CN118246370A - Basin water sand model set evaluation method - Google Patents
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Abstract
The invention discloses a watershed water sand model set evaluation method, which comprises the following steps: constructing a basin foundation database, performing GIS rasterization treatment on the data, inputting a basin hydrological model taking grids as calculation units, performing evaporation, canopy interception, runoff production and confluence calculation, and simulating a hydrological process; calculating soil erosion in a river basin sand production model by adopting a corrected MMF model, an HSPF model, a DHSVM model, a SHETRAN model, a GUEST model and a WEPP model respectively; optimizing a plurality of soil erosion models by adopting Nash efficiency coefficient, relative peak value error, root mean square error and fitting goodness-of-fit coefficient index parameters, and analyzing the applicability of water sand models coupled with different soil erosion models in a research area; the invention realizes the coupling of the hydrologic model and a plurality of soil erosion sand production models, and has higher forecasting precision and popularization practicability.
Description
Technical Field
The invention relates to the technical field of soil erosion, hydrology and soil conservation, in particular to a watershed water sand model set evaluation method.
Background
Soil erosion has been one of the major factors affecting agricultural production, land degradation and ecological environmental deterioration. With the continuous increase of climate warming and human activity intensity, regional water and soil loss is more serious, especially serious water and soil loss caused by extreme storm events damages local agricultural production, and serious river channel reservoir accumulation is caused. Research at home and abroad shows that serious soil and water loss causes land resource degradation, grain production is threatened, river and lake water quality is deteriorated, river basin flood risk is aggravated and the like, and the social and economic development and ecological environment protection of the region are seriously affected. Therefore, the water and soil loss evaluation and simulation on the drainage basin scale can be further developed to provide a technical method for quantifying the space-time distribution characteristics of the drainage basin soil erosion and identifying the important erosion sand-producing hot spot areas, and provide a technological support for reasonably developing the comprehensive management of the drainage basin and realizing the sustainable development of the areas.
The soil erosion model is one of the key fields of soil erosion research, and is a main tool for simulating a historical soil erosion process, predicting a future soil erosion change trend and designing and evaluating water and soil loss treatment measures. At present, the common soil erosion models at home and abroad mainly comprise RUSLE, USLE, WEPP, SWAT, waTEM/SEDEM models and the like, but the applicability and the precision of different models in different areas are not high.
Disclosure of Invention
The invention provides a watershed water sand model set evaluation method, which aims to solve the problems of low applicability and low precision of a soil erosion model commonly used in the prior art in different areas.
The invention provides a watershed water sand model set evaluation method, which comprises the following steps:
Step 1, constructing a watershed basic database, wherein the data of the watershed basic database comprises precipitation data, vegetation types, coverage data, meteorological data, land utilization, DEM data and soil data, performing GIS rasterization on the data, and unifying the spatial resolution and the boundary of the data;
Step 2, inputting the data of the basin foundation database into a basin hydrological model which takes a grid as a calculation unit, carrying out evaporation, canopy interception, runoff generation and confluence calculation, and simulating a hydrological process;
Step 3, in the river basin soil erosion and sand conveying model, adopting six soil erosion models of a correction MMF model, an HSPF model, a DHSVM model, a SHETRAN model, a GUEST model and a WEPP model to carry out calculation of river basin sand production and sand conveying;
and 4, evaluating six soil erosion models by adopting Nash efficiency coefficient, relative peak value error, root mean square error and fitting goodness coefficient index parameters, and analyzing the applicability of water-sand process models coupled with different soil erosion models in a research area, so as to screen an optimal water-sand coupling model suitable for the research area.
Further, in the step2, the calculation of the produced flow adopts a double-layer produced flow mode, the loss of the ground surface evaporation and the loss of the canopy interception are calculated, the confluence of the slope surface and the ground surface of the river channel is calculated through a motion wave equation, and the underground confluence is calculated by simulating a linear reservoir method.
Further, in the step 3, the flow field erosion sand production model adopts a corrected MMF model to calculate soil erosion, and the method comprises the following steps according to a formula (1):
step 3.1, respectively calculating rainfall splash erosion, surface runoff scouring and sediment deposition to obtain net sand production according to different soil particle compositions: respectively calculating rainfall splashing amount F and runoff scouring amount H according to a formula (1) and a formula (2), and calculating to obtain sand production amount G of each space unit in a time step according to a formula (3):
（1）
（2）
（3）
In the method, in the process of the invention, Is the sand production amount; /(I)The rainfall splashing amount is used; /(I)The percentages of different textures in the soil respectively represent the percentage contents of clay grains, separation and sand grains of the surface soil; /(I)Is soil corrodibility; /(I)Is the earth surface coverage; /(I)The method comprises the steps of intercepting rainfall kinetic energy for rainfall kinetic energy, including canopy interception rainfall kinetic energy and penetration rainfall kinetic energy; /(I)The flushing amount is the runoff flushing amount; /(I)The soil particle dispersion rate; /(I)To accumulate the surface runoff; /(I)Is sediment deposition rate; s is the surface gradient;
step 3.2, calculating the sand transportation and calculating the runoff sand carrying capacity according to the formula (4)
（4）
In the method, in the process of the invention,Is a roughness factor reflecting spatial heterogeneity; /(I)Is single wide flow; /(I)And/>Is a model parameter, and the value is corrected according to the model.
