A method for basin hydrological simulation considering litter

Abstract

The present invention provides a method for simulating watershed hydrology taking litter into consideration, belonging to the technical field of ecohydrological simulation. The present invention constructs a parameter set of litter characteristics and remote sensing data, a litter characteristic and intercepted water characteristic equation, and a correction equation of litter characteristics and surface roughness, and provides a method for obtaining litter hydrological characteristics through remote sensing data; the present invention provides a method for increasing litter interception precipitation and delayed slope confluence in a watershed hydrological model, improving the physical mechanism of the watershed hydrological model, and the method can be applied to hydrological models of all watershed scales. The present invention makes up for the practical problem that the existing hydrological model does not consider the regulating effect of the litter layer when simulating the hydrological process.

Description

Technical Field

[0001] The invention belongs to the technical field of ecohydrological simulation, and in particular relates to a watershed hydrological simulation method taking litter into consideration. Background Art

[0002] In forest areas, due to the falling of vegetation branches and leaves, a litter layer will be formed on the ground. Through literature research, it is found that litter has a certain role in intercepting precipitation. The maximum interception amount can account for about 20% of the annual rainfall, which affects the slope runoff process; at the same time, the litter layer covers the soil surface, changes the surface roughness, and affects the slope runoff; and through the investigation of existing watershed hydrological models, it is found that none of the models considers the impact of litter on the slope runoff process. And from the literature research, the accumulation of litter is different in terrestrial ecosystems in different regions. The increase in the accumulation of litter will further lead to an increase in its impact on the basin runoff process, which is mainly reflected in the increase in the role of litter in intercepting rainfall and the increase in the role of delayed rainfall caused by the increase in surface roughness. Therefore, it is particularly important to construct a basin hydrological simulation method that considers litter. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a watershed hydrological simulation method taking litter into consideration, which solves the problem that the existing watershed hydrological model does not take into account the regulatory effect of litter on the slope runoff generation and convergence process.

[0004] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0005] This scheme provides a watershed hydrological simulation method considering litter, including the following steps:

[0006] S1. Construct a litter hydrological characteristic dataset;

[0007] S2. Based on the litter hydrological characteristic dataset, the basin hydrology is simulated using the basin hydrological model.

[0008] The beneficial effects of the present invention are as follows: the present invention forms a data set, equations, etc. by constructing the relationship between the characteristics of litter and remote sensing data, and adds the input and equations of relevant remote sensing data to the basin hydrological model, which will provide theoretical and technical support for identifying the nonlinear changes of basin flood processes and contribute to flood prevention and early warning work in forest areas.

[0009] Furthermore, the step S1 includes the following steps:

[0010] S101, constructing a parameter set of litter characteristics and vegetation cover type, coverage and leaf area index;

[0011] S102, collecting litter with different characteristics, and constructing water interception and holding characteristic equations IL of different litter;

[0012] S103. Use the chain method to measure the surface roughness and construct the equation for the effect of different litter on the surface roughness. s ;

[0013] S104, according to the parameter set, the water interception and holding characteristic equation IL of different litter and the influence equation r s , completing the construction of the litter hydrological characteristics dataset.

[0014] The beneficial effect of the above further scheme is that the litter hydrological characteristic data set constructed by the present invention can be used to analyze the water interception and retention characteristics of litter in different regions and its impact on surface roughness. The corresponding equation can be called according to remote sensing data (vegetation cover type, coverage and leaf area index), and it has strong universality and generalizability.

[0015] Furthermore, the step S102 includes the following steps:

[0016] S1021. Collect litter with different characteristics and measure its thickness, accumulation, bulk density and initial water content;

[0017] S1022, according to the measurement results, litter with different characteristics is placed in a litter frame, placed at the initial collection location, and the weight change of the litter in different rainfall events is observed to obtain the water interception capacity;

[0018] S1023, based on the obtained water holding capacity, water is poured onto the litter, and after the weight of the litter no longer changes, the litter is weighed to obtain the maximum water holding capacity of the litter;

[0019] S1024. According to the maximum water holding capacity of litter, a fitting relationship between litter characteristics and water holding capacity is established through in-situ observation experiments, and the water holding characteristic equation IL of different litter is obtained.

[0020] The beneficial effect of the above further scheme is that the present invention establishes a quantitative relationship between the litter characteristics and the litter water interception characteristic equation through observation experiments, and has the universality of being extended from the patch scale to the watershed scale.

[0021] Furthermore, the step S103 includes the following steps:

[0022] S1031. Use the chain method to measure the roughness of the surface covered with litter;

[0023] S1032. After removing litter, use the chain method to measure the surface roughness of the ground without litter cover;

[0024] S1033. Determine four sample plots in the sample plot using the S-shaped sampling method and measure the characteristics of litter;

[0025] S1034. According to the measured litter characteristics, a fitting relationship between litter characteristics and surface roughness is established to obtain the influence equation r of different litter on surface roughness. s .

