Method for constructing river water and sediment model in land surface process of cold region

Abstract

The invention discloses a cold region land surface process river water and sediment model construction method, which comprises the following steps: selecting a target research drainage basin, extracting a drainage basin range ROI (Region of Interest), and collecting water and sediment data and related basic data in the drainage basin range; calculating a thermal erosion amount caused by temperature rise in the river reach, a snow melting erosion amount caused by snow melting, a water erosion amount induced by rainfall and a river ice erosion amount caused by ice running or flow ice scraping erosion of river ice in winter and spring; selecting landform characteristic parameters according to a river flow direction to construct a sediment transport coefficient of a river reach, establishing a cold region river water and sediment model according to the sediment transport coefficient and each erosion source item, and obtaining a sediment content simulation result based on the established cold region river water and sediment model; and evaluating the simulation performance of the model based on the established evaluation index. The method can dynamically respond to the erosion sand production and runoff sand transportation process of the cold region, provides timely and high-precision sand content calculation, and has important significance on water and soil conservation management and water and sand risk regulation and control of the cold region.

Description

Technical Field

[0001] The present invention relates to the technical field of eco - hydrology, and particularly to a method for constructing a river water - sediment model for cold - region land surface processes. Background Art

[0002] Cold - region basins (such as the Qinghai - Tibet Plateau) are important sources of global water resources. The water - sediment dynamics in these regions are significantly exacerbated by glacier melting, permafrost degradation, snow cover changes, and extreme precipitation events. These changes not only affect the downstream water resource supply but also pose threats to the ecosystem, flood control safety, and infrastructure construction. Mathematical models are one of the main research methods for soil erosion and water - sediment dynamics in cold regions at present. However, traditional water - sediment mathematical models cannot effectively simulate physical processes unique to cold regions, such as thermal erosion (sediment release caused by glacier, snow, and permafrost melting), water erosion (driven jointly by rainfall), and water - ice - sediment coupling processes (scouring erosion of ice floes on riverbanks). In addition, existing models rarely consider the influence of geomorphic features (such as river length, river width, and slope) and water - sediment connectivity of cold - region rivers on sediment transport, resulting in simulation results deviating from reality. Moreover, under high - flow or extreme climate conditions, the simulation accuracy of traditional models decreases, making it difficult to meet the needs of future water - sediment flux prediction. To address the above problems, there is an urgent need for a cold - region water - sediment hydrological model that can comprehensively consider cryosphere processes, geomorphic features, and water - sediment connectivity and has high - precision prediction capabilities to cope with the technical challenges of cold - region basin management under the background of climate change. Summary of the Invention

[0003] The present invention provides a method for constructing a river water - sediment model for cold - region land surface processes to solve problems such as the inapplicability of existing river water - sediment models to cold regions and the overly simplistic generalization of processes such as thermal erosion, snowmelt erosion, and ice - scraping erosion of river ice in winter and spring seasons.

[0004] According to a first aspect, in one embodiment, a method for constructing a river water - sediment model for cold - region land surface processes is provided. The method includes:

[0005] Select a target research basin, extract the basin range ROI according to the DEM and the location of the basin outlet, and collect water - sediment data and relevant basic data within the basin range;

[0006] Calculate the thermal erosion amount due to temperature rise, the snowmelt erosion amount due to snowmelt, the water erosion amount induced by precipitation, and the river - ice erosion amount caused by ice floods or ice - floe scouring erosion of river ice in winter and spring seasons;

[0007] Select geomorphic feature parameters according to the river flow direction to construct the sediment transport coefficient of the river reach. Based on the sediment transport coefficient and each erosion source term, establish a cold - region river water - sediment model, and obtain the simulated sediment - concentration result based on the established cold - region river water - sediment model;

[0008] Evaluate the simulation performance of the river water and sediment model in cold regions based on the established evaluation indexes.

[0009] Furthermore, the calculation of the thermal erosion amount caused by temperature rise includes:

[0010] Based on the runoff data and air temperature data of the corresponding catchment sub-basins of the river reaches, calculate the increased erosion amount caused by temperature rise:

[0011]

[0012] In the formula, T i represents the air temperature on the given i-th day, with the unit of °C; Q i is the runoff on the given i-th day, with the unit of m 3 / s; a1 and b1 are fitting parameters.

[0013] Furthermore, the calculation of the snowmelt erosion amount caused by snowmelt includes:

[0014] Establish the sub-basin boundary to restrain the snowmelt on the catchment slope, consider the potential impact of vegetation on snowmelt and sediment concentration, and calculate the vegetation coverage of the corresponding catchment slope:

[0015]

[0016] In the formula, NDVI max is the normalized difference vegetation index NDVI value when the vegetation completely covers the ground, NDVI s is the NDVI value of bare soil, and f c is the vegetation coverage of a certain catchment slope;

[0017] Calculate the effective snowmelt runoff SM e of a certain river reach:

[0018]

[0019] In the formula, is the reciprocal of the vegetation coverage, is the maximum value of the reciprocal of the vegetation coverage within a hydrological year; SM is the snowmelt runoff of a certain catchment slope, which is calculated from the snowmelt runoff product or snow cover spatio-temporal distribution dataset of the corresponding ROI;

[0020] Calculate the effective snowmelt erosion amount of a certain river reach:

[0021]

[0022] In the formula, a2 and b2 are fitting parameters; SM e is the snowmelt runoff of a certain catchment slope.