Further, in the step 3, the flow field soil erosion sand production model adopts an HSPF model to calculate soil erosion, and simulates four processes of sediment deposition, splash erosion, transportation and scouring, and the method comprises the following steps:
Step 4.1, calculating sediment storage amount according to the formula (5)
（5）
In the method, in the process of the invention,And/>The sediment storage amounts of the current time step and the last time step are respectively; A proportion of sediment storage that decreases daily as a result of soil compaction; /(I) For the silt change parameter, the net external increase or decrease of silt caused by human activity or wind action is represented, and the decrease is represented by a negative value;
step 4.2, calculating the rainfall splash erosion amount according to the formula (6) ：
（6）
In the method, in the process of the invention,The rainfall splashing amount is used; /(I)Time step hours; /(I)For the proportion of the ground surface covered by snow and other coverings; /(I)For the management measure factor, it can be regarded as a water and soil conservation measure P factor in USLE; As a stripping coefficient, depending on the soil properties, the soil corrosiveness K factor in USLE; /(I) Is rainfall; Is a peeling index, depending on soil properties;
Step 4.3, calculating the sediment transport capacity according to the formula (7) ：
（7）
In the method, in the process of the invention,Is sediment transport capacity; /(I)Is a transfer coefficient; /(I)The depth of water storage for the ground surface; /(I)Is the surface runoff depth; /(I)Is a transport index;
Step 4.4, calculating the runoff scouring amount according to a formula (8) ：
（8）
In the method, in the process of the invention,The flushing amount is the runoff flushing amount; /(I)Is a scouring coefficient; /(I)Is the flush index.
Further, in the step 3, the soil erosion is calculated by a DHSVM model in the river basin soil erosion sand production model, and splash erosion, migration and runoff scouring are simulated, and the method comprises the following steps:
Step 5.1, calculating the splash erosion amount according to the formula (9) ：
（9）
In the method, in the process of the invention,The splash erosion amount; /(I)Is the splash erosion coefficient; /(I)Is a water depth correction coefficient; /(I)The soil ratio covered by the ground cover; /(I)The soil ratio covered by the canopy is the soil ratio; /(I)Squaring the momentum of penetrating rain drops; /(I)Squaring the momentum of the canopy raindrops;
step 5.2, calculating the runoff scouring amount according to the formula (10) ：
（10）
In the method, in the process of the invention,Is the runoff scouring amount; /(I)Is a function of soil cohesion for separation efficiency; /(I)Is the length of the grid; is the sedimentation rate of soil particles; /(I) Sand entrainment for runoff;
and 5.3, calculating sediment transport according to the relation between the runoff sand carrying capacity and the total erosion amount.