[0026] The beneficial effect of the above further scheme is that the present invention establishes an equation for the influence of litter characteristics on surface roughness through sample site investigation, which has the universality of being extended from the patch scale to the watershed scale.

[0027] Furthermore, step S2 includes the following steps:

[0028] S201, adding the input of remote sensing data to the watershed hydrological model, and obtaining different litter characteristics according to the parameter set obtained in step S101;

[0029] S202, using different litter interception and holding water characteristic equations IL, adding the calculation of litter interception and holding water to the slope runoff in the basin hydrological model;

[0030] S203, adding the surface roughness correction after litter cover in the slope confluence of the watershed hydrological model, wherein the correction equation of the surface roughness correction is the influence equation r s ;

[0031] S204, according to the different litter characteristics obtained in step S201, the basin hydrology is simulated using a basin hydrological model that adds litter interception and holding capacity calculation and surface roughness correction.

[0032] The beneficial effect of the above further scheme is that the watershed hydrological model constructed by the present invention reflects the regulatory effect of litter on the runoff generation and convergence process of the watershed, and simulates the real hydrological cycle process of the forest area.

[0033] Furthermore, the step S202 includes the following steps:

[0034] S2021. In the slope runoff generation in the watershed hydrological model, calculate the maximum amount of water intercepted by litter:

[0035] IL max =(W lm -W l0 )v w t hk

[0036] Among them, IL max Indicates the maximum amount of water retained by litter (in mm), W l0 and W lmrepresent the initial water content (in kg / kg) and the maximum water content (in kg / kg) of the litter, v w Indicates the litter bulk density (in kg / m 3 ), t hk represents the litter thickness (in m);

[0037] S2022. Calculate the water retention capacity of litter according to the maximum water retention capacity of litter using the water retention characteristic equation IL of different litter:

[0038]

[0039] Where IL represents the water interception capacity of litter (in mm), M l Indicates the litter accumulation per unit area (in kg / m 2 ), P G represents the amount of water falling on the litter (unit: mm), and a and b represent the water interception and holding parameters of the litter.

[0040] The beneficial effect of the above further scheme is that the present invention simulates the interception amount of litter in the forest area through the above steps, reflecting the real slope runoff generation process.

[0041] Furthermore, the influence equation r in step S203 s The expression is as follows:

[0042] r s =c1r b +c2t hk +c3M l +c4

[0043] Among them, r s Indicates the surface roughness when covered with litter, r b It represents the surface roughness when there is no litter cover, and c1, c2, c3 and c4 are the coefficients of the litter influence equation.

[0044] The beneficial effect of the above further solution is that the present invention takes into account the influence of litter on the surface roughness when simulating slope confluence, reflecting the real slope confluence process. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0046] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0047] Example

[0048] like Figure 1 As shown, the present invention provides a basin hydrological simulation method considering litter, and the implementation method is as follows:

[0049] S1. Construct a litter hydrological characteristic dataset. The implementation method is as follows:

[0050] S101, constructing a parameter set of litter characteristics and vegetation cover type, coverage and leaf area index;

[0051] S102, collecting litter with different characteristics, and constructing different litter interception and holding water characteristic equations IL, the implementation method of which is as follows:

[0052] S1021. Collect litter with different characteristics and measure its thickness, accumulation, bulk density and initial water content;

[0053] S1022, according to the measurement results, litter with different characteristics is placed in a litter frame, placed at the initial collection location, and the weight change of the litter in different rainfall events is observed to obtain the water interception capacity;

[0054] S1023, based on the obtained water holding capacity, water is poured onto the litter, and after the weight of the litter no longer changes, the litter is weighed to obtain the maximum water holding capacity of the litter;

[0055] S1024. According to the maximum water holding capacity of litter, a fitting relationship between litter characteristics and water holding capacity is established through in-situ observation experiments to obtain water holding characteristic equations IL for different litter.

[0056] S103. Use the chain method to measure the surface roughness and construct the equation for the effect of different litter on the surface roughness. s , which is implemented as follows:

[0057] S1031. Use the chain method to measure the roughness of the surface covered with litter;

[0058] S1032. After removing litter, use the chain method to measure the surface roughness of the ground without litter cover;

[0059] S1033. Determine four sample plots in the sample plot using the S-shaped sampling method and measure the characteristics of litter;

[0060] S1034. According to the measured litter characteristics, a fitting relationship between litter characteristics and surface roughness is established to obtain the influence equation r of different litter on surface roughness. s ;

[0061] S104, according to the parameter set, the water interception and holding characteristic equation IL of different litter and the influence equation r s , completing the construction of the litter hydrological characteristics dataset.

