General drainage basin non-point source nitrogen pollution simulation method and system

Abstract

The invention discloses a universal drainage basin non-point source nitrogen pollution simulation method and system, and the method comprises the steps: obtaining the type and model structure of a coupled hydrological model configured by a user through a universal interface provided by the system, and obtaining the basic information of a drainage basin configured according to a corresponding format requirement; obtaining drainage basin agricultural nitrogen input configured by a user through a universal interface, and extracting spatio-temporal characteristics of environmental surplus based on the drainage basin agricultural nitrogen input; hydrological process simulation information obtained through hydrological model calculation is read; under the driving of a hydrological process, simulating space-time dynamic change of drainage basin nitrogen on the basis of a nitrogen transport and transformation process description method and a parameterization scheme; and analyzing a simulation result, and identifying a high-risk time period and a high-risk area of the non-point source nitrogen pollution. The method has good compatibility for different types of basin conceptual hydrological models, and can conveniently realize accurate simulation of basin nitrogen space-time dynamic balance and river control section nitrate nitrogen concentration.

Description

Technical Field

[0001] The present invention belongs to the technical field of watershed water environment pollution prevention and management, and specifically relates to a universal watershed non-point source nitrogen pollution simulation method and system. Background Art

[0002] The nitrogen cycle is an important material guarantee for the healthy operation of ecosystems and the realization of ecological service functions. The development of industrialization has caused the cycle of nutrients such as nitrogen to greatly exceed the "safe operation range" of the earth system, causing a series of problems such as surface and groundwater pollution and the outbreak of blue algae blooms in lakes and reservoirs. At present, on a global scale, non-point source emissions from river basins have become the main source of nitrate and other nutrient pollution in surface water bodies. However, the non-point source material cycle in river basins is affected by many factors such as the geographical characteristics of the river basin, hydrological and meteorological conditions, and human activities, showing a high degree of mechanism complexity and spatiotemporal heterogeneity, making non-point source pollution prevention and control a bottleneck problem and global challenge for further improving the water environment of the river basin. The conceptual mechanism model of the river basin is a scientific summary and generalization of people's understanding of the laws of water-material cycle in the river basin. River basin models with different characteristics have been proposed one after another, and they have been continuously improved and expanded in terms of the spatiotemporal representativeness of river basin characteristics and the description of the water-energy-quality cycle mechanism of the river basin, providing a powerful support tool for river basin water science research and water resources and water environment management.

[0003] The migration process of non-point source nitrogen and other pollutants at the basin scale is mainly driven by the basin hydrological process, and complex biogeochemical transformations occur during the migration process. Therefore, the research and development of existing basin hydrological and water quality coupling simulation models are often based on a specific hydrological simulation platform or hydrological model structure to expand the water quality simulation module. Although this technical route can fully utilize the technical advantages of a specific hydrological simulation platform, the implementation and application of water quality simulation are often subject to the hydrological simulation platform (including its limitations in model generalization or data requirements), resulting in insufficient versatility. On the one hand, this lack of universality leads to a relatively single type of water quality simulation models to choose from. For example, among the 257 watershed water quality simulation research cases counted by Wellen et al. (Wellen, et al., Evaluation of the Current State of Distributed Watershed Nutrient Water Quality Modeling, Environ. Sci. Technol., 2015, 49, 3278–3290), about 80% of them used only five models (SWAT model, INCA model, AGNPS / AnnAGNPS model, HPSF model and HBV-NP / HYPE model). On the other hand, the lack of universality of watershed water quality models makes it impossible to fully utilize the existing watershed hydrological simulation basic platform, which seriously restricts the theoretical research and practical management of watershed non-point source pollution prevention and control.

[0004] In response to the above problems, there is an urgent need to develop a universal watershed water quality simulation method that is compatible with the model structure of different hydrological models and the generalized description of hydrological processes, so as to more conveniently achieve accurate simulation of the migration and transformation of pollutants such as non-point source nitrogen in the watershed, and guide the effective prevention and control of non-point source pollution risks in the watershed. Summary of the invention

[0005] Purpose of the invention: In view of the shortcomings of existing basin water quality simulation technology, the present invention proposes a universal basin non-point source nitrogen pollution simulation method, which has good compatibility with different types of basin conceptual hydrological models, and can conveniently realize the accurate simulation of the spatiotemporal dynamic balance of basin nitrogen and the nitrate nitrogen concentration in the river control section based on the existing hydrological simulation, thereby providing a scientific basis for the prevention and control of basin non-point source pollution.

[0006] Another object of the present invention is to provide a universal basin non-point source nitrogen pollution simulation system, computer equipment and computer storage medium.

