Method for measuring saturated hydraulic conductivity of soil

Abstract

The invention discloses a method for measuring saturated hydraulic conductivity of soil, and belongs to the field of soil detection. Acquiring a remote sensing image of the to-be-measured area, acquiring vegetation coverage data of the to-be-measured area and gradient size data of the to-be-measured area from the remote sensing image, and acquiring ground temperature data of the to-be-measured area on site; the method comprises the following steps: preprocessing vegetation coverage data, gradient size data and ground temperature data obtained from a to-be-measured area so as to obtain a vegetation coverage correction factor, a gradient correction factor and a ground temperature correction factor of the to-be-measured area; and constructing a soil saturated hydraulic conductivity measurement optimization coefficient of the to-be-measured area. According to the method, the soil saturation hydraulic conductivity optimization coefficient is constructed through the vegetation coverage correction factor, the slope correction factor and the ground temperature correction factor, and the soil saturation hydraulic conductivity reference value is regulated and controlled through the optimization coefficient, so that more accurate soil saturation hydraulic conductivity can be measured, and more accurate guidance can be provided for agricultural production.

Description

Technical Field

[0001] The present invention relates to soil detection, and in particular to a method for measuring soil saturated hydraulic conductivity. Background Art

[0002] Saturated hydraulic conductivity is the amount of water that passes through a unit area per unit time under a unit water potential gradient when soil pores are completely filled with water. Following Darcy's law, water flux is proportional to the soil water potential gradient. This parameter, a core indicator of soil hydraulic properties, directly affects soil water infiltration and fertility retention in agricultural production. Excessively high or low saturated hydraulic conductivity can negatively impact crop growth. Therefore, measuring soil saturated hydraulic conductivity is crucial for modern agricultural production. Existing methods for measuring soil saturated hydraulic conductivity, such as CN117309719A, measure the soil's saturated hydraulic conductivity by placing a soil sample in a measuring device and then adding water to the sample. Existing methods for measuring soil saturated hydraulic conductivity are direct methods, measuring the soil's saturated hydraulic conductivity by directly injecting water into the soil sample. However, because hydraulic conductivity can be affected by external factors (such as soil temperature and slope), soil saturated hydraulic conductivity measured in this way can suffer from significant errors and cannot provide accurate guidance for agricultural production. Summary of the Invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a method for measuring soil saturated hydraulic conductivity to solve the problem of large measurement error in current soil saturated hydraulic conductivity measurement methods.

[0004] Technical solution: A method for measuring soil saturated hydraulic conductivity, comprising: obtaining a remote sensing image of an area to be measured, and collecting vegetation coverage data and slope data of the area to be measured from the remote sensing image, and collecting ground temperature data of the area to be measured on site; preprocessing the vegetation coverage data, slope data and ground temperature data obtained from the area to be measured, so as to obtain a vegetation coverage correction factor, a slope correction factor and a ground temperature correction factor of the area to be measured; integrating the obtained vegetation coverage correction factor, slope correction factor and ground temperature correction factor, so as to construct a soil saturated hydraulic conductivity measurement optimization coefficient for the area to be measured; then measuring the soil saturated hydraulic conductivity of the area to be measured, and using the measurement result as a soil saturated hydraulic conductivity reference value for the area to be measured; and then regulating the soil saturated hydraulic conductivity reference value by using the obtained soil saturated hydraulic conductivity measurement optimization coefficient, so as to obtain the soil saturated hydraulic conductivity.

[0005] Preferably, when collecting ground temperature data of the area to be measured, several detection points are arbitrarily calibrated from the area to be measured, and temperature probes are inserted into each detection point at a depth of 5 to 10 cm to monitor and collect the temperature. The temperature data of each detection point is then aggregated and averaged to obtain the ground temperature data of the area to be measured.

