A method and system for integrated surface-groundwater simulation coupled with a glacier module

Abstract

The application provides a kind of coupling ice module surface water-groundwater integrated simulation method and system, which is based on the extended SWAT-GL model, and inputs rainfall, snowmelt and glacial melt water as daily effective rainfall, transfers the infiltration recharge and river level to MODFLOW through daily interface, simulates the change of groundwater head and the exchange amount of surface water-groundwater by using three-dimensional groundwater flow equation, and feeds back the results to SWAT-GL river water balance, realizes the two-way dynamic coupling of the whole process of glacier-snow-surface-groundwater. The system breaks through the limitation that it is difficult to simultaneously depict the glacier mass balance and groundwater dynamics in cold region simulation, and can reveal the recharge and regulation mechanism of glacial melt water to groundwater system under the driving of climate change at a fine time scale, significantly improving the simulation capability of key processes of water cycle in cold regions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrology and water resources simulation and groundwater numerical modeling, and particularly relates to a surface water-groundwater integrated simulation method coupled with a glacier module and a system thereof. BACKGROUND

[0002] Glacier meltwater is not only an important source of regional water resources, but also a key input item of the groundwater system. In arid and semi-arid regions, groundwater is a core element for maintaining the ecological environment and supporting social and economic development, and its dynamic change is closely related to glacier meltwater. Glacier retreat directly affects the balance of groundwater budget at different stages by changing the total amount of meltwater and the recharge path, and will cause fluctuations in regional water resources in the long term. Therefore, it is urgent to clarify the response mechanism between snow, glaciers, surface water and groundwater systems through accurate hydrological simulation tools.

[0003] At present, although domestic and foreign scholars have carried out a large number of researches on the characteristics and mechanisms of glacier change and its influence on surface water, there are still significant deficiencies in the simulation technology of complex hydrological processes in glacier basins: the simulation accuracy of traditional models is limited, and the applicability in high mountain glacier regions is poor, which cannot accurately quantify the contribution of glacier meltwater to the overall hydrological system, resulting in large deviation in the simulation of related hydrological processes; the existing researches mostly use single hydrological model or statistical method, which is difficult to depict the correlation between systems and cannot fully capture the complex interaction between snow, glaciers, surface water and groundwater, limiting the overall and dynamic correlation of the hydrological system; at present, there is no integrated simulation tool that can consider glacier mass balance, surface runoff evolution and dynamic change of groundwater at the same time, which makes it difficult to realize the unified simulation and analysis of key hydrological processes in glacier basins. In addition, on the fine time scale, the precise simulation technology for the exchange process of glacier-surface water-groundwater is still lacking, which makes it difficult to meet the research needs of short-term dynamic changes of hydrological processes.

[0004] Therefore, it has become a key technical problem to be solved in the current glacier hydrology research field to develop an integrated model system that can accurately simulate the complex hydrological processes in glacier basins. SUMMARY

[0005] The embodiment of the present application provides a surface water-groundwater integrated simulation method coupled with a glacier module, which aims to solve the deficiencies of traditional SWAT and MODFLOW models in simulating hydrology in alpine regions, such as the lack of dynamic basis for simulating groundwater in the traditional SWAT model, which mainly relies on empirical formula; the MODFLOW model lacks a detailed description of multi-source recharge such as glaciers and snow, and is difficult to fully present the whole process of water cycle.

[0006] In order to achieve the above purpose, the technical scheme of the embodiment of the present application is:

[0007] In a first aspect, the present application provides a method for coupling glacial module of surface water-groundwater integrated simulation, comprising:

[0008] acquiring meteorological data, soil data, land use data and glacial remote sensing data of a target basin;

[0009] inputting the acquired data into a SWAT-GL model, calculating rainfall, glacial melt water and snow melt water of each hydrological response unit in the target basin on a daily basis, and determining daily effective precipitation based on the daily snowfall; based on the daily effective precipitation, calculating surface runoff, and further calculating daily infiltration recharge and river water level;

[0010] converting the daily infiltration recharge into a source-sink item of an aquifer unit, inputting the river water level as a river boundary condition into a MODFLOW model, combining aquifer parameters, and calculating groundwater head and surface water-groundwater exchange through a three-dimensional groundwater flow equation;

[0011] feedback the surface water-groundwater exchange to the SWAT-GL model to dynamically correct the river flow; wherein the SWAT-GL model and the MODFLOW model exchange data bidirectionally through daily time steps to realize coupling simulation of glacial-snow-surface water-groundwater.

[0012] In some embodiments, the daily effective precipitation is obtained by summing the rainfall, the snow melt water and the glacial melt water after deducting the daily snowfall, and the specific calculation formula is:

[0013] ;

[0014] In the formula: P is the daily effective precipitation, R is the rainfall, S is the snow melt water, G is the glacial melt water, F is the daily snowfall.

[0015] In some embodiments, the glacial remote sensing data includes glacial thickness data and glacial area data; the glacial melt water is dynamically calculated by introducing elevation zone division and glacial annual scale evolution mechanism, specifically including:

[0016] dividing the glacial area of the hydrological response unit into multiple elevation zones according to the altitude; calculating the glacial melt rate on a daily basis in each elevation zone, and calculating the glacial melt water by combining the glacial sublimation rate, the glacial accumulation rate and the refreezing factor of the melt body; at the end of each glacial year, updating the glacial thickness and the glacial area of each elevation zone according to the annual glacial water equivalent change, and updating the range of the glacial area in the case of no ice elevation zone where the glacial thickness is reduced to zero.

[0017] In some embodiments, the formula for calculating the glacier melting rate is:

[0018] ;

[0019] In the formula: is the glacier melting rate, is the daily maximum temperature, is the glacier melting threshold temperature, and are the glacier coverage area and snow coverage area, respectively; wherein the glacier melting factor is calculated by the formula: ; , are the maximum and minimum glacier melting factors in a year, respectively, and t is the tth day;

[0020] The formula for calculating the glacier meltwater amount is:

[0021] ;

[0022] In the formula: is the glacier meltwater amount, is the glacier melting rate, is the glacier sublimation rate, is the glacier accumulation rate, is the refreezing factor of meltwater.

[0023] In some embodiments, the snow meltwater amount is calculated by the following process:

[0024] The snow meltwater amount is calculated based on the degree-day factor method:

[0025] ;

[0026] In the formula: is the snow meltwater amount, SMF is the snowmelt rate, is the snow coverage ratio, is the snow surface temperature, is the maximum air temperature, is the snowmelt temperature threshold.

[0027] In some embodiments, the surface runoff is calculated based on the daily effective precipitation, including: when the daily effective precipitation is greater than the initial loss , the formula for calculating the surface runoff is: ; when the daily effective precipitation is less than or equal to the initial loss , ;

[0028] wherein, is daily effective precipitation; is surface runoff; initial loss satisfies the relationship , empirical coefficient; the relationship between the possible storage S and the curve number CN of the target watershed satisfies ).

