +β 2 ×Q 2 , where Qf is the suitable ecological flow for fish spawning and reproduction, and β 1 +β 2=1;

[0013] For the maintenance of aquatic habitats, a multi-parameter comprehensive evaluation method is used, where the flow corresponding to the water depth suitable for the survival of different aquatic organisms is Q 3 , with weight γ 1 The flow rate required to maintain the appropriate water quality is Q 4 , with weight γ 2 , the calculation formula for suitable ecological flow is: Q h =γ 1 ×Q 3 +γ 2 ×Q 4 , where Q h Maintaining ecologically appropriate flows for aquatic habitats, and γ 1 +γ 2 =1;

[0014] The growth demand of riparian vegetation is based on the minimum flow rate required for soil saturation in the root layer of vegetation, which is set as Q 5 Considering the changes in water demand at different stages of the vegetation growth cycle, the appropriate ecological flow for riparian vegetation growth is determined through time series analysis. The time series analysis function is assumed to be f (t) , then the appropriate ecological flow calculation formula is: Q v =Q 5 ×f (t) , where Q v Provide suitable ecological flow for the growth of riparian vegetation;

[0015] Step 6: Integrate the suitable ecological flow calculated for each ecologically sensitive target, and use the maximum value method to determine the final suitable ecological flow for alpine canyon streams, that is, the final suitable ecological flow is the maximum value of the suitable ecological flow for each ecologically sensitive target.

[0016] Furthermore, in step one, when collecting the average runoff over many years, statistical analysis is performed using at least 30 years of continuous runoff monitoring data to ensure the reliability and representativeness of the data; the topographic data within the basin are obtained by combining high-precision satellite remote sensing images with field measurements, where field measurements include the use of total stations, GPS and other equipment to locate and measure the elevation of key topographic feature points of streams, and satellite remote sensing images are used to obtain a wide range of terrain undulation information and the distribution range of different landform types, so as to more accurately determine the river slope of the stream and the spatial variation characteristics of the river width and water depth data of different river sections, providing more accurate basic data support for subsequent calculations.

[0017] Furthermore, in step 2, when determining the infiltration coefficient, infiltration test plots are established for different vegetation cover types and soil types; different precipitation intensity simulation devices are set up in the test plots, and the changes in the infiltration water volume over time during the precipitation process are monitored, and the Horton infiltration formula is used: f = f c +(f 0 -f c ) -k (where f is the infiltration rate, f c To stabilize the infiltration rate, f 0 The infiltration coefficient under different combinations of vegetation coverage and soil types is obtained by fitting calculation, and then the comprehensive infiltration coefficient of the entire basin is obtained by weighted average according to the area proportion of each type in the basin, thereby improving the accuracy and scientificity of the determination of the infiltration coefficient and making the calculation result of the natural base flow closer to the actual situation.

[0018] Furthermore, in step four, when determining the water requirement parameters for fish spawning and reproduction, the flow corresponding to the suitable water temperature range during the spawning period is obtained by establishing an empirical relationship model between water temperature and flow; first, the water temperature and flow at different locations of the stream are synchronously monitored during the fish spawning period, and multiple groups of data are collected, and then regression analysis methods, such as multivariate linear regression or nonlinear regression, are used to determine the mathematical relationship expression between water temperature and flow, and then the corresponding flow range is calculated according to the suitable water temperature range; for the flow corresponding to the suitable flow velocity range, an acoustic Doppler current meter is used to measure the flow velocity at different water depths and cross-sectional positions of the stream, and a flow velocity and flow relationship curve is established in combination with the measured flow data, and the corresponding flow parameters are determined according to the suitable flow velocity range for fish spawning, providing a basis for accurately calculating the suitable ecological flow for fish spawning and reproduction.

[0019] Furthermore, in step 4, when determining the water requirement parameters for maintaining aquatic habitats, for the flow corresponding to the water depth suitable for different aquatic organisms, according to the biological characteristics and ecological habits of different aquatic organisms, refer to relevant aquatic biological research literature and field survey data to determine the minimum, suitable and maximum water depth ranges required for various types of aquatic organisms at different growth stages; then use hydraulic models, such as the HEC-RAS model, to simulate the water depth distribution of streams under different flow conditions, and determine the flow range that meets the water depth range suitable for various types of aquatic organisms through comparative analysis; for the flow required to maintain suitable water quality, analyze the relationship between the concentration of major pollutants and flow based on the water quality monitoring data of the stream, establish a water quality model, such as the QUAL2K model, and calculate the minimum flow required to maintain the stream to a certain water quality standard through model simulation. These parameters are combined to provide comprehensive data support for the calculation of suitable ecological flow for maintaining aquatic habitats.

[0020] Furthermore, in step 5, when the multi-parameter comprehensive evaluation method is used to calculate the suitable ecological flow for fish spawning and reproduction, the weight β 1 and β 2 The determination of β was carried out by using the analytic hierarchy process (AHP). First, a judgment matrix was constructed, and experts compared and scored the relative importance of the suitable water temperature range and the suitable flow velocity range during the spawning period to fish spawning and reproduction. Then, the eigenvector of the judgment matrix was calculated using mathematical methods to obtain β. 1 and β 2 value; in practical applications, the weights are regularly adjusted and optimized according to the characteristics of different fish species and the ecological and environmental characteristics of the stream to ensure that the calculated suitable ecological flow can more accurately meet the needs of fish spawning and reproduction, and ensure the stability and reproduction of fish populations.