[0006] Preferably, in the process of constructing the soil saturated hydraulic conductivity measurement optimization coefficient, the vegetation influence coefficient, slope attenuation coefficient and water viscosity-temperature coefficient are first obtained according to experimental calibration, and then the vegetation coverage data, slope size data and ground temperature data obtained in the measured area are integrated to obtain the vegetation coverage correction factor, slope correction factor and ground temperature correction factor of the measured area. Then, the vegetation coverage correction factor, slope correction factor and ground temperature correction factor are integrated to obtain the soil saturated hydraulic conductivity measurement optimization coefficient of the measured area. α :

[0007] in, k v is the vegetation impact coefficient, C v is the vegetation coverage, k is the slope attenuation coefficient, i is the slope size, β is the viscosity-temperature coefficient, T 0 is the reference temperature of the area to be measured, T For ground temperature.

[0008] Preferably, the historical annual average temperature of the current measurement area in the season to which the measurement time point belongs is obtained, and the historical annual average temperature is combined to obtain the reference temperature of the area to be measured. T 0 :

[0009] in, T avg,i is the average temperature of the current season in each year i in history, T avg,max 、 T avg,min are the highest average temperature and the lowest average temperature of the current season in historical years, N The total number of historical years.

[0010] Preferably, the soil saturated hydraulic conductivity of the area to be measured is measured by the Philip-Dunne infiltration method or the knife-ring method, and the measurement result is used as the reference value of the soil saturated hydraulic conductivity of the area to be measured.

[0011] Preferably, when the soil saturated hydraulic conductivity reference value is regulated by the soil saturated hydraulic conductivity measurement optimization coefficient, there are:

[0012] in, K opt is the saturated hydraulic conductivity of the soil, α Optimize coefficients for soil saturated hydraulic conductivity measurements, K s It is the reference value of soil saturated hydraulic conductivity.

[0013] Preferably, the vegetation coverage data of the area to be measured is obtained from the remote sensing image by a pixel decomposition model method, and the slope data of the area to be measured is obtained from the remote sensing image by a digital elevation model.

[0014] Beneficial Effects: When measuring soil saturated hydraulic conductivity, the present invention obtains a vegetation cover correction factor, a slope correction factor, and a ground temperature correction factor for the area to be measured based on the vegetation cover, slope, and ground temperature of the area to be measured. The vegetation cover correction factor, slope correction factor, and ground temperature correction factor are then used to construct a soil saturated hydraulic conductivity optimization coefficient. This optimization coefficient is used to regulate the soil saturated hydraulic conductivity baseline value, thereby enabling more accurate soil saturated hydraulic conductivity measurements and providing more precise guidance for agricultural production. Furthermore, when deriving the ground temperature correction factor, the ground temperature correction factor is derived from two dimensions (actual ground temperature data obtained from actual measurements at several monitoring points in the area to be measured and a regional reference temperature obtained from the historical average temperature of the current measurement area during the current measurement time point and season) combined with the viscosity-temperature coefficient of water. This makes the ground temperature correction factor more accurate, and thus the resulting saturated hydraulic conductivity more precise. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of the method. DETAILED DESCRIPTION

[0016] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Example like Figure 1 As shown in the figure, a method for measuring soil saturated hydraulic conductivity is to obtain a remote sensing image of the area to be measured, and obtain the vegetation coverage data of the area to be measured from the remote sensing image through a pixel decomposition model method. C v =0.8, and obtain the slope data of the measured area (θ = 5°) from the remote sensing image using a digital elevation model. Simultaneously, several random detection points are calibrated within the measured area, and a temperature probe is inserted at a depth of 5-10 cm at each detection point to monitor and collect temperature. The temperature data from each detection point is then aggregated and averaged to obtain the ground temperature data for the measured area. Five detection points are calibrated within the measured area, and a temperature probe is inserted at a depth of 6 cm at each detection point. The temperatures detected at each detection point are then aggregated: T1 = 25°C, T2 = 27°C, T3 = 23°C, T4 = 25°C, and T5 = 25°C. T = (T1 + T2 + T3 + T4 + T5) / 5 = (25 + 27 + 23 + 25 + 25) / 5 = 25°C ≈ 298K.