[0029] In some embodiments, the source-sink term of the aquifer unit is calculated by the following formula:

[0030] ;

[0031] ;

[0032] In the formula, is the source-sink term of the aquifer unit, is the daily infiltration recharge, is the aquifer thickness, is the surface runoff, is the interception evaporation.

[0033] In some embodiments, the formula for calculating the surface water-groundwater exchange amount is:

[0034] ;

[0035] In the formula, is the river water level output by the SWAT-GL model, is the cell groundwater head calculated by the MODFLOW model, is the aquifer transmissivity.

[0036] In a second aspect, the application provides a coupled simulation system for implementing the method of any one of the first aspect, comprising:

[0037] an acquisition module configured to acquire meteorological data, soil data, land use data, and glacial remote sensing data of a target watershed;

[0038] a calculation module configured to input the acquired data into a SWAT-GL model, calculate the rainfall, glacial melt water, and snowmelt water of each hydrological response unit in the target watershed on a daily basis, and determine the daily effective precipitation in combination with the daily snowfall; based on the daily effective precipitation, calculate the surface runoff, and further calculate the daily infiltration recharge and the river water level;

[0039] The computing module is further configured to convert the daily infiltration supplement into a source-sink item of an aquifer unit, input the river water level as a river boundary condition into a MODFLOW model, combine aquifer parameters, and calculate groundwater head and surface water-groundwater exchange through a three-dimensional groundwater flow equation;

[0040] The correction module is configured to feed back the surface water-groundwater exchange to the SWAT-GL model to dynamically correct the river flow, wherein the SWAT-GL model and the MODFLOW model exchange data bidirectionally through a daily time step to realize coupled simulation of glacier-snow-surface water-groundwater.

[0041] The surface water-groundwater integrated simulation method coupled with the glacier module provided by the application realizes dynamic bidirectional coupling of the SWAT-GL and the MODFLOW model through a daily time step. The SWAT-GL transmits the net infiltration supplement (derived from rainfall, snowmelt and glacier meltwater) and the river water level time sequence to the MODFLOW; the MODFLOW feeds back the simulated surface water-groundwater exchange, groundwater level and groundwater evaporation to the SWAT-GL for accurate correction of the river flow and the evapotranspiration process. In the base flow simulation aspect, the original empirical distribution method of the SWAT is abandoned, and the groundwater dynamics simulation based on the physical mechanism of the MODFLOW is adopted, which significantly improves the simulation accuracy and physical authenticity of the groundwater contribution. Through the bidirectional coupling mechanism, the model can dynamically simulate the recharge-discharge relationship and state switching between the groundwater and the river water under the input condition of snowmelt and ice melt, and breaks through the limitation of the traditional unidirectional coupling model. Meanwhile, the application explicitly includes the glacier and snow process into the watershed recharge module, first constructs the complete circulation chain of snow-ice-surface water-groundwater, significantly improves the simulation accuracy of the total runoff, base flow division and groundwater storage change, realizes quantitative analysis of the respective recharge contribution of the glacier meltwater and the snowmelt, and thus supports comprehensive evaluation of the response of the climate change-glacier retreat-groundwater system, and provides a scientific basis for water resource management and policy making in cold regions. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 FIG. 1 is a flowchart of the surface water-groundwater integrated simulation method coupled with the glacier module provided by the embodiment of the application;

[0043] Figure 2 FIG. 2 is a model architecture diagram of the GLSWATMOD model provided by the embodiment of the application;

[0044] Figure 3 FIG. 3 is a comparison diagram of the runoff simulation value and the observation value provided by the application;

[0045] Figure 4is a comparison chart of glacier melt water and snow melt water of a target basin provided by the embodiment of the present application;

[0046] Figure 5 is an evolution chart of glacier water equivalent of a target basin provided by the embodiment of the present application;

[0047] Figure 6 is a spatial distribution chart of characteristic annual surface water-groundwater exchange of a target basin provided by the embodiment of the present application. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings, and the described embodiments should not be regarded as limiting the present application, and all other embodiments obtained by those skilled in the art without creative labor shall fall within the scope of protection of the present application.

[0049] In the following description, "some embodiments" are related to a subset of all possible embodiments, but it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present application are the same as the meanings commonly understood by those skilled in the art of the technical field to which the embodiments of the present application belong. The terms used in the embodiments of the present application are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0050] The following illustrates an exemplary application of the surface water-groundwater integrated simulation device coupled with the glacier module of the embodiments of the present application. The surface water-groundwater integrated simulation device coupled with the glacier module provided by the embodiments of the present application can be implemented as a terminal or a server. In one implementation, the surface water-groundwater integrated simulation device coupled with the glacier module provided by the embodiments of the present application can be implemented as various types of terminals such as a notebook computer, a tablet computer, a desktop computer, a mobile device, etc.; in another implementation, the surface water-groundwater integrated simulation device coupled with the glacier module provided by the embodiments of the present application can also be implemented as a server, wherein the server can be a standalone physical server, a server cluster or a distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud service, cloud database, cloud computing, cloud function, cloud storage, network service, cloud communication, middleware service, domain name service, security service, content delivery network (CDN), and big data and artificial intelligence platform, etc. The terminal and the server can be directly or indirectly connected through wired or wireless communication, which is not limited in the embodiments of the present application. In the following, an exemplary application of the surface water-groundwater integrated simulation device coupled with the glacier module as a server will be described.

[0051] The embodiment of the present application provides a surface water-groundwater integrated simulation method coupled with a glacier module, referring to Figure 1 , Figure 1 The embodiment of the present application provides a flowchart of a surface water-groundwater integrated simulation method coupled with a glacier module, which will be described by combining the steps shown in the figure. Figure 1

[0052] In step S110, meteorological data, soil data, land use data and glacier remote sensing data of a target basin are acquired.

[0053] In some embodiments, the target basin refers to a natural hydrological unit with a clear geographical boundary targeted by the present application. The boundary is usually demarcated by a topographic watershed, so that the precipitation, surface runoff and groundwater runoff within the range finally converge to a common outlet section. For example, it can be the Yellow River basin, a tributary basin of the upper reaches of the Yangtze River or a specific experimental small basin. In the present application, the target basin is the spatial range for glacier-snow-surface water-groundwater coupling simulation.

[0054] In some embodiments, the meteorological data refers to physical quantity data describing the atmospheric state and phenomena of the target basin, which is the key input data for driving the hydrological model. It usually includes but is not limited to: daily precipitation, air temperature (maximum temperature, minimum temperature), solar radiation, relative humidity, wind speed, etc. These data can be obtained from ground weather stations, reanalysis data or remote sensing inversion products.

[0055] In some embodiments, the soil data refers to spatial distribution data describing the physical and chemical properties of the soil in the target basin. These properties directly affect the infiltration, storage and migration of water. Soil data includes: soil layer thickness, soil texture, soil bulk density, saturated hydraulic conductivity, field capacity and wilting coefficient, etc.

