A method for determining vegetation coverage based on the protection of groundwater resources

Abstract

The present invention discloses a method and system for determining vegetation coverage based on the protection of groundwater resources. The vegetation coverage is calculated by the following formula: #imgabs0# where P max represents the maximum vegetation coverage; α1 represents the regional precipitation infiltration coefficient under the condition of no vegetation; A, B, and C are constants; a and b are constants. This method first gives the threshold of the regional groundwater recharge amount, combines the vegetation water consumption with the groundwater recharge amount, and gives the appropriate vegetation coverage in the western mining area through the constraint of the groundwater recharge amount threshold, so as to achieve the purpose of coordinating the protection of the mining area's groundwater resources and the restoration of the ecological environment.

Description

Technical Field

[0001] The present invention belongs to the cross - technical field of coal mining and mine ecological restoration, and relates to a method for determining vegetation coverage based on the protection of groundwater resources. Background Art

[0002] The coal resources in six western provinces (Shanxi, Shaanxi, Inner Mongolia, Ningxia, Gansu, and Xinjiang) account for about 84.7% of the country's total. In 2018, the coal output accounted for 76.5% of the country's total, while the water resources accounted for only 7.9% of the country's total, and the water resources are extremely scarce. In recent years, with the continuous increase in the development intensity of coal resources, the phenomenon of ecological environment degradation in western mining areas has been obvious. In recent years, with the construction of green mines entering the "comprehensive promotion" stage from the "pilot exploration" stage, in order to improve the current situation of the fragile ecological environment in mining areas, different coal mines have carried out high - intensity vegetation restoration projects. The vegetation coverage of some coal mines has increased from less than 10% before restoration to about 90%.

[0003] However, in western mining areas, especially in desert mining areas in the west, the proportion of precipitation infiltration recharge in the total groundwater recharge generally exceeds 70%. That is to say, atmospheric precipitation is the main recharge source of groundwater in such areas. Generally, precipitation first falls to the ground and forms soil water through infiltration. The water moves vertically in the soil. When it reaches the water table, it forms groundwater. And high - intensity ecological restoration directly leads to the consumption of soil water formed by precipitation for vegetation growth. Therefore, precipitation cannot recharge groundwater through the soil vadose zone or the amount of precipitation recharging groundwater will decrease, resulting in the attenuation of regional groundwater resources. How to find a method to determine the appropriate vegetation coverage in water - scarce mining areas in the west has become an urgent technical problem.

[0004] To alleviate the contradiction between water resource shortage and ecological restoration in western mining areas and avoid the attenuation of regional groundwater resources caused by high - intensity ecological restoration, the present invention proposes a method for determining the vegetation coverage of ecological restoration in western mining areas based on the protection of groundwater resources. Summary of the Invention

[0005] The present invention proposes a method for determining vegetation coverage based on the protection of groundwater resources. This method first gives the threshold of regional groundwater recharge, combines the vegetation water consumption with the groundwater recharge, and gives the appropriate vegetation coverage in western mining areas through the constraint of the groundwater recharge threshold, so as to achieve the purpose of coordinating the protection of groundwater resources and the ecological environment restoration in mining areas.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for determining vegetation coverage based on the protection of groundwater resources, wherein the vegetation coverage is calculated by the following formula:

[0008]

[0009] In the formula, P max represents the maximum vegetation coverage; α1 represents the regional precipitation infiltration coefficient under vegetation-free conditions; A, B, and C are constants; a and b are constants.

[0010] Optionally, the method for obtaining the regional precipitation infiltration coefficient α1 under vegetation-free conditions specifically includes:

[0011] Construct a soil water dynamics equation under vegetation-free conditions, and its equation is as follows:

[0012]

[0013] In the formula, θ is the soil moisture content, cm 3 / cm 3 ; is the soil water potential, cm; t is the time, d; z is the depth, cm; K(θ) is the unsaturated hydraulic conductivity, cm / d; input the above parameters into the HYDRUS finite element simulation software, and the soil water flux F at different depths of the model can be obtained. If the precipitation is P, then the regional precipitation infiltration coefficient α1 under vegetation-free conditions = F / P.

[0014] Optionally, the method for obtaining the constants a and b includes:

[0015] Construct a relationship curve between the leaf area index and vegetation coverage in the mining area;

[0016] LAI = aP + b;

[0017] In the formula, LAI is the leaf area index, P is the vegetation coverage, and a and b are the relevant parameters of the curve.

[0018] Optionally, the method for obtaining the constants A, B, and C includes:

[0019] Construct a relationship curve between the leaf area index and the precipitation infiltration coefficient α2 under different leaf area index conditions;

[0020] α2 = C + Aexp(-B×LAI);

[0021] In the formula, α2 is the precipitation infiltration coefficient under different leaf area index conditions, LAI is the different leaf area index, and A, B, and C are the relevant parameters of the curve.