[0018] Then, the vegetation impact coefficient was constructed based on the soil hydrological model. k v The objective function is:

[0019] in, i obs To measure soil moisture, i model is the hydrological model simulation value obtained by the HYDRUS model, C v is the vegetation coverage. Then the PEST parameter estimation tool uses the least squares algorithm to automatically calibrate k v For example, in hilly areas, the fusion of Sentinel-1 radar and MODIS LAI data can be used to invert k v =0.2 .

[0020] The viscosity of water μ varies with temperature T and obeys the Arrhenius equation. Therefore, the viscosity of water at different temperatures can be measured using a capillary viscometer or a tuning fork vibrator. m T . Fit ln m T The linear relationship with 1 / T, the slope is the viscosity-temperature coefficient β:

[0021] At 25°C, μ=0.89×10 −3 Pa\cdotps, at 10℃, μ=1.31×10 −3 Pa\cdotps, the viscosity-temperature coefficient β is calculated to be 2400K.

[0022] The landslide stability coefficient K is:

[0023] The slope attenuation coefficient k is related to the shear strength of the acid soil. For gentle slope (θ<20°): k=0.2. For steep slope (θ≥20°): k=0.3~0.4.

[0024] Then, the vegetation coverage data, slope size data and ground temperature data obtained from the to-be-measured area are preprocessed: the vegetation coverage data, slope size data and ground temperature data are respectively combined with the vegetation influence coefficient k v , the slope attenuation coefficient k and the viscosity-temperature coefficient β to obtain the vegetation coverage correction factor α v , the slope correction factor α s and the ground temperature correction factor α t .

[0025]

[0026]

[0027]

[0028] wherein, T 0 is the reference temperature of the to-be-measured area: the historical average temperature of each year of the season to which the measurement time point belongs is obtained, and the historical average temperature of each year is integrated, so that the reference temperature of the to-be-measured area T 0

[0029] wherein, T avg,i is the average temperature of the current season of the i-th year in history, T avg,max , T avg,min are the highest average temperature and the lowest average temperature of the current season in the history year respectively, N is the total number of history years. For example, the season to which the current measurement time point belongs is spring, the average temperature of the current to-be-measured area in spring of each of the previous 5 years is obtained, which is: 18℃, 21℃, 20℃, 22℃, 19℃. Thus, the reference temperature of the to-be-measured area at the current measurement time point T 0 =20℃≈293k can be obtained. Thus, the vegetation coverage correction factor α v , the slope correction factor α s ​and the ground temperature correction factor α t respectively α v =1+0.2·ln(1+0.8)≈1.12 .

[0030] α s =cos 0.2 (5°)≈0.99 .

[0031] α t =e 2400(1 / 293-1 / 298) ≈1.25 .

[0032] The vegetation coverage correction factor, the slope correction factor and the ground temperature correction factor are integrated to construct the soil saturated hydraulic conductivity measurement optimization coefficient of the region to be measured α=α v ·α s ·α t =1.12×1.25×0.99≈1.39 The soil saturated hydraulic conductivity of the region to be measured is then determined by the Philip-Dunne infiltration method or the ring method (the soil saturated hydraulic conductivity measured by the ring method is 10 cm / hr), and the determination result is taken as the soil saturated hydraulic conductivity reference value of the region to be measured K s The soil saturated hydraulic conductivity reference value is then regulated by the obtained soil saturated hydraulic conductivity measurement optimization coefficient, so that the soil saturated hydraulic conductivity K opt is K opt =α·K s =1.39×10=13.9 cm / hr.