[0056] In some embodiments, the land use data refers to spatial distribution data describing the land cover and human land use in the target basin. Different land use types (such as forest land, grassland, farmland, construction land, water area, glacier snow, etc.) have different hydrological characteristics, which directly affect the generation of surface runoff, the intensity of evapotranspiration and the migration of pollutants.

[0057] In some embodiments, the glacier remote sensing data refers to data obtained by satellite or aerial remote sensing technology for identifying, monitoring and analyzing the characteristics of glaciers. These data include but are not limited to: glacier boundary, glacier surface elevation (used to calculate glacier mass balance), ice surface temperature, snowline height, etc. For example, multispectral images of Landsat series satellites can be used to interpret the glacier range, or ICESat laser altimetry satellite data can be used to monitor the change of glacier thickness. ​

[0058] Step S120: Input the acquired data into the SWAT-GL model, calculate the rainfall, glacial meltwater and snowmelt of each hydrological response unit in the target watershed on a daily basis, and determine the daily effective precipitation by combining the daily snowfall; based on the daily effective precipitation, calculate the surface runoff, and further calculate the daily infiltration recharge and river level.

[0059] In some implementations, the SWAT-GL model is an improved distributed hydrological model of this invention. The SWAT model integrating the glacier module is an enhanced version of the SWAT model, improving its simulation capabilities for glacier and snow accumulation processes. The SWAT model itself is a long-term, distributed watershed hydrological model based on physical processes, dividing the watershed into hydrological response units to simulate the transport and transformation of water, sediment, nutrients, and pesticides. The SWAT-GL model specifically integrates a glacier ablation module, enabling more accurate calculation of the contribution of glacial meltwater to river runoff.

[0060] In some implementations, the hydrological response unit is the basic spatial unit used in calculations within the SWAT-GL model. It is a homogeneous region within a sub-watershed, consisting of a unique combination of land use, soil type, and slope.

[0061] In some implementations, glacial meltwater volume refers to the volume or equivalent depth of glacial ice that transforms into liquid water due to the absorption of heat (mainly from solar radiation and sensible heat) within a specific time period (such as daily in this invention). It is an important source of replenishment for rivers in glacial regions, and its calculation is typically based on the degree-day factor method or the energy balance method.

[0062] In some implementations, snowmelt volume refers to the volume or equivalent water depth of solid snow in the snow layer that is converted into liquid water due to melting within a specific time period. Its calculation also considers thermal factors such as air temperature and radiation; melting occurs when the snow temperature reaches its melting point and the energy input is positive.

[0063] In some implementations, daily effective precipitation refers to the portion of water that actually participates in the watershed's hydrological cycle and generates runoff or replenishes groundwater within a single day. In this invention, it is composed of the day's rainfall, glacial meltwater, and snowmelt, and the day's additional snowfall needs to be deducted (because additional snowfall does not participate in the liquid water cycle but accumulates in the snow layer). Therefore, daily effective precipitation = rainfall + glacial meltwater + snowmelt - snowfall.

[0064] In some implementations, surface runoff refers to the daily effective precipitation, after deducting losses such as vegetation interception, depression filling, and infiltration, flowing along the surface slope and ultimately flowing into the river channel. It is typically calculated using methods such as the SCS curve number method or the Green-Ampt infiltration equation.

[0065] In some implementations, daily infiltration recharge refers to the amount of water that infiltrates downwards through the vadose zone of the soil within a day, ultimately reaching and recharging the groundwater aquifer. It is a key variable connecting surface hydrological processes and groundwater hydrological processes, and is further derived from the infiltration process in the surface runoff calculation stage.

[0066] In some implementations, river level refers to the elevation of the river surface at a specific cross-section relative to a particular reference surface. It is an important hydraulic parameter reflecting the amount of water in the river channel. In this invention, it is calculated by the SWAT-GL model based on confluence and is passed to the groundwater model as a boundary condition.

[0067] Step S130: The daily infiltration recharge is converted into the source and sink terms of the aquifer unit, and the river water level is input into the MODFLOW model as the river boundary condition. Combined with the aquifer parameters, the groundwater head and surface water-groundwater exchange volume are calculated through the three-dimensional groundwater flow equation.

[0068] In some implementations, aquifer units are the basic spatial units used in calculations within the MODFLOW model. The model discretizes the entire subsurface space of the study area in three dimensions, dividing it into numerous regular cuboid grids, each of which represents an aquifer unit. Each unit is assigned specific hydrogeological parameters (such as permeability coefficient and specific yield) to characterize its water storage and conduction capabilities.

[0069] In some implementations, the source and sink terms of an aquifer unit in the MODFLOW model refer to all water quantities entering (source) or exiting (sink) the groundwater system. Common source terms include rainfall infiltration recharge, river seepage recharge, and irrigation return; common sink terms include well pumping, evaporation discharge, and discharge into rivers. In this invention, the daily infiltration recharge calculated by the SWAT-GL model is converted into the source terms of the corresponding aquifer unit in the MODFLOW model.

[0070] In this invention, the MODFLOW model predicts the distribution of groundwater head and flow exchange in aquifers by solving the three-dimensional groundwater flow equations that describe groundwater movement.

[0071] In some implementations, the river boundary condition is a boundary type used in the MODFLOW model to handle the interaction between surface water and groundwater. It generalizes the river channel as a system hydraulically connected to an aquifer, where the water level (provided by the SWAT-GL model) and the permeability of the riverbed sediment jointly determine the direction (recharge and discharge) and amount of exchange between the river channel and groundwater.

[0072] In some implementations, aquifer parameters refer to physical parameters used to quantitatively describe the hydrogeological characteristics of aquifer strata. These mainly include: permeability coefficient, which reflects the water-conducting capacity of the aquifer medium; water storage rate (for confined aquifers) or specific yield (for unconfined aquifers); and porosity. These parameters form the basis for the MODFLOW model calculations.

[0073] In practical applications, groundwater head can be approximated as the elevation of groundwater level. It is a core variable used to describe the spatial distribution of groundwater potential field, and its distribution determines the flow direction and speed of groundwater.

[0074] In some implementations, the surface water-groundwater exchange law refers to the amount of water exchanged between surface water bodies and groundwater aquifers via the riverbed per unit time. When the river level is higher than the adjacent groundwater level, river water seeps into the groundwater, resulting in a positive exchange rate; conversely, when the river level is lower, groundwater discharges into the river, resulting in a negative exchange rate.

[0075] Step S140: Feed the surface water-groundwater exchange volume back to the SWAT-GL model to dynamically correct the river flow; wherein, the SWAT-GL model and the MODFLOW model exchange data bidirectionally through daily time steps to realize the coupled simulation of glacier-snow cover-surface water-groundwater.

[0076] In this invention, feedback specifically refers to the data transfer and interaction mechanism within the coupled model. Specifically, it means returning the surface water-groundwater exchange volume calculated by the MODFLOW model to the river confluence calculation module of the SWAT-GL model. This exchange volume dynamically increases or decreases the river flow, thereby correcting the river flow value originally derived only considering surface hydrological processes.

