Method for identifying rainy season runoff water source composition and confluence path in high and cold frozen soil region

Abstract

The invention discloses a rainy season runoff water source composition and confluence path identification method. The rainy season runoff water source composition of an alpine region is analyzed by combining collection of water body samples such as drainage basin surface water and underground water and environmental tracers (including stable isotopes and hydrochemistry); carrying out watershed rainy season runoff segmentation based on a Bayesian mixture model; a runoff water source confluence path is analyzed by using a reaction solute tracer (including dissolved Si, dissolved inorganic carbon DIC and the like), so that the water source analysis means in a high and cold frozen soil drainage basin with obvious spatial heterogeneity and high hydrological research implementation difficulty are enriched; reliable support is provided for water resource development and protection of the Qinghai-Tibet Plateau region, water demand policy making of the Tibet autonomous region and the downstream region and reasonable water resource allocation.

Description

Technical Field

[0001] The invention relates to the technical field of hydrological forecasting, and is particularly applicable to a method for identifying the composition of runoff sources and confluence paths in rainy seasons in alpine frozen soil areas. Background Art

[0002] In recent years, the Qinghai-Tibet Plateau, known as the "Asian Water Tower", has seen glacier retreat, permafrost melting, and increased instability in the "water tower"'s functions. At the same time, meteorological disasters and derivative disasters have increased, resulting in a series of water resource and ecological environmental problems, posing more severe challenges to the local comprehensive utilization of water resources and environmental protection.

[0003] Due to their special geographical location and natural conditions, the alpine frozen soil areas represented by the Qinghai-Tibet Plateau have the coexistence of seasonal frozen soil and permafrost, diverse river water sources, and complex spatial combination characteristics of water sources. Especially in the rainy season with precipitation as the link in the large-scale water cycle, the water source composition of river runoff shows a high degree of temporal and spatial differences. Therefore, the alpine frozen soil areas are faced with the theoretical and practical problems of unclear runoff water source composition and water source confluence paths, and the inability to scientifically guide the comprehensive utilization of local water resources and environmental protection.

[0004] As far as the current research status is concerned, researchers at home and abroad have made great progress in stable isotope tracing and water source analysis in high-altitude and cold river basins, but it is still relatively difficult to identify runoff water sources in high-altitude and cold areas.

[0005] This is because the alpine permafrost area has a special geographical location and complex terrain, making it difficult to carry out various hydrological surveys and obtain various data, which makes it difficult to apply traditional hydrological methods. At the same time, for alpine basins, the underlying surface of the basin is highly heterogeneous, with complex climate and terrain conditions, and the uncertainty of various water source stable isotopes increases, resulting in greater uncertainty in the results of river runoff segmentation. At present, in alpine basins where permafrost and seasonal frozen soil are widely distributed, most hydrological process research remains at the empirical relationship level, and the sub-basin is still a "black box" with unclear structure. Summary of the invention

[0006] The present invention aims to provide a method for identifying the composition and confluence path of runoff sources in rainy season in alpine permafrost areas, so as to solve the problem of runoff source identification in alpine permafrost areas.

[0007] To achieve the above object, the present invention adopts the following technical solutions: The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas of the present invention comprises the following steps: S1, analyze the source composition of runoff in rainy season; Qualitatively determine the recharge sources of river water in the basin runoff through environmental tracers and hydrochemical characteristics of snowmelt, groundwater, precipitation and river water; S2, split rainy season runoff source composition; The improved Bayesian mixed model is used to output the posterior distribution map and statistical information of the water sources of the river water in the basin runoff, and quantitatively analyze the water source composition of the river water in the basin runoff; S3, analyzing the runoff source confluence path; Through the evolution characteristics and response characteristics of solute tracers in the basin runoff river water and the soil freeze-thaw process in the basin, the paths of precipitation and snowmelt water entering the basin runoff river water can be identified.

[0008] Furthermore, step S1 is specifically as follows: S1.1, sample and analyze the spatial characteristics of stable isotopes in snowmelt water, groundwater, and precipitation in the basin, and identify the water supply sources and water circulation patterns in the basin runoff river water; S1.2, sampling and analysis of δ 2 H and δ 18 The variation characteristics of O value on time scale can be used to identify the recharge sources of river water in the basin runoff at different periods of the rainy season; S1.3, sample and analyze the basic physical and chemical parameters, hydrochemical composition and influencing factors of precipitation, snowmelt, groundwater and river water, identify the response relationship between river water hydrochemical ions and precipitation, and qualitatively analyze the sources of runoff recharge in different periods of the rainy season in the basin through a three-end member mixed model.

[0009] Furthermore, the improved Bayesian mixed model in step S2 is MixSIAR; the input parameters of the improved Bayesian mixed model are the concentration values, means and variances of environmental tracers in snowmelt water, groundwater and precipitation; and the output statistical information includes median, mean and variance.

[0010] Furthermore, step S3 is specifically as follows: according to the evolution characteristics of the reaction solute tracer, the reaction solute tracer content in the river water decreases, and the runoff source confluence is mainly discharged directly by surface runoff; the reaction solute tracer content in the river water increases, and the runoff source confluence is mainly discharged by groundwater.

[0011] Furthermore, step S3 specifically uses a three-end-member mixed model to analyze the response characteristics of the solute tracer in the runoff river water of the basin. If the water source end-member shows a trend away from the groundwater point, it indicates that the runoff water source confluence is mainly discharged directly by surface runoff.

[0012] Furthermore, step S3 is specifically as follows: based on the quantitative analysis results of the runoff water source in the rainy season, the response characteristics of the reaction solute tracer, and the freezing and thawing process of the soil in the basin, if the concentration of the reaction solute tracer shows a decreasing trend, the runoff water source confluence is mainly discharged directly by surface runoff.

[0013] Furthermore, the reaction solute tracer includes DIC and dissolved Si.

