Quantification method for supporting effect of underground water on vegetation in different precipitation areas

Abstract

The invention discloses a method for quantifying the supporting effect of underground water on vegetation in different precipitation areas, and the method comprises the steps: determining the Normalized Vegetation Index (NDVI) of the vegetation in a research area; the method comprises the following steps: determining the groundwater depth (GD) of a research area; the method comprises the following steps: determining land utilization and land coverage data (Land Use and Land Cover Change, LUCC) of a research area; determining precipitation of the research area; determining a relation curve of the NDVI and the GD of the research area; determining a quantitative formula of the supporting effect of the GD in the research area on the NDVI; and determining the supporting degree of the underground water on the vegetation diversity under different rainfall conditions. According to the quantitative technology for determining the supporting effect of the underground water on the vegetation in the different northern rainfall areas, the physical process and the action mechanism are clear, and the method has universality for determining the supporting effect of the underground water on the ecological diversity of the vegetation in the arid areas; reliable theoretical and technical support is provided for guiding reasonable development of underground water in the arid region and vegetation ecological environment protection and restoration.

Description

Technical Field

[0001] The present invention relates to the technical field of quantification of ecological restoration, and in particular to a method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas. Background Art

[0002] Determining the supporting role of groundwater on vegetation in arid areas is of great significance for groundwater development and utilization and vegetation ecological restoration. It is also a technical difficulty that needs to be overcome in quantifying the supporting role of groundwater on vegetation from the perspective of eco-hydrological conditions.

[0003] In arid areas with scarce precipitation, groundwater becomes the main source of water for vegetation growth. Groundwater provides a stable water supply for surface vegetation through capillary action and root absorption. Adequate groundwater supply not only promotes plant growth, but also increases vegetation coverage and biodiversity, thereby enhancing the stability and resistance of the ecosystem. In dry seasons or drought years, groundwater recharge is particularly important, as it can ensure the normal growth of vegetation, avoid large-scale vegetation death and deterioration of the ecological environment. There is a close relationship between groundwater and vegetation growth, which can be quantified by the Normalized Difference Vegetation Index (NDVI) in remote sensing technology. Changes in groundwater levels will directly affect the growth of surface vegetation, thereby affecting changes in NDVI values. By quantifying the relationship between groundwater levels and NDVI, we can better understand the impact of groundwater on vegetation growth and provide a scientific basis for the rational management of groundwater resources.

[0004] At present, there is a lack of specific quantitative formulas for the quantitative relationship between groundwater level and NDVI. Although experts and scholars have analyzed the relationship between groundwater level and NDVI, there is a lack of quantitative calculation methods to clearly define the role of groundwater in supporting vegetation ecological diversity. Research on the role of groundwater in supporting vegetation in arid areas can effectively control the development and utilization of groundwater, maintain a reasonable groundwater depth, thereby ensuring the ecological health of regional vegetation and thus ensuring the ecological security of arid areas.

[0005] Therefore, it is necessary to propose a quantitative method to measure the supporting effect of groundwater on vegetation in different precipitation zones in order to solve the problem of quantitative calculation of the supporting effect of groundwater on vegetation ecological diversity. Summary of the invention

[0006] Aiming at the problem that there is no clear quantitative method for the current relationship between groundwater level and NDVI, the present invention proposes a quantitative method for the supporting effect of groundwater on vegetation in different precipitation areas.

[0007] The method for quantifying the supporting effect of local groundwater on vegetation in different precipitation zones includes the following steps:

[0008] S1. Determine the Normalized Vegetation Index (NDVI) of the study area;

[0009] S2. Determine the groundwater depth (GD) in the study area;

[0010] S3. Determine the land use and land cover change (LUCC) data of the study area;

[0011] S4. Determine the precipitation in the study area;

[0012] S5. Determine the relationship curve between NDVI and GD in the study area;

[0013] S6. Determine the quantitative formula for the supporting effect of GD on NDVI in the study area. The specific method is:

[0014] According to the relationship curve between NDVI and GD, the maximum and minimum NDVI values ​​in the study area are determined, that is, NDVI max With NDVI min , using NDVI max With NDVI min , we can get the quantitative formula of GD's supporting effect on NDVI:

[0015]

[0016] S7. Determine the extent to which groundwater supports vegetation diversity under different precipitation conditions.