[0021] Furthermore, in step 5, when the multi-parameter comprehensive evaluation method is used to calculate the appropriate ecological flow for the maintenance of aquatic habitats, the weight γ 1 and γ 2 The entropy weight method is used to determine the suitable ecological flow for aquatic habitats. First, the flow data corresponding to the suitable living depths of different aquatic organisms and the flow data required to maintain suitable water quality are standardized, and then the information entropy of each data is calculated, and the weight of each parameter is determined based on the information entropy. The entropy weight method can objectively reflect the amount of information contained in the data itself, avoid the influence of subjective factors on the determination of weights, and make the calculation results of the suitable ecological flow for aquatic habitats more scientific and reasonable, which can better balance the relationship between different ecological needs and maintain the ecological integrity of aquatic habitats.

[0022] Furthermore, in step 5, when the appropriate ecological flow is determined through time series analysis for the growth demand of riparian vegetation, the time series analysis function f (t) The ARIMA model is constructed; first, the soil moisture data and the corresponding flow data within the historical vegetation growth cycle are tested for stationarity and differential processing, and then the order of the model is determined according to the autocorrelation function and partial autocorrelation function. The model parameters are estimated by the least squares method to obtain the ARIMA model expression; the model is used to predict the vegetation growth demand flow at different time points in the future, and the suitable ecological flow for riparian vegetation growth is determined according to the prediction results; and the model data is updated regularly to adapt to the influence of factors such as vegetation changes and climate change in the basin on the relationship between riparian vegetation growth and water demand, so as to ensure the timeliness and accuracy of the calculation results.

[0023] Furthermore, in step six, when integrating the suitable ecological flows calculated for each ecologically sensitive target, in addition to using the maximum value method to determine the final suitable ecological flow, an ecological flow adjustment mechanism is also established; the suitable ecological flow of each ecologically sensitive target is dynamically adjusted according to the seasonal variation characteristics of the stream, the resilience of the ecosystem, and the degree of interference from human activities; in the rainy season, the ecological demand restrictions on stream flow are appropriately reduced to take into account the needs of human activities such as flood control; in the dry season, priority is given to ensuring the flow demand of ecologically sensitive targets that are crucial to the stability of the ecosystem. Through this dynamic adjustment mechanism, the ecological flow management of high mountain canyon streams is made more flexible and sustainable, and while protecting the ecological environment, it achieves coordinated progress with the development of human society.

[0024] Furthermore, during the implementation of the entire calculation method, a data quality monitoring and evaluation system will be established; real-time monitoring and regular evaluation will be carried out on the collected basic data, the intermediate data in the calculation process, and the suitable ecological flow data finally calculated; data anomalies and calculation deviations will be discovered in a timely manner through comparison with historical data, the results of different calculation methods, and field ecological monitoring data, so as to optimize and adjust the calculation methods and parameters; at the same time, the data quality monitoring and evaluation results will be recorded and archived to provide data reference and experience for subsequent stream ecological flow research and management, and continuously improve the accuracy and reliability of suitable ecological flow calculations for high mountain canyon streams.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] By comprehensively collecting basic data on alpine canyon streams, including multi-year average runoff, topography, vegetation, soil, climate and other information, we can gain an in-depth understanding of the basic characteristics of stream ecosystems, providing a solid data foundation for the accurate calculation of suitable ecological flows. Based on high-precision topographic data, we determine parameters such as river slope, river width and water depth, combine vegetation and soil types to determine the infiltration coefficient, and then use the water balance equation to calculate the natural base flow. This method fully considers the special geographical environment factors of alpine canyon streams, making the calculation results of natural base flow more accurate and reliable, and more in line with actual conditions.

[0027] For different ecologically sensitive targets such as fish spawning and reproduction, maintenance of aquatic habitats, and growth of riparian vegetation, the corresponding water demand parameters are determined respectively, and scientific and reasonable calculation methods are adopted. For example, for fish spawning and reproduction, a multi-parameter comprehensive evaluation method is adopted, which comprehensively considers the flow corresponding to the suitable water temperature and flow velocity, and through scientific weight determination methods (such as hierarchical analysis method), the ecological flow that meets the needs of fish reproduction can be accurately calculated, which is helpful to protect the reproduction and stability of fish populations. For the maintenance of aquatic habitats, the multi-parameter comprehensive evaluation method is also used in combination with the entropy weight method to determine the weights, and the flow required for the maintenance of water depth and water quality suitable for different aquatic organisms is comprehensively considered, which can effectively maintain the ecological integrity of aquatic habitats and ensure the diversity of aquatic organisms. For the growth needs of riparian vegetation, the changes in water demand at different stages of the vegetation growth cycle are considered using time series analysis, which can ensure that the riparian vegetation is reasonably supplied with water, promote the stability of the riparian ecosystem, and enhance the soil and water conservation and ecological buffering functions of the stream.

