Method and system for dynamic simulation and evaluation of soil carbon pool of basin silt dam system

Abstract

The present application relates to water and soil conservation and basin carbon cycle simulation technical field, especially to a kind of basin silt dam system soil carbon pool dynamic simulation evaluation method and system, the basin is divided into several sub-basins and hydrological response unit, based on the water and sediment process simulation of SWAT model, carry out carbon flux process simulation and export each sub-basin outlet water and sediment carbon flux;Each sub-basin outlet water and sediment carbon flux is used as the input boundary condition of dam system carbonization simulation in basin, traverses dam system topology, the outflow of upstream dam is used as the inflow of downstream dam input, establishes basin non-point source and channel dam system flux transfer dynamic response relationship and dam system deposition silt organic carbon dynamic decomposition evolution dynamics, obtains the time series matrix of the multivariate of whole basin silt dam soil carbon pool, to be visualized by recording time series matrix with year-by-year carbon pool data The carbon sink capacity of silt dam in the basin is displayed. The present application can realize the synchronous continuous dynamic simulation of the carbon sink process of multiple dams at the basin scale.

Description

Technical Field

[0001] This invention relates to the field of soil and water conservation and watershed carbon cycle simulation technology, and in particular to a method and system for dynamic simulation and assessment of soil carbon pool in watershed silt-dam systems, which is aimed at water-sediment-carbon coupled migration simulation and dynamic assessment of soil carbon pool in silt-dam systems of the Loess Plateau. Background Technology

[0002] Silt-block dam carbon sequestration is a unique dual carbon sequestration mechanism of the Loess Plateau, combining physical interception and biological carbon fixation. Physical interception involves the dam directly intercepting carbon-containing sediment washed down from upstream, preventing the organic carbon from being mineralized and decomposed during the sediment's flow into the Yellow River. Simultaneously, the intercepted sediment creates a dry, oxygen-deficient, and high-capacity environment within the dam, allowing for the long-term stable storage of organic carbon. In biological carbon fixation, the siltation creates dammed land with excellent water and fertilizer conditions, providing a good foundation for the growth of vegetation and crops.

[0003] The static estimation technique for soil carbon pool based on sediment volume surveys of silt-trapping dams estimates the total carbon pool by measuring the total volume of sediment deposited in the dam area and combining it with bulk density and organic carbon content. This method has the following significant drawbacks: First, it can only estimate the total sediment volume up to the present, failing to capture the dynamic changes in carbon sinks over historical periods and lacking the ability to characterize the temporal evolution of carbon sinks. Second, it cannot distinguish the differences in carbon interception under different construction periods and different water and sediment inflow conditions, treating all deposited carbon as having a homogeneous source and ignoring the phased characteristics of carbon sink formation. Third, it assumes that intercepted carbon is permanently sealed, completely ignoring the long-term mineralization and decomposition process of deposited organic carbon in the dam area, leading to a systematic overestimation bias in carbon sink estimation. Fourth, it cannot reflect the impact of reservoir capacity decay due to siltation on sediment interception efficiency, statically assuming a fixed dam-reservoir state, which does not match the actual physical process of silt-trapping dams: "used while silting, ineffective when full." The carbon sink history inversion technique based on the excavation or drilling of sedimentary profiles of silt-trapping dams reconstructs the historical carbon sink process of a single silt-trapping dam through stratified sampling, isotope dating, and analytical testing of the sedimentary profile. This method has the following prominent drawbacks: First, it is costly, time-consuming, and labor-intensive. A single dam requires excavating a profile several meters deep or conducting multi-layer drilling for sampling. Combined with professional experiments such as isotope dating, the testing cycle can take several months, making it difficult to promote its application at the watershed scale. Second, it cannot be used for carbon sink assessment of dam systems composed of multiple silt-retaining dams within a watershed. There are numerous silt-retaining dams in a watershed (e.g., 808 in the Yanhe River Basin), and the cost and time of excavating profiles one by one are completely unacceptable. Third, it is limited by the preservation status of silt-retaining dams. Some silt-retaining dams are already silted up, damaged, or modified, resulting in incomplete or missing sedimentary profiles, making it impossible to obtain continuous historical records. Fourth, it has limited spatial representativeness. Single-point excavation or drilling cannot represent the carbon sink status of the entire dam area, resulting in significant spatial variability.Furthermore, in response to the current practical needs for improving the accuracy of soil carbon pool assessment for silt-retaining dams and for future planning and layout, both methods share the following common technical shortcomings: First, neither can simulate the process of sedimentation from the watershed to the silt-retaining dam. Both methods are essentially based on "post-hoc" retrospective analysis and inversion of existing sediments, falling under the category of static assessment, and cannot simulate the full-scale water-sediment-carbon coupling migration patterns of silt-retaining dam systems across slopes, channels, and watersheds. Second, both lack mathematical characterization methods for the dynamic release of sedimentary organic carbon. Existing technologies lack the ability to quantitatively characterize the mineralization and decomposition processes of sedimentary organic carbon, and cannot establish quantifiable models. Third, neither method can predict future scenarios; both methods can only "look backward" to invert history and cannot predict the carbon sequestration potential of silt-retaining dams under different future working conditions (such as new silt-retaining dams, reinforcement, and climate change). Fourth, neither method can assess the overall carbon sequestration synergy of the dam system in the basin. Existing technologies mainly focus on single dam assessments and cannot consider the impact of the series and parallel relationships between upstream and downstream dams in the dam system network on carbon sequestration. Fifth, neither method has a coupling mechanism with the basin sediment yield model and cannot use watershed-scale hydrological, meteorological, and land use driving data to achieve dynamic simulation of the carbon sequestration process.