[0077] In some implementations, bidirectional data exchange refers to the interaction between the SWAT-GL model and the MODFLOW model within each computation time step. Specifically, the SWAT-GL model provides the MODFLOW model with daily infiltration recharge (source and sink terms) and river level (boundary conditions); the MODFLOW model then calculates the surface water-groundwater exchange rate based on this and feeds it back to the SWAT-GL model to correct for river flow. This iterative data transfer constitutes the bidirectional coupling of the models.

[0078] The surface water-groundwater integrated simulation method with coupled glacier modules provided by this invention achieves dynamic bidirectional coupling between the SWAT-GL and MODFLOW models through daily time steps. SWAT-GL transmits net infiltration recharge (derived from rainfall, snowmelt, and glacial meltwater) and river water level time series to MODFLOW; MODFLOW, in turn, feeds back the simulated surface water-groundwater exchange, groundwater level, and groundwater evaporation to SWAT-GL for accurate correction of river flow and evapotranspiration processes. In baseflow simulation, the original empirical allocation method of SWAT is abandoned in favor of MODFLOW's physical mechanism-based groundwater dynamics simulation, significantly improving the simulation accuracy and physical realism of groundwater contribution. Through the bidirectional coupling mechanism, the model can dynamically simulate the recharge-discharge relationship and state switching between groundwater and river water under glacial meltwater input conditions, overcoming the limitations of traditional unidirectional coupling models. Meanwhile, this invention explicitly incorporates glacier and snow accumulation processes into the watershed recharge module, and for the first time constructs a complete cycle chain of ice and snow-surface water-groundwater, significantly improving the simulation accuracy of total runoff, baseflow segmentation, and groundwater storage changes. It also enables quantitative analysis of the respective recharge contributions of glacier meltwater and snowmelt, thereby supporting a comprehensive assessment of the response of climate change-glacier retreat-groundwater system and providing a scientific basis for water resource management and policy formulation in cold regions.

[0079] In some embodiments, the daily effective precipitation is obtained by summing the rainfall, the snowmelt, and the glacier meltwater after deducting the daily snowfall. The specific calculation formula is as follows:

[0080] ;

[0081] In the formula: Daily effective precipitation For rainfall, This refers to the amount of water from snowmelt. This refers to the amount of glacial meltwater. This represents the amount of snowfall that day.

[0082] Based on the foregoing embodiments, in some embodiments, the glacier remote sensing data includes glacier thickness data and glacier area data; the glacier meltwater volume in step S120 is dynamically calculated by introducing elevation zone division and glacier annual scale evolution mechanism, which may specifically include the following steps S121 to S123:

[0083] Step S121: Divide the glacier region of the hydrological response unit into multiple elevation zones according to altitude.

[0084] Step S122: Calculate the glacier melting rate daily within each elevation zone, and calculate the glacier meltwater volume by combining the glacier sublimation rate, glacier accumulation rate, and refreezing factor of the melt.

[0085] Step S123: At the end of each glacier year, update the glacier thickness and glacier area of ​​each elevation zone according to the annual glacier water equivalent change, and update the range of the glacier region if there is an ice-free elevation zone where the glacier thickness is reduced to zero.

[0086] In some embodiments, the formula for calculating the glacier melting rate is:

[0087] ;

[0088] In the formula: For the rate of glacier melting, The highest temperature of the day, This refers to the glacier melting threshold temperature. and These are glacier coverage area and snow cover area, respectively; among which, glacier melting factor... The calculation formula is: ; , , representing the maximum and minimum glacier melting factors within the year, respectively, and t represents day t.

[0089] The formula for calculating the amount of glacial meltwater is as follows:

[0090] ;

[0091] In the formula: It is the amount of glacial meltwater. It is the glacial meltwater volume on day t-1. It is the rate of glacier melting. It is the rate of glacial sublimation. It is the rate of glacier accumulation. The refreezing factor for the melt.

[0092] In this invention, high-resolution remote sensing data (glacier thickness and glacier area data) and field monitoring data (meteorological data monitored by meteorological stations) are introduced and combined with process models to focus on simulating the water-heat dynamic evolution process of solid water bodies in glaciers and snow cover. In the calculation of watershed energy and water balance, this invention plays a role in connecting the relationship between changes in precipitation, glacier and snow cover stock and ice melt and snowmelt runoff, revealing the contribution of glacier and snowmelt changes to surface water resources.

[0093] In some embodiments, the snowmelt volume is calculated using the following process:

[0094] The snowmelt volume was calculated based on the day-degree factor method.

[0095] ;

[0096] In the formula: SMF represents the snowmelt water volume, and SMF represents the snowmelt rate. The percentage of snow cover. Snow surface temperature The highest temperature, This represents the snow melting temperature threshold.

[0097] In some embodiments, calculating the surface runoff based on the daily effective precipitation includes:

[0098] When the daily effective precipitation is greater than the initial loss At that time, the formula for calculating the surface runoff is: When the daily effective precipitation is less than or equal to the initial loss hour, ;

[0099] in, Daily effective precipitation; Surface runoff; initial loss The relationship between the potential water storage capacity S and the water storage capacity S is satisfied. , Empirical coefficients; the relationship between the potential water storage capacity S and the number of curves CN corresponding to the target watershed. ).

[0100] In some embodiments, the source and sink terms of an aquifer element are calculated using the following formula:

[0101] ;

[0102] ;

[0103] In the formula, For the source and sink terms of aquifer units, This is the daily infiltration replenishment amount. For the thickness of the aquifer, Surface runoff, To retain the amount of evaporation.

[0104] In some embodiments, the formula for calculating the surface water-groundwater exchange volume is:

[0105] ;

[0106] In the formula: The river level output by the SWAT-GL model. The groundwater head calculated for the cell in the MODFLOW model. is the hydraulic conductivity of the aquifer.

[0107] The following will describe an exemplary application of the embodiments of the present invention in a practical application scenario.

[0108] To address the current lack of technology in glacier basin hydrological simulation that makes it difficult to co-depict glacier processes and groundwater dynamics, this paper proposes a deep coupling of the SWAT-GL model (i.e., the SWAT model integrating glacier modules), which can accurately calculate glacier mass balance and simulate the glacier ablation-accumulation evolution process, with the MODFLOW model, which can finely describe the distribution of groundwater flow field in three-dimensional space and the groundwater recharge-runoff-discharge process. This will construct a complete, parameter-coordinated, and process-linked surface water-groundwater coupled modeling system suitable for glacier basins, filling the technical gap in the integrated simulation of glacier processes and groundwater systems, and realizing a holistic representation of the hydrological system of glacier basins.

[0109] The aforementioned coupled modeling system, by strengthening the dynamic correlation between glacial meltwater generation and transport processes and surface water runoff evolution and groundwater recharge processes, accurately quantifies the proportion of glacial meltwater in the total watershed runoff and the impact of glacial meltwater on surface water-groundwater exchange. It effectively improves the analytical accuracy of the runoff composition structure of glacial watersheds, the simulation accuracy of groundwater recharge and intensity, and the prediction accuracy of changes in total water resources and the evolution of spatiotemporal distribution patterns under the background of climate change, providing reliable technical support for the study of the evolution law of water resources in glacial watersheds.