[0007] Technical solution: In order to achieve the above-mentioned invention object, the present invention proposes a universal basin non-point source nitrogen pollution simulation method, which is based on a universal basin non-point source nitrogen pollution simulation system. The method comprises the following steps:

[0008] Step 1: Through the universal interface provided by the universal watershed non-point source nitrogen pollution simulation system, the type and model structure of the coupled hydrological model configured by the user are obtained, and the basic information of the watershed configured according to the corresponding format requirements are obtained, including: the specification of the distributed or semi-distributed model type; the input data of the basic information of the watershed configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the universal water storage body storage-flux interaction structure;

[0009] Step 2: Obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using a three-parameter empirical growth curve method, and identify the environmental surplus after nitrogen fertilizer is absorbed by crops and its spatiotemporal characteristics;

[0010] Step 3: Read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological process and intermediate state variable information;

[0011] Step 4: Driven by the hydrological process, based on the description method and parameterization scheme of nitrogen transport and transformation process, simulate the spatiotemporal dynamic changes of nitrogen in the basin, including: matching the basic information of the basin with the characteristic information of agricultural nitrogen source input to determine the nitrogen model structure; based on the nitrogen model structure, the spatiotemporal characteristics of agricultural nitrogen input in the basin, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, build a hydrological and water quality coupling model, and simulate the spatiotemporal dynamics of nitrogen in the basin;

[0012] Step five: Analyze the simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate ammonia concentrations in key sections of the river; identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

[0013] Furthermore, the types of hydrological models include fully distributed models and semi-distributed models. The generalized interface supports the configuration of watershed discretization schemes. For fully distributed models, regular grids are used as basic computing units for discretization. For semi-distributed models, sub-watersheds are used for spatial discretization, and hydrological response units are defined in the sub-watersheds according to the geographical landscape types.

[0014] The generalized interface supports configuration of structures and corresponding variable names of different hydrological models, and supports configuration of all conceptual water storage bodies and their input and output items contained in different hydrological models;

[0015] The basic information of the watershed includes one or more of elevation, flow direction, slope, land cover, and soil type.

[0016] Furthermore, the method of estimating crop nitrogen absorption by using an empirical growth curve method based on three parameters includes:

[0017] The theoretical nitrogen absorption of crops is calculated using the three-parameter empirical growth curve:

[0018]

[0019] help=(up1-up2)·e -up3·(ΔDS)

[0020] Where U P is the nitrogen absorption capacity of the crop after sowing, up1, up2, and up3 are three empirical parameters of the growth curve, and ΔDS is the number of days from the current calculation time to the sowing date;

[0021] Estimate the actual crop uptake by considering the limitations of soil moisture and nitrogen storage:

[0022] U3=min{U { ,f θ ·S N}

[0023]

[0024] Where U A is the actual nitrogen absorption, f θ is the soil moisture limiting factor, which is related to soil moisture content θ and wilting coefficient θ w Related, S N is the soil nitrogen storage.

[0025] Furthermore, the hydrological process simulation information calculated by the hydrological model is read, including:

[0026] According to the consensus that the hydrological process simulation information is stored in the network universal data format netCDF, the hydrological simulation information corresponding to the netCDF file is read by specifying the variable name in the universal interface file.

[0027] Furthermore, the basic information of the watershed is matched with the characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the hydrological process simulation information, the biogeochemical transformation process between different nitrogen forms and its generalized description method are determined, and a hydrological and water quality coupling model is constructed to simulate the spatiotemporal dynamics of nitrogen in the watershed, including:

[0028] According to the basic information of the watershed and the coupled hydrological model structure configured in step 1, match the model structure of nitrogen simulation, including the landscape type and its area proportion within the basic calculation unit, and the soil stratification setting;

[0029] After the nitrogen model structure is determined, the agricultural nitrogen source input of each soil layer water storage body is configured according to the results of the agricultural nitrogen source input characteristic analysis in step 2, and the initial value of the dissolved nitrogen concentration of each water storage body is given;

[0030] According to the input-output items of each water storage body configured in step 1, a nitrogen spatiotemporal dynamic simulation process is performed, wherein according to the mass balance principle, based on the hydrological process simulation information in step 3, the dissolved nitrogen undergoes storage-flux exchange with the water flow in the vertical direction and the horizontal direction, wherein the vertical direction refers to the hydraulic connection between different water storage bodies in the same basic calculation unit, and the horizontal direction refers to the hydraulic connection between water storage bodies in different calculation units;

[0031] According to the soil layer, the main forms of soil nitrogen are dissolved inorganic nitrogen DIN, dissolved organic nitrogen DON, solid and easily degradable organic nitrogen SON. a and non-degradable organic nitrogen SON i Four, establish the biogeochemical transformation processes between them, including: activation from non-degradable to easily degradable organic forms, mineralization from organic to inorganic forms, dissolution from easily degradable solid to dissolved forms, and denitrification of nitrate nitrogen under anaerobic conditions, and use reaction kinetics methods to quantitatively estimate the transformation amount;

[0032] The nitrogen form of the river water considered in each calculated river section is dissolved organic nitrogen (DON). w and dissolved inorganic nitrogen DIN w , while considering the photosynthetic absorption process and denitrification process in the river channel, and performing generalized calculations.

[0033] Furthermore, the reaction kinetics method is used to quantitatively estimate the conversion amount, including:

[0034] R 活化 Indicates the activation from non-degradable to readily degradable organic forms, R 矿化 Represents the mineralization from organic to inorganic forms, R 溶解 represents the dissolution from a readily degradable solid to a soluble state, R反硝化 It represents the denitrification of nitrate nitrogen under anaerobic conditions and is calculated as follows:

[0035] R 活化 =r degdt ·f st ·f sm ·S SONi

[0036] R 矿化 =r minrl ·f st ·f sm ·(S DiN +S SONa )

[0037] R 溶解 =r dissl ·f st ·f sm ·S SONa

[0038] R 反硝化 =r denis ·f st ·f sm ·f smc ·S DIN

[0039] In the formula, r degdt 、r minrl 、r dissl 、r denis Represents the conversion rate of each process, as a parameter introduced into the model; S SONi , S DON , S SONa , S DIN is the storage amount of nitrogen in various soils; st 、f sm 、f smc They are soil temperature influencing factor, soil moisture influencing factor and soil water and nitrogen concentration influencing factor;