[0022] A method for determining vegetation coverage based on the protection of groundwater resources includes:

[0023] 1) Obtain the regional precipitation infiltration coefficient α1 under vegetation-free conditions;

[0024] 2) Construct the relationship curve between the leaf area index and vegetation coverage in the mining area, and obtain the constants a and b;

[0025] 3) Construct the relationship curves between the leaf area index in the mining area and the vegetation water consumption, and the precipitation infiltration coefficient α2 under different leaf area index conditions: obtain the precipitation infiltration coefficient α1 under different leaf area index conditions and the constants A, B, and C;

[0026] 4) Determine the vegetation coverage: under the vegetation coverage condition, α1 ≥ 0.6α1.

[0027] Optionally, the step of 1) obtaining the regional precipitation infiltration coefficient α1 under the vegetation-free condition specifically includes:

[0028] Construct the soil water dynamics equation under the vegetation-free condition, and the equation is as follows:

[0029]

[0030] In the formula, θ is the soil moisture content, cm 3 / cm 3 ; is the soil water potential, cm; t is the time, d; z is the depth, cm; K(θ) is the unsaturated permeability coefficient, cm / d; input the above parameters into the HYDRUS finite element simulation software, and the soil water flux F at different depths of the model can be obtained. If the precipitation is P, then the regional precipitation infiltration coefficient α1 under the vegetation-free condition = F / P.

[0031] Optionally, the step of 2) constructing the relationship curve between the leaf area index and vegetation coverage in the mining area specifically includes:

[0032] LAI = aP + b;

[0033] In the formula, LAI is the leaf area index, P is the vegetation coverage, and a and b are the relevant parameters of the curve.

[0034] Optionally, the step of constructing the relationship curves between the leaf area index in the mining area and the vegetation water consumption, and the precipitation infiltration coefficient α2 under different leaf area index conditions specifically includes:

[0035] α2 = C + Aexp(-B×LAI);

[0036] In the formula, α2 is the precipitation infiltration coefficient under different leaf area index conditions, LAI is the different leaf area index, and A, B, and C are the relevant parameters of the curve.

[0037] Optionally, α2 = C + Aexp(-B×LAI max ); LAI max = aP max + b;

[0038] That is,

[0039] In the formula, P max represents the maximum vegetation coverage; α1 represents the regional precipitation infiltration coefficient under the condition of no vegetation; LAI max is the maximum leaf area index; A, B, and C are constants; a and b are constants.

[0040] The beneficial effects of the present invention are as follows:

[0041] The method of the present invention can, while carrying out the ecological environment restoration of the mining area, maximize the consideration of the protection of groundwater resources, avoid the phenomenon of a significant reduction in the groundwater resources in the mining area caused by high-intensity ecological restoration, and at the same time can save a large amount of ecological restoration funds, providing a technical approach for the green and sustainable development of the western mining areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification, and are used together with the following specific embodiments to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0043] Figure 1 is the distribution map of the investigation sample plots within the square block;

[0044] Figure 2 is the relationship curve between the leaf area index LAI and the vegetation coverage P;

[0045] Figure 3 is the relationship curve between the leaf area index LAI and the precipitation infiltration coefficient α2.

[0046] Figure 4 The relationship curve between the leaf area index LAI and the vegetation coverage P of a certain mining area;

[0047] Figure 5 The relationship curve between the leaf area index LAI and the precipitation infiltration coefficient α2 of a certain mining area. SPECIFIC EMBODIMENTS

[0048] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0049] For the method for determining the vegetation coverage based on the protection of groundwater resources of the present invention, the vegetation coverage is calculated by the following formula:

[0050]

[0051] In the formula, P max represents the maximum vegetation coverage; α1 represents the regional precipitation infiltration coefficient under the condition of no vegetation; A, B, and C are constants; a and b are constants. Specifically, at least 5 groups of vegetation water consumption and mine area precipitation infiltration coefficient data can be obtained, and the Matlab software can be used to fit the mathematical equation between the two, and then the values of A, B, and C can be calculated; at least 5 groups of leaf area index and precipitation infiltration coefficient data can be obtained, and then the values of a and b can be calculated.