[0014] The advantages of the present invention are that the composition of the runoff source in the rainy season in the high-altitude cold region is analyzed by combining the collection of surface water, groundwater and other water samples in the basin and environmental tracers (including stable isotopes and water chemistry); the runoff segmentation in the rainy season in the basin is carried out based on the Bayesian mixed model; and the runoff source confluence path is analyzed by using reactive solute tracers (including dissolved Si, dissolved inorganic carbon DIC, etc.), which enriches the means of carrying out water source analysis in the high-altitude cold frozen soil basin with obvious spatial heterogeneity and greater difficulty in implementing hydrological research, and provides reliable support for the development and protection of water resources in the Qinghai-Tibet Plateau region, the formulation of water demand policies in the Tibet Autonomous Region and downstream areas, and the rational allocation of water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a flow chart of a method for identifying the composition of runoff sources and confluence paths in rainy seasons.

[0016] Figure 2 This is a characteristic diagram of runoff changes during soil freezing and thawing in high-altitude cold basins.

[0017] Figure 3 This is a trend chart of soil temperature and humidity changes in high-altitude cold river basins.

[0018] Figure 4 δ of various water bodies in a certain alpine basin 18 O~δ 2 H relationship diagram.

[0019] Figure 5 The δ 18 O, δ 2 HSeasonal change trend chart.

[0020] Figure 6 The δ 18 O, δ 2 H month change trend chart.

[0021] Figure 7 The precipitation in the high-altitude cold basin is 18 O, δ 2 H month change trend chart.

[0022] Figure 8 TDS and Cl of precipitation in high-cold basins - , DIC, and Si monthly variation characteristics.

[0023] Fig. 9 It is a three-end member mixed map of the high-altitude cold river basin.

[0024] Fig.10It is the posterior probability density of the runoff source contribution ratio in each altitude zone of the alpine basin.

[0025] Fig.11 This is the posterior probability density distribution map of the runoff water source contribution ratio of each tributary in the alpine basin.

[0026] Fig.12 This is the monthly variation trend of DIC and Si in the alpine basin. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1 like Figure 1 As shown, the method for identifying the composition of runoff sources and confluence paths in the rainy season in the alpine frozen soil region of the present invention comprises the following specific steps: S1, analyze the source composition of runoff in rainy season; In the high-cold permafrost basin with lack of basic data and complex underlying surface, a variety of environmental tracer methods are used to calibrate each other to verify whether the collected end-member water samples can represent the runoff segmentation end-members, so as to ensure the reliability of quantitative segmentation of runoff water sources in the basin during the rainy season.

[0029] The present invention combines the collection of water samples such as snowmelt water, groundwater, precipitation and river water in the basin and the detection data of environmental tracers, and conducts qualitative analysis of the replenishment source of basin runoff through the response relationship between the stable isotopes and water chemical characteristics of snowmelt water, groundwater, precipitation and river water on a time scale. The specific steps are as follows: S1.1. Sample and analyze the spatial variation characteristics of stable isotopes in snowmelt water, groundwater and precipitation in different areas of the basin to identify the recharge sources in the basin runoff river water.

[0030] S1.2, sampling and analysis of δ 2 H and δ 18 The variation characteristics of O value on time scale can be used to identify the recharge sources of river water in the basin runoff at different periods of the rainy season.

[0031] S1.3, sample and analyze the basic physical and chemical parameters and water chemical ion composition of precipitation, snowmelt, groundwater and river water, identify the response relationship between river water water chemical ions and precipitation, and qualitatively analyze the source of runoff recharge in different periods of the rainy season in the basin through a three-end member mixing model.

[0032] S2, split rainy season runoff source composition; The improved Bayesian mixed model is used to quantitatively analyze the composition of runoff water sources in different stages of the rainy season and in different altitude vegetation type zones in the alpine permafrost basin, and the posterior distribution map and statistical information of the water sources of the basin runoff river water are output to achieve quantitative analysis of the water source composition of the basin runoff river water.

[0033] The improved Bayesian mixed model is MixSIAR; the input parameters of the improved Bayesian mixed model are the concentration value, mean and variance of environmental tracers in snowmelt water, groundwater and precipitation; the output statistical information includes the median, mean and variance of the contribution rate of each water source in the river water of the basin runoff. The specific implementation steps are as follows: S2.1, determine the runoff segmentation period: Since the river runoff segmentation and water source confluence paths are very different in the early rainy season, middle rainy season, and late rainy season, the runoff segmentation period can be divided into three periods according to the characteristics of the rainy season and freeze-thaw process in the study area, as well as the special hydrological input method of the basin, namely, the early rainy season, middle rainy season, and late rainy season.

[0034] Taking the Qinghai-Tibet Plateau as an example, frozen soil is widely distributed on the Qinghai-Tibet Plateau. At the same time, the existence of frozen soil leads to weak soil permeability, which blocks the exchange and migration of surface water and groundwater in the basin. According to the characteristics of the rainy season process and the freeze-thaw process, as well as the special hydrological input mode of the basin, the runoff segmentation period can be divided into three periods, namely the early rainy season (from mid-May to early June, overlapping with the soil melting process period, the hydrological input mode is snowmelt and precipitation), the middle rainy season (late June to late September, overlapping with the soil complete melting period, the hydrological input mode is snowmelt and precipitation), and the late rainy season (from early September to October, overlapping with the soil freezing process period, the hydrological input mode is snowmelt).

[0035] S2.2, establish a Bayesian mixed model: The runoff segmentation model based on the Bayesian framework can realize the accurate quantification of the runoff water source components, and the obtained water source contribution ratio is a probability distribution result. The principle is to take the contribution ratio of each water source as the value to be solved, and obtain the posterior information of the water source contribution ratio based on the prior information of the water source contribution ratio and the water source isotope sample information.

[0036] Assuming mixed water stable isotope abundance values X ij In the basic assumption of the stable isotope mixing model, for a given stable isotope, the mixing water ( δ M ) is defined as follows: Where: f i It is iThe proportion of water sources contributing to the mixed water body, δ i It is i The stable isotope abundance of the water source, γ i It is i Stable isotope fractionation index of water sources.

[0037] Bayesian techniques estimate all ( f i ), which is randomly generated during the process. q possible water source contribution ratio vector f q , where f q All elements in f i The sum is 1. Based on Bayes' theorem, f q The probability calculation formula is as follows: In the formula, x is the observed value of stable isotopes in river water; f q for q The contribution rate of each possible water source to runoff; L ( x |f q ) is a given f q the likelihood of observations of stable isotopes in lower river water; p (f q ) indicates that f appears in the natural state based on “prior information” q The prior probability of L ( x |f q )* p (f q ) represents the likelihood of the marginal probability of the observed value of stable isotopes in river water; the numerator L ( x |f q )* p (f q ) represents the given f based on data and “prior information” q The unstandardized likelihood of .

