A method for calculating runoff yield of slope units considering the regulation effect of litter

Abstract

The invention discloses a method for calculating the flow production of a slope unit considering the regulating effect of litter, comprising the following steps: S1, calculating the total evapotranspiration of the slope unit; S2, calculating the canopy interception; S3, calculating the throughfall of the slope unit; S4, calculating the litter interception of the slope unit; S5, calculating the soil infiltration according to the Green-Ampt model; S6, calculating the surface filling amount according to the total evapotranspiration, throughfall, litter interception and soil infiltration of the slope unit; S7, calculating the flow production of the slope unit according to the surface filling amount. The invention solves the problem that the prior art lacks a method for accurately calculating the flow production of a slope covered with litter.

Description

Technical Field

[0001] The invention relates to the field of hydrological technology, and in particular to a method for calculating runoff generation of a slope unit taking into account the regulating effect of fallen leaves. Background Art

[0002] Litter refers to the general term for organic matter that is returned to the surface of the earth after the above-ground parts of plants (including branches, leaves, bark, reproductive organs, etc.) fall. Its decomposition plays an important role in the nutrient cycle and carbon balance between the soil and the atmosphere. At the same time, litter covers the soil surface like a "sponge" that "absorbs and permeates water". Its role in intercepting precipitation changes the original water supply at the atmosphere-soil interface, and it makes the water diffusion conditions on the soil surface worse, affecting the soil evaporation process. Current technology often conducts research on the regulatory effect of litter on the water cycle through experiments, and generally speaking, most of the regulatory effects of litter on a single element of the water cycle are obtained. There is still a lack of an accurate simulation method for slope unit runoff that takes into account the regulatory effect of litter on the entire process of slope runoff generation. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for calculating the runoff yield of a slope unit taking into account the regulating effect of litter, which solves the problem that the prior art lacks a method for accurately calculating the runoff yield of a slope covered with litter.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a method for calculating the runoff of a slope unit taking into account the regulation effect of litter, comprising the following steps:

[0005] S1. Calculate the total evapotranspiration of the slope unit;

[0006] S2, calculate canopy interception;

[0007] S3. Calculate the penetration rainfall of the slope unit based on the canopy interception;

[0008] S4, calculating the litter interception amount of the slope unit;

[0009] S5. Calculate soil infiltration according to the Green-Ampt model;

[0010] S6. Calculate the surface filling volume based on the total evapotranspiration, throughfall, litter interception and soil infiltration of the slope unit;

[0011] S7. Calculate the flow yield of the slope unit based on the surface fill volume.

[0012] Furthermore, the formula for calculating the total evapotranspiration of the slope unit in step S1 is:

[0013] E=E tr+E i +E l +E s

[0014]

[0015]

[0016] Where E is the total evapotranspiration, E tr is the transpiration of vegetation, E i is canopy evaporation, E l is the litter evaporation, E s is the soil evaporation under litter cover, Δ is the derivative of saturated water vapor pressure with respect to temperature, R NL is the net radiation of the litter layer, R NS is the net radiation of the soil layer, ρ a is the air density, C p is the constant pressure specific heat of air, γ is the air humidity constant, δ e is the difference between the actual water vapor pressure and the saturated water vapor pressure, r a is the aerodynamic impedance, λ is the latent heat of vaporization of water, r l is the resistance of the litter layer to water vapor transport, r s is the soil surface resistance.

[0017] Furthermore, the formula for calculating the penetration rainfall of the slope unit in step S3 is:

[0018]

[0019]

[0020] W rmax =0.2·LAI

[0021] PIN=R r ·F veg +P·F soil

[0022] Among them, PIN is the penetration rainfall of the slope unit, E i is canopy evaporation, W r is the canopy interception, W rmax is the maximum interception capacity of the canopy, LAI is the leaf area index, R r is the canopy penetration rainfall in the canopy coverage domain, P is the rainfall in the canopy gap domain, and F veg is the canopy coverage domain, F soil is the canopy gap area, and t is the time.