[0023] Furthermore, the calculation of water erosion amount induced by precipitation includes:

[0024] Calculating the change in runoff of a certain river section:

[0025]

[0026] In the formula, I i represents the change in runoff between the i-th day and the (i - 1)-th day, with the unit of m 3 / s; Q i is the runoff of the i-th day, and Q i-1 is the runoff of the (i - 1)-th day;

[0027] Calculating the water erosion amount triggered by the change in runoff of a certain river section:

[0028]

[0029] In the formula, is the reciprocal of vegetation coverage, is the maximum value of the reciprocal of vegetation coverage within a hydrological year, and I e is the effective water erosion amount of the corresponding river section.

[0030] Furthermore, the calculation of river ice erosion amount caused by the ice flood or ice drift scraping erosion of river ice in winter and spring seasons includes:

[0031] First, make the following assumptions: River ice and suspended sediment move downstream along the water flow direction during transportation, without lateral flow and scraping, and there is only a single movement vector α of sediment movement x ; The sediment transport rate per unit width remains unchanged when considering the movement of sediment particles, and the relative velocity between river ice and water flow during movement is u; The particle size of suspended sediment particles is uniform and does not change along the way;

[0032] Generalize the river water-ice-sediment coupling equation as:

[0033]

[0034] In the formula, t is time; x is the water flow direction; q s is the sediment transport rate per unit width, with the unit of kg / s; The movement velocity of sediment particles relative to the water flow is u, with the unit of m / s; α x is the transmission coefficient of river ice moving downstream along the river channel along the water flow, which is a constant and is calibrated by measured data or calculated by an empirical formula, or given by remote sensing measurement data;

[0035] Expand the above formula to obtain:

[0036]

[0037] According to the assumption, there is no relative acceleration between river ice movement and water flow, so the second term in the above equation is eliminated, and since α x is a constant, the fourth term is eliminated, and the equation is simplified to a first-order linear partial differential equation:

[0038]

[0039] The characteristic line method is used to solve the above equation. The component of the characteristic line along time represents the transmission path of sediment generated by the movement of river ice in length x over time t, that is:

[0040]

[0041] Calculate the sediment yield related to the water-ice-sediment coupling process involved in the ice flood and ice drift scraping erosion of river ice in a certain river section during winter and spring seasons:

[0042]

[0043] In the formula, the sediment transport rate per unit width q s is a function of the sediment transport length and the water flow velocity, and is obtained by training with machine learning methods; W is the river width, in meters; Q i is the runoff of the i-th day.

[0044] Furthermore, select geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river section. Based on the sediment transport coefficient and each erosion source term, establish a cold region river water-sediment model. Based on the established cold region river water-sediment model, obtain the simulated sediment concentration results, specifically including:

[0045] Select geomorphic characteristic parameters including river length L, river width W, slope G, and water-sediment connectivity IC to establish the sediment transport coefficient of the river section. Among them, the support vector machine method is used to train the river sediment transport coefficient K i , and the Sigmoid function is used to scale K i to between 0 and 1 to establish the boundary conditions of the model, that is:

[0046]

[0047] Furthermore, select geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river section. Based on the sediment transport coefficient and each erosion source term, establish a cold region river water-sediment model. Based on the established cold region river water-sediment model, obtain the simulated sediment concentration results, specifically including:

[0048] The control equation for establishing the cold region river water-sediment model is:

[0049]

[0050] Among them, SSC is the simulated sediment concentration result; a1, b1, a2, b2, a3 are fitting parameters.

[0051] Furthermore, based on the established evaluation indicators, the simulation performance of the cold-region river water-sediment model is evaluated, specifically including:

[0052] The model evaluation indicators include the Nash-Sutcliffe efficiency coefficient NSE, the Kling-Gupta efficiency coefficient KGE, and the coefficient of determination R 2 ;

[0053] Calculate the coefficient of determination R 2 :

[0054]

[0055] In the formula, O i and S i respectively represent the observed value and the simulated value of sediment concentration; and respectively represent the average values of the observed and simulated sediment concentrations; σ O and σ S respectively represent the standard deviations of the observed and simulated sediment concentrations; n represents the number of samples;

[0056] Calculate the Nash-Sutcliffe efficiency coefficient NSE:

[0057]

[0058] In the formula, O i and S i respectively represent the observed value and the simulated value of sediment concentration; represents the average value of the observed sediment concentration; n represents the number of samples;

[0059] Calculate the Kling-Gupta efficiency coefficient (KGE):

[0060]

[0061] In the formula, and respectively represent the average values of the observed and simulated sediment concentrations; σ O and σ S respectively represent the standard deviations of the observed and simulated sediment concentrations; n represents the number of samples.