[0038] In order to calculate a given f q Likelihood of stable isotope observations in mixed water L ( x |f q ), the contribution ratio of each water source is combined with the distribution of its stable isotope information to form the river water stable isotope joint distribution function. The distribution of the stable isotope abundance value of each mixed water body is obtained through mathematical expectation ( û j ) and standard deviation ( σ j ) is determined as follows: In the formula, m jsourcei It is i The water source j The mathematical expectation of stable isotopes, m jfraci It is i Water source j The mathematical expectation of the fractionation coefficient of the stable isotopes; s jsourcei It is i Water source j The standard deviation of the stable isotopes, s jfraci It is i Water source j The standard deviation of the stable isotope fractionation coefficient. û j and ̂σ j Determine that the likelihood value of the stable isotope abundance of a given mixed water body (river runoff) is calculated as: In the formula, x kj Indicates k In the mixed water sample j Finally, based on the “prior information”, f appears in the natural state. q The prior probability p (f q ) multiplied by the given f q Likelihood of stable isotope abundance values ​​in mixed water L ( x |f q ), and finally the target value can be obtained.

[0039] S2.3, Model input: In alpine permafrost areas, runoff water bodies are usually divided into three water sources, including snowmelt, groundwater and precipitation. The Bayesian mixed model uses tracers (δ 18 O、Cl - ) concentration values ​​and their statistical information such as mean and variance.

[0040] S2.4, model output: Based on the improved Bayesian runoff segmentation model MixSIAR, the posterior distribution map of runoff water source contribution ratio and its statistical information, including median, mean, variance, etc., are output to comprehensively judge the contribution ratio of groundwater, precipitation and snowmelt water in the Qinghai-Tibet Plateau basin at different stages of the rainy season.

[0041] S3, analyze the runoff source confluence path.

[0042] Through the changing trend of the reactive solute tracers in the runoff river water and the freezing and thawing process of the soil in the basin, the path of precipitation and snowmelt water entering the runoff river water in the basin can be identified. The reactive solute tracers include DIC and dissolved Si.

[0043] S3.1. Based on the evolution characteristics of dissolved Si and DIC in river water during the rainy season, determine whether the path taken by precipitation and snowmelt water before entering the river is above ground or underground, so as to clarify whether the way new water replenishes the river is by direct discharge of surface runoff or by entering the underground to drive out groundwater.

[0044] In general, the content of hydrochemical solute tracers (such as DIC and dissolved Si) in precipitation and snowmelt water is low, while that in groundwater is high. For river water, due to the replenishment of various water sources, its hydrochemical solute content will fluctuate to a certain extent. When replenished by precipitation and snowmelt water, its hydrochemical solute content will decrease; when replenished by groundwater, its content will increase. Based on this characteristic, the evolution characteristics of dissolved Si and DIC in river water during the rainy season are used to determine whether the path taken by precipitation and snowmelt water before entering the river is on the ground or underground, so as to clarify whether the way new water replenishes the river is whether it is directly discharged into the river by surface runoff or enters the ground to drive out groundwater.

[0045] That is to say, according to the evolution characteristics of reaction solute tracers, when the content of reaction solute tracers in river water decreases, the runoff source confluence is mainly direct discharge of surface runoff; when the content of reaction solute tracers in river water increases, the runoff source confluence is mainly groundwater inflow.

[0046] S3.2, the three-end member mixed model was used to analyze the response characteristics of dissolved Si and DIC in the river water during the rainy season in the basin, and δ 2 H and DIC are used to determine the composition of river water sources in the study area. Precipitation, snowmelt and groundwater are used as water source end members. If the river water sample points in the three-end member mixing diagram show a trend away from the groundwater point, it indicates that during this period, precipitation and snowmelt with lower DIC concentrations contribute the most to river water, affecting the DIC concentration in river water. It also indicates that snowmelt and precipitation are difficult to infiltrate into the ground, but flow along the soil surface to replenish river water, and do not enter the ground to mix with the higher content of DIC in groundwater. In other words, in the three-end member mixing model, if the water source end member shows a trend away from the groundwater point, it indicates that the runoff water source confluence is mainly discharged directly by surface runoff. Otherwise, it is mainly confluence by groundwater.

[0047] S3.3, based on the quantitative analysis results of runoff water sources in the rainy season, the response characteristics of dissolved Si and DIC in river water with precipitation, and the freezing and thawing process of soil in the basin, the possible paths that precipitation and snowmelt water in the basin may flow through before being discharged into the river are analyzed.

[0048] In alpine basins where permafrost is widely distributed, factors such as snowmelt, permafrost thawing, and concentrated precipitation will have a series of effects on the recharge mechanism of runoff water sources in the rainy season. If the concentration of reactive solute tracers in river water shows a significant downward trend, it can be inferred that snowmelt and precipitation are difficult to infiltrate into the ground, but flow along the soil surface to replenish river water. At this time, the water source confluence path is reflected in that most precipitation and snowmelt do not interact with organic matter in the soil and mix with DIC of carbonate rock weathering, but directly flow into the river from the soil surface in the form of overland flow. That is, if the concentration of reactive solute tracers shows a downward trend, the runoff water source confluence is mainly discharged directly by surface runoff.

[0049] Example 2 The method for identifying the source composition and confluence path of rainy season runoff in a high-cold frozen soil area of ​​the present invention is used to identify the source composition and confluence path of rainy season runoff in a river basin in a high-cold area, specifically: 1) Collect data for the study area. A river basin in a high-altitude cold region with a drainage area of ​​16,350 km 2 , the river is about 460km long. From 2016 to 2019, 14 water sampling points were evenly distributed according to the altitude gradient, vegetation type zone, and the location of the main and tributary rivers. Samples of various water bodies (river water, snowmelt water, groundwater and precipitation) were collected. Sample testing included Ca 2+ Mg 2+ Isochemical ions, as well as isotopic parameters (δ 2 H and δ 18 O).