[0040] Take U gpp represents the photosynthetic absorption process, R 河道反硝化 It represents the denitrification process in the river channel, and its generalized calculation method is as follows:

[0041] U gpp =U amax ·f GR ·(1-f LAI )

[0042] R 河道反硝化 =r deniw ·f wt ·f wnc

[0043] Where U amax is the maximum photosynthetic absorption; f GR is the photosynthetic radiation factor; f LAI is the canopy shading factor of river vegetation, r deniw is the river denitrification rate, used as a model parameter; f wt and f wnc are the influencing factors of river water temperature and river water nitrate nitrogen concentration respectively.

[0044] Furthermore, the high-risk periods are identified from the dynamic changes of nitrate concentrations in key sections of the river; high-risk areas are identified from the spatial distribution of nitrogen balance in the basin, including:

[0045] Based on the spatiotemporal dynamic simulation of nitrogen in the basin, continuous calculations are performed on a daily scale to provide continuous simulation results of nitrogen discharge from the basin's land surface to receiving water bodies and identify high-risk periods for non-point source nitrogen pollution;

[0046] Based on the output function of the dynamic intermediate state of nitrogen in the basin, including one or more of the crop nitrogen absorption, denitrification absorption, soil nitrogen storage, and land surface output with runoff, the spatial distribution and dynamic changes of the basin's nitrogen balance are simulated to identify high-risk sub-areas for non-point source nitrogen pollution.

[0047] The present invention also provides a universal basin non-point source nitrogen pollution simulation system, comprising:

[0048] The hydrological model and basin basic information configuration module is used to obtain the type and model structure of the coupled hydrological model configured by the user through a universal interface, and obtain the basin basic information configured according to the corresponding format requirements, including: the specification of the distributed or semi-distributed model type; the basin basic information input data configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the universal water storage body storage-flux interaction structure;

[0049] The watershed agricultural nitrogen feature extraction module is used to obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using the empirical growth curve method based on three parameters, and identify the environmental surplus and its spatiotemporal characteristics after nitrogen fertilizer is absorbed by crops;

[0050] The hydrological simulation information reading module is used to read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological process and intermediate state variable information;

[0051] The spatiotemporal simulation module of nitrogen in the watershed is used to simulate the spatiotemporal dynamic changes of nitrogen in the watershed driven by hydrological processes, based on the description method and parameterization scheme of nitrogen transport and transformation processes, including: matching basic information of the watershed with characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the simulation information of the hydrological process, determining the biogeochemical transformation process between different nitrogen forms and its generalized description method, constructing a hydrological and water quality coupling model, and conducting spatiotemporal dynamic simulation of nitrogen in the watershed;

[0052] The risk identification module is used to analyze simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate ammonia concentrations in key sections of rivers; and identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

[0053] The present invention also provides a computer device, comprising: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the generalized watershed non-point source nitrogen pollution simulation method are implemented as described above.

[0054] The present invention also provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the generalized method for simulating non-point source nitrogen pollution in a watershed as described above are implemented.

[0055] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0056] (1) Use the universal interface to configure the type and model structure of the coupled hydrological model, and configure the basic information of the basin's hydrological meteorology, geography, human activities, etc. according to the corresponding format requirements, so as to be compatible with basin hydrological models of different types and complexities. Make full use of the existing hydrological model platform and conveniently use its hydrological simulation information to perform spatiotemporal simulation of basin nitrogen dynamics, supporting detailed prevention and control of basin non-point source nitrogen pollution;

[0057] (2) Provide a description method and parameterization scheme for the nitrogen transport and transformation process, which can accurately describe the spatiotemporal impact of agricultural activities on nitrogen pollution in the watershed. In view of the difficulty in obtaining spatial information on crop planting structure, it is proposed to use the spatial distribution of crop rotation types and the types of crops in each type of rotation to fully characterize the spatial differences and interannual changes in crop planting structure;

[0058] (3) It provides a universal water quality simulation environment that can synchronously couple multiple hydrological models for cross-comparison to evaluate the impact of hydrological simulation on the simulation of non-point source nitrogen pollution in the watershed. A flexible parameterization scheme is adopted to fully characterize the spatial heterogeneity of watershed characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a general flow chart of the simulation method of watershed non-point source nitrogen pollution;

[0060] Figure 2 The basic situation of the watershed used in the embodiment;

[0061] Figure 3 The simulation results of coupling EcH2O-iso and mHM in the embodiment;

[0062] Figure 4 The simulation results and comparison of watershed nitrogen balance by coupling EcH2O-iso and mHM simulation in the example. DETAILED DESCRIPTION

[0063] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0064] The present invention provides a universal watershed non-point source nitrogen pollution simulation method, which is implemented based on a universal watershed non-point source nitrogen pollution simulation system. The universal watershed non-point source nitrogen pollution simulation system is a flexible and universal watershed non-point source nitrogen pollution simulation tool, hereinafter referred to as the system, which provides an interactive interface for hydrological models and data configuration, and provides a spatiotemporal dynamic change characterization and display function of nitrogen in the watershed according to input information. The method and system have good compatibility with different types of conceptual hydrological models of watersheds, and can conveniently realize the accurate simulation of the spatiotemporal dynamic balance of nitrogen in the watershed and the concentration of nitrate nitrogen in the river control section on the basis of existing hydrological simulation, thereby providing a scientific basis for the prevention and control of non-point source pollution in the watershed.