[0062] According to the second aspect, in one embodiment, a cold-region land surface process river water-sediment model construction system is provided, and the system includes:

[0063] A data acquisition module, configured to select a target research watershed, extract the watershed range ROI according to the DEM and the watershed outlet location, and collect water-sediment data and relevant basic data within the watershed range;

[0064] An erosion amount calculation module for calculating the thermal erosion amount caused by temperature rise, the snowmelt erosion amount caused by snowmelt, the water erosion amount induced by precipitation, and the river ice erosion amount caused by the ice flood or ice run scraping erosion of river ice in winter and spring seasons;

[0065] A model construction module for selecting geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river reach, establishing a cold region river water-sediment model based on the sediment transport coefficient and each erosion source term, and obtaining the sediment concentration simulation result based on the established cold region river water-sediment model;

[0066] A model evaluation module for evaluating the simulation performance of the cold region river water-sediment model based on the established evaluation index.

[0067] According to a third aspect, an electronic device is provided in an embodiment, and the device includes: a processor and a memory;

[0068] The memory is used for storing one or more program instructions;

[0069] The processor is used for running one or more program instructions to execute the steps of a cold region land surface process river water-sediment model construction method as described in any one of the above.

[0070] According to a fourth aspect, a computer-readable storage medium is provided in an embodiment. A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of a cold region land surface process river water-sediment model construction method as described in any one of the above are implemented.

[0071] The present invention provides a cold region land surface process river water-sediment model construction method, which has the following beneficial effects:

[0072] (1) The model provided by the present invention can systematically integrate the sediment transport processes in cold regions including water erosion and thermal erosion processes, expand the description of erosion and sediment production at a single point to the sediment transport dynamics of different river reaches at the basin scale, and enrich the significance of the river water-sediment model and its applicability in cold region basins.

[0073] (2) The model provided by the present invention can calculate the spatial distribution law of sediment transport parameters of different rivers in cold regions and the spatio-temporal evolution characteristics of sediment transport indices of each river reach, providing a solid scientific basis for accurately predicting the future change trend of sediment transport in cold region rivers.

[0074] (3) The model provided by the present invention comprehensively considers the influence of various erosion source and sink terms in cold regions on the sediment concentration and sediment transport of river reaches, greatly improving the simulation ability of water-sediment processes in cold regions, and providing scientific arguments for water resource management and water-sediment disaster risk control in river source areas. Description of the Drawings

[0075] Figure 1Flow chart of a method for constructing a river water and sediment model of cold region land surface processes provided by an embodiment of the present invention;

[0076] Figure 2 Specific implementation framework diagram of a method for constructing a river water and sediment model of cold region land surface processes provided by an embodiment of the present invention;

[0077] Figure 3 Model calibration and verification result diagram of a method for constructing a river water and sediment model of cold region land surface processes provided by an embodiment of the present invention;

[0078] Figure 4 Annual sediment concentration verification result diagram of a method for constructing a river water and sediment model of cold region land surface processes provided by an embodiment of the present invention;

[0079] Figure 5 Adjustment curve diagram of river water and sediment matching parameters in the Yangtze River source area of a method for constructing a river water and sediment model of cold region land surface processes provided by an embodiment of the present invention;

[0080] Figure 6 Critical sediment concentration along the main stream of the four major river source areas on the Qinghai-Tibet Plateau in a method for constructing a river water and sediment model of cold region land surface processes provided by an embodiment of the present invention. Specific implementation manners

[0081] The present invention will be further described in detail below in conjunction with the accompanying drawings through specific implementation manners. Similar elements in different implementation manners are labeled with related similar element numbers. In the following implementation manners, many detailed descriptions are provided to enable a better understanding of the present invention. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification to avoid inundating the core part of the present invention with excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the descriptions in the specification and general technical knowledge in the art.

[0082] In addition, the features, operations, or characteristics described in the specification can be combined in any appropriate manner to form various implementation manners. At the same time, the steps or actions in the method description can also be reordered or adjusted in a manner obvious to those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean a necessary sequence unless it is stated that a certain sequence must be followed.

[0083] Such as Figure 1As shown, a method for constructing a river water and sediment model of land surface processes in cold regions provided by the first embodiment of the present invention. The following will be described in detail in conjunction with Figure 1 and Figure 2 for a detailed description.

[0084] As Figure 1 shown, in step S100, a target research basin is selected, the basin range ROI is extracted according to the DEM and the basin outlet location, and the water and sediment data and related basic data within the basin range are collected.

[0085] Specifically, in this embodiment, four typical river source areas on the Qinghai-Tibet Plateau are selected as the main research areas, including the Indus River source area dominated by glacier-dominated runoff and sediment production processes (glacier proportion > 12%), the Yangtze River source area dominated by permafrost with both glaciers and snow cover, the Heihe River source area dominated by snowmelt processes (snowmelt runoff proportion > 16.1%), and the Yellow River source area dominated by precipitation and mixed with various processes. According to their DEM and basin outlet location, the basin range is extracted, and the water and sediment data and related climate, geomorphology, cryosphere, vegetation element data, etc. within the basin range are collected.

[0086] As Figure 1 shown, in step S200, the thermal erosion amount caused by temperature rise, the snowmelt erosion amount caused by snowmelt, the water erosion amount induced by precipitation, and the river ice erosion amount caused by the ice flood or ice scraping erosion of river ice in winter and spring seasons are calculated.

[0087] The above steps specifically include:

[0088] S210, using the thermal erosion module to calculate the surface erosion amount caused by temperature rise in the corresponding river section.