[0004] Existing static estimation and profile inversion techniques suffer from bottlenecks such as high cost, inability to dynamically simulate, and difficulty in being extended to watershed dam systems, failing to meet the dual demands of improving the accuracy of carbon sequestration assessment and planning layout of silt-retaining dams in the Loess Plateau under the new circumstances. Therefore, there is an urgent need for a low-cost, high-efficiency, dynamic assessment scheme for carbon sequestration of silt-retaining dams that can simulate the entire process and predict future scenarios to meet the carbon sequestration requirements of silt-retaining dams. Summary of the Invention

[0005] To address the problems of existing assessments of carbon sinks in silt-retaining dam systems being crude, costly, and time-consuming, this invention provides a method and system for dynamic simulation assessment of soil carbon pools in watershed silt-retaining dam systems. Based on water-sediment-carbon coupled migration, it achieves low-cost and high-efficiency dynamic simulation assessment of soil carbon pools in watershed silt-retaining dam systems.

[0006] According to the design scheme provided by the present invention, on the one hand, a method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems is provided, comprising:

[0007] Acquire multi-source data for the watershed, including: basic watershed data, silt-retaining dam ledger data, watershed water and sediment process data, and slope runoff micro-plot observation data;

[0008] The basin is divided into several sub-basins and hydrological response units. Based on multi-source data of the basin and using the SWAT model to simulate water and sediment processes, carbon flux process simulation is carried out and the outlet water, sediment and carbon flux of each sub-basin is output.

[0009] The outflow of water and sediment carbon flux from each sub-basin is used as the input boundary condition for simulating soil carbonization in the dam system within the basin. Through topological traversal of the dam system, the outflow from the upstream dam is used as the inflow input from the downstream dam to establish the dynamic decomposition and evolution relationship of sedimentary organic carbon between the watershed non-source and channel dam systems, as well as the dynamic response relationship of flux transfer.

[0010] A separate simulation start time is set for each silt-retention dam. Based on the flux transfer dynamic response relationship, a time series matrix of multivariate soil carbon pools of silt-retention dams in the whole basin is obtained, and a spatiotemporal dataset of carbon sinks of dam system in the basin is formed. The spatiotemporal dataset is used to visualize the carbon sink capacity of silt-retention dams in the basin. The time series matrix records the annual carbon sink data of each silt-retention dam in the basin from the year of construction to the target year.

[0011] As a method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to the present invention, further, based on multi-source watershed data and using the SWAT model for water and sediment process simulation, carbon flux process simulation is carried out and the outlet water, sediment and carbon fluxes of each sub-watershed are output, including:

[0012] Based on slope runoff plot observation data, the soil organic carbon migration enrichment coefficient equation was fitted in the form of a power function to obtain the ratio of organic carbon content in eroded sediment to organic carbon content in source soil.

[0013] The water and sediment transport parameters in the SWAT model were calibrated using slope runoff plot observation data, so as to simulate the hydrological response runoff and erosion intensity per unit time using the SWAT model.

[0014] The soil organic carbon content during the migration of eroded sediment was obtained by comparing the ratio of organic carbon content in eroded sediment to that in the source soil and the organic carbon content in the surface soil.

[0015] The dynamic interception efficiency of water, sediment and carbon at silt-retaining dams is set based on the ratio of remaining reservoir capacity to total inflow. The total inflow carbon, including upstream dam input and slope unit carbon input, is constructed based on the dynamic interception efficiency, and the reservoir capacity and intercepted carbon amount are updated step by step over time.

[0016] As a method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to the present invention, the dynamic interception efficiency of water, sediment, and carbon by silt-retaining dams is further expressed as: ,in, Let t be the total inflow of water to the silt-retaining dam j. This represents the remaining storage capacity.

[0017] As a dynamic simulation and evaluation method for soil carbon pool in watershed silt-retaining dam systems according to the present invention, the process of updating the pool capacity step by step over time is further represented as follows: , The remaining reservoir capacity of the silt-retaining dam at time t is given. For time step, Let t be the amount of sediment retained by the silt-retaining dam j. The bulk density of the sediment.

[0018] As a dynamic simulation and assessment method for soil carbon pool in watershed silt-retaining dam systems according to the present invention, the update process for the amount of intercepted carbon is further expressed as follows: ,in, The carbon content of the sediment intercepted by the silt-retaining dam at time t is given.

[0019] As a method for dynamic simulation and assessment of soil carbon pool in watershed silt-dam systems according to the present invention, further, the dynamic decomposition and evolution relationship of sedimentary organic carbon and flux transfer dynamic response relationship between watershed non-source heat pumps and gully dam systems are established, including:

[0020] Carbon decomposition loss and net carbon sink were quantitatively determined using the decomposition rate constant, and the mineralization decomposition process of deposited organic carbon was simulated using a first-order kinetic equation to obtain the cumulative organic carbon storage of the silt-retaining dam over a specified time period.

[0021] The carbon interception and cumulative organic carbon storage of each silt-retaining dam are obtained at each time step, forming a continuous time carbon sink sequence for each silt-retaining dam from its construction year to the target annual fee within a specified time period.