[0062] In this embodiment, the litter characteristics include five types, namely, litter thickness, accumulation, bulk density, initial water content, and saturated water content. The above five characteristics of litter are measured in different climate zones, vegetation cover types, and seasons, and the correlation between these five characteristics and vegetation cover type, coverage, and leaf area index is established, thereby building a parameter set of litter characteristics and remote sensing data (vegetation cover type, coverage, and leaf area index), and realizing remote sensing interpretation to obtain litter characteristics.

[0063] In this embodiment, the water-holding characteristic equation IL of different litter can be obtained through in-situ observation experiments, specifically: collect litter with different characteristics, measure its thickness, accumulation, bulk density, and initial water content; then install it in a self-made litter frame, place it in the place where it was initially collected, observe the weight change of litter in different rainfalls, and obtain the water-holding capacity; after obtaining a certain amount of data, pour water on the litter, and when the weight of the litter no longer changes, weigh it to obtain the maximum water-holding capacity of the litter. Through the in-situ observation experiment, a fitting relationship between litter characteristics and water holding capacity can be established to obtain the water-holding characteristic equation IL of different litter.

[0064] In this embodiment, the influence equation of different litter on the surface roughness is: s It can be obtained through plot surveys, specifically: first use the chain method to measure the surface roughness of litter cover; after removing the litter, use the chain method again to measure the surface roughness of the ground without litter cover; after measuring the surface roughness, determine 4 sample plots in this plot according to the S-shaped sampling method to measure litter thickness, accumulation and other characteristics. After obtaining certain data through plot surveys, the fitting relationship between litter characteristics and surface roughness can be established, and the influence equation r of different litter on surface roughness can be obtained. s .

[0065] S2. Based on the litter hydrological characteristic dataset, the basin hydrological model is used to simulate the basin hydrology. The implementation method is as follows:

[0066] S201, adding the input of remote sensing data to the watershed hydrological model, and obtaining different litter characteristics according to the parameter set obtained in step S101;

[0067] S202, using different litter interception and holding water characteristic equations IL, add the calculation of litter interception and holding water to the slope runoff in the basin hydrological model, and the implementation method is as follows:

[0068] S2021. In the slope runoff generation in the watershed hydrological model, calculate the maximum amount of water intercepted by litter:

[0069] IL max =(W lm -W l0 )v w t hk

[0070] Among them, IL max Indicates the maximum amount of water retained by litter (in mm), W l0 and W lm represent the initial water content (in kg / kg) and the maximum water content (in kg / kg) of the litter, v w Indicates the litter bulk density (in kg / m 3 ), t hk represents the litter thickness (in m);

[0071] S2022. Calculate the water retention capacity of litter according to the maximum water retention capacity of litter using the water retention characteristic equation IL of different litter:

[0072]

[0073] Where IL represents the water interception capacity of litter (in mm), M l Indicates the litter accumulation per unit area (in kg / m 2 ), P G It represents the amount of water falling on the litter (unit: mm), which is generally the rainfall in the forest. a and b both represent the water interception and holding parameters of the litter, which are obtained based on in-situ observation experiments.

[0074] S203, adding the surface roughness correction after litter cover in the slope confluence of the watershed hydrological model, wherein the correction equation of the surface roughness correction is the influence equation r s :

[0075] r s =c1r b +c2t hk +c3M l +c4

[0076] Among them, r s Indicates the surface roughness when covered with litter, r b represents the surface roughness when there is no litter cover, c1, c2, c3 and c4 all represent the coefficients of the litter influence equation;

[0077] S204, according to the different litter characteristics obtained in step S201, the basin hydrology is simulated using a basin hydrological model that adds litter interception and holding capacity calculation and surface roughness correction.

[0078] In this embodiment, the input vegetation cover type, EVI and LAI data can be added to the watershed hydrological model, and these data can be obtained through remote sensing interpretation; among them, EVI (Enhanced Vegetation Index) data is used to calculate vegetation coverage, and LAI (Leaf Area Index) data refers to leaf area index data. The watershed hydrological model can obtain the hydrological characteristics of different litter by inputting the above three types of data and using the parameter set constructed by S1.1.

[0079] In this embodiment, the construction of the litter hydrological characteristic dataset provides basic support for watershed hydrological simulation.

[0080] In this embodiment, the relationship between remote sensing data and hydrological characteristics such as litter characteristics, water retention characteristics, and the impact on surface roughness is established in step S1. Step S2 only needs to add the input of remote sensing data to the watershed hydrological model, and the litter characteristics can be obtained through the data set established in S1; at the same time, the maximum water retention capacity IL of litter is added to the watershed hydrological model. max A basin hydrological simulation model considering litter is constructed based on the calculation formula of litter interception and surface roughness correction, and the basin hydrology is simulated using the basin hydrological model.