[0023] Furthermore, the formula for calculating the litter interception amount of the slope unit in step S4 is:

[0024]

[0025] Among them, I l is the litter interception amount of the slope unit, M l is the litter accumulation per unit area, W lm is the maximum water content of litter, W l0 is the initial water content of litter, C l is the effective interception coefficient of litter, and P is the rainfall in the canopy gap domain.

[0026] Furthermore, the formula for calculating the surface filling amount in step S6 is:

[0027] H t =H 0 +PIN-I l -EF

[0028] Among them, H t is the surface filling volume at time t, H 0 is the surface filling volume at the initial moment, PIN is the throughfall of the slope unit, E is the total evapotranspiration, F is the soil infiltration calculated according to the Green-Ampt model, I l is the litter interception amount of the slope unit.

[0029] Furthermore, the formula for calculating the flow rate of the slope unit in step S7 is:

[0030]

[0031] H max =F veg ·e LAI +5·F soil

[0032] Where R is the flow rate of the slope unit, H t is the surface filling volume at time t, H max is the maximum value of the surface filling volume, F veg is the canopy coverage domain, F soil is the canopy gap area, and LAI is the leaf area index.

[0033] In summary, the beneficial effects of the present invention are: a method for calculating the flow production of slope units taking into account the regulating effect of litter, by taking into account the interception effect of litter and its influence on soil evaporation, combining total evapotranspiration, throughfall, litter interception and surface filling, the flow production of slope units is accurately calculated, which is convenient for accurately estimating the flow production of the water cycle process in forest areas covered with litter. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of a method for calculating runoff yield of slope units taking into account the regulating effect of litter. DETAILED DESCRIPTION

[0035] 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.

[0036] like Figure 1 As shown, a method for calculating the runoff of a slope unit taking into account the regulation effect of litter and fallen leaves comprises the following steps:

[0037] S1. Calculate the total evapotranspiration of the slope unit;

[0038] The formula for calculating the total evapotranspiration of the slope unit in step S1 is:

[0039] E=E tr +E i +E l +E s

[0040]

[0041]

[0042] Where E is the total evapotranspiration, E tr is the transpiration of vegetation, E i is canopy evaporation, E l is the litter evaporation, E s is the soil evaporation under litter cover, Δ is the derivative of saturated water vapor pressure with respect to temperature, R NL is the net radiation of the litter layer, R NS is the net radiation of the soil layer, ρ a is the air density, C p is the constant pressure specific heat of air, γ is the air humidity constant, δ e is the difference between the actual water vapor pressure and the saturated water vapor pressure, r a is the aerodynamic impedance, λ is the latent heat of vaporization of water, r l is the resistance of the litter layer to water vapor transport, r s is the soil surface resistance.

[0043] S2, calculate canopy interception;

[0044] S3. Calculate the penetration rainfall of the slope unit based on the canopy interception;

[0045] The formula for calculating the penetration rainfall of the slope unit in step S3 is:

[0046]

[0047]

[0048] W rmax =0.2·LAI

[0049] PIN=R r ·F veg +P·F soil

[0050] Among them, PIN is the penetration rainfall of the slope unit, E i is canopy evaporation, W r is the canopy interception, W rma x is the maximum interception capacity of the canopy, LAI is the leaf area index, R r is the canopy penetration rainfall in the canopy coverage domain, P is the rainfall in the canopy gap domain, and F veg is the canopy coverage domain, F soil is the canopy gap area, and t is the time.

[0051] S4, calculating the litter interception amount of the slope unit;

[0052] The formula for calculating the litter interception amount of the slope unit in step S4 is:

[0053]

[0054] Among them, I l is the litter interception amount of the slope unit, M l is the litter accumulation per unit area, W lm is the maximum water content of litter, W l0 is the initial water content of litter, C l is the effective interception coefficient of litter, and P is the rainfall in the canopy gap domain.

[0055] S5. Calculate soil infiltration according to the Green-Ampt model;

[0056] S6. Calculate the surface filling volume based on the total evapotranspiration, throughfall, litter interception and soil infiltration of the slope unit;

[0057] The formula for calculating the surface filling amount in step S6 is:

[0058] H t =H0 +PIN-I l -EF

[0059] Among them, H t is the surface filling volume at time t, H 0 is the surface filling volume at the initial moment, PIN is the throughfall of the slope unit, E is the total evapotranspiration, F is the soil infiltration calculated according to the Green-Ampt model, I l is the litter interception amount of the slope unit.