[0028] The appropriate ecological flow calculated for each ecologically sensitive target is integrated, and the final appropriate ecological flow is determined by the maximum value method. This can give priority to the flow demand of the most critical ecologically sensitive targets for ecosystem stability on the basis of meeting different ecological needs. At the same time, the established data quality monitoring and evaluation system and ecological flow adjustment mechanism can dynamically adjust and optimize the ecological flow according to factors such as seasonal changes in streams, ecosystem resilience, and the degree of interference from human activities, making the ecological flow management of alpine canyon streams more scientific, flexible, and sustainable, achieving a coordinated balance between water resource development and utilization and ecological environmental protection, and providing strong technical support for the ecological protection and sustainable development of alpine canyon streams. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0030] See also Figure 1 The present invention provides a method for calculating the suitable ecological flow of a high mountain canyon stream, comprising the following steps:

[0031] 1. Data Collection Phase

[0032] Obtain stream runoff monitoring data for at least 30 consecutive years from local hydrological monitoring stations. Organize and screen these data to remove data points that are obviously abnormal, such as outliers caused by instrument failure or extreme weather events (such as short-term floods caused by local rainstorms, whose runoff data may exceed the normal range and are not representative). Use statistical analysis methods, such as calculating the arithmetic mean and median of the multi-year average runoff, and conduct comparative analysis to determine a value that best represents the long-term runoff level of the stream. For example, if the arithmetic mean is 4500 cubic meters per second and the median is 4300 cubic meters per second, after comprehensive analysis (taking into account the data distribution, the degree of influence of outliers, etc.), it is determined that the multi-year average runoff is 4400 cubic meters per second.

[0033] Use high-resolution satellite remote sensing images, such as commercial satellite images with a resolution better than 1 meter. Use image processing software to interpret the images and extract information such as the direction of the stream channel and the boundary of the watershed. At the same time, identify different types of topography and landforms, such as mountains, hills, river valley plains, etc., based on the grayscale value and texture characteristics of the image, and determine their distribution range and area. For example, in a high mountain canyon stream basin, it was found through satellite image interpretation that the mountain area accounts for 70% of the total basin area, mainly distributed in the upper reaches and both sides of the basin; the river valley plain area accounts for 20%, located in the relatively flat area in the middle and lower reaches of the stream; the hilly area accounts for 10%, distributed in the transition zone between the mountains and the river valley plains.

[0034] Use total stations, GPS and other high-precision measuring equipment to conduct field measurements of key terrain feature points of streams. In different sections of the stream, set up measurement sections at certain intervals (such as 500 meters) to measure the elevation, river width, water depth and other parameters of the section. For the slope of the river, measure the elevation difference at different locations on each measurement section, and calculate the slope based on the measurement distance. For example, in a certain measurement section, the elevation of the upstream point is 1000 meters, the elevation of the downstream point is 990 meters, and the distance between the two points is 100 meters. Then the slope of this section of the river is (1000-990) / 100=0.01. Compare and verify the field measurement data with the results of satellite remote sensing image analysis to ensure the accuracy of the topographic data.

[0035] The method of combining satellite remote sensing vegetation index analysis with field survey is adopted. Vegetation indexes such as the Normalized Difference Vegetation Index (NDVI) are used to calculate the vegetation index values ​​of different regions through satellite images. Different vegetation cover types, such as forest, grassland, shrub forest, etc., are divided according to the range of vegetation index values, and their coverage is estimated. For example, when the NDVI value is greater than 0.6, it is determined to be forest vegetation. By statistically analyzing the proportion of such vegetation pixels to the total pixels in the image, the forest vegetation coverage is 55%. At the same time, multiple sample plots are set up in the basin (for example, 50 sample plots are set up according to the distribution of different vegetation types and terrain conditions) to conduct field vegetation surveys, record the vegetation type, height, density and other information in the sample plots, calibrate and supplement with the satellite remote sensing analysis results, and further improve the accuracy of vegetation cover type and coverage data.

[0036] Collect local soil survey data to understand the approximate distribution of soil types in the basin. Then conduct soil sampling in the basin, and set up sampling points according to different topography and vegetation coverage areas (such as 30 sampling points in mountains, river valley plains, and different vegetation types). After collecting soil samples, analyze the soil texture, structure, organic matter content, etc. in the laboratory to determine the soil type. For example, in mountainous forest areas, soil analysis results show loam, which has good water retention and air permeability; near farmland in river valley plains, the soil is sandy loam with relatively low fertility. Combine soil survey data and sampling analysis results to draw a soil type distribution map in the basin.

[0037] Obtain data such as multi-year average precipitation, multi-year average temperature, and multi-year average evaporation from the local meteorological station. For precipitation data, analyze its intra-annual and inter-annual variation characteristics, such as calculating the monthly average and seasonal average of precipitation, as well as the coefficient of variation of precipitation in different years. For example, the multi-year average precipitation in the stream basin is 1,000 mm, of which summer precipitation accounts for 50% of the whole year, and the inter-annual precipitation coefficient of variation is 0.2, indicating that the precipitation has certain fluctuations but is relatively stable. For temperature data, also analyze its seasonal and inter-annual variation patterns, such as calculating the multi-year average maximum temperature, minimum temperature and the months in which they occur, as well as the inter-annual variation trend of temperature. Evaporation data is used for the subsequent calculation of the water balance equation to understand the loss of water in the basin.