[0022] As a method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to the present invention, the dynamic response relationship of flux transfer between watershed non-source heat pumps and gully dam systems is further expressed as follows:

[0023] when hour, ;

[0024] when hour, ;

[0025] in, Silt-retention dam Construction time, For time t silt dam The cumulative organic carbon storage, For time t silt dam The amount of carbon interception, where T is the target year. The rate constant for the decomposition of organic carbon

[0026] Furthermore, this invention also provides a dynamic simulation and evaluation system for soil carbon pools in watershed silt-retaining dam systems, comprising: a data acquisition module, a flux output module, a coupled response module, and an output display module, wherein...

[0027] The data acquisition module is used to acquire multi-source data of the watershed, including: watershed basic data, silt-retaining dam ledger data, watershed water and sediment process data, and slope runoff plot observation data;

[0028] The flux output module is used to divide the watershed into several sub-watersheds and hydrological response units, and to conduct carbon flux process simulation based on multi-source watershed data and using the SWAT model to simulate water and sediment processes and output the outlet water, sediment and carbon flux of each sub-watershed.

[0029] The coupled response module is used to take the outflow of water, sediment and carbon flux of each sub-basin as the input boundary condition for the simulation of soil carbonization of dam system in the basin. Through the topological traversal of the dam system, the outflow of the upstream dam is taken as the inflow input of the downstream dam, and the dynamic decomposition and evolution relationship of sedimentary organic carbon of watershed non-source and gully dam system and the dynamic response relationship of flux transfer are established.

[0030] The output display module is used to set a simulation start time for each silt-retaining dam individually, obtain a time series matrix of multivariate soil carbon pools of silt-retaining dams in the whole basin based on the flux transfer dynamic response relationship, and form a spatiotemporal dataset of carbon sinks of dam system in the basin. The spatiotemporal dataset is used to visualize the carbon sink capacity of silt-retaining dams in the basin. The time series matrix records the annual carbon sink data of each silt-retaining dam in the basin from the year of construction to the target year.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention sets a separate simulation start time for each silt-retaining dam, calculating carbon sequestration step-by-step from its construction year. Silt-retaining dams that have not yet been constructed are not included in the simulation. A five-level aggregation system is established, namely "individual silt-retaining dam → construction period → sub-basin → whole basin". This enables multi-scale, multi-dam carbon sequestration assessment considering differences in construction time. It can output a continuous time dynamic sequence of the total carbon sequestration of each silt-retaining dam and the basin dam system, effectively solving the bottleneck problem of existing technologies being limited to static assessment of single dams and unable to reflect the dynamic construction process of the basin dam system.

[0033] 2. This invention dynamically updates the remaining capacity of each silt-retaining dam at each time step, realistically reflecting the physical process of silt-retaining dams "being used while silting up, and becoming ineffective when full." Simultaneously, it constructs a kinetic equation for the decomposition of sedimentary organic carbon, realizing the dynamic measurement of the total soil carbon pool of silt-retaining dams. The simulation step size for water and sediment decomposition and sedimentary carbon decomposition is consistent with the watershed water and sediment process model, achieving continuous dynamic simulation of the carbon sink process and overcoming the shortcomings of existing static estimation techniques that cannot reflect capacity decay and carbon decomposition loss.

[0034] 3. This invention addresses the lack of coupling between watershed non-point source sediment yield and gully-dam interception processes, achieving for the first time a unified framework for simulating the coupled migration of water, sediment, and carbon within a watershed silt-dam system, encompassing the entire chain from slope to gully to dam site and sediment. Starting from multi-source driving data including hydrological, meteorological, and land use data at the watershed scale, it ultimately achieves an assessment of soil carbon pool changes in silt-dam areas under dynamic underlying surface and climatic conditions. Validated by a case study in the Yanhe River basin, the simulated sediment NSE reaches 0.60–0.92.

[0035] 4. Based on mathematical models and computer simulation technology, this invention eliminates the need for large-scale field profile excavation and batch isotope dating tests, reducing the assessment cost of a single watershed by more than 90% compared to traditional profile inversion methods. It can also generate various spatiotemporal dynamic visualization products. Regarding the temporal dynamics of the soil carbon pool in silt-retaining dams, this includes interannual variation curves of the total carbon sink of the watershed dam system and ranking maps of carbon sinks for each silt-retaining dam. Spatial distribution includes point distribution maps of carbon sinks in silt-retaining dams, aggregated maps of carbon sinks in sub-watersheds, and identification maps of carbon sink hotspot dam systems, enabling efficient display and sharing of assessment results. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the dynamic simulation and evaluation process of the soil carbon pool of the watershed silt-retaining dam system in the embodiment;

[0037] Figure 2 This is a schematic diagram of the watershed-scale carbon migration simulation results in the examples;

[0038] Figure 3 The simulation results for retaining organic carbon content are shown in the examples, considering and not considering long-term storage.

[0039] Figure 4 This is a schematic diagram illustrating the time evolution of the carbon sequestration capacity of the Yanhe River silt-retaining dam in the embodiment;

[0040] Figure 5 This is a schematic diagram illustrating the spatial distribution of carbon sequestration capacity of silt-retaining dams from different eras in the Yanhe River Basin, as shown in the example. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer and more understandable, the invention will be further described in detail below with reference to the accompanying drawings and technical solutions.