[0052] In order to avoid the attenuation of regional groundwater resources caused by high-intensity ecological restoration and give the appropriate vegetation coverage for mine area ecological restoration, the following technical solutions are needed to achieve it:

[0053] 1) Determine the regional precipitation infiltration coefficient α1 under the condition of no vegetation;

[0054] Collect the meteorological data of the mine area with meteorological records over the years, and conduct indoor tests on the ultimate evaporation depth and soil mechanical parameters of the mine area soil to construct the soil hydrodynamics equation under the condition of no vegetation. The equation is as follows:

[0055]

[0056] In the formula, θ is the soil moisture content (cm 3 / cm 3 ); is the soil water potential (cm); t is the time, with the unit of d; z is the depth (cm), K(θ) is the unsaturated permeability coefficient, in cm / d. Input the above parameters into the HYDRUS finite element simulation software, and the soil water flux at different depths of the model can be obtained; assume that the ultimate evaporation depth of the groundwater in the study area is H, the precipitation is P, and the soil water flux at the depth of H is F, then the mine area precipitation infiltration coefficient α1 = F / P.

[0057] 2) Construct the relationship curve between the leaf area index and vegetation coverage of the mine area;

[0058] ① Based on remote sensing data (with a resolution of N), interpret the vegetation coverage at the mine area scale and draw the mine area vegetation coverage distribution map;

[0059] ② Randomly select 5 square blocks (at least 5) within the mine area, and set their side lengths to 3N;

[0060] ③ Set 5 (at least 5) 1m×1m survey plots (such as Figure 1 ) in the square blocks, and use the leaf area index tester to conduct on-site tests on the vegetation inside the plots. The average vegetation leaf area index in each plot is recorded as LAI y1 、LAI y2, LAI y3 , LAI y4 and LAI y5 , from which the leaf area index within each square block is calculated as follows:

[0061] LAI q = 1 / 5 × (LAI y1 + LAI y2 + LAI y3 + LAI y4 + LAI y5 );

[0062] ④ Read the average vegetation coverage of 5 square blocks in the mine area vegetation coverage distribution map, denoted as P1, P2, P3, P4, and P5 respectively. From this, the vegetation coverage within the mine area is calculated as follows:

[0063] P q = 1 / 5 × (P1 + P2 + P3 + P4 + P5);

[0064] ⑤ Use 5 groups of LAIq and Pq data to fit a mathematical equation for the two (such as Figure 2 ). Generally:

[0065] LAI = aP + b;

[0066] In the formula, LAI is the leaf area index, P is the vegetation coverage, and a and b are curve - related parameters.

[0067] 3) Construct the relationship curves between the leaf area index of the mine area, the vegetation water consumption, and the precipitation infiltration coefficient α2 under different leaf area index conditions;

[0068] Collect the meteorological data of previous years with meteorological records in the mine area, and conduct indoor tests on the ultimate evaporation depth of the mine area soil, soil mechanical parameters, and vegetation root parameters. Construct the soil hydro - dynamics equation 1 - 2 with vegetation water absorption, and its equation is as follows:

[0069]

[0070] In the formula, θ is the soil moisture content (cm 3 / cm 3 ); is the soil water potential (cm); t is the time, with the unit of d; z is the depth (cm), K(θ) is the unsaturated permeability coefficient, cm / d, S(z,t) is the root water absorption rate (1 / cm), and is related to the vegetation leaf area index.

[0071] Assume that when the vegetation coverage is 100%, the vegetation leaf area index is LAI max , and in the calculation, the leaf area index is recommended to be given as: 0.1LAI max, 0.3LAI max , 0.5LAI max , 0.7LAI max , LAI max , that is, 5 calculation conditions (must be greater than 5). The above parameters are input into HYDRUS finite element simulation software to inversely calculate the vegetation water consumption T and the precipitation infiltration coefficient α2 of the mining area under different leaf area index conditions.

[0072] Using five sets of vegetation water consumption T under different leaf area index conditions and precipitation infiltration coefficient α2 under different leaf area index conditions, the mathematical equations of the two were fitted (such as Figure 3 ), in general:

[0073] α2=C+Aexp(-B×LAI);

[0074] Where α2 is the precipitation infiltration coefficient under different leaf area index conditions, LAI is different leaf area index, and A, B and C are related parameters of the curve.

[0075] 4) Determine vegetation coverage:

[0076] ① Based on many years of meteorological data, the regional precipitation infiltration coefficient under no vegetation conditions is obtained as α1. Combined with previous research and field experience, it is believed that the regional precipitation infiltration coefficient α2 under vegetation coverage conditions cannot be less than 0.6α1.

[0077] ②Therefore, it can be judged that: C+Aexp(-BLAI)≥0.6α1;

[0078] ③Therefore, it can be judged that:

[0079] ④Therefore, it can be judged that:

[0080] ⑤Therefore, it can be judged that: Under the premise of considering the protection of regional groundwater resources, P max That is the maximum vegetation coverage for ecological restoration in the western mining area.