[0038] 2. Parameter determination stage

[0039] Infiltration test plots were established in the basin according to different vegetation cover types and soil types, with a total of 6 test plots, including forest and loam, forest and sand, grassland and loam, grassland and sand, shrubs and loam, shrubs and sand. Each test plot has an area of ​​10 square meters, and boundaries are set around it to prevent lateral water flow interference. A precipitation simulation device is installed in the test plot, and different precipitation intensities can be set (such as 20 mm / hour, 50 mm / hour, 100 mm / hour, etc.). During the precipitation process, soil moisture sensors are used to monitor the changes in soil moisture content at different depths (such as 10 cm, 20 cm, 30 cm, etc.) in real time, and the precipitation time and amount are recorded at the same time. According to the monitoring data, the Horton infiltration formula is used: f=f c +(f 0 -f c ) -kt (where f is the infiltration rate, f c To stabilize the infiltration rate, f 0 For example, in the forest and loam test plots, when the precipitation intensity is 50 mm / h, f is obtained by data fitting. c =5 mm / h, f 0 =20 mm / h, k=0.5. After calculating the infiltration coefficient of each experimental plot under different precipitation intensities, the weighted average method is used to calculate the comprehensive infiltration coefficient of the basin according to the area proportion of each vegetation cover type and soil type in the basin. For example, if the forest-loam area accounts for 30% of the total basin area, its infiltration coefficient weighted value is 0.3×forest and loam infiltration coefficient, and the weighted values ​​of other types are calculated in turn, and finally the sum of the comprehensive infiltration coefficient of the basin is 0.25.

[0040] During the spawning period of fish (determined to be from April to June each year through historical data and field observations), water temperature monitoring points (a total of 10 monitoring points) were set up in different sections of the stream, and high-precision water temperature sensors were used to monitor the water temperature every 2 hours, while flow meters were used to measure the flow during this period. Monitoring data for at least 3 consecutive years were collected to establish a database of water temperature and flow. Regression analysis methods, such as the multivariate linear regression model Q = aT + b (where Q is flow, T is water temperature, and a and b are regression coefficients) were used to fit the data. For example, after regression analysis, a = 10, b = 50 was obtained. When the suitable water temperature range was 18 ° C-22 ° C, the corresponding flow range was 10 × 18 + 50 = 230 cubic meters / second to 10 × 22 + 50 = 270 cubic meters / second. The middle value of 250 cubic meters / second was taken as the flow corresponding to the suitable water temperature range during the spawning period.

[0041] Use an acoustic Doppler current meter to measure flow velocity at different water depths (such as 0.5 meters, 1 meters, 1.5 meters, etc.) and cross-sectional locations in the stream. Set up 5 measurement points in each cross-section and measure the flow of the cross-section at the same time. Perform multiple measurements during the fish spawning period (such as 3 times a month) and collect data to establish a velocity-flow relationship curve. For example, through measurement and analysis, it is found that when the appropriate velocity range is 0.6 meters / second to 0.9 meters / second, the corresponding flow range is 200 cubic meters / second to 280 cubic meters / second, and the average value of 240 cubic meters / second is taken as the flow corresponding to the appropriate velocity range.

[0042] Based on the survey of aquatic organisms in the basin (including 20 aquatic organisms such as fish, shellfish, aquatic insects, etc.), and referring to relevant aquatic organism research literature, the minimum, suitable and maximum water depth ranges required by various aquatic organisms at different growth stages are determined. For example, the suitable survival depth range for a certain fish larvae is 0.5 meters to 1 meter, and the adult stage is 1 meter to 1.5 meters. Using hydraulic models, such as the HEC-RAS model, the topographic data of the stream (including river slope, river width, water depth), roughness coefficient (determined according to riverbed material and vegetation conditions) and other parameters are input to simulate the water depth distribution of the stream under different flow conditions. The flow range that meets the suitable survival depth range of various aquatic organisms is determined by comparative analysis. For example, for the above-mentioned fish, the flow range that meets the suitable survival depth range for its juvenile and adult stages is 300 cubic meters / second-350 cubic meters / second.

[0043] Water quality monitoring points are set up in different sections of the stream (a total of 8 monitoring points are set up), and water quality indicators such as chemical oxygen demand (COD), ammonia nitrogen, total phosphorus, etc. are monitored regularly (once a week). According to the water quality monitoring data of the stream, the relationship between the concentration and flow of the main pollutants is analyzed. Using a water quality model, such as the QUAL2K model, the hydrological parameters of the stream (flow, flow rate, etc.), pollution source data (such as upstream sewage treatment plant discharge data, agricultural non-point source pollution data, etc.), and water quality parameters (pollutant degradation coefficient, etc.) are input, and the minimum flow required to maintain the stream to meet certain water quality standards (such as surface water Class III water quality standards) is calculated through model simulation. For example, after model simulation calculation, the flow required to maintain the Class III water quality standard of the stream is 320 cubic meters per second.