Further, in the step 3, the GUEST model in the river domain erosion sand production model performs soil erosion calculation, and the method comprises the following steps:
step 6.1, calculating the concentration of sediment generated by rainfall stripping based on rainfall intensity according to a formula (11) ：/>（11）
In the method, in the process of the invention,The concentration of sediment produced for rainfall stripping; /(I)Is associated with depth of flow/>The related rainfall corrosiveness; /(I)Is rainfall intensity; /(I)Is the proportion of soil not protected by vegetation or rock; /(I)The sedimentation rate is the average sedimentation rate of all suspended sediment;
step 6.2, calculating the sediment concentration generated by the runoff stripping based on the runoff kinetic energy according to the formula (12) ：
（12）
In the method, in the process of the invention,The concentration of sediment produced for runoff stripping; /(I)A ratio of the power of the runoff that is effective during the erosion process; /(I)For the proportion of soil completely immersed in runoff,/>；/>For average flow rate,/>；/>Is a gradient; /(I)And/>Wet densities of water and silt, respectively; /(I)Is the hydraulic radius; /(I)Is a form factor; /(I)Is a modification factor; /(I)Is the resistance coefficient/>, carried by soil to runoff；/>Is one/>To/>The numerical value is used for parameter calibration; /(I)Is a surface coverage factor; /(I)The power is the runoff power of the narrow ditches; /(I)For critical runoff power, get/>。
Further, in the step 3, a WEPP model is adopted in the river basin sand production model to calculate soil erosion, and the method comprises the following steps:
step 7.1, rate of transfer of erosion mud between the fine furrows to the fine furrows Calculated according to formula (13):
（13）
Wherein: is the corrosiveness coefficient between the fine furrows; /(I) Covering the vegetation with an impact factor; /(I)A ground cover influencing factor; Inter-fine erosion adjustment factors for which certain factors are ignored; /(I) Is the effective rainfall intensity; /(I)Is the fine groove spacing; /(I)Is the width of the narrow groove;
step 7.2, thin trench erosion or deposition Rate Calculated according to formula (14):
（14）
In the method, in the process of the invention, A thin trench ablation or deposition rate; /(I)Is the fine groove corrodibility coefficient; /(I)Fine erosion adjustment factors to ignore certain effects; /(I)Shear stress for water flow acting on soil particles; /(I)Critical shear stress for soil stripping; the sediment transporting capability of the water flow in the fine ditch;
Step 7.3, calculating sediment transport amount according to the continuity equation (15) in the sediment transport process ：
（15）
In the method, in the process of the invention,Sediment load of unit time unit width; /(I)Is the distance of a certain point along the downhill direction; /(I)The rate of transport of erosion silt between the fine furrows to the fine furrows; /(I)A thin trench ablation or deposition rate; /(I)And/>Is irrelevant and always positive; whileThe ablation is positive and the deposition is negative.
Further, in step 4, 3 evaluation indexes are adopted to evaluate each soil erosion model, and the method comprises the following steps:
step 8.1 calculates the nash efficiency coefficient NSE according to formula (16):
（16）
Wherein, Is the observed value of runoff or sediment; /(I)Model simulation values for runoff or sediment; /(I)Is the average value of the observed value of runoff or sediment;
Step 8.2, calculating the relative peak error RPE according to formula (17):
（17）
Wherein, Maximum value of observed value of runoff or sediment,/>Maximum value of model simulation value of runoff or sediment;
Step 8.3 calculates an absolute coefficient R 2 according to equation (18):
（18）
Wherein, The average value of model simulation values of runoff or sediment; the closer the two indexes NSE and R 2 are to 1, the higher the accuracy and fitting degree of the model are; /(I)The closer to 0, the higher the model fitting degree.
The invention has the following beneficial effects: according to the method for evaluating the watershed water-sand model set, the distributed water-sand model is constructed according to the yield confluence characteristic of the arid and semiarid regions, the respective coupling of the water-sand model and the soil erosion models is realized, the coupling simulation of the watershed water-sand, the soil erosion and the sand production process is carried out by taking the daily scale as the calculation step length, the modeling construction and the parameter localization research of the watershed water-sand-erosion coupling model are realized, and the optimal water-sand coupling model aiming at the research region is screened, so that a convenient visual approach is provided for the soil erosion sand production simulation of the arid and semiarid regions, and the method has popularization practicability.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic flow chart of a watershed water sand model set evaluation method in an embodiment of the invention;
FIG. 2 is a technical framework of a watershed water-sand model set evaluation method in an embodiment of the invention;
FIG. 3 is a simulation example of a watershed hydrological process in an embodiment of the invention;
FIG. 4 is a simulation result of a watershed water sand model in an embodiment of the invention;
Fig. 5 is a schematic diagram of a simulated spatial distribution of river basin soil erosion in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The following describes in detail the technical solutions provided by the embodiments of the present invention with reference to the accompanying drawings.
Referring to fig. 1, the method for evaluating a watershed water sand model set provided by the invention comprises the following steps:
Step 1, constructing a river basin multisource database, wherein the data of the river basin multisource database comprises precipitation data, vegetation index data, meteorological data, DEM data, soil data and hydrologic station monitoring sand conveying data, performing data GIS rasterization on the data, and unifying the spatial resolution and the spatial range of the data.
And 2, inputting the data of the drainage basin multisource database into a drainage basin hydrological model which takes a grid as a calculation unit, performing evaporation, canopy interception, runoff production and confluence calculation, and simulating a hydrological process.
Specifically, a double-layer flow production mode is adopted for calculating the flow, the loss of evaporation and canopy interception is considered, the confluence of the slope surface and the river surface is calculated through a motion wave equation, and the underground confluence is calculated by simulating a linear reservoir method.