[0081] In this embodiment, the chain method refers to: using a chain of fixed length L1 (cm) and placing it on the ground along the direction of the maximum slope gradient of the sample plot; the horizontal length of the chain at the beginning and end will become shorter due to the undulation of the surface; using a steel tape measure to measure the horizontal length of the chain at this time, L2 (cm). The surface roughness r can be calculated according to the following formula:

[0082] r=1-L2 / L1

[0083] In this embodiment, the watershed hydrological model includes but is not limited to the SHE model, the TOMPODEL model, the SWAT model, the VIC model and the WEP model.

[0084] The present invention constructs a parameter set of litter characteristics and remote sensing data, a litter characteristic and intercepted water characteristic equation, and a modified equation of litter characteristics and surface roughness, and provides a method for obtaining litter hydrological characteristics through remote sensing data; the present invention adds a method for litter interception and retention of precipitation and delayed slope confluence in a basin-scale hydrological model, improves the physical mechanism of the basin hydrological model, and the method can be applied to all basin-scale hydrological models. The present invention will provide theoretical and technical support for identifying nonlinear changes in basin flood processes and contribute to flood prevention and early warning work in forest areas.

Claims

1. A basin hydrological simulation method considering litter, characterized in that: The following steps are involved: S1. Construct a litter hydrological characteristic dataset, which is as follows: S101, constructing a parameter set of litter characteristics and vegetation cover type, coverage and leaf area index; S102. Collect litter with different characteristics and construct water retention characteristic equations for different litter IL : in, IL Indicates the water interception capacity of litter, in mm. M l Indicates the accumulation of litter per unit area, in kg / m 2 , P G Indicates the amount of water that falls on the litter, in mm. and All represent litter water interception and holding parameters; S103. Use the chain method to measure the surface roughness and construct the equation for the effect of different litter on the surface roughness ; S104, according to the parameter set, different litter interception and holding water characteristic equations IL and the influence equation r s , complete the construction of the litter hydrological characteristics dataset, where the influence equation The expression is as follows: in, Indicates the surface roughness when covered with litter. Indicates the surface roughness when there is no litter cover. , , and Both represent the coefficients of litter influence equation, t hk Indicates the litter thickness, in m; S2. Based on the litter hydrological characteristic dataset, the basin hydrology is simulated using the basin hydrological model.

2. The basin hydrological simulation method considering litter according to claim 1 is characterized in that: The step S102 includes the following steps: S1021. Collect litter with different characteristics and measure its thickness, accumulation, bulk density and initial water content; S1022, according to the measurement results, litter with different characteristics is placed in a litter frame, placed at the initial collection location, and the weight change of the litter in different rainfall events is observed to obtain the water interception capacity; S1023, based on the obtained water holding capacity, water is poured onto the litter, and after the weight of the litter no longer changes, the litter is weighed to obtain the maximum water holding capacity of the litter; S1024. According to the maximum water holding capacity of litter, through in-situ observation experiments, the fitting relationship between litter characteristics and water holding capacity is established to obtain the water holding characteristic equations of different litter IL .

3. The basin hydrological simulation method considering litter according to claim 2 is characterized in that: The step S103 comprises the following steps: S1031. Use the chain method to measure the roughness of the surface covered with litter; S1032. After removing litter, use the chain method to measure the surface roughness of the ground without litter cover; S1033. Determine four sample plots in the sample plot using the S-shaped sampling method and measure the characteristics of litter; S1034. According to the measured litter characteristics, establish the fitting relationship between litter characteristics and surface roughness, and obtain the influence equation of different litter on surface roughness. .

4. The basin hydrological simulation method considering litter according to claim 3 is characterized in that: The step S2 comprises the following steps: S201, adding the input of remote sensing data to the watershed hydrological model, and obtaining different litter characteristics according to the parameter set obtained in step S101; S202, using different litter interception and water holding characteristic equations , add the calculation of litter interception and holding capacity to the slope runoff in the watershed hydrological model; S203, adding the surface roughness correction after litter cover in the slope confluence of the watershed hydrological model, wherein the correction equation of the surface roughness correction is the influence equation r s ; S204, according to the different litter characteristics obtained in step S201, the basin hydrology is simulated using a basin hydrological model that adds litter interception and holding capacity calculation and surface roughness correction.

5. The basin hydrological simulation method considering litter according to claim 4 is characterized in that: The step S202 comprises the following steps: S2021. In the slope runoff generation in the watershed hydrological model, calculate the maximum amount of water intercepted by litter: in, IL max Indicates the maximum amount of water intercepted by litter, in mm. W l0 and W lm They represent the initial water content of litter in kg / kg and the maximum water content in kg / kg. v w Indicates the litter bulk density, in kg / m 3 ; S2022. Based on the maximum water retention capacity of litter, use the water retention characteristic equations of different litter IL , calculate the water interception and holding capacity of litter.

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