[0110] By leveraging the multi-process simulation capabilities of this coupled modeling system, the impact mechanism of glacial meltwater changes on surface water-groundwater exchange flux, groundwater level dynamics, and groundwater storage evolution under the background of glacial retreat is clearly revealed. This provides a scientific model tool for water resource assessment, water resource development and utilization planning, and ecological water security scheme formulation in glacial watersheds, helping to address the challenges of climate change to water resource security in glacial watersheds.

[0111] This embodiment provides a surface water-groundwater coupling modeling method that considers glacier evolution, including the following steps:

[0112] Step 1, Effective Precipitation and Runoff Calculation: The SWAT-GL module is used to calculate the rainfall, snowmelt and glacier meltwater, and the daily effective precipitation is obtained after deducting the new snowfall of the day; the daily effective precipitation is allocated to the daily surface runoff, initial loss and daily infiltration recharge; among them, the surface runoff is calculated using the curve number method, and the infiltration part enters the groundwater module.

[0113] Step 2, Infiltration and River Level Transfer: The daily infiltration recharge calculated by SWAT-GL is converted into the source and sink terms of the aquifer unit, and the simulated river level is input into MODFLOW as the river boundary condition.

[0114] Step 3, Groundwater Dynamics Calculation: In the MODFLOW module, based on the three-dimensional groundwater flow equation and combined with aquifer parameters, the groundwater head, recharge and discharge are calculated, and the surface water-groundwater exchange flow, groundwater recharge and groundwater discharge are further calculated.

[0115] Step 4, Two-way feedback mechanism: The surface water level changes contributed by glaciers, snowmelt, and rainfall calculated by SWAT-GL are transmitted to MODFLOW to calculate the groundwater level. The recharge and discharge flow rate W of the surface water-groundwater exchange output by the MODFLOW module is fed back to the SWAT-GL river network water balance to realize effective precipitation, runoff, infiltration, and dynamic two-way exchange between groundwater and rivers.

[0116] Step 5: Through the calculation and exchange of daily time steps, establish an integrated water cycle simulation system covering snow cover, glaciers, precipitation, surface water, and groundwater, and obtain results including the evolution of total runoff, baseflow, groundwater level, and groundwater storage.

[0117] The surface water-groundwater integrated simulation system provided in this embodiment adopts a modular modeling + dynamic coupling strategy, and is divided into three sub-modules:

[0118] 1. Glacier and Snow Accumulation Module

[0119] This embodiment introduces high-resolution remote sensing data (glacier thickness and glacier area data) and field monitoring data (meteorological data monitored by meteorological stations), and combines them with a process model to focus on simulating the water-thermal dynamic evolution process of solid water bodies such as glaciers and snow cover. It plays a role in connecting the relationship between precipitation, changes in glacier and snow cover stock and ice melt and snowmelt runoff in watershed energy and water balance calculations, and reveals the contribution of glacier and snowmelt changes to surface water resources.

[0120] Glacier Section: Glacier melt and accumulation are calculated in each Hydrological Response Unit (HRU). Within specific hydrological response units, glacier mass balance calculations and glacier evolution models are performed. Glacier meltwater volume for each elevation zone (ES) is calculated daily using the following formula:

[0121] ;

[0122] In the formula: It represents the amount of glacial meltwater (mm). It represents the glacial meltwater volume (mm) on day t-1. It is the glacier melting rate (mm / day). It is the glacier sublimation rate (mm / day). It is the glacier accumulation rate (mm / day). It is the refreezing factor of the melt, a variable calibration parameter that can be used to reduce high melt rates.

[0123] Glacier melting rate The calculation formula is:

[0124] ;

[0125] In the formula: This represents the highest daily temperature (°C). The threshold temperature for glacier melting (°C) is given. The value represents the glacier melting factor (mm / ℃·day). and These are the areas covered by snow and glaciers, respectively.

[0126] It should be noted that the glacier will only begin to melt when the highest temperature of the day reaches the critical threshold temperature and the glacier HRU is not completely covered by snow.

[0127] Glacier melting factor The annual variation of follows a sine function, and the calculation formula is as follows:

[0128] ;

[0129] In the formula: and denoted as the maximum glacier melting factor (mm / ℃·day) and the minimum glacier melting factor (mm / ℃·day) within the year, respectively, where t is the day t.

[0130] In theory, the temperature factor of ice is usually higher than that of snow. If the diurnal factor of snow exceeds that of ice, the model will automatically correct itself and apply the diurnal factor of snow to ice as well, in order to maintain the physical relationship.

[0131] The glacier evolution model transforms interannual glacier mass balance changes into spatially distributed changes in glacier thickness and area. On a time scale, glacier evolution is updated according to the glacier year (October 1 – September 30 of the following year), synchronized with the mass balance calculation, and called at the end of each glacier year.

[0132] In this embodiment, the glacier volume is estimated from the glacier area, and the calculation formula is as follows:

[0133] ;

[0134] In the formula: Annual total glacier volume change (m) 3 A represents the glacier area (m²). 2 ), This represents the annual variation in glacial water equivalent (mm).

[0135] here, Parameterization is an empirical relationship used to describe the vertical distribution characteristics of ice thickness variations. At low altitudes, ablation is strongest, resulting in significant ice thinning; at high altitudes, the ice thickness is reduced little or even positively, as the ice thickness approaches the accumulation zone.

[0136] The elevation of each elevation segment is normalized to the range of 0 to 1.

[0137] ;

[0138] In the formula: This is the elevation of the highest point of the glacier. This is the elevation of the lowest point of the glacier. The actual elevation of each ES; The normalized elevation for each ES.

[0139] Glaciers are categorized into three types based on size (large, medium, and small), each using different coefficients a, b, c, and y. Here, 'a' is a horizontal translation factor used to change the starting point of the curve, aligning different glacier elevation ranges; 'b' is a linear term coefficient, controlling the linear trend of ice thickness variation with elevation; 'c' is a constant term representing the baseline offset of ice thickness variation; and 'y' is a curve shape exponent, controlling the degree of non-linear curvature in the overall relationship and determining the intensity of variation in low-elevation areas (ablation zones). These coefficients are specifically categorized into three types, with different coefficients used for glaciers of different sizes. The formula for calculating normalized ice thickness variation is as follows:

[0140] ;

[0141] In the formula: To normalize the ice thickness variation, it indicates which part of the ice thickness varies the most.

[0142] according to Parametric method, mass balance module calculation The volume is consistent with the volume obtained from the relative ice thickness variation in each elevation zone, therefore:

[0143] ;

[0144] In the formula: As a scaling factor, the relative height distribution ( The curve is converted into a true ice thickness change that conforms to the overall mass conservation law. Let be the area of ​​elevation zone i, and n be the total number of i.