[0042] In the static estimation technique of soil carbon pool based on the sediment volume survey of silt-retaining dams, the total volume of sediment deposited at the dam site is investigated and measured. Combined with the bulk density of the sediment and the measured organic carbon content, the total amount of soil organic carbon intercepted by the silt-retaining dam is estimated. The basic calculation formula is:

[0043] Formula (1)

[0044] in, The total volume of sediment deposited in the dam area ( ), The bulk density of the sediment ( ), The average organic carbon content of sediment ( ).

[0045] This method can estimate the total soil carbon pool up to date for any silt-trapping dam with sediment interception capacity, and is suitable for a rough assessment of silt-trapping dam carbon sinks.

[0046] In the carbon sequestration history inversion based on the excavation or drilling of sedimentary profiles of silt-dams, layered excavation or drilling sampling of the sedimentary profiles of silt-dams is performed, combined with radiometric dating (such as... Isotope dating or sedimentary cycle identification methods are used to determine the depositional age of each sedimentary layer, calculate the sediment deposition and organic carbon content of each layer, and thus reconstruct the historical carbon sink process of a single silt-trapping dam. The basic process involves excavating a sedimentary profile or drilling samples at the dam site, collecting sediment samples layer by layer, measuring the thickness, bulk density, and organic carbon content of each layer, using isotope dating or sedimentary cycle identification to determine the depositional age of each layer, and reconstructing the historical carbon sink sequence of the silt-trapping dam.

[0047] Formula (2)

[0048] This represents the total number of sediment layers. This method, which represents the sedimentary layer, can obtain the historical carbon sequestration dynamics of a single silt-retaining dam with high accuracy, but it is costly and time-consuming.

[0049] Therefore, this invention provides a method for dynamic simulation and assessment of soil carbon pool in watershed silt-retaining dam systems, such as... Figure 1 As shown, it specifically includes the following content:

[0050] S101. Obtain multi-source data of the watershed, including: watershed basic data, silt-retention dam ledger data, watershed water and sediment process data, and slope runoff plot observation data.

[0051] The basic watershed data may include: digital elevation models, land use maps, soil type maps, and daily meteorological data. Silt-retaining dam records may include the dam code, construction date, initial reservoir capacity, design siltation period, and spatial location of each dam. Watershed water and sediment process data may include daily-scale runoff and sediment transport observation data from hydrological stations. Slope runoff plot observation data may include runoff, sediment transport, and sediment organic carbon content under different rainfall events.

[0052] S102. Divide the watershed into several sub-watersheds and hydrological response units. Based on multi-source watershed data and using the SWAT model to simulate water and sediment processes, conduct carbon flux process simulation and output the water, sediment and carbon flux at the outlet of each sub-watershed.

[0053] Specifically, based on slope runoff plot observation data, the soil organic carbon migration enrichment coefficient equation can be fitted in the form of a power function to obtain the ratio of organic carbon content in eroded sediment to organic carbon content in source soil; the water and sediment migration parameters in the SWAT model can be calibrated using slope runoff plot observation data to simulate the hydrological response flow and erosion intensity per unit time using the SWAT model; the soil organic carbon content in eroded sediment migration can be obtained based on the ratio of organic carbon content in eroded sediment to organic carbon content in source soil and the organic carbon content in surface soil; the dynamic interception efficiency of water, sediment and carbon in silt-retaining dams can be set based on the ratio of remaining reservoir capacity to total inflow, and the total inflow carbon including upstream dam input and slope unit carbon input can be constructed based on the dynamic interception efficiency, and the reservoir capacity and intercepted carbon amount can be updated step by step over time.

[0054] Based on slope runoff plot observation data, a power function equation for soil organic carbon migration and enrichment coefficients was constructed:

[0055] Formula (3)

[0056] in, The ratio of organic carbon content in eroded sediment to organic carbon content in source soil (dimensionless). Sediment transport per unit area ( ); The value is taken as 1 for the reference sediment transport per unit area. This is used to ensure dimensional consistency. and These are empirical coefficients calibrated using runoff plot observation data.

[0057] Using the simulation step size and spatial partitioning framework of the SWAT model, the watershed was divided into several sub-watersheds and hydrological response units. The water and sediment transport module of the SWAT model was run, and after parameter calibration and model validation using runoff and sediment transport observation data from watershed hydrological stations, the hydrological response units were simulated. In time Production flow ( ) and erosion intensity ( )( ).

[0058] Calculate the soil organic carbon content in eroded and transported sediment:

[0059] Formula (4)

[0060] in, To erode the organic carbon content in the sediment ( ), The organic carbon content of the topsoil ( ).

[0061] For each time step Following the topological order of the dam system, traverse each silt-retaining dam sequentially from upstream to downstream. Obtain the total inflow of any silt-retaining dam j at time t. Total amount of sand coming in Actual water interception volume and actual sediment retention volume .

[0062] The actual sediment interception capacity is dynamically calculated based on the sediment interception efficiency of the silt-retaining dam with variable reservoir capacity:

[0063]

[0064] =

[0065] Time t silt-retaining dam j dam-controlled watershed inflow sediment carbon total for:

[0066] Formula (5)

[0067] In the formula: Number the upstream silt-retention dam. This represents the total number of upstream silt-retention dams; Carbon emissions from upstream silt-retaining dams ; Number the hydrological response unit. This represents the total number of hydrological response units. Area of ​​hydrological response unit ;coefficient Used for unit conversion.