[0065] Reference Figure 1 , the method comprises the following steps:

[0066] Step 1: Configure the coupled hydrological model structure and basic basin information in the corresponding format.

[0067] This method is suitable for coupling different types of watershed hydrological models, including fully distributed and semi-distributed models. It can also adapt to the different requirements of different types of models in watershed discretization schemes and corresponding watershed basic information formats. The watershed discretization scheme is configured using the universal interface provided by the system. The fully distributed model uses regular grids as the basic calculation unit for discretization processing, while the semi-distributed model uses sub-basins for spatial discretization and defines hydrological response units in the sub-basins according to the geographical landscape type; at the same time, the basic information input data of the watershed is configured according to the corresponding format requirements, including elevation, flow direction, slope, land cover, soil type, etc.

[0068] This method is applicable to the different ways in which different models describe the generalization of the hydrological process in the watershed. This method considers the water bodies (i.e., conceptual water storage tanks) such as the vegetation canopy, surface, soil (divided into three layers) and groundwater in the basic calculation unit of the model and the water exchange between them in the vertical direction; in the horizontal direction, the water exchange between the basic units through the surface, soil and underground is considered. At the same time, the land surface runoff (three runoff components: surface runoff, soil flow and underground runoff) and river confluence processes are considered. In particular, for fully distributed simulations, this method can set up independent river confluence grids, so that river confluence calculations can be performed only between grids containing real rivers. When coupling a specific hydrological model, the structure of the model and the corresponding variable names are configured in the generalized interface.

[0069] This method proposes a universal storage-flux interaction structure to adapt to the differences in water exchange processes of different conceptual water storage bodies. This universal structure can consider all hydrological flux input and output methods, including input from the upper tank, output to the upper tank, input from the lower tank, output to the lower tank, lateral input from the same tank of the upstream calculation unit, and lateral output to the same tank of the downstream unit; at the same time, this universal structure can consider additional flux inputs (such as irrigation, inter-basin water transfer, etc.) and outputs (such as evapotranspiration, runoff, etc.). When coupling a specific hydrological model, all conceptual water storage bodies contained in the model are specified in the universal interface, and the input and output items of each water storage body are configured (specifying the variable name of each variable).

[0070] In the embodiment of the present invention, the method is used to realize the coupling of two basin hydrological models with different characteristics, namely the EcH2O-iso model and the mHM model (see Table 1 for the comparison of model structures), and a basin with an area of ​​99 km 2 A case study was conducted in the basin of . The basin terrain is mainly forest and agricultural land. This case study collected basic information such as basin terrain, land use, and soil characteristics. At the same time, daily meteorological data from 2010 to 2018 were collected. Daily flow and nitrate nitrogen concentration observation data from 2010 to 2018 were collected at the basin outlet hydrological station.

[0071] Table 1 Comparison of the structures of the basin hydrological models EcH2O-iso and mHM

[0072]

[0073]

[0074] The EcH2O-iso and mHM models used in this case are both grid-based distributed models, and the grid accuracy of the land surface hydrological simulation is set to 1×1km. The difference between the two is that the former uses a confluence simulation grid that matches the actual river network, that is, only when rivers appear is the river confluence and the river migration and transformation process of nitrate nitrogen considered; the latter uses a confluence spatial resolution of 2×2km to simulate river hydrological and water quality processes. Figure 2 The basic information of the watershed in the case application, where (a) is the digital elevation model - DEM (30-meter resolution), river network and outlet hydrological stations; (b) is the land cover type; (c) is the river simulation grid of EcH2O-iso based on the actual river network location; (d) is the 2×2 km simulation grid of the river in the entire mHM basin.

[0075] According to the respective structures of the hydrological models, basic conditions such as basin topography and geography are configured in the general interface, including spatial distribution information such as elevation (and the slope and flow direction information generated by it), land use, and soil type.

[0076] Step 2: Identify the spatiotemporal characteristics of agricultural nitrogen inputs and their environmental surpluses in the watershed.

[0077] The watershed agricultural information that this method needs to obtain includes the types of crops in the watershed and the sowing time, harvesting time, number of fertilizations, time of each fertilization, and amount of each fertilization, etc.

[0078] In view of the difficulty in obtaining the spatial distribution of crop planting structure in the basin and the large inter-annual variation, this method, based on the basin land use map, obtains the main crop types and rotation methods in different areas of the basin through field surveys and other means, and produces a "spatial distribution map of crop rotation types" and a "crop type lookup table" (defining the crop types and rotation order in each rotation type), thereby effectively considering the spatial differences and inter-annual variations of crop planting in the basin. Combined with the above-mentioned crop fertilization management information, the spatiotemporal characteristics of agricultural nitrogen input in the basin can be obtained.