[0044] First, the main vegetation types in the riparian zone (such as willows, poplars, herbaceous plants, etc.) were determined, and the root layer depth (such as the root layer depth of willow is 1-1.5 meters) and the soil moisture saturation point were understood through field surveys and literature research. Soil moisture monitoring points were set up in the riparian zone (a total of 15 monitoring points were set up), and soil moisture sensors were used to monitor the soil moisture content at different depths, and stream flow was measured at the same time. Data from different seasons (spring, summer, autumn, and winter) were collected to establish the relationship between soil moisture and flow. For example, through analysis, it was found that when the soil moisture content in the root layer of the willow tree reached saturation, the corresponding flow rate was 150 cubic meters per second, which was used as the minimum flow rate required for soil moisture saturation in the root layer of the vegetation. Then, considering the changes in water demand at different stages of the vegetation growth cycle, the appropriate ecological flow for the growth of riparian vegetation was determined through time series analysis. The ARIMA model was used to construct the time series analysis function f (t) First, the soil moisture data and the corresponding flow data in the historical vegetation growth cycle are tested for stability and differential processing. For example, the flow data is stable after the first-order difference. Then the order of the model is determined according to the autocorrelation function and the partial autocorrelation function, such as determining p = 1, d = 1, q = 1. The model parameters are estimated by the least squares method to obtain the ARIMA model expression. The model is used to predict the flow required for vegetation growth at different time points in the future. For example, it is predicted that the suitable ecological flow for the growth of riparian vegetation in the summer vegetation growth period is 180 cubic meters per second.

[0045] 3. Ecological flow calculation stage

[0046] The multi-parameter comprehensive evaluation method is used to calculate the suitable ecological flow. Assume that the flow corresponding to the suitable water temperature range during the spawning period is Q 1 = 250 cubic meters per second, with a weight of β 1 =0.4, the flow rate corresponding to the suitable flow rate range is Q 1 = 240 cubic meters per second, with a weight of β 2 =0.6, the suitable ecological flow calculation formula is: Q f =β 1 ×Q 1 +β 2 ×Q 2 Then Q f =0.4×250+0.6×240=244 cubic meters / second. The weight β 1 and β 2 The determination of the appropriate water temperature range and the appropriate flow velocity range during the spawning period were performed using the analytic hierarchy process (AHP). First, a judgment matrix was constructed by inviting five fishery experts to compare and score the relative importance of the appropriate water temperature range and the appropriate flow velocity range to fish spawning and reproduction. For example, if the expert believes that the appropriate water temperature range is slightly more important than the appropriate flow velocity range, the score result is 3, otherwise it is 1 / 3, and the judgment matrix is ​​constructed. Then, we use mathematical methods to calculate the eigenvector of the judgment matrix and get β 1 =0.4,β 2 =0.6. In actual application, experts are invited to adjust and optimize the weights every three years according to the characteristics of different fish species and the ecological environment of the stream.

[0047] Using the multi-parameter comprehensive evaluation method, the flow corresponding to the suitable living depth of different aquatic organisms is set as Q 3 = 325 cubic meters per second, with a weight of γ 1 =0.5, the flow rate required to maintain the appropriate water quality is Q 4 = 320 cubic meters per second, with a weight of γ 2 =0.5, the suitable ecological flow calculation formula is: Q h =γ 1 ×Q 3 +γ 2 ×Q 4 Then Q h = 0.5 × 325 + 0.5 × 320 cubic meters per second. The weight γ 1 and γ 2 The entropy weight method is used to determine the flow data corresponding to the suitable water depth for survival of different aquatic organisms and the flow data required for maintaining suitable water quality are standardized. 3 and Q 4 The original data matrix is After standardization in Then calculate the information entropy e of each data j , determine the weight of each parameter according to information entropy

[0048] Based on the minimum flow rate required for soil saturation in the root layer of vegetation, Q 5 = 150 cubic meters per second, considering the changes in water demand at different stages of the vegetation growth cycle, the appropriate ecological flow for the growth of riparian vegetation is determined through time series analysis. Assume that the time series analysis function is f (t) , the ARIMA model is constructed, such as the ARIMA (1,1,1) model with p=1, d=1, q=1 determined above, the model expression is (in θ 1 is the model parameter, ∈ t is a white noise sequence). After estimating the model parameters by the least squares method, the model is used to predict the required flow rate for vegetation growth at different time points. For example, in spring, the suitable ecological flow rate for vegetation growth in the riparian zone is predicted to be Q v =160 cubic meters per second.

[0049] 4. Traffic Integration and Adjustment Phase

[0050] The appropriate ecological flow calculated for each ecologically sensitive target was integrated, and the maximum value method was used to determine the final appropriate ecological flow for alpine canyon streams. f =244 cubic meters / second, Q h =322.5 cubic meters / second, Q v =160 cubic meters / second, and the final suitable ecological flow is Q=322.5 cubic meters / second.