[0145] In actual updates, the actual thickness change for each elevation band is as follows:

[0146] ;

[0147] In the formula: For ES i Ice thickness updated after one glacial year, ES i The thickness of the ice layer that was replenished after a glacial year, if If it is zero, then ES i Assuming to be ice-free, the extent of the glacier is updated accordingly.

[0148] Snow accumulation: Based on daily average temperature, precipitation is divided into rain and snow. The snowmelt temperature threshold is a key condition for snow melting. For calculating snowmelt water volume, the Snow Water Equivalent (SWE) is used to represent the amount of water stored in the snow, and its calculation formula is as follows:

[0149] ;

[0150] In the formula: The snow water equivalent (mm) on day t; For the first Snow water equivalent per day (mm); P is precipitation (mm); E is sublimation (mm); SM is snowmelt water volume (mm). Snowfall increases SWE, while sublimation and snowmelt consume SWE. This balance equation allows for dynamic updates to snow storage, ensuring a clear water source for snowmelt calculations.

[0151] Snow melting is assessed using the traditional degree-day method. When the air temperature exceeds a threshold temperature, the snow melts at a certain rate, as shown in the following formula:

[0152] ;

[0153] Where: SMF is the snow melting rate (mm / ℃·day); Snow cover percentage (%) Snow surface temperature (°C); The highest temperature (°C); This represents the snowmelt temperature threshold (°C). When the daily average temperature exceeds the threshold, the amount of snowmelt increases with the excess temperature, while also being constrained by the snow cover area.

[0154] Instead of being a fixed constant, it varies with the seasons. By associating the rate factor with the day number through a sine function, the model reflects the realistic characteristic of high rates in summer and low rates in winter, thereby improving the physical plausibility of the model.

[0155] In complex terrain, snow cover is not uniform across the watershed and must be described using empirical curves. Snow cover rate The calculation formula is:

[0156] ;

[0157] In the formula: To simulate the daily water content (mm) of snow cover; The snow depth threshold (mm) for 100% coverage is a watershed-level parameter. When this threshold is exceeded, the snow will cover the sub-watershed 100%. The threshold depth will depend on vegetation distribution, wind load on snow, wind scouring, interception and spatial redistribution of snow. and The parameters of the empirical curve determine the curve shape (affected by slope, wind force, and underlying surface type). A nonlinear function is used to reflect local snow cover, ensuring more realistic simulation results.

[0158] The final output of glacial meltwater and integral meltwater is transmitted to the surface runoff or infiltration process through HRU, and further fed back to the groundwater model MODFLOW, realizing a complete coupled closed-loop simulation of snow cover, glacial meltwater, surface water and groundwater.

[0159] 2. SWAT-GL module

[0160] It should be noted that the SWAT model divides the entire watershed into multiple sub-watersheds. Based on various combinations of soil type, land use patterns, and slope characteristics, each sub-watershed is further divided into one or more hydrological response units. Traditional conceptual models are applied to these units to estimate rainfall, followed by runoff calculations to obtain the outlet cross-sectional discharge. The SWAT model simulates precipitation runoff, soil water dynamics, and preliminary groundwater recharge. By integrating snow cover and glacier modules, it further enhances the dynamic simulation capabilities of snow and glacier meltwater processes and optimizes the interaction module between surface water and shallow groundwater.

[0161] In the SWAT model, the HRU is the basic unit for simulating soil moisture content, surface runoff, nitrogen content, and sediment yield. The SWAT model is driven by a water balance equation based on the water cycle:

[0162] ;

[0163] In the formula: This indicates the final soil water content (mm). This indicates the daily effective precipitation (mm). It represents surface runoff (mm). This indicates the evaporation rate (mm). This indicates the leakage of soil water into the shallow aquifer (mm). This indicates the amount (mm) of shallow groundwater flowing out into the river.

[0164] The formula for calculating the amount of glacial and snowmelt water that flows into the effective precipitation of the day is as follows:

[0165] ;

[0166] In the formula: Daily effective precipitation For rainfall, This refers to the amount of water from snowmelt. This refers to the amount of glacial meltwater. This represents the amount of snowfall that day.

[0167] Surface runoff was calculated using the SCS-CN curve number method, and the formula is as follows:

[0168] ;

[0169] In the formula: It represents surface runoff (mm). Initial loss (mm) indicates the portion that seeps or is trapped before the flow occurs. This represents the potential water storage capacity (mm), which is related to the soil's water storage capacity. S generally satisfies an empirical relationship, as shown in the following formula:

[0170] ;

[0171] The relationship between S and the number of curves CN is shown in the following formula:

[0172] ;

[0173] In the formula: CN is the curve number, which reflects soil type, land cover use and wetting conditions. The larger the CN, the stronger the runoff generation capacity.

[0174] When calculating surface runoff, if precipitation is low, it may be completely absorbed, resulting in no runoff. When precipitation exceeds the initial loss, the remaining portion is converted into surface runoff according to the SCS-CN formula. The entire process is strongly correlated with soil infiltration capacity and surface cover conditions.

[0175] The daily infiltration recharge is obtained through daily water balance, using the following formula:

[0176] ;

[0177] In the formula: The daily infiltration replenishment amount is (mm). This indicates the daily effective precipitation (mm). It represents surface runoff (mm). To retain evaporation (mm).

[0178] Daily infiltration recharge enters the soil moisture content stratification and is further manifested as soil evapotranspiration, infiltration into groundwater, or as delayed baseflow when the soil layer is saturated. The distribution of infiltration is determined by soil parameters (saturated hydraulic conductivity, field capacity, saturated water content, etc.).

[0179] 3. MODFLOW groundwater module

[0180] The MODFLOW model essentially solves for the three-dimensional unsteady flow equations of groundwater, as shown in the following formula:

[0181] ;

[0182] In the formula: h is the groundwater head (m). , , The anisotropic hydraulic conductivity (m / s) is given. For specific water storage ( W represents the source and sink terms of the aquifer unit, with recharge being positive and discharge being negative (m). 3 / s / m 3 Changes in water head are driven by both water-conducting capacity and recharge and discharge terms, simulating the spatiotemporal evolution of water volume in underground aquifers.

[0183] Source and sink terms of aquifer units Including precipitation infiltration recharge, groundwater evaporation, and surface water-groundwater exchange, the source and sink terms of an aquifer unit are calculated using the following formula:

[0184] ;

[0185] In the formula: This represents the daily infiltration replenishment rate (mm / day). The thickness of the aquifer is in meters (m).

[0186] Surface-groundwater exchange The interaction between the simulated river network module and groundwater is illustrated by the following formula:

[0187] ;

[0188] In the formula: The water level (m) is from the SWAT-GL model. The groundwater head (m) is the unit cell. The hydraulic conductivity of the aquifer (m) 2 / s).