[0068] Carbon content of inflow sediment to silt-retaining dams for:

[0069] Formula (6)

[0070] Assuming the carbon content of the inflow sediment, the carbon content of the intercepted sediment, and the carbon content of the outflow sediment are the same:

[0071] Formula (7)

[0072] Formula (8)

[0073] time silt-retaining dams Carbon interception for:

[0074] Formula (9)

[0075] when At that time, carbon emissions Represented as:

[0076] Formula (10)

[0077] Update the remaining reservoir capacity of silt-retention dam j based on the sediment interception volume at this time step:

[0078] Formula (11)

[0079] in, For remaining storage capacity , The bulk density of the sediment ( (Value range: 1.2~1.5).

[0080] when At that time, the dam is marked as silted up, and subsequent time steps will no longer have the function of interception.

[0081] S103. The outflow of water, sediment and carbon flux from each sub-basin is used as the input boundary condition for soil carbonization simulation of the dam system within the basin. Through topological traversal of the dam system, the outflow from the upstream dam is used as the inflow input from the downstream dam to establish the dynamic decomposition and evolution relationship of sedimentary organic carbon between the basin non-source and channel dam systems, as well as the dynamic response relationship of flux transfer.

[0082] Specifically, carbon decomposition loss and net carbon sink can be quantitatively determined using the decomposition rate constant, and the mineralization and decomposition process of deposited organic carbon can be simulated using a first-order kinetic equation to obtain the cumulative organic carbon storage of silt-retaining dams over a specified time period. The carbon interception and cumulative organic carbon storage of each silt-retaining dam can be obtained step by step over time to form a continuous time carbon sink sequence for each silt-retaining dam from its construction year to the target annual cost within a specified time period.

[0083] For each silt-retaining dam, the intercepted and deposited organic carbon is simulated using a dynamic release and storage equation to model its long-term mineralization and decomposition process. The decomposition rate of deposited organic carbon is directly proportional to the current deposited carbon content:

[0084] Formula (12)

[0085] The discrete form is:

[0086] Formula (13)

[0087] in, The accumulated storage of organic carbon deposited in the dam area. The rate constant for the decomposition of organic carbon ( (Value range: 0.01~0.03).

[0088] For accumulated over time The sedimentary layer, over time The organic carbon content is expressed as:

[0089] Formula (14)

[0090] All sedimentary layers in time The cumulative organic carbon storage (soil carbon sink) is expressed as:

[0091] Formula (15)

[0092] Based on the dam system topology, all silt-retaining dams within the basin are traversed in a topological order from upstream to downstream, with each time step counting. Due to the varying silt-retaining dams... Construction time Inconsistencies exist; some dams may not have been constructed at certain points in time, therefore each silt-retaining dam needs to be examined. Set its simulation start time separately:

[0093] Formula (16)

[0094] Regarding time During the period described, the silt-retaining dam did not yet exist and was not included in the simulation; upstream water and sediment were directly transmitted downstream. Regarding the time... During a given period, the carbon interception amount was calculated by analyzing the single dam's water-sediment carbon balance and carbon decomposition processes at each time step. and net carbon storage This forms the basis for the formation of various silt-retention dams based on their respective construction years. up to the current year Continuous-time carbon sink sequence:

[0095] when hour: Formula (17)

[0096] when hour: Formula (18)

[0097] S104. Set a separate simulation start time for each silt-retention dam, obtain a time series matrix of multivariate soil carbon pools of silt-retention dams in the whole basin based on the flux transfer dynamic response relationship, and form a spatiotemporal dataset of carbon sinks of dam system in the basin. The spatiotemporal dataset is used to visualize the carbon sink capacity of silt-retention dams in the basin. The time series matrix records the annual carbon sink data of each silt-retention dam in the basin from the year of construction to the target year.

[0098] By traversing topological order and determining construction time, it is ensured that upstream dams are put into operation sequentially according to their respective construction times, and their outflow serves as the inflow input for downstream dams (if a downstream dam has not yet been completed, the flow continues downstream). This achieves continuous-time dynamic reconstruction of carbon sinks across the entire basin's dam system, considering inconsistencies in construction time. The final output is a carbon sink time-series matrix for N silt-retaining dams within the basin, where the start time of each dam's sequence is unique.

[0099] Formula (19)

[0100] The carbon sequestration calculation results of each silt-trapping dam are aggregated at multiple scales according to spatial affiliation: First, the silt-trapping dams are grouped by construction date, and the carbon sequestration contribution of dam groups built in different periods is calculated; then, spatial aggregation is performed by sub-basin units, summing the carbon sequestration of all silt-trapping dams belonging to the same sub-basin to calculate the total carbon sequestration of the silt-trapping dam system in each sub-basin, and outputting the total carbon sequestration of the entire basin's silt-trapping dam system. Simultaneously, the silt-trapping dams are classified and aggregated according to type (backbone dams, medium-sized dams, small dams), and the carbon sequestration contribution rate of different types of silt-trapping dams is calculated. This is achieved by establishing... The four-level aggregation system enables multi-scale carbon aggregation assessment that takes into account differences in construction time, effectively solving the bottleneck problem that existing technologies are limited to single-dam assessment and cannot reflect the dynamic construction process of dam systems in the basin.