[0051] According to the seasonal variation characteristics of streams, the resilience of ecosystems, and the degree of interference from human activities, the appropriate ecological flow of each ecologically sensitive target is dynamically adjusted. In the rainy season (such as June to September), due to the large amount of precipitation and sufficient stream flow, the ecological demand restrictions on stream flow are appropriately reduced. For example, the appropriate ecological flow for fish spawning and reproduction is adjusted to 80% of the original calculated value, that is, 244×0.8=195.2 cubic meters / second, the appropriate ecological flow for maintaining aquatic habitats is adjusted to 90% of the original calculated value, that is, 322.5×0.9=290.25 cubic meters / second, and the appropriate ecological flow for vegetation growth in the riparian zone is adjusted to 95% of the original calculated value, that is, 160×0.95=152 cubic meters / second, so as to take into account the needs of human activities such as flood control, and at the same time, the basic stability of the ecosystem can be guaranteed under the condition of sufficient flow, because natural precipitation can supplement part of the ecological water demand at this time, and appropriately reducing the flow requirements will not cause a major impact on the ecosystem.

[0052] In the dry season (such as December to February of the following year), priority is given to ensuring the flow demand of ecologically sensitive targets that are crucial to the stability of the ecosystem. Through long-term monitoring and research on stream ecosystems, it is determined that the maintenance of aquatic habitats in the dry season plays a key role in the stability of the entire ecosystem. At this time, the final suitable ecological flow is set according to the demand for maintaining a suitable ecological flow for aquatic habitats, that is, it is maintained at around 322.5 cubic meters per second. The flow demand of other ecologically sensitive targets is taken into account as much as possible on the basis of meeting the maintenance of aquatic habitats. For example, for fish spawning and reproduction, if there are a small number of fish spawning at this time, the flow rate that is not less than their minimum survival needs can be provided through local water area regulation and other methods, which is about 60% of the original calculated value, that is, 244×0.6=146.4 cubic meters per second; for the growth of riparian vegetation, auxiliary measures such as artificial water replenishment can be used to supplement some water so that it can maintain its basic growth state at a lower flow rate, and the flow rate can be maintained at 70% of the original calculated value, that is, 160×0.7=112 cubic meters per second.

[0053] At the same time, an ecological flow early warning mechanism is established. A flow threshold is set in the stream flow monitoring system, and a warning signal is issued in a timely manner when the flow is lower than or higher than the preset ecological flow range. For example, when the flow is lower than the minimum ecological flow requirement in the dry season (such as 300 cubic meters per second), the early warning system is activated, and relevant departments can take measures such as restricting water use and initiating emergency water replenishment; when the flow is higher than the safe flow threshold in the rainy season (such as 500 cubic meters per second), flood control dispatching, increasing downstream flow control and other measures are taken to ensure the safety of the stream ecosystem and surrounding human activities.

[0054] In addition, the ecological flow calculation method and adjustment mechanism are regularly evaluated and optimized. A comprehensive ecological survey of the entire alpine canyon stream ecosystem is conducted every five years, including changes in the species and number of aquatic organisms, changes in riparian vegetation coverage and species diversity, and changes in water quality. According to the survey results, the effectiveness of the current ecological flow calculation method and adjustment mechanism is analyzed, and the calculation parameters, weight distribution, and adjustment range are optimized and adjusted. For example, if it is found that the number of a certain rare fish continues to decrease, it may be that the current calculation of the ecological flow suitable for fish spawning and reproduction is inaccurate or the adjustment mechanism is unreasonable. Further in-depth research on the ecological habits and flow requirements of the fish, re-determine the flow parameters corresponding to its suitable water temperature and flow velocity, and the flow adjustment ratio in different seasons, so as to continuously improve the scientificity and effectiveness of the calculation and management of suitable ecological flow for alpine canyon streams, and achieve long-term coordinated development of water resources development and utilization and ecological environmental protection.

[0055] In terms of data quality monitoring and evaluation, a strict data review process is established. For the collected basic data, such as runoff data, a multi-source data comparison and verification method is adopted. In addition to the data from the hydrological monitoring station, the accuracy of the runoff data is comprehensively analyzed using the water area change data monitored by satellite remote sensing and the groundwater level monitoring data. For topographic data, regular field reviews are conducted to check whether the coordinates and elevations of key topographic feature points have changed. If there are any changes, the data will be updated in a timely manner. During the calculation process, the rationality of each calculation result is checked. For example, if the calculated natural base flow obviously deviates from the historical data range or differs too much from the natural base flow data of the same type of streams, recheck the accuracy of data such as precipitation, evaporation and infiltration coefficient during the calculation process and whether the calculation method is correct. For the final suitable ecological flow result, a comparative evaluation is conducted with the actual ecological status of the stream. If, under the set appropriate ecological flow, the stream ecosystem still experiences problems such as water quality deterioration and biodiversity reduction, in-depth analysis of the reasons may be that the water demand parameters of ecologically sensitive targets are inaccurate or the flow adjustment mechanism is imperfect. Targeted improvements and optimizations should be made to ensure the reliability and practicality of the calculation method for suitable ecological flow for alpine canyon streams, providing solid technical support for the ecological protection and sustainable utilization of alpine canyon streams.