And 3, respectively coupling the hydrologic model with a modified MMF (Morgan-Morgan-Finney) model, an HSPF (Hydrological Simulation Program-Fortran) model, a DHSVM (Distributed Hydrology Soil Vegetation Model) model 、SHETRAN（The sediment transport implemented in the Système Hydrologique Européen hydrological model） model, a GUEST (THE GRIFFITH University Erosion SYSTEM TEMPLATE) model and a WEPP (Water Erosion Prediction Project) model in the river basin sand production model to form a hydrologic-soil erosion-sediment transport multi-model coupling simulation system for calculating river basin hydrologic and sand production.
A specific implementation framework of the present invention is shown in fig. 2.
Specifically, in step 3, the hydrologic model is coupled with the modified MMF model for calculating soil erosion and sand production and delivery, specifically: the method comprises the following steps according to the formula (1):
Step3.1, calculating net sand production according to rainfall splash erosion, surface runoff scouring and sediment deposition with different textures: respectively calculating rainfall splashing amount F and runoff scouring amount H according to a formula (1) and a formula (2), and calculating to obtain net sand production amount G of each grid unit in a time step according to a formula (3):
（1）
（2）
（3）
In the method, in the process of the invention, To produce sand/>；/>For the rainfall splash/erosion amount；/>Is the percentage of different textures in soil/>Representing the percentage content of surface soil clay particles, separation and sand particles respectively; /(I)Is soil erodibility/>；/>Is the earth surface coverage/>；/>For kinetic energy of rainfall/>The method comprises the steps of intercepting rainfall kinetic energy and penetrating rainfall kinetic energy by a canopy; /(I)For runoff scouring volume/>；/>Is the soil particle dispersion rate/>；/>To accumulate the surface runoff/>；For sediment deposition rate/>S is the surface gradient.
Step 3.2, calculating the sand transportation and calculating the runoff sand carrying capacity according to the formula (4)
（4）
In the method, in the process of the invention,Is a roughness factor reflecting spatial heterogeneity; /(I)Is a single wide flow；/>And/>Is a model parameter, and the value is corrected according to the model.
And step 3, coupling the hydrologic model and the HSPF model for soil erosion and sand production and transportation calculation, and simulating four processes of sediment deposition, splash erosion, transportation and scouring, wherein the method comprises the following steps of:
Step 4.1, calculating sediment storage amount according to the formula (5)
（5）
In the method, in the process of the invention,And/>The sediment storage amounts of the current time step and the last time step respectively；/>A proportion of sediment storage that decreases daily as a result of soil compaction; /(I)For varying parameters of sedimentIndicating a net external increase or decrease in silt caused by human activity or wind action, and negative values are used to indicate a decrease.
Step 4.2, calculating the rainfall splash erosion amount according to the formula (6)：
（6）
In the method, in the process of the invention,For the rainfall splash/erosion amount；/>For time step hours；/>For the proportion of land covered by snow and other coverings; /(I)To support the management measure factors, it can be considered as water and soil conservation measure P factors in USLE; /(I)Is the peeling coefficientDepending on the nature of the soil, the soil corrosiveness K-factor in USLE can be considered; /(I)Is rainfall/>；/>The peel index depends on the soil properties.
Step 4.3, calculating the sediment transport capacity according to the formula (7)：
（7）
In the method, in the process of the invention,For sediment transport capacity/>；/>Is the transport coefficient/>；/>For the depth/>, of water storage on the ground surface；/>Is the depth of surface runoff/>；/>Is a migration index.
Step 4.4, calculating the runoff scouring amount according to a formula (8)：
（8）
In the method, in the process of the invention,For runoff scouring volume/>；/>Is a scouring coefficient; /(I)Is the flush index.
In the step 3, the hydrologic model is coupled with the DHSVM model and is used for soil erosion and sand production and transportation calculation, and splash erosion, transportation and runoff scouring are simulated, and the method comprises the following steps:
Step 5.1, calculating the splash erosion amount according to the formula (9) ：
（9）
In the method, in the process of the invention,For the splash erosion amount/>；/>For the splash erosion coefficient/>；/>Is a water depth correction coefficient; /(I)The soil ratio covered by the ground cover; /(I)The soil ratio covered by the canopy is the soil ratio; /(I)To penetrate the rain drop momentum square；/>Is the square of the momentum of the canopy raindrops/>。
Step 5.2, calculating the runoff scouring amount according to the formula (10)：
（10）
In the method, in the process of the invention,Is runoff scouring amount/>；/>Is a function of soil cohesion for separation efficiency; /(I)For grid length/>；/>Is the sedimentation rate of soil particles/>；/>For the sand-carrying capacity of runoff/>。
Step 5.3, calculating sediment transport according to the relation between the runoff sand carrying capacity and the total erosion amount
Step 3, coupling the hydrological model and the GUEST model for calculating soil erosion and sand production, and comprising the following steps:
step 6.1, calculating the concentration of sediment generated by rainfall stripping based on rainfall intensity according to a formula (11) ：/>（11）
In the method, in the process of the invention,Concentration of sediment produced for rain stripping/>；/>Is associated with depth of flow/>Related rainfall erodibility/>；/>For rainfall intensity/>；/>Is the proportion of soil not protected by vegetation or rock; /(I)For sedimentation rate/>I.e. the average sedimentation velocity of all suspended sediment.