[0079] In this case, the crops planted in the agricultural land in the basin are winter wheat and rapeseed. Since the agricultural management methods in the basin are similar and the agricultural land is relatively small, all agricultural land is classified into the same rotation type, that is, winter wheat and winter rapeseed. In this case, the fertilizer application of the two crops (158 and 182 kgNha respectively) is obtained. -1 yt -1 ), fertilization date, sowing and harvesting and other agricultural management information (see Table 2). At the same time, this method uses a three-parameter empirical growth function to describe the nitrogen absorption capacity of crops, and the calculation method is as follows:

[0080]

[0081] help=(up1-up2)·e -up3·(ΔSS)

[0082] Where U P The nitrogen absorption capacity after sowing (gNm -2 d -1 ), up1, up2, and up3 are the three empirical parameters of the growth curve, and ΔDS is the number of days from the current calculation time to the sowing date. The values ​​of up1, up2, and up3 parameters of the growth function for winter wheat and winter rapeseed in the basin of this case are shown in Table 2.

[0083] Table 2 Parameters of crop fertilization, field management and nitrogen absorption capacity in the case basin

[0084]

[0085] The actual amount of crop absorption is further limited by soil moisture and nitrogen storage:

[0086] U3=min{U { ,f θ ·S N}

[0087]

[0088] Where U A is the actual nitrogen absorption (gNm -2 d -1 ), f θ is the soil moisture limiting factor, which is related to soil moisture content θ and wilting coefficient θ w Related, S N is the soil nitrogen storage (gNm -2 ). The part after deducting the absorption of crops is the environmental surplus of nitrogen, which is also the direct cause of non-point source nitrogen pollution in the basin.

[0089] Step 3: Use the Network Common Data Format (netCDF) to read the hydrological simulation information.

[0090] All hydrological information calculated by the hydrological model is stored in the network universal data format - netCDF. This method reads the hydrological simulation information corresponding to the netCDF file through the variable names specified in the universal interface file. Therefore, the variable names in the netCDF file must correspond one-to-one to the variable names specified in the universal interface file.

[0091] The time series data obtained from the EcH2O-iso and mHM models include: (1) meteorological driving input data of the model, including precipitation, temperature, humidity, and solar radiation; (2) state variables and hydrological process fluxes calculated by the hydrological model, such as evapotranspiration, soil moisture dynamics in each layer, runoff composition, and river flow in each calculation period.

[0092] Step 4: Simulate the spatiotemporal dynamics of nitrogen in the watershed.

[0093] The nitrogen transport process in the basin is mainly driven by hydrological processes. Therefore, it is necessary to match the model structure of nitrogen simulation according to the basic information of the basin and the coupled hydrological model structure configured in step 1, including the landscape type (land use, soil type, etc.) and its area proportion within the basic calculation unit, soil stratification settings (number of layers and depth of each layer), etc.

[0094] After determining the nitrogen model structure, the agricultural nitrogen source input of each soil layer water storage body is configured according to the results of the agricultural nitrogen source input characteristic analysis in step 2 (generally allocated to the first and second layer soil water storage bodies at a given ratio). In addition, the initial value of the dissolved nitrogen concentration of each water storage body must be given, and a certain warm-up period is generally set in the simulation calculation to obtain a more reasonable initial value.

[0095] In the spatiotemporal dynamic simulation of nitrogen, according to the mass balance principle, based on the hydrological information in step 3, dissolved nitrogen undergoes storage-flux exchange with water flow in the vertical direction (hydraulic connection between different water bodies in the same basic calculation unit) and the horizontal direction (hydraulic connection between water bodies in different calculation units). This method assumes that all nitrogen input items entering the water body are completely mixed within the calculation period, so the dissolved nitrogen concentration of the water body output item is the nitrogen concentration of the water body at the end of the period.

[0096] While nitrogen is transported over the land surface of the basin, it also undergoes a complex biogeochemical transformation process. This method considers the main forms of soil nitrogen in the basin in each soil layer as dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), solid easily degradable organic nitrogen (SON), and nitrogen in the soil. a ) and non-degradable organic nitrogen (SON i ) and simulated the biogeochemical transformation processes between them, including activation (R 活化 , gNm -2 d -1 ), mineralization (R 活化 , gNm -2 d -1 ), dissolution (R 溶解 , gNm -2 d -1 ) and denitrification of nitrate nitrogen under anaerobic conditions (R 反硝化 , gNm-2 d -1 ), calculated as follows:

[0097] R 活化 =r degdt ·f st ·f sm ·S SoNi

[0098] R 矿化 =r minrl ·f st ·f sm ·(S DON +S SONa )

[0099] R 溶解 =r dissl ·f st ·f sm ·S SONa

[0100] R 反硝化 =r denis ·f st ·f sm ·f smc ·S DIN

[0101] In the formula, r degdt 、r minrl 、r dissl 、r denis Represents the conversion rate of each process (d -1 ), as a parameter introduced into the model; S SONi , S DON , S SONa , S DIN is the nitrogen storage capacity of various soils (gNm -2 );f st 、f sm 、f smc They are the soil temperature (st) influencing factor, soil moisture (sm) influencing factor and soil water N concentration (smc) influencing factor, and are calculated as follows:

[0102]

[0103] Where sm_sat is the saturated soil moisture content.