[0189] The coupling employs a daily time-step exchange interface, establishing an interface file between the HRU and the MODFLOW grid. Surface water level changes, calculated by SWAT-GL and contributed by glaciers, snowmelt, and rainfall, are transmitted to the river section, flowing into the HRU and then into the river channel, forming the river network boundary conditions. In addition, stratigraphic attribute data such as permeability zoning, specific yield zoning, and aquifer top and bottom elevations are used as inputs to the MODFLOW model to calculate groundwater levels and groundwater discharge into the river, feeding back the water balance of the SWAT-GL channel.

[0190] Each module is loosely coupled through a data exchange interface, dynamically transmitting input and output data, and optimizing system response efficiency through daily time step iterations.

[0191] This invention achieves the simulation of the physical mechanisms and the integration of all elements of hydrological processes by establishing a daily dynamic bidirectional coupling between SWAT-GL and MODFLOW. Specifically, SWAT-GL provides MODFLOW with net infiltration recharge and channel water level boundaries; MODFLOW, in turn, provides feedback on exchange rates, groundwater levels, and evapotranspiration to correct for SWAT-GL's channel flow and evapotranspiration. MODFLOW's groundwater dynamics calculations replace SWAT's original empirical baseflow simulation, and through bidirectional coupling, dynamically characterizes the surface water-groundwater interaction driven by glacial meltwater. This invention explicitly integrates glacial and snow accumulation processes, constructing a complete cycle chain from glaciers to groundwater, thereby significantly improving the simulation accuracy of runoff, baseflow, and groundwater storage, and quantitatively distinguishing the contribution of different meltwater flows to groundwater recharge, providing a scientific basis for water resource management in response to climate change.

[0192] The following will describe an exemplary application of the embodiments of the present invention in another practical application scenario.

[0193] The target flow rate is the catchment area above a certain hydrological station (coordinates: ), with an area of ​​approximately 1.14 × 10 4 km 2 The area ranges in altitude from 2038 to 5780 m. It has a typical continental arid climate, with an average annual temperature of approximately -4 °C and an average annual precipitation of about 388 mm, 90% of which occurs between May and September. Runoff is primarily supplied by glacier and snowmelt, accounting for the vast majority of the annual runoff. Modern glaciers above 4500 m in elevation cover approximately 421 km². 2 It accounts for 3.7% of the drainage area; the permafrost area is 9447 km². 2 This accounts for over 80%. The multi-year average runoff is 10.31 × 10⁻⁶. 8 m 3 The flood season, from May to September, accounts for 80% of the total, while the dry season is from October to April of the following year.

[0194] Figure 2 The following is a detailed diagram of the GLSWATMOD model architecture provided in this embodiment of the invention, and the detailed creation process is as follows:

[0195] SWAT-GL model (i.e.) Figure 2 The SWAT model of the extended glacier module was established: By coupling the distributed watershed hydrological model SWAT (SWAT-GL) of the extended glacier module with the three-dimensional groundwater flow model MODFLOW, an integrated simulation of glacial meltwater, snowmelt, surface runoff, and groundwater recharge processes in a cold watershed was achieved. In the modeling stage, the SWAT model was first constructed based on meteorological data, DEM digital elevation model, land use, and soil type data. The upstream area of ​​the target watershed was discretized into 761 HRUs and 13 sub-watersheds. The glacier module was introduced, defining the glacier area and thickness, determining whether each HRU unit was glacialized, calculating glacial meltwater using the temperature index method, and combining it with the snow module to calculate snowmelt. A glacier evolution model was constructed, and the glacier volume V and area A were updated annually. Surface runoff, daily infiltration recharge, and river level were output. The runoff monitoring hydrological station is located in sub-basin 1. The daily runoff data of this hydrological station is used for the calibration period (i.e., January 1, 2005 - December 31, 2015) and the verification period (i.e., January 1, 2016 - December 31, 2020).

[0196] MODFLOW Model Establishment: A three-dimensional groundwater flow model was established using VisualMODFLOWFlex 6.1 software. Aquifer thickness and parameter partitioning were imported based on geological conditions to determine the spatial distribution of permeability coefficient and specific yield. The upstream region of the target watershed was used as the study boundary, the northwest as a constant outflow boundary, the north and south as non-flow boundaries, and the southeast as an inflow boundary. Boundary inflow and outflow fluxes were estimated using the Darcy cross section method and determined during calibration. Since SWAT-MODFLOW's simulation of surface water-groundwater interaction mainly occurs in rivers and unconfined aquifers, the aquifer was set as a single layer for parameter partitioning and model calibration. This model represents three-dimensional transient groundwater flow in heterogeneous and anisotropic porous media. The calibration and validation periods were January 1, 2005 to December 31, 2015, and January 1, 2016 to December 31, 2020, respectively.

[0197] GLSWATMOD Coupling: The coupling process operates on a daily time-step basis, with data transfer achieved through an interface file established between the HRU and MODFLOW grids. Surface water level changes calculated by SWAT-GL, influenced by the combined effects of glacial meltwater, snowmelt, and rainfall, are first transferred to the sub-basin river segments, then input to the HRU, and finally converge to form the river network boundary conditions. Simultaneously, groundwater parameters such as formation permeability coefficient, specific yield zoning, and aquifer top and bottom elevations are input into MODFLOW. Groundwater levels and their discharge into the river channels are calculated, and the results are fed back to the SWAT-GL river network water balance module. Throughout this process, the various model modules are loosely coupled via the interface program, ensuring dynamic exchange of input and output data and continuous updates through daily iterations to optimize system response efficiency.

[0198] Sensitivity analysis and parameter calibration of the surface water model were performed using the SUFI 2 algorithm in SWAT CUP software. This algorithm can simultaneously consider uncertainties in input data, model structure, and observation data, and reflects these uncertainties in the results through 95% confidence intervals. Based on existing research, 18 key parameters were selected, and each simulation was performed 1000 times with multiple iterations. The sensitivity ranking of runoff and snow / glacier parameters was determined using t-stat and p-values, and the parameter ranges were continuously adjusted during the iteration process. Finally, the same optimized parameters were used for both the SWAT and SWAT GL models. The top 10 most sensitive parameters for the watershed are shown in Table 1.

[0199] Table 1 Ranking of model parameter sensitivity

[0200] ;

[0201] Model performance was evaluated using various metrics, including Nash-Sutcliffe Efficiency (NSE) and correlation coefficient (R²). 2 Rm and root mean square error (RMSE). RMSE represents the difference between simulated and observed data; a smaller value indicates better simulation performance. 2 R describes the degree of correlation between observed data and simulated data. 2 The higher the absolute value, the stronger the correlation. NSE evaluates the simulation performance of the model; values ​​close to 1 indicate better model performance. The formulas for calculating each parameter are as follows:

[0202] ;

[0203] ;

[0204] ;

[0205] In the formula: and These are the observed and simulated runoff values ​​within time step i, respectively. and denoted as the observed average and simulated average of runoff within time step i, respectively, and n is the total number of data points.