Step 6.2, calculating the sediment concentration generated by runoff stripping based on the runoff kinetic energy according to the formula (12)：
（12）
In the method, in the process of the invention,Concentration of silt produced for runoff stripping/>；/>Ratio of runoff power effective in erosion process/>；/>To fully immerse the proportion of soil in the runoff,；/>Is the average flow rate/>，/>；/>Is a gradient; /(I)And/>Wet density of water and silt respectively/>；/>Is hydraulic radius/>；/>Is a form factor; /(I)Is a modification factor; /(I)Is the resistance coefficient/>, carried by soil to runoff；/>Is one/>To/>The numerical value of the two can be used for parameter calibration; /(I)Is a surface coverage factor; /(I)For the fine channel runoff power/>；/>Is critical runoff power/>Normally take。
And step 3, coupling the hydrological model with the WEPP model for calculating soil erosion and sand production, wherein the method comprises the following steps of:
step 7.1, rate of transfer of erosion mud between the fine furrows to the fine furrows Calculated according to formula (13):
（13）
In the method, in the process of the invention, Is the erodibility coefficient between fine furrows/>；/>Covering the vegetation with an impact factor; /(I)A ground cover influencing factor; /(I)Inter-trench erosion adjustment factors for which certain factors (e.g., stone coverage) are ignored; /(I)To be effective rainfall intensity/>；/>Is the fine groove spacing/>；/>Is the width of the narrow groove/>。
Step 7.2, thin trench erosion or deposition RateCalculated according to formula (14):
（14）
In the method, in the process of the invention, For thin trench ablation or deposition rate/>；/>Is the erodibility coefficient of the fine groove；/>Fine groove erosion adjustment factors for which certain effects (such as flow conditions) are ignored; /(I)Shear stress/>, for water flow acting on soil particles；/>Critical shear stress for soil stripping/>；/>To the sediment transport capacity of the water flow in the fine ditches。
Step 7.3, calculating sediment transport amount according to the continuity equation (15) in the sediment transport process：
（15）
In the method, in the process of the invention,Silt load per unit time per unit width ]；/>Distance of a point along downhill direction/>。/>Rate of transport of erosion mud and sand between the fine furrows to the fine furrows/>；/>For thin trench ablation or deposition rate/>。/>And/>Is irrelevant and always positive; and/>The ablation is positive and the deposition is negative.
And 4, screening the six soil erosion models by adopting Nash efficiency coefficient, relative peak value error, root mean square error and fitting goodness coefficient index parameters, and analyzing the applicability of the water sand models coupled with different soil erosion models in a research area, thereby screening the optimal water sand coupling models suitable for different research areas.
Specifically, in step 4, 3 evaluation indexes are adopted to evaluate each soil erosion model, and the method comprises the following steps:
Step 8.1, calculating a Nash efficiency coefficient NSE according to a formula (16):
（16）
Wherein, Is the observed value of runoff or sediment; /(I)Model simulation values for runoff or sediment; /(I)Is the average value of the observed value of runoff or sediment.
Step 8.2, calculating the relative peak error RPE according to formula (17):
（17）
Wherein, Maximum value of observed value of runoff or sediment,/>Is the maximum value of the model simulation value of runoff or sediment.
Step 8.3, calculating an absolute coefficient R 2 according to formula (18):
（18）
Wherein, Is the average value of model simulation values of runoff or sediment. The closer the two indexes NSE and R 2 are to 1, the higher the accuracy and fitting degree of the model are; /(I)The closer to 0, the higher the model fitting degree.
The river basin water sand model set evaluation method of the invention is described below with reference to specific cases.
S1, taking a loess plateau typical river basin as an example, collecting a river basin multisource database which comprises vegetation, soil, topography, land utilization, soil, weather, hydrology and sediment data.