[0104] Non-point source nitrogen enters the river channel along with the hydrological process of the basin, and also undergoes transformation in the river channel. In this method, the nitrogen form of the river water body considered in each calculated river section is dissolved organic nitrogen (DON w ) and dissolved inorganic nitrogen (DIN w), taking into account the photosynthetic absorption process and denitrification process in the river. gpp , mgNm -2 d -1 ) mainly considers the photosynthesis of algae, which is closely related to the primary productivity of rivers. The generalized calculation method is as follows:

[0105] U gpp =U amax ·f GR ·(1-f LAI )

[0106] Where U amax is the maximum photosynthetic absorption (which can be directly determined based on measured data or used as a model parameter); in this embodiment, it is determined to be 283 mgNm based on the measured data of the case basin. -2 d -1 ;f GR is the photosynthetic radiation factor (the value range is [0, 1], obtained by normalizing the measured photosynthetically active radiation data); f LAI is the canopy shading factor of river vegetation (the value range is [0, 1], obtained by normalizing the measured leaf area index -LAI of the vegetation along the river). 河道反硝化 , mgNm -2 d -1 ) is calculated as follows:

[0107] R 河道反硝化 =r deniw ·f wt ·f wnc

[0108] In the formula, r deniw is the river denitrification rate (mgNm -2 d -1 ), as a model parameter for calibration; f wt and f wnc are the influencing factors of river water temperature and river water nitrate nitrogen concentration, and the estimation method is consistent with the above-mentioned soil temperature and concentration.

[0109] The method supports flexible parameterization schemes to fully characterize the spatial heterogeneity of watershed characteristics. The introduced model parameters can be classified according to watershed landscape types (such as land use type or soil type); in addition, watershed landscape types can be merged to reduce the number of parameters that need to be calibrated in the model (for example, land use types can be merged into agricultural and non-agricultural types). In the embodiment, the introduced parameter r degdt 、r minrl 、r dissl 、r denis and r deniwThey are all defined as land use dependent and further integrated into two categories: agricultural and non-agricultural. That is, the same process parameter is calibrated as two independent parameters under agricultural and non-agricultural land use.

[0110] This implementation case conducted a coupled simulation of basin hydrology and water quality by coupling the two hydrological models EcH2O-iso and mHM. Figure 3 The dynamic changes of nitrate nitrogen concentration simulated by the two coupling models at the outlet of the case basin during 2012-2018 and the comparison with the measured values. The upper inset shows the flow at the outlet of the basin, and the lower inset shows the simulation results of nitrate concentration. Figure 4 The results show that the nitrate nitrogen concentration at the outlet of the river simulated by the two coupling models has high accuracy (Kling-Gupta Efficiency coefficient KGE is above 0.70, and the deviation PBIAS is within ±11.5%); at the same time, the spatial and temporal distribution of each nitrogen balance item in the simulated basin is also very consistent.

[0111] Step 5: Identify high-risk periods and areas for non-point source nitrogen pollution.

[0112] Based on the spatiotemporal dynamic simulation of nitrogen in the watershed in step 4, this method is suitable for continuous calculations on a daily scale. Therefore, it can provide continuous simulation results of nitrogen discharge from land surfaces in the watershed to rivers and other receiving water bodies, thereby effectively identifying high-risk periods of non-point source nitrogen pollution.

[0113] This method can conveniently simulate the spatial distribution and dynamic changes of nitrogen balance in a watershed, and provide output functions of the intermediate states of nitrogen dynamics in the watershed (such as nitrogen absorption by crops / vegetation, absorption by denitrification, soil nitrogen storage, land surface output with runoff, etc.). These refined simulation information helps to identify high-risk sub-areas for non-point source nitrogen pollution.

[0114] For these high-risk periods and high-risk areas, this method can be used to evaluate the improvement effect of non-point source nitrogen pollution in the basin under different control measures, and provide a scientific basis for refined prevention and control in the basin.

[0115] from Figure 3 The daily dynamic variation pattern of nitrate nitrogen concentration at the outlet of the basin shows that the nitrate nitrogen concentration in the surface water of the case basin shows significant seasonal variation. The high concentration generally occurs from December to May, reaching about 4 mgNl -1At the same time, the seasonal pattern of concentration is highly consistent with the seasonal variation of flow. This is because the nitrogen enrichment in the basin is mainly driven by the strong hydrological process in the rainy season, and is discharged from the land to the river water. It can be seen that the high-risk period for non-point source nitrogen pollution in the case basin is the rainy season or flood period when the hydrological process is more active. Figure 4 The results of nitrogen spatial distribution in the basin show that the nitrogen enrichment and non-point source nitrogen pollution in the basin show significant spatial heterogeneity. Due to the influence of human agricultural activities, the nitrogen level in the basin is much higher in agricultural land than in forest areas, so these areas are also high-risk areas for non-point source nitrogen pollution in the basin.

[0116] This case shows that the basin nitrogen simulation method provided by the present invention can adapt well to different hydrological model structures, and can accurately simulate the spatiotemporal dynamic changes of basin nitrogen. Therefore, this method provides a flexible and universal basin non-point source nitrogen pollution simulation tool, which can provide a scientific basis for the comprehensive assessment of basin water quantity and water quality, and provide strong technical support for the research and refined prevention and control of basin non-point source nitrogen pollution.