[0081] Embodiment 1:

[0082] A mining area has carried out a high-intensity vegetation restoration project. Shenhua Mining Area has invested more than 3 billion yuan in ecological environment construction, which has increased the vegetation coverage rate from 10% in the early stage of development to more than 80%, and the ecological environment of the mining area has been greatly improved. However, due to the large water consumption of vegetation, the amount of groundwater recharge from precipitation in the mining area has decreased, and the contradiction between the ecological environment of the mining area and the protection of groundwater resources has become prominent. Therefore, it is necessary to determine the vegetation coverage suitable for ecological restoration in the mining area.

[0083] (1) Collect the meteorological data of the mining area for 60 years, conduct indoor tests on the ultimate evaporation depth of wind-blown sand on the surface of the mining area and soil mechanical parameters, construct the soil hydrodynamics equation under bare soil conditions, and inversely calculate the precipitation infiltration coefficient α1 of the mining area to be 0.54.

[0084] (2) Use remote sensing data to obtain the vegetation coverage map of the study area. At the same time, randomly select 5 square blocks within the mining area to obtain the vegetation coverage values of the square blocks. The relationship curve is as Figure 4 shown:

[0085] Using 5 groups of LAI and P data, fit the mathematical equation between the two (as Figure 2 ), and its equation is:

[0086] LAI = 7.8007P - 4.1505 (1);

[0087] (3) Collect the meteorological data of the mining area for 60 years, conduct indoor tests on the ultimate evaporation depth of wind-blown sand on the surface of the mining area, soil mechanical parameters, and root parameters of vegetation, construct the soil hydrodynamics equation under vegetation coverage conditions, and inversely calculate the precipitation infiltration coefficient α2 of the mining area under different leaf area index conditions. The relationship curve is as Figure 5 shown:

[0088] Using 6 groups of leaf area index LAI and precipitation infiltration coefficient α2 data, fit the mathematical equation between the two, and its equation is:

[0089] α2 = 0.6029exp(-6.52LAI) (2);

[0090] From equations (1) and (2), it can be seen that:

[0091] a = 7.8007, b = -4.1505, A = 0.6029, B = 6.52, C = 0

[0092] Substitute the above parameters into

[0093] to obtain P max = 0.544;

[0094] Therefore, it can be judged that on the premise of protecting groundwater resources, the most suitable vegetation coverage for ecological restoration in this mining area is 54.4%. At present, the vegetation coverage of more than 80% in this mining area is not conducive to the protection of groundwater resources. If ecological restoration is carried out according to the vegetation coverage of 54.4%, more than 1 billion yuan of ecological environment construction funds can be saved.

[0095] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0096] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination methods.

[0097] Furthermore, any combination can be made between the various different embodiments of the present disclosure as long as it does not violate the idea of the present disclosure, and it should also be regarded as the content disclosed by the present disclosure.

Claims

1. A method for determining vegetation coverage based on the protection of underground water resources, characterized in that Including: 1) Obtain the regional precipitation infiltration coefficient under vegetation-free conditions ; 2) Construct a relationship curve between the leaf area index and vegetation coverage in the mining area to obtain constants a and b; The specific steps of 2) constructing the relationship curve between the leaf area index and vegetation coverage in the mining area are as follows: ； In the formula, is the leaf area index, is the vegetation coverage, and a and b are the relevant parameters of the curve; 3) Construct the relationship curves between the leaf area index in the mining area, the vegetation water consumption, and the precipitation infiltration coefficient α2 under different leaf area index conditions: Obtain the precipitation infiltration coefficient under different leaf area index conditions and the constants A, B, and C; specifically including: ； In the formula, is the precipitation infiltration coefficient under different leaf area index conditions, is the different leaf area index, and A, B, and C are the relevant parameters of the curve; 4) Determine the vegetation coverage: Under the vegetation coverage condition, ; The vegetation coverage is calculated by the following formula: ； In the formula, represents the maximum vegetation coverage; represents the regional precipitation infiltration coefficient under the condition of no vegetation; A, B, and C are constants; a and b are constants.

2. The method for determining vegetation coverage based on the protection of groundwater resources according to claim 1, wherein The described 1) obtaining the regional precipitation infiltration coefficient under vegetation-free conditions Specifically, it includes: Construct a soil hydrodynamics equation under the condition of no vegetation, and the equation is as follows: ； In the formula, θ is the soil water content, cm 3 / cm 3 ; is the soil water potential, cm; is time, d; depth, cm; is the unsaturated hydraulic conductivity, cm / d; Input the above parameters into the HYDRUS finite element simulation software to obtain the soil water flux at different depths of the model , the precipitation is , then the regional precipitation infiltration coefficient under the condition of no vegetation .

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