Rainfall, runoff and sand content data of the river basin flood event come from yellow river hydrologic annual book issued by yellow river water committee of water conservancy department, and river basin flood element extract data are collected and arranged. The land utilization data adopts high-resolution remote sensing images, is classified by supervision and is verified in the open field, and the land utilization types comprise 6 types of forests, grasslands, bare lands or unused lands, cultivated lands, water bodies and urban lands. The soil type map acquires a 30m resolution soil attribute map by resampling according to 1:50 ten thousand soil data provided by a loess plateau data sharing center.
Specifically, arcGIS software is adopted to preprocess vegetation data, topographic data, soil data and the like, and the range of space data and the resolution of raster data are unified;
S2, data input is based on a distributed hydrological model of a double-layer runoff generating mode, steam distribution, canopy interception, runoff generating and converging calculation are carried out, and a hydrological process is simulated.
S3, calculating the flow domain sand production and the sand transportation by using six soil erosion models including an MMF model, an HSPF model, a DHSVM model, a SHETRAN model, a GUEST model and a WEPP model in the flow domain water sand model system.
As shown in table 1, a typical watershed water sand simulation was performed using different water sand coupling models.
TABLE 1 simulation results of model
As shown in fig. 3, fig. 3 (a) is a 1981-6-30 field flood event basin hydrologic process simulation example, and fig. 3 (b) is a 1988-7-15 field flood event basin hydrologic process simulation example. The model confluence module has better simulation result, the average Nash efficiency coefficient is 0.74, the average correlation coefficient is 0.83, and the average relative peak error is-20%. The watershed water-sand simulation results are shown in fig. 4, fig. 4 (a) is a 1981-6-30 field flood event watershed water-sand simulation result, and fig. 4 (b) is a 1988-7-15 field flood event watershed water-sand simulation result. MMF, DHSVM, WEPP has better simulation results, the average Nash efficiency coefficient is above 0.63, the average correlation coefficient is above 0.75, and the average relative peak error is within-30%; secondly, HSPF and GUEST, wherein the average Nash efficiency coefficient is between 0.5 and 0.6, and the average correlation coefficient is above 0.76; SHETRAN has the worst simulation result, but the relative peak error is-40%, and the model severely underestimates the sand delivery of the river basin.
To further illustrate the model simulation, a simulation result of the runoff amount and the sand conveying amount is shown by selecting two typical field processes of a river basin (1981-06-30 and 1988-07-15 are taken as examples). As can be seen from fig. 3, the simulation of the confluence process is consistent with the actual measurement, and is mainly reflected on the simulation of the flow, the peak shape and the peak value, the simulated runoff process is smoother than the actual measurement, and the peak value of the flood peak is smaller. The simulation accuracy of the sand production process is different due to the fact that different models are adopted, the MMF model and the HSPF, GUEST, WEPP model are better in simulation, and the DHSVM, SHETRAN model is adopted. In order to better show the simulation results of different models on soil erosion, fig. 5 shows the simulation results of different erosion models on a river basin, and according to the spatial distribution and the numerical value of erosion, it is not difficult to find that the simulation values of MMF and GUEST are relatively close, the simulation results of the HSPF model and WEPP model have similarity in space, but the simulation values of the DHSVM model show that the water and soil loss value of the river basin is higher.
From the above, the present invention realizes the coupling of the hydrologic model and the plurality of erosion models based on the GIS. Firstly, calculating the flow in a flow converging module by adopting a double-layer flow producing mode, considering the loss of evaporation and canopy interception, calculating the converging of a slope surface and the surface of a river channel through a motion wave equation, and selecting a linear reservoir method for simulation calculation by underground converging; secondly, calculating soil erosion in the sand production and delivery module based on six soil erosion simulation frameworks at home and abroad, namely correcting an MMF model, an HSPF model, a DHSVM model, a SHETRAN model, a GUEST model and a WEPP model; and finally, analyzing the applicability of the water-sand model coupled with different soil erosion modules in a research area by adopting index parameters such as Nash efficiency coefficient, average absolute error, root mean square error, fitting goodness coefficient and the like. The invention couples the hydrologic model and the soil erosion sand production model, fully considers the sand production process mechanisms of the sand production flows with different scales, can accurately simulate the runoff sand delivery quantity (runoff quantity and erosion sand production quantity/sand delivery quantity) of large and medium-sized watercourses, and has higher forecasting precision and popularization practicability.
The embodiments of the present invention described above do not limit the scope of the present invention.