[0089] In this embodiment, the continuous rivers in the four river source areas are divided into one river section every 5 kilometers, numbered in sequence, and the runoff data and air temperature data of the corresponding catchment sub-basins of the river section are extracted to calculate the increased erosion amount caused by temperature rise.

[0090] Specifically, according to the sediment availability model, the thermal erosion equation of a given river section in a cold region basin is summarized, which generally shows the proximal erosion of the selected river section, that is, the surface or river bank erosion caused by factors such as temperature rise and permafrost degradation, including processes such as near-river thermal melting and collapse and bank freeze-thaw erosion. This equation can be summarized as:

[0091]

[0092] In the formula, T i represents the air temperature (°C) on the given i-th day, Q i is the runoff (m 3 / s) on the given i-th day, and a1, b1 are fitting parameters.

[0093] S220. Calculate the effective snowmelt volume and the corresponding snowmelt erosion amount for the corresponding river reach using the snowmelt erosion module.

[0094] In this embodiment, by extracting the NDVI data and snowmelt runoff data of the corresponding sub-watershed of a certain river reach, the erosion amount caused by snowmelt is calculated.

[0095] Specifically, snow and ice ablation on the slope mostly occurs in the early spring (initial melting period). During this period, vegetation can stabilize the soil, reduce snow erosion, intercept and delay water flow. We need to consider the interaction between the snowmelt process and vegetation cover in this item. Therefore, the calculation of snowmelt erosion needs to be subdivided, specifically including:

[0096] S221. Using the existing NDVI (Normalized Difference Vegetation Index) dataset, select the catchment slope based on the boundary of the sub-watershed, and divide the scope of the sub-watershed through geographical information data such as the Digital Elevation Model (DEM), so as to determine the boundary of the catchment slope. Establish the sub-watershed boundary to restrict the snowmelt of its catchment slope, consider the potential impact of vegetation on snowmelt and sediment concentration, and calculate the vegetation cover of this catchment slope:

[0097]

[0098] In the formula, NDVI max is the NDVI value when the vegetation completely covers the ground, NDVI s is the NDVI value of bare soil, and f c is the vegetation cover of a certain catchment slope.

[0099] The calculation formula of NDVI is:

[0100]

[0101] Among them, NIR is the reflectance of the near-infrared band, and RED is the reflectance of the red band.

[0102] S222. Calculate the effective snowmelt runoff SMe of a certain river reach:

[0103]

[0104] In the formula, is the reciprocal of the vegetation cover, is the maximum value of this value within a hydrological year, SM is the snowmelt runoff of a certain catchment slope, which can be calculated from the snowmelt runoff product or snow cover spatio-temporal distribution dataset of the corresponding ROI.

[0105] S223. Calculate the effective snowmelt erosion amount of a certain river reach:

[0106]

[0107] In the formula, a2, b2, etc. are fitting parameters, and SM e is the snowmelt runoff of a certain catchment slope.

[0108] S230. Calculate the water erosion amount induced by precipitation using the water erosion module.

[0109] Water erosion is determined by a series of energy inputs and hydrodynamic processes. The water released by both enters the river channel or the surface slope through confluence, driving the transportation and erosion of sediment and sediment. Therefore, the core of hydraulic erosion is to describe the energy-driven process of water erosion on surface runoff and surface slope, and then to characterize the actual amount of erosion.

[0110] In this embodiment, the runoff and NDVI data of the catchment sub-basin corresponding to a certain river section are extracted, and the water erosion amount induced by precipitation is calculated using the water erosion module. Specifically, it includes:

[0111] S231. Calculate the change amount of the runoff of a certain river section:

[0112]

[0113] In the formula, Ii represents the change amount of the 2-day runoff on the given i-th day (m 3 / s), Q i is the runoff on the i-th day, and Q i-1 is the runoff on the (i - 1)-th day.

[0114] S232. Calculate the water erosion amount stimulated by the change in the runoff of a certain river section:

[0115]

[0116] In the formula, is the reciprocal of the vegetation coverage, is the maximum value of this value within a hydrological year, and I e is the effective water erosion amount of this river section.

[0117] S240. Calculate the erosion amount caused by the ice run and ice scraping erosion of river ice in winter and spring using the river ice module.

[0118] According to the two-dimensional river water-ice-sediment coupling mathematical model, improve the cold region and one-dimensional water-sediment model, and calculate the erosion amount stimulated by the water-ice-sediment coupling process (such as ice scraping erosion of the ice bank). In this example, the river ice distribution data, sediment transport rate, runoff, etc. of the catchment sub-basin corresponding to a certain river section are extracted to calculate the erosion amount caused by the ice scraping in winter and spring. Specifically, it includes:

[0119] S241. Assume that (1) river ice and suspended sediment flow downstream along the water flow direction during transportation, without lateral flow and scraping, and there is only a single movement vector α of sediment movement. x . (2) The sediment transport rate per unit width remains unchanged when considering the movement of sediment particles, and the relative velocity between river ice and water flow during movement is u. (3) Assume that the particle size of suspended sediment is uniform and does not change along the way. The coupled equation of river water-ice-sediment is generalized as:

[0120]

[0121] In the formula, t is time, x is the water flow direction, q s is the sediment transport rate per unit width, with the unit of kg / s, the movement velocity of sediment particles relative to the water flow is u, with the unit of m / s, and α x is the transmission coefficient (constant) of river ice moving downstream along the river channel with the water flow, which is generally calibrated by measured data or calculated by empirical formulas, or can be given by remote sensing measurement data.