[0060] S7. Calculate the flow yield of the slope unit based on the surface fill volume.

[0061] The formula for calculating the flow rate of the slope unit in step S7 is:

[0062]

[0063] H max =F veg ·e LAI +5·F soil

[0064] Where R is the flow rate of the slope unit, H t is the surface filling volume at time t, H max is the maximum value of the surface filling volume, F veg is the canopy coverage domain, F soil is the canopy gap area, and LAI is the leaf area index.

[0065] The present invention takes into account the interception effect of litter and its influence on soil evaporation, combines the total evapotranspiration, throughfall, litter interception and surface filling, and accurately calculates the flow production of slope units, so as to accurately estimate the flow production of the water cycle process in forest areas covered by litter.

Claims

1. A method for calculating runoff of a slope unit taking into account the regulation effect of litter, characterized in that: The following steps are involved: S1. Calculate the total evapotranspiration of the slope unit; S2, calculate canopy interception; S3. Calculate the penetration rainfall of the slope unit based on the canopy interception; S4, calculating the litter interception amount of the slope unit; The formula for calculating the litter interception of a slope unit is: Among them, I l is the litter interception amount of the slope unit, M l is the litter accumulation per unit area, W lm is the maximum water content of litter, W l0 is the initial water content of litter, C l is the effective interception coefficient of litter, P is the rainfall in the canopy gap domain; S5. Calculate soil infiltration according to the Green-Ampt model; S6. Calculate the surface filling volume based on the total evapotranspiration, throughfall, litter interception and soil infiltration of the slope unit; The formula for calculating the surface fill volume is: H t =H0+PIN-I l -E-F Among them, H t is the surface filling volume at time t, H0 is the surface filling volume at the initial time, PIN is the throughfall of the slope unit, E is the total evapotranspiration, F is the soil infiltration calculated according to the Green-Ampt model, I l is the litter interception of the slope unit; S7. Calculate the flow yield of the slope unit based on the surface fill volume.

2. The method for calculating runoff of a slope unit considering the regulation effect of litter according to claim 1 is characterized in that: The formula for calculating the total evapotranspiration of the slope unit in step S1 is: E=E tr +E i +E l +E s Where E is the total evapotranspiration, E tr is the transpiration of vegetation, E i is canopy evaporation, E l is the litter evaporation, E s is the soil evaporation under litter cover, Δ is the derivative of saturated water vapor pressure with respect to temperature, R NL is the net radiation of the litter layer, R NS is the net radiation of the soil layer, ρ a is the air density, C p is the constant pressure specific heat of air, γ is the air humidity constant, δ e is the difference between the actual water vapor pressure and the saturated water vapor pressure, r a is the aerodynamic impedance, λ is the latent heat of vaporization of water, r l is the resistance of the litter layer to water vapor transport, r s is the soil surface resistance.

3. The method for calculating runoff of a slope unit considering the regulation effect of litter according to claim 1 is characterized in that: The formula for calculating the penetration rainfall of the slope unit in step S3 is: <h2 style=";text-align:left;direction:ltr">W<h2 style=";text-align:left;direction:ltr"> rmax <h2 style=";text-align:left;direction:ltr"> <0.2 LAI PIN=R r ·F veg +P·F soil Among them, PIN is the penetration rainfall of the slope unit, E i is canopy evaporation, W r is the canopy interception, W rmax is the maximum interception capacity of the canopy, LAI is the leaf area index, R r is the canopy penetration rainfall in the canopy coverage domain, P is the rainfall in the canopy gap domain, and F veg is the canopy coverage domain, F soil is the canopy gap area, and t is the time.

4. The method for calculating runoff of a slope unit taking into account the regulation effect of litter according to claim 1, It is characterized in that The formula for calculating the flow rate of the slope unit in step S7 is: H max =F veg ·e LAI +5·F soil Where R is the flow rate of the slope unit, H t is the surface filling volume at time t, H max is the maximum value of surface filling volume, F veg is the canopy coverage domain, F soil is the canopy gap area, and LAI is the leaf area index.

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