Claims (8)
1. The river basin water sand model set evaluation method is characterized by comprising the following steps of:
Step 1, constructing a watershed basic database, wherein the data of the watershed basic database comprises precipitation data, vegetation types, coverage data, meteorological data, land utilization, DEM data and soil data, performing GIS rasterization on the data, and unifying the spatial resolution and the boundary of the data;
Step 2, inputting the data of the basin foundation database into a basin hydrological model which takes a grid as a calculation unit, carrying out evaporation, canopy interception, runoff generation and confluence calculation, and simulating a hydrological process;
Step 3, in the river basin soil erosion and sand conveying model, adopting six soil erosion models of a correction MMF model, an HSPF model, a DHSVM model, a SHETRAN model, a GUEST model and a WEPP model to carry out calculation of river basin sand production and sand conveying;
and 4, evaluating six soil erosion models by adopting Nash efficiency coefficient, relative peak value error, root mean square error and fitting goodness coefficient index parameters, and analyzing the applicability of water-sand process models coupled with different soil erosion models in a research area, so as to screen an optimal water-sand coupling model suitable for the research area.
2. The method for evaluating the river basin water and sand model set according to claim 1, wherein in the step 2, the calculation of the produced flow adopts a double-layer produced flow mode, the loss of surface evaporation and canopy interception is calculated, the surface confluence of a slope and a river channel is calculated through a motion wave equation, and the underground confluence is calculated by adopting a linear reservoir method.
3. The method for evaluating a set of river basin water-sand models according to claim 1, wherein the calculation of soil erosion by the river basin erosion sand production model in step3 using the corrected MMF model comprises the steps of:
step 3.1, respectively calculating rainfall splash erosion, surface runoff scouring and sediment deposition to obtain net sand production according to different soil particle compositions: respectively calculating rainfall splashing amount F and runoff scouring amount H according to a formula (1) and a formula (2), and calculating to obtain sand production amount G of each space unit in a time step according to a formula (3):
（1）
（2）
（3）
In the method, in the process of the invention, Is the sand production amount; /(I)The rainfall splashing amount is used; /(I)The percentages of different textures in the soil respectively represent the percentage contents of clay grains, separation and sand grains of the surface soil; /(I)Is soil corrodibility; /(I)Is the earth surface coverage; /(I)The method comprises the steps of intercepting rainfall kinetic energy for rainfall kinetic energy, including canopy interception rainfall kinetic energy and penetration rainfall kinetic energy; /(I)The flushing amount is the runoff flushing amount; /(I)The soil particle dispersion rate; /(I)To accumulate the surface runoff; /(I)Is sediment deposition rate; s is the surface gradient;
step 3.2, calculating the sand transportation and calculating the runoff sand carrying capacity according to the formula (4) ；
（4）
In the method, in the process of the invention,Is a roughness factor reflecting spatial heterogeneity; /(I)Is single wide flow; /(I)And/>Is a model parameter, and the value is corrected according to the model.
4. The method for evaluating a watershed water sand model set according to claim 1, wherein in the step 3, the watershed soil erosion sand production model adopts an HSPF model to calculate soil erosion, and simulates four processes of sediment deposition, splash erosion, transportation and scouring, and the method comprises the following steps:
Step 4.1, calculating sediment storage amount according to the formula (5) ；
（5）
In the method, in the process of the invention,And/>The sediment storage amounts of the current time step and the last time step are respectively; /(I)A proportion of sediment storage that decreases daily as a result of soil compaction; /(I)For the silt change parameter, the net external increase or decrease of silt caused by human activity or wind action is represented, and the decrease is represented by a negative value;
step 4.2, calculating the rainfall splash erosion amount according to the formula (6) ：
（6）
In the method, in the process of the invention,The rainfall splashing amount is used; /(I)Time step hours; /(I)For the proportion of the ground surface covered by snow and other coverings; /(I)For the management measure factor, it can be regarded as a water and soil conservation measure P factor in USLE; /(I)As a stripping coefficient, depending on the soil properties, the soil corrosiveness K factor in USLE; /(I)Is rainfall; /(I)Is a peeling index, depending on soil properties;
Step 4.3, calculating the sediment transport capacity according to the formula (7) ：
（7）
In the method, in the process of the invention,Is sediment transport capacity; /(I)Is a transfer coefficient; /(I)The depth of water storage for the ground surface; /(I)Is the surface runoff depth; /(I)Is a transport index;
Step 4.4, calculating the runoff scouring amount according to a formula (8) ：
（8）
In the method, in the process of the invention,The flushing amount is the runoff flushing amount; /(I)Is a scouring coefficient; /(I)Is the flush index.