[0122] S242. Expand the above formula to obtain:

[0123]

[0124] According to the above assumptions, there is no relative acceleration between river ice movement and water flow, so the second term in the above formula is eliminated. And, since α x is a constant, the fourth term can be eliminated. Then, this equation can be simplified to a first-order linear partial differential equation:

[0125]

[0126] S243. Use the method of characteristic lines to solve this equation. The component of the characteristic line along time This represents the transmission path of sediment generated by the movement of river ice along the length x over time t, that is:

[0127]

[0128] S244. Calculate the sediment yield related to the coupled process of water-ice-sediment such as ice flood and ice drift scraping erosion of river ice in a certain river section during winter and spring seasons:

[0129]

[0130] In the formula, the sediment transport rate per unit width q s is a function of the sediment movement length and water flow velocity, which can be obtained by training with machine learning methods; W is the river width, with the unit of meter, and Q i is the runoff of the i-th day.

[0131] Such as Figure 1As shown, in step S300, select geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river reach, establish a cold-region river water and sediment model based on the sediment transport coefficient and each erosion source term, and obtain the simulated sediment concentration result based on the established cold-region river water and sediment model.

[0132] In this embodiment, a cold-region river water and sediment model is established, including boundary conditions and governing equations.

[0133] In this embodiment, parameters including river length (L), river width (W), slope (G), water-sediment connectivity (IC), river channel slope (S), turbidity, etc. for constructing the geomorphic sediment transport coefficient (K, boundary condition) of a certain river reach are selected, and the governing equation of the cold-region river water and sediment model is established. The calculation steps are as follows:

[0134] S310, use the support vector machine method to train the river sediment transport coefficient K i for construction, and use the Sigmoid function to scale K i to between 0 and 1 to establish the boundary condition of the model, that is:

[0135]

[0136] S320, calculate the governing equation of the cold-region river water and sediment model:

[0137]

[0138] where SSC is the simulated sediment concentration result; a1, b1, a2, b2, a3 are fitting parameters

[0139] As Figure 1 shown, in step S400, evaluate the simulation performance of the cold-region river water and sediment model based on the established evaluation indicators.

[0140] In this embodiment, the model evaluation indicators include Nash-Sutcliffe efficiency coefficient NSE, Kling-Gupta efficiency coefficient KGE, and coefficient of determination R 2 .

[0141] Calculate the coefficient of determination R 2 :

[0142]

[0143] In the formula, O i and S i respectively represent the observed value and the simulated value of the sediment concentration; and respectively represent the average values of the observed value and the simulated value of the sediment concentration; σ O and σ S respectively represent the standard deviations of the observed value and the simulated value of the sediment concentration; n represents the number of samples;

[0144] Calculate the Nash efficiency coefficient NSE:

[0145]

[0146] Wherein, O i and S i respectively represent the observed value and the simulated value of the sediment concentration; represents the average value of the observed values of the sediment concentration; n represents the number of samples;

[0147] Calculate the Kling-Gupta efficiency coefficient (KGE):

[0148]

[0149] Wherein, and respectively represent the average values of the observed value and the simulated value of the sediment concentration; σ O and σ S respectively represent the standard deviations of the observed value and the simulated value of the sediment concentration; n represents the number of samples.

[0150] Furthermore, in this embodiment, it is also possible to: according to the simulated sediment concentration results of the cold-region river water-sediment model established, calculate sediment transport indexes such as the sediment transport ratio and the sediment inflow coefficient for further engineering applications.

[0151] Specifically, assuming that the initial sediment concentration of a certain river section is SSC0 (obtained according to the measured value or according to the model simulation), then for this river section, its sediment-carrying capacity SSC * (also known as the critical sediment concentration) can be calculated as:

[0152]

[0153] Wherein, θ is the sediment transport coefficient, which is related to the cumulative sediment deposition amount in the previous period of the river bed and can be calibrated from the previous river sediment concentration; and a11, b11 are sediment transport indexes, and generally in statistics, the sum of a11 and b11 is approximately equal to 2.

[0154] The sediment transport ratio is an index to measure the sediment transport efficiency from the erosion source to the basin outlet (such as a river cross-section) in the basin. It can reflect the sediment transport capacity of the basin and cannot be calculated in the previous cold-region river sediment models. Based on this model, the sediment transport ratio along the river can be calculated as:

[0155]

[0156] Wherein, SDR is the sediment transport ratio (sediment discharge ratio) of the river, which is the ratio of the sediment concentration at the outlet to the sediment concentration at the inlet, SSC0 is the initial sediment concentration, SSC is the sediment concentration of a certain river section, SSC *is the sediment-carrying capacity of water flow; a12 is the sediment transport index.

[0157] The sediment coefficient is mainly used to describe the relationship between sediment content and flow rate in a river. Calculate the sediment coefficient:

[0158]

[0159] In the formula, SSC0 is the initial sediment concentration, Q is the runoff of this river section, and a13 and b13 are both sediment transport indexes.