[0017] In a preferred embodiment of the present invention, the method for determining the NDVI of the study area in S1 is: obtaining the annual NDVI data of the study area through the MODIS data published on the official website of the Geospatial Data Cloud, and drawing the spatial distribution of NDVI in different areas.

[0018] In a preferred embodiment of the present invention, the method for determining the study area GD in S2 is: construct multiple groundwater level monitoring points in the study area, collect groundwater level data in different time periods in the area, and use the inverse distance weighted method to perform interpolation analysis on the groundwater level data.

[0019] In a preferred embodiment of the present invention, the method for determining the LUCC of the study area in S3 is: determining the land use and coverage characteristics of the study area according to the data, and determining the vegetation types at different locations.

[0020] In a preferred embodiment of the present invention, the method for determining the precipitation in the study area in S4 is: obtaining the actual annual precipitation in the study area through the meteorological station data in the study area.

[0021] In a preferred embodiment of the present invention, the method for determining the relationship curve between NDVI and GD in the study area in S5 is: by analyzing the raster data of NDVI and GD, determining the GD value corresponding to the NDVI value on each cell, and drawing the relationship curve between NDVI and GD.

[0022] In a preferred embodiment of the present invention, the method for determining the degree of support of groundwater to vegetation diversity under different precipitation conditions in S7 is: by selecting areas under different precipitation conditions for analysis, determining the supporting role of groundwater to vegetation ecology in different areas, and comparing and analyzing the degree of support of groundwater to vegetation diversity under different precipitation conditions.

[0023] Furthermore, regions under different precipitation conditions include arid regions, semi-arid regions, and sub-humid regions.

[0024] Implementing the embodiments of the present invention has the following beneficial effects:

[0025] The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas of the present invention determines the relationship curve between NDVI and GD in the study area by determining the normalized difference vegetation index NDVI, groundwater depth GD, land use and land cover data LUCC and precipitation in the study area; then determines the quantitative formula for the supporting effect of GD on NDVI in the study area; and finally determines the supporting degree of groundwater on vegetation diversity under different precipitation conditions. The physical process and action mechanism of the present invention are clear, and it is universal for determining the supporting effect of groundwater on the ecological diversity of vegetation in arid areas, and provides reliable theoretical and technical support for guiding the rational development of groundwater in arid areas and the protection and restoration of vegetation ecological environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the process flow of the quantification technology of the supporting effect of groundwater on vegetation in different precipitation areas provided by the present invention;

[0028] Figure 2 This is an overview of the location of the study area and its sub-areas;

[0029] Figure 3 This is the spatial distribution map of NDVI in different regions in 2020;

[0030] Figure 4The spatial distribution map of groundwater monitoring wells in different regions;

[0031] Figure 5 This is the land use type distribution map of different regions in 2020;

[0032] Figure 6 This is the curve of NDVI changing with groundwater depth in different regions;

[0033] Figure 7 This is a graph showing the changes in the supporting role of groundwater on vegetation in different regions. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The present invention provides a quantitative technology for the supporting effect of groundwater on vegetation in different precipitation zones. The principle is as follows: the diversity of vegetation ecosystems is fundamentally dependent on groundwater, especially in arid areas. Changes in groundwater depth have a significant impact on vegetation that is significantly dependent on groundwater. Excessive groundwater development even causes damage to regional ecosystems, and ecosystem damage can be reflected by the Normalized Difference Vegetation Index (NDVI). At present, based on the relationship between GD and NDVI in a specific area, the degree of dependence of NDVI on GD can be qualitatively described, but there is a lack of quantitative description methods. Therefore, it is impossible to compare and analyze the degree of dependence of NDVI on GD in different regions. Therefore, we propose a quantitative technology for the supporting effect of groundwater on vegetation in different precipitation zones in the north, which can be used to quantify the degree of dependence of regional NDVI on GD, and compare and analyze the degree of dependence of NDVI on GD between different regions.