[0050] 2) Analysis of the composition of rainy season runoff sources: like Figure 2 As shown, the rainy season in the high-cold basin mainly includes three stages of soil freezing and thawing: from April to June, the basin is in the soil melting process; from June to September: the soil is completely thawed; from September to December: the basin is in the soil freezing process. From December to April of the following year, the high-cold basin is in the soil completely frozen period, and the river runoff water source input method is relatively simple, which is not within the scope of this invention.

[0051] like Figure 3The figure shows the trend of soil temperature and humidity in the alpine basin. According to the observation and analysis of soil temperature and soil humidity during the freezing and thawing process of soil in the alpine basin, the soil is frozen from November to March of the following year and begins to thaw in April of the following year. According to the change process of soil temperature in the year, it can be roughly divided into four periods: from February to July, the soil temperature is in an upward stage; from July to September, the soil temperature remains at a stable level; from September to December, the soil temperature begins to drop; from December to February, the soil is frozen, the temperature is less than 0℃ and is relatively stable. During the whole year, the average daily soil temperature is 6.49℃, and its change trend is similar to that of the temperature.

[0052] Due to the freeze-thaw process of soil in permafrost areas, the soil moisture content also shows periodic changes. From mid-April to early June, the basin is in a period of soil melting. The soil begins to melt as the temperature rises, and the soil moisture content rises to a maximum of 15.7%; from late June to late September, the basin is in a period of complete soil melting, and the soil moisture content reaches the highest and remains stable; from late September to early December, the basin is in a period of soil freezing, the temperature begins to drop, and the soil moisture content decreases.

[0053] Based on the above information, we can obtain the changing characteristics of soil temperature and soil moisture content in the active layer of frozen soil in the rainy season in the high-cold river basin: soil melting process period (mid-April to early June, the temperature rises, the frozen soil begins to melt, the soil moisture content rises rapidly and reaches the maximum value), soil complete melting period (late June to late September, the temperature is high, the soil is completely melted, the soil moisture content rises to the highest and the fluctuation range is small), soil freezing process period (late September to early December, the temperature drops, the melted soil begins to freeze, the soil moisture content drops rapidly and reaches the minimum value).

[0054] In high-altitude river basins where permafrost is widely distributed, factors such as snow melting, permafrost thawing, and concentrated precipitation will have a series of impacts on the rainy season runoff water supply mechanism.

[0055] Based on the quantitative analysis results of rainy season runoff sources and the response characteristics of dissolved Si and DIC in rainy season river water with precipitation, combined with the analysis of soil freeze-thaw process in high-altitude cold basins, the possible paths through which precipitation and snowmelt water in the basin may flow before being discharged into the river are analyzed.

[0056] (1) May to early June In May, the frozen soil is in the process of melting, and the soil temperature and humidity begin to rise, but since most of the permafrost active layer is still frozen, it hinders the infiltration of surface water. There is less rainfall during this period, but the concentration of dissolved Si in the river water has a downward trend. The reason is that the snowmelt water replenishes the river channel, reducing the concentration of dissolved Si in the river water.

[0057] Starting from May, the basin began to enter the rainy season and was in the soil melting process. At this time, the shallow soil made the temperature rise, and the soil temperature gradually increased from the lowest temperature of -11.87℃. The frozen soil active layer began to melt, and the soil moisture content increased from 9.5% to 15.5%. The soil active layer began to melt, but the active layer that had not yet thawed and the permafrost below it showed the properties of a strong impermeable layer due to their extremely poor permeability. The groundwater was more easily saturated in the soil surface area near the surface and above the frozen active layer. The existence of frozen soil restricted the infiltration of snowmelt water. From the decreasing trend of the concentration of reactive solute tracers in the river water, it can be inferred that snowmelt water and precipitation are difficult to infiltrate into the ground, but flow along the soil surface to replenish the river water. Therefore, the water source confluence path at this time is reflected in the fact that the snowmelt water did not interact with the organic matter in the soil and did not mix with the DIC of carbonate weathering, but directly flowed into the river from the soil surface in the form of overland flow. During this period, the sources of water for the river runoff hydrological process are snowmelt, precipitation and base flow, and the groundwater is in a storage process.

[0058] (2) Late June to August From June to August, the concentrations of dissolved Si and DIC in river water showed the opposite trend to the precipitation, indicating that the replenishment source of river water in the basin was precipitation and snowmelt water containing low concentrations of dissolved Si and DIC.

[0059] From late June to August, the soil gradually transitioned from the thawing process to the complete thawing period, with soil moisture reaching a peak of about 15.7%. The active soil layer completely melted, and soil moisture changes were relatively active, but the permafrost below the active layer continued to play the role of a strong aquiclude. During this period, a large amount of snowmelt water was released, and precipitation events were extremely frequent and abundant. A large amount of snowmelt water and precipitation continued to infiltrate the unsaturated zone of the soil. The soil surface near the surface and above the still frozen active layer was more easily saturated, and the infiltration rate of precipitation was lower than the recharge rate, which made it easier to form over-storage slope flow to recharge the river channel.

[0060] Since the concentration of reactive solute tracers in river water showed a significant downward trend, it can be inferred that snowmelt and precipitation are difficult to infiltrate into the ground, but flow along the soil surface to replenish the river water. Therefore, the water source confluence path at this time is reflected in that most precipitation and snowmelt do not interact with organic matter in the soil and mix with DIC of carbonate weathering, but directly flow into the river from the soil surface in the form of overland flow. During this period, groundwater is still in a storage process. The segmentation results based on the Bayesian runoff segmentation model also show that the contribution of precipitation, snowmelt and groundwater to runoff are 37%, 43.4% and 19.6% respectively.

[0061] (3) Late August to September From August to September, the basin is still in the period of complete soil melting. During this period, the rainfall is large, the runoff shows a certain response relationship, and the runoff is relatively stable. However, the concentrations of dissolved Si and DIC in the river water at this stage show an obvious increasing trend over time, indicating that a large amount of water with high concentrations of dissolved Si and DIC enters the river at this time, which is significantly different from June to August, which is also the period of soil melting.