[0160] In this embodiment, four typical river source areas on the Qinghai-Tibet Plateau are selected as the main research areas, including the Indus River source area, the Yangtze River source area, the Heihe River source area, and the Yellow River source area. According to their DEM and the positions of the basin outlets, the basin range ROI is extracted, and the water and sediment data and related climate, geomorphology, cryosphere, vegetation elements, etc. data within the river source areas are collected. The similarities and differences in the parameterization schemes of the boundary conditions and input variables of the water and sediment models in the river source areas controlled by different dominant factors are compared, and the changes in the sediment transport parameters along the way are quantitatively characterized. The main operation steps are as follows:

[0161] (1) Collect and integrate the data required to run this model, including the elevation data of the river source areas on the Qinghai-Tibet Plateau, the runoff, sediment concentration, sediment transport volume, air temperature, precipitation, NDVI, snowmelt runoff, slope, aspect, river length, slope ratio, river width, water and sediment connectivity index, and river ice in winter and spring seasons and other spatio-temporal distribution data. Install the software required to run and process the model, such as Qgis and Python, etc. Among them, the runoff, sediment concentration, and sediment transport volume data come from the suspended sediment concentration and flux dataset on the Qinghai-Tibet Plateau and the China River Sediment Bulletin. The air temperature, precipitation, and NDVI come from the China Regional Surface Meteorological Element Driving Dataset (CMFD) and the ERA5 dataset. The snowmelt runoff comes from the snowmelt runoff products on the Qinghai-Tibet Plateau and the snow cover spatio-temporal distribution dataset. The slope, aspect, river length, slope ratio, river width, and water and sediment connectivity index come from the National Tibetan Plateau Scientific Data Center. The river ice data in winter and spring seasons come from the Qinghai-Tibet Plateau river ice distribution dataset processed by Landsat remote sensing images.

[0162] (2) Use the coefficient of determination (R2), Nash efficiency coefficient (NSE), and Kling-Gupta efficiency coefficient (KGE) as the objective functions to calibrate the model parameters, and evaluate the simulation performance of the model from multiple aspects such as runoff and sediment concentration.

[0163] The results after the implementation of the technical solution are shown in Figure 3 and Figure 4 As shown, the river water and sediment model (CHSM) shows satisfactory results in the four major river source areas on the Qinghai-Tibet Plateau, and its R 2, the values of NSE and KGE are above 0.77, 0.76, and 0.79 respectively. Generally speaking, in terms of the daily-scale changes in river sediment concentration, the calibrated model accurately reproduced the daily dynamic changes in river sediment concentration during the validation period. And when comparing the CHSM model developed in this invention with the current mainstream cold-region sediment availability model (SATM), the performance of CHSM is more robust. For the source regions of the Indus River and the Heihe River dominated by glaciers and snow cover, both CHSM and SATM can better restore the water-sediment relationship during low runoff periods. However, when there are sediment transport peak events caused by extreme rainstorms / high mountain floods, SATM shows relatively discrete performance while CHSM has a more stable distribution. Figure 3 shows the dynamic changes between the measured sediment concentration and the CHSM simulation values in the time series of the source regions of the Yangtze River and the Yellow River. In the source region of the Yangtze River where there are erosive disturbances in glaciers, snow cover, and permafrost, CHSM overestimated the sediment concentration dynamics during low flow (the bottom 25% quantile) to a certain extent, but effectively captured the sediment dynamics during medium and high flow (i.e., the top 25% quantile), which led to NSE and KGE values of 0.82 and 0.83 respectively in the Yangtze River source region during the validation period. For the source region of the Yellow River dominated by precipitation and mixed with multiple processes, the NSE and KGE values during its validation period are 0.85 and 0.91 respectively, and the overall simulation performance is better than that of the Yangtze River source region. And this model can reveal the spatial variation law of sediment transport parameters of the main rivers on the Qinghai-Tibet Plateau ( Figure 5 ), as well as the spatio-temporal variation of the critical sediment concentration in different river reaches ( Figure 6 ). The evaluation index results of the river water-sediment model in this embodiment for different river source regions are shown in Table 1.

[0164] Table 1 Comparison of CHSM model performance in different river source regions

[0165]

[0166] Corresponding to the above-disclosed method for constructing a cold-region land surface process river water-sediment model, the embodiment of the present invention also discloses a cold-region land surface process river water-sediment model construction system, which specifically includes:

[0167] A data acquisition module, used to select the target study basin, extract the basin range ROI according to the DEM and the location of the basin outlet, and collect the water-sediment data and relevant basic data within the basin range;

[0168] An erosion amount calculation module, used to calculate the thermal erosion amount caused by temperature rise, the snowmelt erosion amount caused by snow cover ablation, the water erosion amount induced by precipitation, and the river ice erosion amount caused by the ice flood or ice scraping erosion of river ice in winter and spring seasons;

[0169] A model construction module, configured to select geomorphic feature parameters according to the river flow direction to construct the sediment transport coefficient of a river reach, establish a cold-region river water-sediment model based on the sediment transport coefficient and each erosion source term, and obtain the simulated sediment concentration result based on the established cold-region river water-sediment model;

[0170] A model evaluation module, configured to evaluate the simulation performance of the cold-region river water-sediment model based on the established evaluation index.