[0036] See also Figure 1 , Figure 1 The flowchart of the quantitative technology of the supporting effect of groundwater on vegetation in different precipitation zones in the north provided by the present invention is as follows; the quantitative method of the supporting effect of groundwater on vegetation in different precipitation zones comprises the following steps:

[0037] Step 1: Determine the Normalized Vegetation Index (NDVI) of the study area: Obtain the annual NDVI data of the study area through the MODIS data published on the official website of the Geospatial Data Cloud, and draw the spatial distribution of NDVI in different areas.

[0038] Step 2: Determine the groundwater depth (GD) in the study area: Construct multiple groundwater level monitoring points in the study area, collect groundwater level data at different time periods in the area, and use the inverse distance weighted method to perform interpolation analysis on the groundwater level data.

[0039] Step 3: Determine the land use and land cover data (LUCC) of the study area: Determine the land use and cover characteristics of the study area based on the data and determine the vegetation types at different locations.

[0040] Step 4: Determine the precipitation in the study area: Obtain the actual annual precipitation in the study area through the meteorological station data in the study area.

[0041] Step 5. Determine the relationship curve between NDVI and GD in the study area: By analyzing the raster data of NDVI and GD, determine the GD value corresponding to the NDVI value in each cell, and draw the relationship curve between NDVI and GD.

[0042] Step 6: Determine the quantitative formula for the supporting effect of GD on NDVI in the study area. The specific method is:

[0043] According to the relationship curve between NDVI and GD, the maximum and minimum NDVI values ​​in the study area are determined, that is, NDVI max With NDVI min , using NDVI max With NDVI min , we can get the quantitative formula of GD's supporting effect on NDVI:

[0044]

[0045] Step 7. Determine the degree of support of groundwater to vegetation diversity under different precipitation conditions: By selecting areas with different precipitation conditions (arid areas, semi-arid areas and semi-humid areas) for analysis, determine the supporting role of groundwater on vegetation ecology in different areas, and compare and analyze the degree of support of groundwater to vegetation diversity under different precipitation conditions.

[0046] The following are specific examples of arid, semi-arid and semi-humid areas in northern China:

[0047] Eight sub-regions in northern China, including the Shiyang River Basin, the Ningxia Yellow River Irrigation Area, the Inner Mongolia Hetao Irrigation Area, the Maowusu Sandy Land, the Xiliaohe River Basin, the Guanzhong Plain, and the Haihe River Basin Plain, were selected as case areas and sorted in the order of a to h. Their spatial locations are shown in the figure. Figure 2By collecting NDVI data, groundwater depth, and land use data in the study area, and using the constructed quantitative formula to quantify the dependence of NDVI on GD in a specific area, we finally compared and analyzed the supporting role of groundwater on vegetation in the case areas in 8 different precipitation gradient zones.

[0048] This embodiment is a method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas, comprising the following steps:

[0049] Step 1: Determine the Normalized Vegetation Index (NDVI) of the study area. Through the MODIS data published on the official website of the Geospatial Data Cloud, you can obtain the annual NDVI spatial distribution raster data of the eight case areas with a spatial resolution of 1 km. Here, the NDVI of the eight case areas in 2020 is spatially displayed and distributed, as shown in the figure below: Figure 3 During the data processing, ArcGIS was used to convert the raster to a table to obtain the NDVI value of each pixel unit. The length of the time series was based on the collected groundwater depth time series. The specific time series of each case area are shown in Table 1.