[0062] During this period, the basin is still in the period of complete soil thawing. As the degree of permafrost melting increases, or even completely melts, the infiltration capacity of precipitation and permafrost melting water increases and continues to infiltrate. The water level of the frozen active layer on the permafrost layer in the permafrost zone rises, displacing more groundwater to replenish the river water, causing the concentration of the river water reaction solute tracer to show an upward trend. Therefore, the water source confluence path at this time is reflected in the interaction of most precipitation and snowmelt with organic matter in the soil and the mixing process with DIC of carbonate rock weathering. It is no longer mainly replenished in the form of overland flow, but precipitation and snowmelt infiltration promote the rise of groundwater levels, displacing more groundwater to replenish the river water. During this period, the soil aquifer gradually becomes saturated, the storage is stable, and the storage and release of groundwater reach a balance.

[0063] (4) September ~ October From September to October, the basin was in the soil freezing process, when both precipitation and runoff decreased significantly, and the concentrations of dissolved Si and DIC in the river water remained high and stable.

[0064] After September, the basin is in the soil freezing process, the soil profile is in the freezing process, the active layers of surface water in the high mountainous area, permafrost area and seasonal frozen soil area gradually turn into frozen state, the aquifer in the permafrost area becomes less active in water conduction function, and the soil moisture decreases significantly, gradually decreasing to about 11%; at the same time, the amount of snowmelt water gradually decreases, precipitation events become sparse, and both precipitation and river flow show a downward trend. Compared with the previous period, the water level of the permafrost layer drops, the overland flow decreases, and the amount of water entering the aquifer decreases, resulting in longer groundwater migration time and water-rock interaction time. The recharge source of river runoff mainly includes groundwater stored in the aquifer with high dissolved Si and DIC concentrations. At this time, the river flow further decreases, and the dissolved Si and DIC concentrations of the river water are relatively stable. Therefore, the water source confluence path at this time is reflected in groundwater recharge, and the overland flow formed by water sources such as precipitation and snowmelt water decreases. During this period, groundwater was in a slow release process, and the results based on Bayesian runoff segmentation also showed that the two types of water sources contributed 14.1% and 85.9% to the runoff respectively.

[0065] In general, through the analysis of the water source confluence paths of the rainy season runoff in the basin, it can be found that there is not much difference in the precipitation runoff response process between the high-altitude frozen soil basin under the influence of frozen soil and the inland basin under the influence of non-frozen soil, but the water source confluence paths are quite different, which are specifically reflected in two aspects.

[0066] First, at the beginning of the rainy season, due to the strong water-repellent effect of the permafrost layer below the active layer of frozen soil that has not yet thawed, the runoff process in the basin responds quickly to snowmelt and precipitation events. At this time, the water source confluence path is reflected in that most of the precipitation and snowmelt do not infiltrate into the ground and interact with the organic matter in the soil and mix with the DIC of carbonate weathering, but directly flow into the river from the soil surface in the form of overland flow.

[0067] Second, in the middle of the rainy season, with the arrival of monsoon precipitation, although the response relationship between runoff and precipitation is more obvious, similar to that from June to August, the infiltration capacity of precipitation, snowmelt and frozen soil melting and water release is enhanced and continues to infiltrate, causing the groundwater level to rise, displacing groundwater to replenish river water. Its confluence path is significantly different from that before August. The water source confluence path at this time is reflected in the increased soil infiltration capacity. A large amount of snowmelt and precipitation continue to infiltrate, no longer flowing along the soil surface to replenish river water, but entering the underground and interacting with organic matter in the soil and mixing with DIC of carbonate rock weathering, displacing more groundwater into the river channel, and the contribution ratio to river water is significantly increased.

[0068] Based on the isotopic parameters (δ 2 H and δ 18 O) and water chemistry and seasonal variation characteristics.

[0069] like Figure 4 is the delta of various water bodies in the basin, including river water, snowmelt water, groundwater, precipitation, etc. 18 O~δ 2 H relationship diagram. Among them, Figure 4 a is the stable isotope δ of various water bodies 18 O Features, Figure 4 d is the stable isotope δ of various water bodies 2 H features, Figure 4 b is the stable isotope δ of various water bodies 18 O-δ 2 The relationship between H characteristics and local precipitation line (LMWL, determined by precipitation isotope δ 18 O-δ 2 The H characteristic relationship is obtained, and its equation is δ 2 H = 7.6δ 18 O+3.4) position relationship diagram, Figure 4c is the river water evaporation line (LRWL, which is determined by the river water isotope δ 18 O-δ 2 The H characteristic relationship is obtained, and its equation is δ 2 H=5.51δ 18 O-31.13) and the position relationship between the local precipitation line (LMWL), Figure 4 e is the groundwater evaporation line (LGWL, which is determined by the groundwater isotope δ 18 O-δ 2 The H characteristic relationship is obtained, and its equation is δ 2 H = 6.74δ 18 O-11.89) and the position relationship between the local precipitation line (LMWL), Figure 4 f is the snowmelt water evaporation line (LMEWL, which is determined by the snowmelt water isotope δ 18 O-δ 2 The H characteristic relationship is obtained, and its equation is δ 2 H = 9.77 δ 18 O+32.27) and the position relationship between the local rainfall line (LMWL).

[0070] As can be seen from the figure, by comparing the stable isotope characteristics of various types of water bodies such as river water, snowmelt water, groundwater, and precipitation, it can be found that there are large differences in the stable isotope values ​​of different types of water bodies. Among them, the difference between river water and snowmelt water is more obvious, δ 18 O phase difference -11.4‰, δ 2 H phase difference -81‰; snowmelt water δ 18 O, δ 2 The H value is large because as the temperature rises in spring, the snow begins to melt, the evaporation fractionation is enhanced, and the heavy stable isotopes in the snowmelt water are increasingly enriched, making δ 18 O, δ 2 H value increases; similarly, δ 2 H and δ 18 The average value of O is between snowmelt, precipitation and groundwater. The river water is characterized by being replenished by multiple water sources, including precipitation, groundwater and snowmelt.

[0071] According to the δ 18 O-δ 2 The H relationship is used to analyze the source of rainy season runoff, where the local rainfall line (LMWL) is expressed as δ 2 H = 7.6δ 18 O+3.4. As can be seen from the figure, all types of water samples are close to the local precipitation line (LMWL), and the river water samples are relatively close to the samples of other types of water bodies (groundwater, precipitation, snowmelt water). 18 O, δ 2The H value is larger than that of precipitation and smaller than that of snowmelt. The river water is characterized by multiple water sources, including precipitation, groundwater and snowmelt. The locations of groundwater samples are relatively concentrated and close to precipitation, indicating that groundwater is mainly generated by δ 18 O, δ 2 The precipitation with a lower H value is infiltrated and recharged, and is newly generated precipitation, so it is less affected by the old water in the pre-existing groundwater aquifer.