Claims

1. A method for calculating suitable ecological flow of alpine canyon streams, characterized in that: The following steps are involved: Step 1: Collect basic data of alpine canyon streams, including the multi-year average runoff of the streams, the topographic data of the basin where the streams are located, the vegetation coverage type and coverage data in the basin, the soil type data in the basin, and the climate data in the basin, where the climate data includes the multi-year average precipitation, multi-year average temperature, and multi-year average evaporation; Step 2: Determine the river slope of the stream and the river width and water depth of different river sections based on the collected topographic data, and determine the infiltration coefficient of the basin based on the vegetation coverage type and coverage data and soil type data; let the infiltration coefficient be α, and the infiltration amount calculation formula is: F = α × P, where P is the average precipitation over many years; Step 3: Based on the multi-year average precipitation, multi-year average evaporation and infiltration coefficient, the natural base flow of the stream is calculated using the water balance equation, which is: Q b =PEF, where Q b is the natural base flow, P is the average precipitation over many years, E is the average evaporation over many years, and F is the infiltration; Step 4: Based on the natural base flow and in combination with the ecologically sensitive targets of the watershed where the stream is located, determine the water demand parameters corresponding to the ecologically sensitive targets, wherein the ecologically sensitive targets include fish spawning and reproduction, maintenance of aquatic habitats, and growth requirements of riparian vegetation, wherein the water demand parameters for fish spawning and reproduction include the flow corresponding to the suitable water temperature range during the spawning period and the flow corresponding to the suitable flow velocity range, the water demand parameters for maintaining aquatic habitats include the flow corresponding to the suitable living water depths of different aquatic organisms and the flow required for maintaining suitable water quality, and the water demand parameters for riparian vegetation growth include the minimum flow required for saturation of soil water in the root layer of vegetation; Step 5: According to the water demand parameters corresponding to different ecological sensitive targets, calculate the appropriate ecological flow of each ecological sensitive target respectively. The calculation method is as follows: For fish spawning and reproduction, if there are multiple water demand parameters, the multi-parameter comprehensive evaluation method is used to calculate the suitable ecological flow. The flow corresponding to the suitable water temperature range during the spawning period is Q1, the weight is β1, the flow corresponding to the suitable flow velocity range is Q2, the weight is β2, and the calculation formula for the suitable ecological flow is: Q f =β1×Q1+β2×Q2, where Qf is the suitable ecological flow for fish spawning and reproduction, and β1+β2=1; For the maintenance of aquatic habitats, a multi-parameter comprehensive evaluation method is used. The flow corresponding to the suitable water depth for different aquatic organisms is set as Q3, the weight is γ1, the flow required for maintaining suitable water quality is Q4, the weight is γ2, and the calculation formula for suitable ecological flow is: Q h =γ1×Q3+γ2×Q4, where Q h Maintaining suitable ecological flow for aquatic habitats, and γ1+γ2=1; For the growth demand of riparian vegetation, the minimum flow rate required for soil saturation of the vegetation root layer is taken as the basis, which is set as Q5. Considering the changes in water demand at different stages of the vegetation growth cycle, the appropriate ecological flow rate for the growth of riparian vegetation is determined through time series analysis. The time series analysis function is set as f (t) , then the appropriate ecological flow calculation formula is: Q v =Q5×f (t) , where Q v Provide suitable ecological flow for the growth of riparian vegetation; Step 6: Integrate the suitable ecological flow calculated for each ecologically sensitive target, and use the maximum value method to determine the final suitable ecological flow for alpine canyon streams, that is, the final suitable ecological flow is the maximum value of the suitable ecological flow for each ecologically sensitive target.

2. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step one, when collecting the average runoff over many years, statistical analysis is performed using at least 30 years of continuous runoff monitoring data to ensure the reliability and representativeness of the data. For the topographic data within the basin, high-precision satellite remote sensing images are combined with field measurements to obtain the data. Field measurements include the use of total stations, GPS and other equipment to locate and measure the elevation of key topographic feature points of streams. Satellite remote sensing images are used to obtain a wide range of terrain undulation information and the distribution range of different landform types, so as to more accurately determine the river slope of the stream and the spatial variation characteristics of the river width and water depth data of different river sections, providing more accurate basic data support for subsequent calculations.

3. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step 2, when determining the infiltration coefficient, infiltration test plots are established for different vegetation cover types and soil types; different precipitation intensity simulation devices are set up in the test plots, and the changes in infiltration water volume over time during precipitation are monitored, and the Horton infiltration formula is used: f = f c +(f0-f c ) -kt (where f is the infiltration rate, f c In order to stabilize the infiltration rate, f0 is the initial infiltration rate, k is the attenuation coefficient, and t is the time) is fitted and calculated to obtain the infiltration coefficient under different combinations of vegetation coverage and soil types. Then, the comprehensive infiltration coefficient of the entire basin is obtained by weighted average based on the area proportion of each type in the basin, thereby improving the accuracy and scientificity of the determination of the infiltration coefficient and making the calculation result of the natural base flow closer to the actual situation.

4. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step 4, when determining the water requirement parameters for fish spawning and reproduction, the flow corresponding to the suitable water temperature range during the spawning period is obtained by establishing an empirical relationship model between water temperature and flow; first, the water temperature and flow at different locations of the stream are synchronously monitored during the fish spawning period, and multiple groups of data are collected. Then, regression analysis methods, such as multivariate linear regression or nonlinear regression, are used to determine the mathematical relationship expression between water temperature and flow, and then the corresponding flow range is calculated according to the suitable water temperature range; for the flow corresponding to the suitable flow velocity range, an acoustic Doppler current meter is used to measure the flow velocity at different water depths and cross-sectional positions of the stream, and a flow velocity and flow relationship curve is established in combination with the measured flow data, and the corresponding flow parameters are determined according to the suitable flow velocity range for fish spawning, providing a basis for accurately calculating the suitable ecological flow for fish spawning and reproduction.

5. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step 4, when determining the water requirement parameters for maintaining aquatic habitats, for the flow corresponding to the water depth suitable for different aquatic organisms, refer to the relevant aquatic organism research literature and field survey data based on the biological characteristics and ecological habits of different aquatic organisms, and determine the minimum, suitable and maximum water depth ranges required for various types of aquatic organisms at different growth stages; then use hydraulic models, such as the HEC-RAS model, to simulate the water depth distribution of streams under different flow conditions, and determine the flow range that meets the water depth range suitable for various types of aquatic organisms through comparative analysis; for the flow required to maintain suitable water quality, analyze the relationship between the concentration of major pollutants and flow based on the water quality monitoring data of the stream, and establish a water quality model, such as the QUAL2K model, and calculate the minimum flow required to maintain the stream to a certain water quality standard through model simulation. These parameters are combined to provide comprehensive data support for the calculation of suitable ecological flow for maintaining aquatic habitats.

6. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step five, when the multi-parameter comprehensive evaluation method is used to calculate the suitable ecological flow for fish spawning and reproduction, the weights β1 and β2 are determined by the analytic hierarchy process (AHP); first, a judgment matrix is ​​constructed, and experts compare and score the relative importance of the suitable water temperature range and the suitable flow velocity range during the spawning period to fish spawning and reproduction, and then the eigenvectors of the judgment matrix are calculated using mathematical methods to obtain the values ​​of β1 and β2; in practical applications, according to the characteristics of different fish species and the ecological and environmental characteristics of the stream, the weights are regularly adjusted and optimized to ensure that the calculated suitable ecological flow can more accurately meet the needs of fish spawning and reproduction, and ensure the stability and reproduction of fish populations.

7. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step 5, when the multi-parameter comprehensive evaluation method is used to calculate the suitable ecological flow for the maintenance of aquatic habitats, the entropy weight method is used to determine the weights γ1 and γ2; first, the flow data corresponding to the suitable living depths of different aquatic organisms and the flow data required for the maintenance of suitable water quality are standardized, and then the information entropy of each data is calculated, and the weight of each parameter is determined according to the information entropy; The entropy weight method can objectively reflect the amount of information contained in the data itself, avoid the influence of subjective factors on the determination of weights, make the calculation results of maintaining suitable ecological flow in aquatic habitats more scientific and reasonable, and can better balance the relationship between different ecological needs and maintain the ecological integrity of aquatic habitats.

8. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1 is characterized in that: In step 5, when determining the appropriate ecological flow rate for riparian vegetation growth requirements through time series analysis, the time series analysis function f (t) The ARIMA model is constructed; first, the soil moisture data and the corresponding flow data within the historical vegetation growth cycle are tested for stationarity and differential processing, and then the order of the model is determined according to the autocorrelation function and partial autocorrelation function. The model parameters are estimated by the least squares method to obtain the ARIMA model expression; the model is used to predict the vegetation growth demand flow at different time points in the future, and the suitable ecological flow for riparian vegetation growth is determined according to the prediction results; and the model data is updated regularly to adapt to the influence of factors such as vegetation changes and climate change in the basin on the relationship between riparian vegetation growth and water demand, so as to ensure the timeliness and accuracy of the calculation results.

9. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1, characterized in that: In step six, when integrating the appropriate ecological flows calculated for each ecologically sensitive target, in addition to using the maximum value method to determine the final appropriate ecological flow, an ecological flow adjustment mechanism is also established; the appropriate ecological flow of each ecologically sensitive target is dynamically adjusted according to the seasonal variation characteristics of the stream, the resilience of the ecosystem, and the degree of interference from human activities; in the rainy season, the ecological demand restrictions on stream flow are appropriately reduced to take into account the needs of human activities such as flood control; in the dry season, priority is given to ensuring the flow demand of ecologically sensitive targets that are crucial to the stability of the ecosystem. Through this dynamic adjustment mechanism, the ecological flow management of high mountain canyon streams is made more flexible and sustainable, and while protecting the ecological environment, it is achieved in coordination with the development of human society.

10. The method for calculating suitable ecological flow of alpine canyon streams according to claim 1, characterized in that: During the implementation of the calculation method, a data quality monitoring and evaluation system is established; real-time monitoring and regular evaluation are carried out on the collected basic data, the intermediate data in the calculation process, and the final calculated suitable ecological flow data; By comparing with historical data, the results of different calculation methods, and field ecological monitoring data, data anomalies and calculation deviations can be discovered in a timely manner, and the calculation methods and parameters can be optimized and adjusted; at the same time, the data quality monitoring and evaluation results are recorded and archived to provide data reference and experience for subsequent stream ecological flow research and management, and continuously improve the accuracy and reliability of suitable ecological flow calculations for high mountain canyon streams.

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