[0101] This proposal integrates the runoff and sediment transport processes simulated by the SWAT model, the carbon migration processes calculated by the enrichment coefficient equation, the silt-trapping dam process, and the sedimentary carbon decomposition process into a unified framework, achieving... The entire chain Coupled migration simulation establishes a complete physical process link from runoff and sediment generation sources to dammed carbon sink terminals. Modules are tightly coupled through flux transfer, ensuring spatial continuity and temporal consistency of carbon migration flux. Dynamic calculation of water, sediment, and carbon interception efficiency of silt-retaining dams based on variable reservoir capacity directly reflects the actual storage capacity of silt-retaining dams for a single flood event. By updating reservoir capacity and intercepted carbon amount at time steps, continuous dynamic calculation of water, sediment, and carbon interception efficiency of silt-retaining dams throughout their entire life cycle from construction to siltation is achieved. Carbon decomposition is incorporated into the silt-retaining dam carbon sink assessment framework. Carbon decomposition loss and net carbon sink are quantitatively calculated using the decomposition rate constant, addressing the problem of systematic overestimation of carbon sinks caused by neglecting carbon decomposition in traditional static estimation methods. Considering the inconsistent construction times of various silt-retaining dams within the basin, a separate simulation start time is set for each dam, outputting a multivariate time-series matrix of soil carbon pools for multiple silt-retaining dams across the entire basin. This matrix records the annual carbon sink data of each silt-retaining dam from the construction year to the target year, forming a complete spatiotemporal dataset of dam-system carbon sinks.

[0102] Furthermore, based on the above method, this embodiment of the invention also provides a dynamic simulation and evaluation system for soil carbon pool in watershed silt-retaining dam systems, comprising: a data acquisition module, a flux output module, a coupled response module, and an output display module, wherein...

[0103] The data acquisition module is used to acquire multi-source data of the watershed, including: watershed basic data, silt-retaining dam ledger data, watershed water and sediment process data, and slope runoff plot observation data;

[0104] The flux output module is used to divide the watershed into several sub-watersheds and hydrological response units, and to conduct carbon flux process simulation based on multi-source watershed data and using the SWAT model to simulate water and sediment processes and output the outlet water, sediment and carbon flux of each sub-watershed.

[0105] The coupled response module is used to take the outflow of water, sediment and carbon flux of each sub-basin as the input boundary condition for the simulation of soil carbonization of dam system in the basin. Through the topological traversal of the dam system, the outflow of the upstream dam is taken as the inflow input of the downstream dam, and the dynamic decomposition and evolution relationship of sedimentary organic carbon of watershed non-source and gully dam system and the dynamic response relationship of flux transfer are established.

[0106] The output display module is used to set a simulation start time for each silt-retaining dam individually, obtain a time series matrix of multivariate soil carbon pools of silt-retaining dams in the whole basin based on the flux transfer dynamic response relationship, and form a spatiotemporal dataset of carbon sinks of dam system in the basin. The spatiotemporal dataset is used to visualize the carbon sink capacity of silt-retaining dams in the basin. The time series matrix records the annual carbon sink data of each silt-retaining dam in the basin from the year of construction to the target year.

[0107] To verify the effectiveness of this proposal, the following explanation is based on experimental data from the dynamic simulation and assessment of the soil carbon pool in the silt-retaining dam system of the Yanhe River Basin:

[0108] The Yan River Basin (area) The study area is located in the central part of the Loess Plateau. The Yellow River is a first-order tributary of the Yellow River. The basin has a temperate continental monsoon climate, with an average annual precipitation of approximately 500 mm, concentrated between June and September (accounting for over 70% of the annual rainfall). There are 808 silt-retention dams within the basin, constructed from the 1950s to the 2010s. These dams are scattered, varying in size and construction date, making it challenging to conduct a comprehensive assessment of their carbon sequestration capacity across the entire basin.

[0109] The data preparation is shown in Table 1.

[0110]

[0111] Based on observation data from five slope runoff plots, a power-law function equation for soil organic carbon migration and enrichment coefficients was fitted. The sediment transport per unit area was then considered. With enrichment coefficient Regression analysis yielded the following results:

[0112] Formula (20)

[0113] coefficient of determination obtained from regression The value of 0.82 indicates that soil erosion intensity can be used. Predicted enrichment coefficient of lost organic carbon

[0114] The Yanhe River Basin was divided into 202 sub-basins and 6053 hydrological response units. The SWAT model was used to simulate the monthly water and sediment processes from 1975 to 2020. Calibration and verification were performed using measured data from the Ganguyi hydrological station in the Yanhe River Basin (1956-1970), as shown in Table 2.

[0115]

[0116] According to the model evaluation criteria, the effectiveness of the runoff and sediment transport simulations is rated as "Good" to "Very Good", which meets the requirements.

[0117] Continuous calculation of runoff generation, sediment yield, and carbon erosion and migration processes at the watershed scale on a per-hydrological response unit basis, such as Figure 2 As shown, the carbon migration distribution of 6053 hydrological units across the entire basin in different years is presented.

[0118] A monthly survey of 808 silt-retention dams was conducted. Taking a key dam (number j=156) as an example, it was built in 1995 with an initial reservoir capacity of 700,000 cubic meters per second. The design siltation period is 25 years, and the controlled watershed area is 10.5 square kilometers. Silt bulk density .

[0119] (1) Simulation in August 1996 (the year after construction, with sufficient storage capacity)

[0120] Upstream runoff depth 23 The total inflow was 241,500 cubic meters per second. Total amount of sediment from upstream Ten thousand Carbon from upstream .

[0121] Because the silt-retention dam has ample storage capacity (remaining capacity 700,000 cubic meters). ), sand-trapping efficiency All water and sand were intercepted:

[0122] Actual sediment retention capacity: Ten thousand

[0123] Actual water interception volume: Ten thousand

[0124] Carbon content of inflow sediment:

[0125] Carbon interception amount:

[0126] Remaining storage capacity updated:

[0127] (2) August 2015 simulation (running for 20 years, remaining storage capacity 130,000) )

[0128] After 20 years of siltation, the dam has accumulated approximately 566,600 cubic meters of sediment. Remaining storage capacity Ten thousand (Last month's value).