[0072] Figure 5 The δ 18 O, δ 2 HSeasonal change trend. Figure 5 a is the δ of river water in the alpine basin 2 The H value changes with the seasons. Figure 5 b is the delta in the river water of the alpine basin 18 O value changes with seasons.

[0073] The results of stable isotope comparison of river water in different periods in the basin show that the δ 18 O, δ 2 H value is larger, stable isotopes are more enriched, while in spring δ 18 O, δ 2 The H value is small and the stable isotope is relatively depleted, which is exactly the opposite of other basins, such as the Urumqi River Basin in the northern foot of the Tianshan Mountains and the Aksu River Basin in the southern part of the Tianshan Mountains. This is due to the large amount of δ 18 O, δ 2 Snowmelt water with a smaller H value flows into the river channel, resulting in a relatively depleted stable isotope composition of the river water in spring. In summer, on the one hand, due to strong evaporation, the δ 18 O, δ 2 On the other hand, it may also be that when a large amount of evaporation fractionation occurs, δ 18 O, δ 2 When snowmelt water with a large H value replenishes the river channel, it causes the stable isotopes of the river water to gradually enrich, δ 18 O, δ 2 H value is relatively large. In the basin, summer snowmelt water mainly comes from the melting of snow in the basin. According to field survey data, as the temperature rises, the snow begins to melt, and snowmelt water begins to form in spring, but the flow rate is not large; as the temperature rises, it undergoes evaporation fractionation and causes δ 18 O, δ 2 As the H value increases, the snow water flow gradually increases and reaches its maximum in July.

[0074] Monthly changes in stable isotopes in river water Figure 6 As shown, Figure 6 a is δ in river water 2 H value change trend over time. Figure 6 b is δ in river water18 The trend of O value over time.

[0075] As can be seen from the figure, in March, the river water δ 18 O, δ 2 The H value has an obvious downward trend. At this time, a large number of δ 18 O, δ 2 Snowmelt water with a smaller H value flows into the river channel, causing the river water δ 18 O, δ 2 The H value decreases sharply as time goes by. At the beginning of summer, on the one hand, due to the strong evaporation, the river water δ 18 O, δ 2 H value is large, on the other hand, it may also be due to the evaporation fractionation, resulting in its δ 18 O, δ 2 The snowmelt water with increased H value flows into the river channel, and the river water δ 18 O, δ 2 H value gradually increased; in June and July, δ 18 O, δ 2 H is in the high value stage with small fluctuations. This is before the arrival of monsoon precipitation, and the runoff is relatively stable. After July, the δ 2 H, δ 18 O shows similarity to δ 2 H, δ 18 The floating trend of O values ​​is relatively consistent, and the δ 2 H, δ 18 The low value of O value can be seen in the runoff δ 2 H, δ 18 O value, but its fluctuation range (5%) is lower than that of precipitation (25%), so the δ 2 H, δ 18 The fluctuation of O value is obviously regulated by the comprehensive regulation of precipitation and snowmelt.

[0076] Monthly changes in stable isotopes of precipitation Figure 7 As shown, Figure 7 a is δ in river water 2 H value change trend over time. Figure 7 b is δ in river water 18 The trend of O value over time.

[0077] It can be seen from the figure that during July and August, the river water δ 18 O, δ 2 The H value is at a low stage. By comparing the δ 18 O, δ 2 The monthly response relationship of H shows that δ 18 O, δ 2Some troughs of H in the basin runoffδ 18 O, δ 2 This can be seen in the monthly changes of H, especially in August, which also reflects the monsoon activity period on the river water δ 18 O, δ 2 The influence of H.

[0078] In general, during the entire rainy season, the river water 18 O, δ 2 The change of H can be divided into three stages: the first stage is from May to June, when the river water δ 18 O, δ 2 H is at a low value but continues to rise, indicating that a large amount of δ 18 O, δ 2 Snowmelt water with a large H value flows into the river channel, with large fluctuations; the second stage is from June to July, with a large δ 18 O, δ 2 H is in the high value stage with small fluctuations. This is before the arrival of monsoon precipitation and is less affected by precipitation. 18 O, δ 2 H is also relatively stable; the third stage is from July to September, especially in August, with the arrival of monsoon precipitation, the precipitation increases, at this time the isotopes in the precipitation are relatively depleted, δ 18 O, δ 2 The H value is extremely small, making the δ 18 O, δ 2 H presents a low-value mutation stage. After these three stages, due to the 18 O, δ 2 H will fluctuate to a certain extent, and the δ18O and δ2H of river water will also fluctuate slightly with the δ18O and δ2H in precipitation and the amount of precipitation, but will generally remain stable.

[0079] Analyze the TDS (soluble solid concentration) and Cl content of river water in the rainy season in the basin - , dissolved inorganic carbon (DIC), dissolved Si, such as Figure 8 shown. Figure 8 a is the trend of the concentration of soluble solids TDS in river water over time. Figure 8 b is Cl in river water and precipitation - The concentration trend over time. Figure 8 c is the trend of dissolved Si concentration in river water and precipitation over time. Figure 8 d is the temporal trend of dissolved inorganic carbon (DIC) concentration in river water and precipitation.

[0080] from Figure 8 It can be seen that TDS and Cl in river water -, dissolved inorganic carbon (DIC), and dissolved Si concentrations show a relatively consistent period, indicating that the mixing ratio of different water supply sources in the river water is also changing at different stages of the rainy season. - Water chemical indicators such as DIC and dissolved Si showed a trend of first decreasing and then increasing, and their fluctuations were basically consistent over time. From late July to early August, the monsoon precipitation arrived and the precipitation reached its maximum. - , DIC, and dissolved Si all showed a sharp downward trend, dropped to the lowest level, and showed a negative correlation with precipitation, indicating that after the rainy season fully arrived, the rivers were more obviously replenished by precipitation, which was more related to the dilution effect of precipitation, and the contribution rate of precipitation reached the maximum.