[0171] It should be noted that the detailed description of a cold-region land surface process river water-sediment model construction system provided in an embodiment of the present invention can refer to the relevant description of a cold-region land surface process river water-sediment model construction method provided in an embodiment of the present invention, which will not be elaborated here.

[0172] In addition, an embodiment of the present invention further provides an electronic device, which includes: a processor and a memory; the memory is used to store one or more program instructions; the processor is used to run one or more program instructions to execute the steps of a cold-region land surface process river water-sediment model construction method as described in any one of the above.

[0173] It should be noted that the detailed description of an electronic device provided in an embodiment of the present invention can refer to the relevant description of a cold-region land surface process river water-sediment model construction method provided in an embodiment of the present application, which will not be elaborated here.

[0174] In addition, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of a cold-region land surface process river water-sediment model construction method as described in any one of the above are implemented.

[0175] It should be noted that the detailed description of a computer-readable storage medium provided in an embodiment of the present invention can refer to the relevant description of a cold-region land surface process river water-sediment model construction method provided in an embodiment of the present application, which will not be elaborated here.

[0176] Those skilled in the art can understand that all or part of the functions of the above-mentioned implementation methods can be realized in a hardware manner or in a computer program manner. When all or part of the functions in the above-mentioned implementation methods are realized in a computer program manner, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, magnetic disk, optical disk, hard disk, etc. The above functions are realized by a computer executing the program. For example, when the program is stored in the memory of a device, all or part of the above functions can be realized when the processor executes the program in the memory. In addition, when all or part of the functions in the above-mentioned implementation methods are realized in a computer program manner, the program can also be stored in a storage medium such as a server, another computer, magnetic disk, optical disk, flash drive or mobile hard disk, and saved to the memory of a local device by downloading or copying, or the system of the local device can be updated in version. When the processor executes the program in the memory, all or part of the functions in the above-mentioned implementation methods can be realized.

[0177] The above uses specific examples to elaborate on the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the technical field to which the present invention belongs, according to the idea of the present invention, several simple deductions, deformations or substitutions can also be made.

Claims

1. A method for constructing a river water and sediment model of land surface processes in cold regions, characterized in that, The method includes: Select a target research basin, extract the basin range ROI according to the DEM and the location of the basin outlet, and collect water and sediment data and related basic data within the basin range; Calculate the thermal erosion amount caused by temperature increase, the snowmelt erosion amount caused by snowmelt, the water erosion amount induced by precipitation, and the river ice erosion amount caused by the ice flood or the scraping erosion of floating ice in the river ice during winter and spring seasons; Select geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river reach, establish a cold region river water-sediment model based on the sediment transport coefficient and each erosion source term, and obtain the simulated sediment concentration result based on the established cold region river water-sediment model; Evaluate the simulation performance of the cold region river water-sediment model based on the established evaluation index.

2. The method for constructing a river water and sediment model for cold region land surface processes according to claim 1, characterized in that, The calculation of the thermal erosion amount caused by temperature increase includes: Based on the runoff data and air temperature data of the corresponding catchment sub-basin of the river reach, calculate the increased erosion amount caused by temperature increase: Where, T i represents the air temperature on the given i-th day, with the unit of °C; Q i is the runoff on the given i-th day, with the unit of m 3 / s; a1 and b1 are fitting parameters.

3. The method for constructing a river water and sediment model for cold region land surface processes according to claim 2, wherein The calculation of the snowmelt erosion amount caused by snowmelt includes: Establish a sub-basin boundary to restrict the snowmelt water on the catchment slope, consider the potential impact of vegetation on snowmelt water and sediment convergence, and calculate the vegetation coverage of the corresponding catchment slope: In the formula, NDVI max is the NDVI value of the normalized difference vegetation index when the vegetation completely covers the ground, and NDVI s is the NDVI value of bare soil, and f c is the vegetation coverage of a certain catchment slope; Calculating the effective snowmelt runoff SM of a certain river reach e : In the formula, is the reciprocal of vegetation coverage, is the maximum value of the reciprocal of vegetation coverage within a hydrological year; SM is the snowmelt runoff yield of a certain catchment slope, which is calculated from the snowmelt runoff product or snow cover spatio-temporal distribution dataset of the corresponding ROI. Calculate the effective snowmelt erosion amount of a certain river reach: where a2 and b2 are fitting parameters; SM e is the snowmelt runoff of a certain catchment slope surface.

4. A method for constructing a river water and sediment model of cold region land surface processes according to claim 3, characterized in that, The calculation of the water erosion amount induced by precipitation includes: Calculate the change amount of the runoff of a certain river reach: Where, I i represents the change in runoff volume between the \(i\)th day and the \((i - 1)\)th day, with the unit of \(m\) 3 / s; \(Q\) i is the runoff volume on the \(i\)th day, and \(Q\) i-1 is the runoff volume on the \((i - 1)\)th day; Calculate the water erosion amount excited by the change of the runoff of a certain river reach: In the formula, is the reciprocal of the vegetation coverage, is the maximum value of the reciprocal of the vegetation coverage within a hydrological year, and I e is the effective water erosion amount of the corresponding river reach.