[0129] The upstream runoff depth for that month was 16. Total water inflow: 168,000 cubic meters Total amount of sediment from upstream Ten thousand Carbon from upstream Because the warehouse capacity is only remaining The efficiency of water and sediment retention decreases:

[0130] The actual water interception volume is Ten thousand ,

[0131] Actual sediment retention capacity: 10,000 tons

[0132] Carbon content of inflow sediment:

[0133] The amount of silt discharged was 0.43 million tons.

[0134] Carbon interception amount:

[0135] Carbon emissions:

[0136] Remaining storage capacity updated: Ten thousand

[0137] For the organic carbon intercepted and deposited in each silt-retaining dam, a first-order kinetic equation is used to simulate its long-term mineralization and decomposition process. Based on measured data from the sedimentary profile of the dam site in the Yanhe River basin, the decomposition rate constant can be taken as:

[0138] Formula (21)

[0139] This value indicates that approximately 1.7% of deposited organic carbon is mineralized and decomposed annually. Based on an annual decomposition rate of 1.7%, the half-life of deposited organic carbon is approximately:

[0140] Formula (22)

[0141] Taking the main dam (j=156) as an example, the annual carbon interception and decomposition calculation results of the dam from 1995 to 2020 are as follows:

[0142] Calculation formula:

[0143] The net carbon retention at the end of 2016 from a certain year's interception was:

[0144] Formula (23)

[0145] The total net carbon sink of the dam is:

[0146] Formula (24)

[0147] 235.2 tons deposited in 1996 As of 2015, as shown in Table 3 and Figure 3 As shown, after 18 years of release, a loss of 27.6% occurred, leaving 170.3. ,

[0148] All-silt-retaining dams during the 20 years from 1996 to 2015:

[0149] Total carbon interception: 3322.0

[0150] Net carbon sink at the end of 2015, after considering decomposition: 2793.5

[0151] Cumulative decomposition loss: 528.5

[0152] Decomposition loss ratio: 15.9%

[0153]

[0154] To maintain consistency with the CCER carbon sequestration measurement units, the carbon mass in the soil carbon pool ( ) converted to carbon dioxide equivalent ( As of 2016, the total carbon sequestration capacity of large and medium-sized silt-retention dams in the Yanhe River Basin was 4.84 million cubic meters per second. The maximum carbon sequestration capacity of a single dam can reach 79,000 cubic meters per second. The average carbon sequestration capacity of each dam is 0.56 million tons. The median is 0.41 million. Based on simulation calculations, such as Figure 4 As shown, the soil carbon pool of the silt-retaining dam system in the Yanhe River Basin has shown a continuous growth trend since the construction of each dam.

[0155] From a spatial distribution perspective, such as Figure 5 As shown, the spatial distribution of carbon sinks in silt-trapping dams in the Yanhe River Basin is not significantly concentrated at the basin scale. The carbon sink capacity of silt-trapping dams in the upper reaches of Xingzi River, the upper reaches of the main stream, and the upper reaches of Xichuan River is relatively low, while the sediment retention capacity of silt-trapping dams in the sub-basins on both sides of the middle reaches of the Yanhe River is relatively high.

[0156] The experimental data above demonstrate that the proposed scheme constructs a carbon decomposition kinetic equation and keeps the simulation step size consistent with the watershed sediment process model, enabling continuous dynamic simulation of the carbon sink process. By establishing a multi-scale carbon pool assessment from a single dam to the dam system and then to the watershed, simultaneous assessment of multiple dams at the watershed scale is achieved. A dynamic simulation framework coupled with the watershed sediment yield model is established, enabling assessment of soil carbon pool changes in silt-retaining dams driven by multi-source data such as hydrology, meteorology, and land use.

[0157] Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0158] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0159] The units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations are not considered to be beyond the scope of this invention.

[0160] Those skilled in the art will understand that all or part of the steps in the above methods can be implemented by a program instructing related hardware, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk. Optionally, all or part of the steps in the above embodiments can also be implemented using one or more integrated circuits. Accordingly, each module / unit in the above embodiments can be implemented in hardware or as a software functional module. This invention is not limited to any particular combination of hardware and software.

[0161] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for dynamic simulation and assessment of soil carbon pool in watershed silt-retaining dam systems, characterized in that, Include: Acquire multi-source data for the watershed, including: basic watershed data, silt-retaining dam ledger data, watershed water and sediment process data, and slope runoff micro-plot observation data; The basin is divided into several sub-basins and hydrological response units. Based on multi-source data of the basin and using the SWAT model to simulate water and sediment processes, carbon flux process simulation is carried out and the outlet water, sediment and carbon flux of each sub-basin is output. The outflow of water and sediment carbon flux from each sub-basin is used as the input boundary condition for simulating soil carbonization in the dam system within the basin. Through topological traversal of the dam system, the outflow from the upstream dam is used as the inflow input from the downstream dam to establish the dynamic decomposition and evolution relationship of sedimentary organic carbon between the watershed non-source and channel dam systems, as well as the dynamic response relationship of flux transfer. A separate simulation start time is set for each silt-retention dam. Based on the flux transfer dynamic response relationship, a time series matrix of multivariate soil carbon pools of silt-retention dams in the whole basin is obtained, and a spatiotemporal dataset of carbon sinks of dam system in the basin is formed. The spatiotemporal dataset is used to visualize the carbon sink capacity of silt-retention dams in the basin. The time series matrix records the annual carbon sink data of each silt-retention dam in the basin from the year of construction to the target year.