5. The method for evaluating a watershed water sand model set according to claim 1, wherein the DHSVM model in the watershed soil erosion sand production model in step 3 performs calculation of soil erosion, simulates splash erosion, migration and runoff scouring, and comprises the following steps:
Step 5.1, calculating the splash erosion amount according to the formula (9) ：
（9）
In the method, in the process of the invention,The splash erosion amount; /(I)Is the splash erosion coefficient; /(I)Is a water depth correction coefficient; /(I)The soil ratio covered by the ground cover; /(I)The soil ratio covered by the canopy is the soil ratio; /(I)Squaring the momentum of penetrating rain drops; /(I)Squaring the momentum of the canopy raindrops;
step 5.2, calculating the runoff scouring amount according to the formula (10) ：
（10）
In the method, in the process of the invention,Is the runoff scouring amount; /(I)Is a function of soil cohesion for separation efficiency; /(I)Is the length of the grid; /(I)Is the sedimentation rate of soil particles; /(I)Sand entrainment for runoff;
and 5.3, calculating sediment transport according to the relation between the runoff sand carrying capacity and the total erosion amount.
6. The method for evaluating a set of river basin water-sand models according to claim 1, wherein the calculation of soil erosion by a guist model in the river basin erosion sand production model in step 3 comprises the following steps:
step 6.1, calculating the concentration of sediment generated by rainfall stripping based on rainfall intensity according to a formula (11) ：（11）
In the method, in the process of the invention,The concentration of sediment produced for rainfall stripping; /(I)Is associated with depth of flow/>The related rainfall corrosiveness; /(I)Is rainfall intensity; /(I)Is the proportion of soil not protected by vegetation or rock; /(I)The sedimentation rate is the average sedimentation rate of all suspended sediment;
step 6.2, calculating the sediment concentration generated by the runoff stripping based on the runoff kinetic energy according to the formula (12) ：
（12）
In the method, in the process of the invention,The concentration of sediment produced for runoff stripping; /(I)A ratio of the power of the runoff that is effective during the erosion process; For the proportion of soil completely immersed in runoff,/> ；/>In order to achieve an average flow rate,；/>Is a gradient; /(I)And/>Wet densities of water and silt, respectively; /(I)Is the hydraulic radius; /(I)Is a form factor; /(I)Is a modification factor; /(I)Is the resistance coefficient/>, carried by soil to runoff；/>Is one/>To/>The numerical value is used for parameter calibration; /(I)Is a surface coverage factor; /(I)The power is the runoff power of the narrow ditches; /(I)For critical runoff power, get/>。
7. The method for evaluating a river basin water sand model set according to claim 1, wherein the calculation of soil erosion in the river basin sand model in step 3 is performed by adopting WEPP model, comprising the following steps:
step 7.1, rate of transfer of erosion mud between the fine furrows to the fine furrows Calculated according to formula (13):
（13）
Wherein: is the corrosiveness coefficient between the fine furrows; /(I) Covering the vegetation with an impact factor; /(I)A ground cover influencing factor; /(I)Inter-fine erosion adjustment factors for which certain factors are ignored; /(I)Is the effective rainfall intensity; /(I)Is the fine groove spacing; /(I)Is the width of the narrow groove;
step 7.2, thin trench erosion or deposition Rate Calculated according to formula (14):
（14）
In the method, in the process of the invention, A thin trench ablation or deposition rate; /(I)Is the fine groove corrodibility coefficient; /(I)Fine erosion adjustment factors to ignore certain effects; /(I)Shear stress for water flow acting on soil particles; /(I)Critical shear stress for soil stripping; /(I)The sediment transporting capability of the water flow in the fine ditch;
Step 7.3, calculating sediment transport amount according to the continuity equation (15) in the sediment transport process ：
（15）
In the method, in the process of the invention,Sediment load of unit time unit width; /(I)Is the distance of a certain point along the downhill direction; /(I)The rate of transport of erosion silt between the fine furrows to the fine furrows; /(I)A thin trench ablation or deposition rate; /(I)And/>Is irrelevant and always positive; and/>The ablation is positive and the deposition is negative.
8. The method for evaluating a set of watershed water and sand models according to claim 1, wherein in step 4, each soil erosion model is evaluated by using 3 evaluation indexes, comprising the steps of:
step 8.1 calculates the nash efficiency coefficient NSE according to formula (16):
（16）
Wherein, Is the observed value of runoff or sediment; /(I)Model simulation values for runoff or sediment; /(I)Is the average value of the observed value of runoff or sediment;
Step 8.2, calculating the relative peak error RPE according to formula (17):
（17）
Wherein, Maximum value of observed value of runoff or sediment,/>Maximum value of model simulation value of runoff or sediment;
Step 8.3 calculates an absolute coefficient R 2 according to equation (18):
（18）
Wherein, The average value of model simulation values of runoff or sediment; the closer the two indexes NSE and R 2 are to 1, the higher the accuracy and fitting degree of the model are; /(I)The closer to 0, the higher the model fitting degree.
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