[0081] River water Cl - The concentration showed a certain fluctuation, and it was consistent with the change trend of precipitation. In May and June, precipitation was scarce and the precipitation Cl - , the dissolved Si concentration has not decreased, but the river water Cl - The concentration is decreasing, indicating that the Cl - The concentration is not controlled by precipitation, but is the result of snowmelt. In June and July, the Cl - The concentration fluctuations are more intense, which is the result of the mixed effect of snowmelt and precipitation.

[0082] In general, during the rainy season, the source of river recharge can be divided into three stages. The first stage is before the rainy season in May and June, when there is less precipitation and the TDS and Cl in the river water are high. - , dissolved Si, and DIC all showed a decreasing trend first, indicating that the concentrations of water chemical indicators such as dissolved Si in the river water during this stage were affected by the enhanced supply of snowmelt water and showed a decreasing trend; in the second stage, from June to August, the concentrations of TDS, Cl - , dissolved inorganic carbon (DIC), and dissolved Si concentrations all showed a certain sharp downward trend, indicating that after the rainy season completely arrived, the river was more obviously replenished by precipitation, which was closely related to the dilution effect of precipitation. That is, with the arrival of monsoon precipitation, precipitation gradually replaced snowmelt water and became the main contributing water source in runoff components. In the third stage, after August, that is, at the end of the complete melting period, the river water TDS, Cl - The concentrations of DIC and dissolved Si showed a continuous upward trend, indicating that the river water was recharged by precipitation and snowmelt water, while the groundwater recharge was enhanced, and the water chemical concentration showed an increasing trend.

[0083] The abundance values ​​of δ2H and Cl in river water from May to August in the selected basin -The concentration value of the river water source in the study area is used to determine the composition of the river water source in the study area. Precipitation, snowmelt water and groundwater are used as three water source end members. The three-end member mixing model is used to analyze the response characteristics of the solute tracer in the basin runoff river water reaction. Fig. 9 shown.

[0084] As time goes by, the river water samples throughout the rainy season basically fall in the area where the three end members pass through. At the same time, the river water samples are close to the triangular area of ​​snowmelt and precipitation, and far away from the groundwater end, which once again shows that the source of runoff recharge in the entire rainy season is dominated by precipitation and snowmelt. At the same time, during May to August, the river water samples move from the snowmelt side to the precipitation end in the middle triangle area, which supports the conclusion of the previous section, that is, with the arrival of monsoon precipitation, precipitation gradually replaces snowmelt as the dominant force in the contribution ratio of rainy season runoff.

[0085] 3) Segmentation of rainy season runoff in the basin: According to the characteristics of the rainy season process and freeze-thaw process, the runoff segmentation period is divided into three periods, namely the early rainy season (from mid-May to early June, overlapping with the soil melting process in time, and the hydrological input is snowmelt and precipitation), the middle rainy season (from late June to late September, overlapping with the soil complete melting period in time, and the hydrological input is snowmelt and precipitation), and the late rainy season (from early September to October, overlapping with the soil freezing process in time, and the hydrological input is snowmelt). Using the improved Bayesian mixed model, the tracer concentration value of the runoff and water source in the study area and its mean and variance and other statistical information are the main input parameters of the model, as shown in Table 1. The runoff water source composition of the basin in different stages of the rainy season and different height vegetation type belts is quantitatively analyzed. The output results include the posterior distribution map of the basin runoff water source and its statistical information, including the median, mean, variance, etc. Figure 4 , Figure 5 shown. Figure 4 It is the posterior probability density of the runoff source contribution ratio in each altitude zone of the alpine basin. Figure 5 This is the posterior probability density distribution map of the runoff water source contribution ratio of each tributary in this alpine basin.

[0086] According to the output results of the Bayesian runoff segmentation model, such as Fig.10 As shown, Fig.10 a is the contribution ratio of groundwater, precipitation and snowmelt water in the alpine meadow zone. According to the horizontal coordinates corresponding to the highest points of each color area in the figure, it can be seen that the contribution ratios of groundwater, precipitation and snowmelt water in the alpine meadow zone are 12.8%, 49.5% and 37.7% respectively. Fig.10 b is the contribution ratio of groundwater, precipitation and snowmelt water in the alpine grassland zone. Similarly, it can be seen from the figure that the contribution ratios of groundwater, precipitation and snowmelt water in the alpine grassland zone are 27.5%, 39.9% and 32.6% respectively. Fig.10c is the contribution ratio of groundwater, precipitation and snowmelt water in the alpine shrub and meadow zones. Similarly, it can be seen from the figure that the contribution ratios of groundwater, precipitation and snowmelt water in the alpine shrub and meadow zones are 16.5%, 42.5% and 41.7% respectively.

[0087] It can be seen from this that the contribution ratio of rainy season runoff components in vegetation type zones of different altitudes is roughly the same, with precipitation and snowmelt water contributing more and groundwater contributing less.

[0088] Based on the above results, we further obtained the posterior probability density distribution diagram of the runoff water source contribution rate of different tributaries in the basin, such as Fig.11 As shown, tributaries 1, 2, 3, and 4 belong to the alpine meadow zone, tributaries 5, 6, 7, and 8 belong to the alpine grassland zone, and tributary 9 belongs to the alpine shrub and meadow zone. Fig.11 a is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 1. The pink, green and blue areas are the posterior probability density distributions of the contribution rates of groundwater, rainwater and snowmelt respectively. According to the distribution, it can be seen that the highest point of the posterior probability density of the contribution rate of groundwater is 6.2%, the highest point of the posterior probability density of the contribution rate of rainwater is 9.4%, and the highest point of the posterior probability density of the contribution rate of snowmelt is 84.4%; Fig.11 b is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 2, the highest point of groundwater contribution rate is 21.1%, the highest point of rainwater contribution rate is 40.5%, and the highest point of snowmelt water contribution rate is 38.4%; Fig.11 c is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 3, the highest point of groundwater contribution rate is 2.3%, the highest point of rainwater contribution rate is 89.6%, and the highest point of snowmelt water contribution rate is 8.1%; Fig.11 d is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 4, the highest point of groundwater contribution rate is 3.3%, the highest point of rainwater contribution rate is 76.5%, and the highest point of snowmelt water contribution rate is 20.2%; Fig.11 e is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 5, the highest point of groundwater contribution rate is 9.7%, the highest point of rainwater contribution rate is 50.7%, and the highest point of snowmelt water contribution rate is 39.6%; Fig.11 f is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 6, the highest point of groundwater contribution rate is 27.3%, the highest point of rainwater contribution rate is 50.7%, and the highest point of snowmelt water contribution rate is 27.0%; Fig.11 g is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 7, the highest point of groundwater contribution rate is 47.7%, the highest point of rainwater contribution rate is 21.8%, and the highest point of snowmelt water contribution rate is 30.5%; Fig.11h is the posterior probability density distribution diagram of the runoff water source contribution rate of tributary 8. The highest point of groundwater contribution rate is 89.6%, the highest point of rainwater contribution rate (green area) is 8.1%, and the highest point of snowmelt water contribution rate is 2.2%; Fig.11 i is the posterior probability density distribution map of the runoff water source contribution rate of tributary 9. The highest point of groundwater contribution rate is 3.1%, the highest point of rainwater contribution rate is 91.5%, and the highest point of snowmelt water contribution rate is 5.4%.