2. The method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to claim 1, characterized in that, Based on multi-source watershed data and using the SWAT model for water and sediment process simulation, carbon flux process simulation was conducted, and the outlet water, sediment, and carbon fluxes of each sub-watershed were output, including: Based on slope runoff plot observation data, the soil organic carbon migration enrichment coefficient equation was fitted in the form of a power function to obtain the ratio of organic carbon content in eroded sediment to organic carbon content in source soil. The water and sediment transport parameters in the SWAT model were calibrated using slope runoff plot observation data, so as to simulate the hydrological response runoff and erosion intensity per unit time using the SWAT model. The soil organic carbon content during the migration of eroded sediment was obtained by comparing the ratio of organic carbon content in eroded sediment to that in the source soil and the organic carbon content in the surface soil. The dynamic interception efficiency of water, sediment and carbon at silt-retaining dams is set based on the ratio of remaining reservoir capacity to total inflow. The total inflow carbon, including upstream dam input and slope unit carbon input, is constructed based on the dynamic interception efficiency, and the reservoir capacity and intercepted carbon amount are updated step by step over time.

3. The method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to claim 2, characterized in that, The dynamic interception efficiency of water, sediment, and carbon by silt-retaining dams is expressed as: ,in, Let t be the total inflow of water to the silt-retaining dam j. This represents the remaining storage capacity.

4. The method for dynamic simulation and assessment of soil carbon pool in watershed silt-retaining dam systems according to claim 2 or 3, characterized in that, The process of updating the storage capacity step by step over time can be represented as: , The remaining reservoir capacity of the silt-retaining dam at time t is given. For time step, Let t be the amount of sediment retained by the silt-retaining dam j. The bulk density of the sediment.

5. The method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to claim 4, characterized in that, The process of updating the amount of intercepted carbon is represented as follows: ,in, The carbon content of the sediment intercepted by the silt-retaining dam at time t is given.

6. The method for dynamic simulation and evaluation of soil carbon pool in watershed silt-retaining dam systems according to claim 1, characterized in that, Establish the dynamic response relationship between watershed non-source heat pumps and channel-dam system flux transfer, as well as the dynamic decomposition and evolution of organic carbon in dam system sediments, including: Carbon decomposition loss and net carbon sink were quantitatively determined using the decomposition rate constant, and the mineralization and decomposition process of deposited organic carbon was simulated using a first-order kinetic equation to obtain the cumulative organic carbon storage of the silt-retaining dam over a specified time period. The calculation process for the cumulative organic carbon storage is expressed as follows: ,in It is the cumulative organic carbon storage of the silt-retaining dam at time T. For the time t silt dam Carbon interception amount, The rate constant for the decomposition of organic carbon; The carbon interception and cumulative organic carbon storage of each silt-retaining dam are obtained at each time step, forming a continuous time carbon sink sequence for each silt-retaining dam from its construction year to the target annual fee within a specified time period.

7. The method for dynamic simulation and assessment of soil carbon pool in watershed silt-retaining dam systems according to claim 1 or 6, characterized in that, The dynamic response relationship of flux transfer between watershed non-source heat pumps and channel-dam systems is expressed as follows: when hour, ; when hour, ; in, Silt-retention dam Construction time, For the time t silt dam The cumulative organic carbon storage, For the time t silt dam The amount of carbon interception, where T is the target year. is the rate constant for the decomposition of organic carbon.

8. A dynamic simulation and assessment system for soil carbon pool in watershed silt-retaining dam systems, characterized in that, It includes: a data acquisition module, a throughput output module, a coupled response module, and an output display module. The data acquisition module is used to acquire multi-source data of the watershed, including: watershed basic data, silt-retaining dam ledger data, watershed water and sediment process data, and slope runoff plot observation data; The flux output module is used to divide the watershed into several sub-watersheds and hydrological response units, and to conduct carbon flux process simulation based on multi-source watershed data and using the SWAT model to simulate water and sediment processes and output the outlet water, sediment and carbon flux of each sub-watershed. The coupled response module is used to take the outflow of water, sediment and carbon flux of each sub-basin as the input boundary condition for the simulation of soil carbonization of dam system in the basin. Through the topological traversal of the dam system, the outflow of the upstream dam is taken as the inflow input of the downstream dam, and the dynamic decomposition and evolution relationship of sedimentary organic carbon of watershed non-source and gully dam system and the dynamic response relationship of flux transfer are established. The output display module is used to set a simulation start time for each silt-retaining dam individually, obtain a time series matrix of multivariate soil carbon pools of silt-retaining dams in the whole basin based on the flux transfer dynamic response relationship, and form a spatiotemporal dataset of carbon sinks of dam system in the basin. The spatiotemporal dataset is used to visualize the carbon sink capacity of silt-retaining dams in the basin. The time series matrix records the annual carbon sink data of each silt-retaining dam in the basin from the year of construction to the target year.

9. An electronic device, characterized in that, include: At least one processor, and a memory coupled to said at least one processor; The memory stores a computer program that can be executed by the at least one processor to implement the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed, enables the implementation of the method as described in any one of claims 1 to 7.

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