[0033] Compared with the traditional direct measurement method, the method comprehensively considers the factors affecting the soil saturated rate and optimizes the measurement value of the soil saturated hydraulic conductivity by taking them as optimization coefficients, so that a more accurate soil saturated rate can be obtained, and more accurate guidance can be provided for agricultural production.

[0034] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for measuring soil saturated hydraulic conductivity, characterized in that: include: Acquire remote sensing images of the area to be measured, and collect vegetation coverage data and slope data of the area to be measured from the remote sensing images, and collect ground temperature data of the area to be measured on site; Preprocessing the vegetation coverage data, slope data and ground temperature data obtained from the area to be measured, so as to obtain the vegetation coverage correction factor, slope correction factor and ground temperature correction factor of the area to be measured; The obtained vegetation coverage correction factor, slope correction factor and ground temperature correction factor are integrated to construct the soil saturated hydraulic conductivity measurement optimization coefficient of the measured area; then the soil saturated hydraulic conductivity of the measured area is measured, and the measurement result is used as the soil saturated hydraulic conductivity reference value of the measured area; then the soil saturated hydraulic conductivity reference value is adjusted by the obtained soil saturated hydraulic conductivity measurement optimization coefficient, so that the soil saturated hydraulic conductivity can be obtained.

2. The method for measuring soil saturated hydraulic conductivity according to claim 1, wherein: When collecting ground temperature data of the area to be measured, several detection points are arbitrarily calibrated from the area to be measured, and temperature probes are inserted into each detection point at a depth of 5 to 10 cm to monitor and collect the temperature. The temperature data of each detection point is then aggregated and averaged to obtain the ground temperature data of the area to be measured.

3. The method for measuring soil saturated hydraulic conductivity according to claim 1, wherein: In the process of constructing the soil saturated hydraulic conductivity measurement optimization coefficient, the vegetation influence coefficient, slope attenuation coefficient and water viscosity-temperature coefficient are first obtained according to experimental calibration. Then, the vegetation coverage data, slope size data and ground temperature data obtained in the measured area are integrated to obtain the vegetation coverage correction factor, slope correction factor and ground temperature correction factor of the measured area. Then, the vegetation coverage correction factor, slope correction factor and ground temperature correction factor are integrated to obtain the soil saturated hydraulic conductivity measurement optimization coefficient of the measured area. α : in, k v is the vegetation impact coefficient, C v is the vegetation coverage, k is the slope attenuation coefficient, θ is the slope size, β is the viscosity-temperature coefficient, T 0 is the reference temperature of the area to be measured, T For ground temperature.

4. The method for measuring soil saturated hydraulic conductivity according to claim 3, characterized in that: Get the historical annual average temperature of the current measurement area in the season of the measurement time point, and combine the historical annual average temperature to obtain the reference temperature of the area to be measured T 0 : in, T avg,i is the average temperature of the current season in each year i in history, T avg,max 、 T avg,min are the highest average temperature and the lowest average temperature of the current season in historical years, N The total number of historical years.

5. The method for measuring soil saturated hydraulic conductivity according to claim 1, wherein: The soil saturated hydraulic conductivity of the measured area is measured by the Philip-Dunne infiltration method or the knife ring method, and the measurement result is used as the reference value of the soil saturated hydraulic conductivity of the measured area.

6. The method for measuring soil saturated hydraulic conductivity according to claim 1, characterized in that: When adjusting the soil saturated hydraulic conductivity benchmark value through the soil saturated hydraulic conductivity measurement optimization coefficient, there are: in, K opt is the saturated hydraulic conductivity of the soil, α Optimize coefficients for soil saturated hydraulic conductivity measurements, K s It is the reference value of soil saturated hydraulic conductivity.

7. The method for measuring soil saturated hydraulic conductivity according to claim 1, characterized in that: The vegetation coverage data of the area to be measured is obtained from the remote sensing image through the pixel decomposition model method, and the slope size data of the area to be measured is obtained from the remote sensing image through the digital elevation model.

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