[0206] Figure 3 The graph showing the comparison between simulated and observed runoff values ​​provided by this invention demonstrates that the GLSWATMOD model exhibits good simulation capabilities for runoff at the outlet of the watershed. The Nash efficiency coefficients during both the calibration period (NSE≈0.71) and the validation period (NSE≈0.65) meet the standards for hydrological models. The model can effectively reproduce seasonal runoff processes, such as the typical characteristics of spring thaw and summer floods, and the interannual flood peak strength trends are consistent. However, the flood peak is locally underestimated, and the performance declines during the validation period, indicating that the model's ability to reproduce extreme runoff events or climate change conditions still has room for improvement.

[0207] Figure 4 The comparison chart of glacial meltwater and snowmelt in the target watershed provided by this invention is from... Figure 4 The data shows that the annual variation trends of glacial meltwater and snowmelt in the basin are as follows: glacial meltwater is relatively stable, decreasing slightly year by year; snowmelt fluctuates significantly from year to year, which is the main driver of interannual differences. The annual average glacial meltwater is approximately 371 mm, and the annual average snowmelt is approximately 239 mm.

[0208] Figure 5 The evolution diagram of glacial water equivalent in the target watershed provided in the embodiments of the present invention shows that, in general, the reduction of glacial water equivalent (GWE) is more intense in low-altitude areas, resulting in a significant decrease in water storage, while the GWE is relatively stable in high-altitude areas, and is less affected by climate warming.

[0209] Figure 6 The spatial distribution of annual surface water-groundwater exchange in the target watershed provided in this embodiment of the invention shows that, spatially, the exchange is intense in the plains at lower altitudes. In low-altitude areas, the general trend is that groundwater replenishes surface water, while in high-altitude areas, the general trend is that surface water seeps into groundwater.

[0210] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

[0211] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of the invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of the invention, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the invention. The sequence numbers of the above-described embodiments of the invention are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0212] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another system, or some features may be ignored or not performed.

[0213] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included 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 surface water-groundwater integrated simulation method coupled with a glacier module, characterized in that, The method includes: Acquire meteorological data, soil data, land use data, and glacier remote sensing data for the target watershed; The acquired data are input into the SWAT-GL model to calculate the rainfall, glacial meltwater and snowmelt in each hydrological response unit within the target watershed on a daily basis, and to determine the daily effective precipitation in combination with the daily snowfall. Based on the daily effective precipitation, the surface runoff is calculated, and the daily infiltration recharge and river level are further calculated. The daily infiltration recharge is converted into source and sink terms for aquifer units, and the river level is input into the MODFLOW model as a river boundary condition. Combined with aquifer parameters, the groundwater head and surface water-groundwater exchange are calculated using the three-dimensional groundwater flow equation. The surface water-groundwater exchange volume is fed back into the SWAT-GL model to dynamically correct the river flow. The SWAT-GL model and the MODFLOW model exchange data bidirectionally through daily time steps to achieve coupled simulation of glacier-snow cover-surface water-groundwater. The daily effective precipitation is obtained by summing the rainfall, snowmelt, and glacier meltwater after deducting the daily snowfall. The specific calculation formula is as follows: In the formula: Daily effective precipitation For rainfall, This refers to the amount of water from snowmelt. This refers to the amount of glacial meltwater. This represents the amount of snowfall that day. The source and sink terms of an aquifer element are calculated using the following formula: ; In the formula, For the source and sink terms of aquifer units, This is the daily infiltration replenishment amount. For the thickness of the aquifer, Surface runoff, To retain evaporation; The formula for calculating the surface water-groundwater exchange rate is as follows: In the formula: The river level output by the SWAT-GL model. The groundwater head calculated for the cell in the MODFLOW model. is the hydraulic conductivity of the aquifer.

2. The method according to claim 1, characterized in that, The glacier remote sensing data includes glacier thickness data and glacier area data; the glacier meltwater volume is dynamically calculated by introducing elevation zone division and glacier annual scale evolution mechanism, specifically including: The glacier region of the hydrological response unit is divided into multiple elevation zones according to altitude; The glacier melting rate was calculated daily within each elevation zone, and the glacier meltwater volume was calculated by combining the glacier sublimation rate, glacier accumulation rate, and refreezing factor of the melt. At the end of each glacial year, the glacier thickness and glacier area of ​​each elevation zone are updated according to the annual glacier water equivalent change, and the extent of the glacier region is updated in the case of an ice-free elevation zone where the glacier thickness decreases to zero.

3. The method according to claim 2, characterized in that, The formula for calculating the glacier melting rate is as follows: ； In the formula: For the rate of glacier melting, The highest temperature of the day, This refers to the glacier melting threshold temperature. and These are glacier coverage area and snow cover area, respectively; among which, glacier melting factor... The calculation formula is: ; , These are the maximum and minimum glacier melting factors within the year, respectively, where t is day t. The formula for calculating the amount of glacial meltwater is as follows: ； In the formula: It is the amount of glacial meltwater. It is the glacial meltwater volume on day t-1. It is the rate of glacier melting. It is the rate of glacial sublimation. It is the rate of glacier accumulation. The refreezing factor for the melt.

4. The method according to claim 1, characterized in that, The amount of snowmelt water is calculated through the following process: The snowmelt volume was calculated based on the day-degree factor method. ； In the formula: SMF represents the snowmelt water volume, and SMF represents the snowmelt rate. The percentage of snow cover. Snow surface temperature The highest temperature, This represents the snow melting temperature threshold.

5. The method according to claim 1, characterized in that, The surface runoff calculated based on the daily effective precipitation includes: When the daily effective precipitation is greater than the initial loss At that time, the formula for calculating the surface runoff is: When the daily effective precipitation is less than or equal to the initial loss hour, ; in, Daily effective precipitation; Surface runoff; initial loss The relationship between the potential water storage capacity S and the water storage capacity S is satisfied. , Empirical coefficients; the relationship between the potential water storage capacity S and the number of curves CN corresponding to the target watershed. .

6. A coupled simulation system for implementing the method as described in any one of claims 1 to 5, characterized in that, include: The acquisition module is used to acquire meteorological data, soil data, land use data, and glacier remote sensing data for the target watershed. The calculation module is used to input various types of acquired data into the SWAT-GL model, calculate the rainfall, glacial meltwater and snowmelt of each hydrological response unit in the target watershed on a daily basis, and determine the daily effective precipitation by combining the daily snowfall; based on the daily effective precipitation, the surface runoff is calculated, and the daily infiltration recharge and river level are further calculated. The calculation module is also used to convert the daily infiltration recharge into the source and sink terms of the aquifer unit, and input the river water level as the river boundary condition into the MODFLOW model. Combined with the aquifer parameters, the groundwater head and surface water-groundwater exchange volume are calculated through the three-dimensional groundwater flow equation. The correction module is used to feed back the surface water-groundwater exchange volume to the SWAT-GL model to dynamically correct the river flow. The SWAT-GL model and the MODFLOW model exchange data bidirectionally through daily time steps to achieve coupled simulation of glacier-snow cover-surface water-groundwater.

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