[0117] Based on the same technical concept as the method embodiment, the present invention also provides a universal basin non-point source nitrogen pollution simulation system, including:

[0118] The hydrological model and basin basic information configuration module is used to obtain the type and model structure of the coupled hydrological model configured by the user through a universal interface, and obtain the basin basic information configured according to the corresponding format requirements, including: the specification of the distributed or semi-distributed model type; the basin basic information input data configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the universal water storage body storage-flux interaction structure;

[0119] The watershed agricultural nitrogen feature extraction module is used to obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using the empirical growth curve method based on three parameters, and identify the environmental surplus and its spatiotemporal characteristics after nitrogen fertilizer is absorbed by crops;

[0120] The hydrological simulation information reading module is used to read the hydrological process simulation information calculated according to the hydrological model through the universal interface file, including meteorological driving data, hydrological process and intermediate state variable information;

[0121] The spatiotemporal simulation module of nitrogen in the watershed is used to simulate the spatiotemporal dynamic changes of nitrogen in the watershed driven by hydrological processes, based on the description method and parameterization scheme of nitrogen transport and transformation processes, including: matching basic information of the watershed with characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the simulation information of the hydrological process, determining the biogeochemical transformation process between different nitrogen forms and its generalized description method, constructing a hydrological and water quality coupling model, and conducting spatiotemporal dynamic simulation of nitrogen in the watershed;

[0122] The risk identification module is used to analyze simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate ammonia concentrations in key sections of rivers; and identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

[0123] It should be understood that the universal watershed non-point source nitrogen pollution simulation system in the embodiment of the present invention can implement all the technical solutions in the above-mentioned method embodiment, and the functions of its various functional modules can be specifically implemented according to the methods in the above-mentioned method embodiments. The specific implementation process can refer to the relevant description in the above-mentioned embodiments, which will not be repeated here.

[0124] The present invention also provides a computer device, comprising: one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the generalized watershed non-point source nitrogen pollution simulation method are implemented as described above.

[0125] The present invention also provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the generalized method for simulating non-point source nitrogen pollution in a watershed as described above are implemented.

[0126] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices (systems), computer equipment or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0127] The present invention is described with reference to a flowchart of a method according to an embodiment of the present invention. It should be understood that each process in the flowchart and a combination of processes in the flowchart can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the process in the flowchart. Figure 1 A device that specifies functions in a process or multiple processes.

[0128] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A function specified in a process or multiple processes.

[0129] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 The steps of a specified function in a process or multiple processes.

Claims

1. A universal method for simulating non-point source nitrogen pollution in a watershed, characterized in that: The following steps are involved: Step 1: Through the universal interface provided by the universal watershed non-point source nitrogen pollution simulation system, the type and model structure of the coupled hydrological model configured by the user are obtained, and the basic information of the watershed configured according to the corresponding format requirements are obtained, including: the specification of the distributed or semi-distributed model type; the input data of the basic information of the watershed configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the universal water storage body storage-flux interaction structure; Step 2: Obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using a three-parameter empirical growth curve method, and identify the environmental surplus after nitrogen fertilizer is absorbed by crops and its spatiotemporal characteristics; Step 3: Read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological process and intermediate state variable information; Step 4: Driven by the hydrological process, based on the description method and parameterization scheme of nitrogen transport and transformation process, simulate the spatiotemporal dynamic changes of nitrogen in the basin, including: matching the basic information of the basin with the characteristic information of agricultural nitrogen source input to determine the nitrogen model structure; based on the nitrogen model structure, the spatiotemporal characteristics of agricultural nitrogen input in the basin, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, build a hydrological and water quality coupling model, and simulate the spatiotemporal dynamics of nitrogen in the basin; Step five: Analyze the simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate ammonia concentrations in key sections of the river; identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

2. The method according to claim 1, characterized in that The types of hydrological models include fully distributed models and semi-distributed models. The generalized interface supports the configuration of watershed discretization schemes. For fully distributed models, regular grids are used as basic calculation units for discretization processing. For semi-distributed models, sub-watersheds are used for spatial discretization, and hydrological response units are defined in sub-watersheds according to geographical landscape types. The generalized interface supports configuration of structures and corresponding variable names of different hydrological models, and supports configuration of all conceptual water storage bodies and their input and output items contained in different hydrological models; The basic information of the watershed includes one or more of elevation, flow direction, slope, land cover, and soil type.

3. The method according to claim 1, characterized in that Furthermore, the method of estimating crop nitrogen absorption by using an empirical growth curve method based on three parameters includes: The theoretical nitrogen absorption of crops is calculated using the three-parameter empirical growth curve: help=(up1-up2)·e -up3·(ΔDS) Where U P is the nitrogen absorption capacity of the crop after sowing, up1, up2, and up3 are three empirical parameters of the growth curve, and ΔDS is the number of days from the current calculation time to the sowing date; Estimate the actual crop uptake by considering the limitations of soil moisture and nitrogen storage: U3=min{U { ,f θ ·S N } Where U A is the actual nitrogen absorption, f θ is the soil moisture limiting factor, which is related to soil moisture content θ and wilting coefficient θ w About S. N is the soil nitrogen storage.

4. The method according to claim 1, characterized in that: Read the hydrological process simulation information calculated by the hydrological model, including: According to the consensus that the hydrological process simulation information is stored in the network universal data format netCDF, the hydrological simulation information corresponding to the netCDF file is read by specifying the variable name in the universal interface file.