5. The method for constructing a river water and sediment model for cold region land surface processes according to claim 4, wherein The calculation of the river ice erosion amount caused by the ice flood or the scraping erosion of floating ice in the river ice during winter and spring seasons includes: First, make the following assumptions: During the transportation process, river ice and suspended sediment flow downstream along the water flow direction, without lateral flow and scraping, and there is only a single motion vector α of sediment movement. x ; The sediment transport rate per unit width remains unchanged when considering the movement of sediment particles, and the relative velocity between river ice and water flow during movement is u; the particle size of suspended sediment particles is uniform and does not change along the way; Generalize the river water-ice-sediment coupling equation as: where t is the time; x is the water flow direction; q s is the sediment transport rate per unit width, with the unit of kg / s; the relative movement speed of sediment particles to the water flow is u, with the unit of m / s; α x is the transmission coefficient for river ice moving downstream along the water flow along the river channel, which is a constant and is determined by measured data or empirical formulas, or given by remote sensing measurement data; Expand the above formula to get: According to the assumption, there is no relative acceleration between the river ice movement and the water flow, so the second term in the above equation is eliminated, and since α x is a constant, the fourth term is eliminated, and the equation is simplified to a first-order linear partial differential equation: Solve the above equations using the method of characteristics, and the component of the characteristic line along time represents the transport path of sediment generated by the transport of river ice along the length x over time t, that is: Calculate the sediment yield related to the water-ice-sediment coupling process involved in the ice flood and the scraping erosion of floating ice in the river ice during winter and spring seasons of a certain river reach: In the formula, the sediment transport rate per unit width q s is a function of the sediment transport length and the water flow velocity, and is obtained by training with machine learning methods; W is the river width in meters; Q i is the runoff on the i-th day.

6. The method for constructing a river water and sediment model of land surface processes in cold regions according to claim 5, wherein Select geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river reach, establish a cold region river water-sediment model based on the sediment transport coefficient and each erosion source term, and obtain the simulated sediment concentration result based on the established cold region river water-sediment model. Specifically, it includes: Select geomorphic characteristic parameters including river length L, river width W, slope G, and water-sediment connectivity IC to establish the sediment transport coefficient of the river reach. Among them, the support vector machine method is used to train the river sediment transport coefficient K i , and the Sigmoid function is used to scale K i to between 0 and 1 to establish the boundary conditions of the model, that is:

7. The method for constructing a river water and sediment model of land surface processes in cold regions according to claim 6, wherein Select geomorphic characteristic parameters according to the river flow direction to construct the sediment transport coefficient of the river reach, establish a cold region river water-sediment model based on the sediment transport coefficient and each erosion source term, and obtain the simulated sediment concentration result based on the established cold region river water-sediment model. Specifically, it includes: The control equation for establishing the cold region river water-sediment model is: Among them, SSC is the simulated sediment concentration result; a1, b1, a2, b2, a3 are fitting parameters.

8. The method for constructing a river water and sediment model of cold region land surface processes according to claim 1, wherein Evaluate the simulation performance of the cold region river water-sediment model based on the established evaluation index. Specifically, it includes: Model evaluation indicators include Nash efficiency coefficient NSE, Kling-Gupta efficiency coefficient KGE, and coefficient of determination R 2 ; Calculate the coefficient of determination R 2 : Where, O i and S i represent the observed value and the simulated value of the sediment concentration respectively; and represent the average values of the observed value and the simulated value of the sediment concentration respectively; σ O and σ S represent the standard deviations of the observed value and the simulated value of the sediment concentration respectively; n represents the sample size; Calculate the Nash efficiency coefficient NSE: where, O i and S i represent the observed value and the simulated value of the sediment concentration respectively; represents the average value of the observed sediment concentration; n represents the number of samples; Calculate the Kling-Gupta efficiency coefficient (KGE): In the formula, and respectively represent the average values of the observed and simulated sediment concentrations; σ O and σ S respectively represent the standard deviations of the observed and simulated sediment concentrations; n represents the sample size.

9. A system for constructing a river water and sediment model of cold region land surface processes, characterized in that, The system includes: A data acquisition module, which is used to select a target research basin, extract the basin range ROI according to the DEM and the location of the basin outlet, and collect water and sediment data and related basic data within the basin range; An erosion amount calculation module, which is used to calculate the thermal erosion amount caused by temperature increase, the snowmelt erosion amount caused by snowmelt, the water erosion amount induced by precipitation, and the river ice erosion amount caused by the ice flood or the scraping erosion of floating ice in the river ice during winter and spring seasons; A model construction module, configured to select geomorphic feature parameters according to the river flow direction to construct the sediment transport coefficient of a river reach, establish a cold-region river water-sediment model based on the sediment transport coefficient and each erosion source term, and obtain the simulated sediment concentration results based on the established cold-region river water-sediment model; A model evaluation module, configured to evaluate the simulation performance of the cold-region river water-sediment model based on the established evaluation indexes.

10. An electronic device, characterized in that, The device includes: a processor and a memory; The memory is used for storing one or more program instructions; The processor is configured to run one or more program instructions to execute the steps of a method for constructing a cold-region land surface process river water-sediment model according to any one of claims 1 to 8.

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