[0089] surface Basin runoff water source δ 18 O、Cl - Statistics 4) Analyze the runoff source confluence path: Use reactive solute tracers (including dissolved Si, dissolved inorganic carbon DIC, etc.) and combine the soil physical characteristics of different stages of the freezing and thawing process in the alpine permafrost basin to explore the runoff source confluence path of the basin in the rainy season under the influence of permafrost, and identify the various transformation processes that may occur on the path of the basin before precipitation and snowmelt water enter the river. Combined with flow processes, such as Fig.12 As shown, 12a is the monthly change trend of Si in the high-cold basin, and 12b is the monthly change trend of DIC in the high-cold basin.

[0090] As can be seen from the figure, in May, due to less precipitation, the contribution of precipitation to runoff was small; at this time, the concentrations of dissolved Si and DIC in the river water showed a decreasing trend, indicating that the recharge of snowmelt and river water was more obvious, which was the main reason for the change in the concentration of water chemical solutes in the river water; in June, the runoff increased with the increase of precipitation, and the response relationship was more obvious. At this time, the concentrations of dissolved Si and DIC in the river water still showed a more significant decreasing trend over time, and continued until the arrival of monsoon precipitation in August. During this period, precipitation and snowmelt had an impact on the concentrations of dissolved Si and DIC in the river water; in August After that, the precipitation and runoff were relatively stable, but the concentrations of dissolved Si and DIC in the river water showed a significant upward trend over time, indicating that a large amount of water with high concentrations of dissolved Si and DIC entered the river at this time. Before entering the river, these water sources flowed underground and mixed with organic matter in the soil and DIC weathered by carbonate rocks, resulting in a high DIC concentration; after September, precipitation was scarce, and the precipitation and runoff decreased significantly at this time. The concentrations of dissolved Si and DIC in the river water changed slightly and maintained a stable trend. The water supply of the river was mainly dominated by groundwater with high concentrations of hydrochemical solutes. It can be seen that the water source confluence path of the basin under the influence of frozen soil is more special than that of the non-frozen basin, which is mainly reflected in the strong water-blocking effect of the permafrost layer and the permafrost layer below the frozen soil active layer that has not yet thawed, which prompts the water source to directly enter the river in the form of overland flow, and the runoff response is faster.

Claims

1. A method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas, characterized in that: The steps include: S1, analyze the source composition of runoff in rainy season; Qualitatively determine the recharge sources of river water in the basin runoff through environmental tracers and hydrochemical characteristics of snowmelt, groundwater, precipitation and river water; S2, split rainy season runoff source composition; The improved Bayesian mixed model is used to output the posterior distribution map and statistical information of the water sources of the river water in the basin runoff, and quantitatively analyze the water source composition of the river water in the basin runoff; S3, analyzing the runoff source confluence path; By using the changing trends of solute tracers in the runoff river water and the freezing and thawing process of soil in the basin, the paths by which precipitation and snowmelt water enter the runoff river water in the basin can be identified.

2. The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas according to claim 1 is characterized by: The specific steps of step S1 are: S1.1, sample and analyze the spatial variation characteristics of stable isotopes in snowmelt water, groundwater and precipitation in different areas of the basin, and identify the recharge sources in the basin runoff river water; S1.2, sampling and analysis of δ 2 H and δ 18 The variation characteristics of O value on time scale can be used to identify the recharge sources of river water in the basin runoff at different periods of the rainy season; S1.3, sample and analyze the basic physical and chemical parameters and water chemical ion composition of precipitation, snowmelt, groundwater and river water, identify the response relationship between river water water chemical ions and precipitation, and use a three-end member mixed model to qualitatively analyze the sources of runoff recharge in different periods of the rainy season in the basin, and compare with steps S1.1 and S1.2 to analyze the composition of rainy season runoff water sources.

3. The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas according to claim 1 is characterized by: The improved Bayesian mixed model described in step S2 is MixSIAR; the input parameters of the improved Bayesian mixed model are the concentration values, means and variances of environmental tracers in snowmelt water, groundwater and precipitation; the output statistical information includes the median, mean and variance of the contribution rate of each water source in the basin runoff river water.

4. The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas according to claim 1, characterized in that: Specifically, step S3 is as follows: according to the evolution characteristics of the reaction solute tracer, the reaction solute tracer content in the river water decreases, and the runoff source confluence is mainly discharged directly by surface runoff; the reaction solute tracer content in the river water increases, and the runoff source confluence is mainly discharged by groundwater.

5. The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas according to claim 1, characterized in that: Specifically, step S3 uses a three-end-member mixing model to analyze the response characteristics of the solute tracer in the runoff river water in the basin. If the water source end-member shows a trend away from the groundwater point, it indicates that the runoff water source confluence is mainly discharged directly by surface runoff.

6. The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas according to claim 1, characterized in that: Specifically, step S3 is as follows: based on the quantitative analysis results of runoff water sources in the rainy season, the response characteristics of the reaction solute tracers, and the freezing and thawing process of the soil in the basin, if the concentration of the reaction solute tracers shows a decreasing trend, the runoff water source confluence will be mainly discharged directly by surface runoff.

7. The method for identifying the source composition and confluence path of runoff in rainy season in alpine frozen soil areas according to claim 1, characterized in that: The reaction solute tracers include DIC and dissolved Si.

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