5. The method according to claim 1, characterized in that Match the basic information of the watershed with the characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, build a hydrological and water quality coupling model, and conduct spatiotemporal dynamic simulation of nitrogen in the watershed, including: According to the basic information of the watershed and the coupled hydrological model structure configured in step 1, match the model structure of nitrogen simulation, including the landscape type and its area proportion within the basic calculation unit, and the soil stratification setting; After the nitrogen model structure is determined, the agricultural nitrogen source input of each soil layer water storage body is configured according to the results of the agricultural nitrogen source input characteristic analysis in step 2, and the initial value of the dissolved nitrogen concentration of each water storage body is given; According to the input-output items of each water storage body configured in step 1, a nitrogen spatiotemporal dynamic simulation process is performed, wherein according to the mass balance principle, based on the hydrological process simulation information in step 3, the dissolved nitrogen undergoes storage-flux exchange with the water flow in the vertical direction and the horizontal direction, wherein the vertical direction refers to the hydraulic connection between different water storage bodies in the same basic calculation unit, and the horizontal direction refers to the hydraulic connection between water storage bodies in different calculation units; According to the soil layer, the main forms of soil nitrogen are dissolved inorganic nitrogen DIN, dissolved organic nitrogen DON, solid and easily degradable organic nitrogen SON. a and non-degradable organic nitrogen SON i Four, establish the biogeochemical transformation processes between them, including: activation from non-degradable to easily degradable organic forms, mineralization from organic to inorganic forms, dissolution from easily degradable solid to dissolved forms, and denitrification of nitrate nitrogen under anaerobic conditions, and use reaction kinetics methods to quantitatively estimate the transformation amount; The nitrogen form of the river water considered in each calculated river section is dissolved organic nitrogen (DON). w and dissolved inorganic nitrogen DIN w , while considering the photosynthetic absorption process and denitrification process in the river channel, and performing generalized calculations.

6. The method according to claim 5, characterized in that The reaction kinetics method is used to quantitatively estimate the conversion amount, including: R 活化 Indicates the activation from non-degradable to readily degradable organic forms, R 矿化 Represents the mineralization from organic to inorganic forms, R 溶解 represents the dissolution from a readily degradable solid to a soluble state, R 反硝化 It represents the denitrification of nitrate nitrogen under anaerobic conditions and is calculated as follows: R 活化 =r degdt ·f st ·f sm ·S SONi R 矿化 =r minrl ·f st ·f sm ·(S DON +S SONa ) R 溶解 =r dissl ·f st ·f sm ·S SONa R 反硝化 =r denis ·f st ·f sm ·f smc ·S DIN In the formula, r degdt 、r minrl 、r dissl 、r denis Represents the conversion rate of each process, as a parameter introduced into the model; S SONi , S DON , S SONa , S DIN is the storage amount of nitrogen in various soils; st 、f sm 、f smc They are soil temperature influencing factor, soil moisture influencing factor and soil water and nitrogen concentration influencing factor; Take U gpp represents the photosynthetic absorption process, R 河道反硝化 It represents the denitrification process in the river channel, and its generalized calculation method is as follows: U gpp =U amax ·f GR ·(1-f LAI ) R 河道反硝化 =r deniw ·f wt ·f wnc Where U amax is the maximum photosynthetic absorption; f GR is the photosynthetic radiation factor; f LAI is the canopy shading factor of river vegetation, r deniw is the river denitrification rate, used as a model parameter; f wt and f wnc are the influencing factors of river water temperature and river water nitrate nitrogen concentration respectively.

7. The method according to claim 1, characterized in that Identify high-risk periods from the dynamic changes in nitrate concentrations at key river sections; Based on the spatial distribution of nitrogen balance in the watershed, high-risk areas were identified, including: Based on the spatiotemporal dynamic simulation of nitrogen in the basin, continuous calculations are performed on a daily scale to provide continuous simulation results of nitrogen discharge from the basin's land surface to receiving water bodies and identify high-risk periods for non-point source nitrogen pollution; Based on the output function of the dynamic intermediate state of nitrogen in the basin, including one or more of the crop nitrogen absorption, denitrification absorption, soil nitrogen storage, and land surface output with runoff, the spatial distribution and dynamic changes of the basin's nitrogen balance are simulated to identify high-risk sub-areas for non-point source nitrogen pollution.

8. A universal basin non-point source nitrogen pollution simulation system, characterized in that: include: The hydrological model and basin basic information configuration module is used to obtain the type and model structure of the coupled hydrological model configured by the user through a universal interface, and obtain the basin basic information configured according to the corresponding format requirements, including: the specification of the distributed or semi-distributed model type; the basin basic information input data configured according to the model corresponding format requirements; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body based on the universal water storage body storage-flux interaction structure configuration; The watershed agricultural nitrogen feature extraction module is used to obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using the empirical growth curve method based on three parameters, and identify the environmental surplus and its spatiotemporal characteristics after nitrogen fertilizer is absorbed by crops; The hydrological simulation information reading module is used to read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological process and intermediate state variable information; The spatiotemporal simulation module of nitrogen in the watershed is used to simulate the spatiotemporal dynamic changes of nitrogen in the watershed driven by hydrological processes, based on the description method and parameterization scheme of nitrogen transport and transformation processes, including: matching basic information of the watershed with characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the simulation information of the hydrological process, determining the biogeochemical transformation process between different nitrogen forms and its generalized description method, constructing a hydrological and water quality coupling model, and conducting spatiotemporal dynamic simulation of nitrogen in the watershed; The risk identification module is used to analyze simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate ammonia concentrations in key sections of rivers; and identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

9. A computer device, characterized in that: include: one or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the generalized watershed non-point source nitrogen pollution simulation method as described in any one of claims 1-7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the generalized watershed non-point source nitrogen pollution simulation method as described in any one of claims 1 to 7 are implemented.

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