[0050] Step 2: Determine the groundwater depth (GD) in the study area. Construct multiple groundwater level monitoring points in the region and collect groundwater level depth data at different time periods in 8 case areas. The groundwater monitoring time periods and the number of pumped wells in different regions are shown in Table 1. Figure 4 ), the groundwater level data were interpolated using the inverse distance weighted method. The spatial resolution was consistent with NDVI, which was also 1 km. The raster conversion was performed in ArcGIS to obtain the GD value of each pixel unit.

[0051] Table 1 Data analysis time series

[0052] Code name Number of groundwater monitoring points Time Series Multi-year average precipitation at the monitoring point / mm a Heihe River Basin 84 2018-2020 P<200 b Shiyang River Basin 74 2000-2018 P<200 c Ningxia Yellow River Irrigation Area 133 2000-2018 200<P<400 d Inner Mongolia Hetao Irrigation District 216 2003-2013 200<P<400 e Xiliaohe River Basin 74 2000-2018 200<P<400 f Maowusu Sandy Land 99 2018-2020 200<P<400 g Guanzhong Plain 439 2010-2018 400<P<800 h Haihe Plain 621 2018-2020 400<P<800 total 1740

[0053] Step 3: Determine the land use and land cover (LUCC) data of the study area. According to the annual land use data published by the Resource and Environmental Science Data Platform, determine the LUCC of the study area with a spatial resolution of 1 km, so as to determine the vegetation distribution types in different regions. The land use types of 8 case areas in 2020 are used as examples for demonstration. Figure 5As shown. At the same time, raster conversion in ArcGIS is used to obtain the land use type of each pixel unit, and based on this, the farmland type is eliminated to obtain the relationship between NDVI and GD under natural vegetation. After processing the above NDVI, GD, and LUCC data, the NDVI, GD, and LUCC corresponding to each pixel unit in different regions and years can be obtained.

[0054] Step 4: Determine the precipitation in the study area. The annual precipitation in the study area is obtained through the meteorological station data in the study area. This is used to determine the precipitation gradients in different case areas, which facilitates comparative analysis of the differences in the support of groundwater to vegetation under different precipitation gradients. The location distribution of meteorological stations in the study area is as follows: Figure 2 shown.

[0055] Step 5: Determine the relationship curve between NDVI and GD in the study area. By analyzing the raster data of NDVI and GD, determine the GD value corresponding to the NDVI value in each cell, and statistically obtain the NDVI of different groundwater depths at intervals of 0.1m, and draw the relationship curve between NDVI and GD in different regions. The relationship curves of different years in each region are drawn in one figure to show the relationship curves in different rainfall years, and then the figures of different regions are compared and analyzed to show the relationship curves under different rainfall scales. Here, the average value of the calculation year is taken, and the drawing results are shown as follows: Figure 6 shown.

[0056] Step 6: Determine the quantitative formula for the supporting effect of GD on NDVI in the study area; Based on the relationship curve between NDVI and GD, the maximum and minimum NDVI values ​​in the study area can be determined, that is, NDVI max With NDVI min , using NDVI max With NDVI min , which is the quantitative formula of the supporting effect of GD on NDVI:

[0057]

[0058] According to the quantitative formula, the specific values ​​of the supporting effect of GD on NDVI in different years in the eight case areas can be calculated, that is, the degree of dependence. Each blue dot in the figure is the degree of dependence of a region in a certain year. After the calculation is completed for all regions and all years, the median value, average value and other data of the supporting effect of GD on NDVI in each region in the long time series can be obtained, such as Figure 7 shown.

[0059] Step 7: Determine the support degree of groundwater to vegetation diversity under different precipitation conditions. The precipitation gradient of the eight case areas is determined by the average precipitation over many years. They are basically divided into arid areas with precipitation less than 200 mm, including the Heihe River Basin and the Shiyang River Basin; semi-arid areas with precipitation greater than 200 mm and less than 400 mm, including the Ningxia Yellow River Irrigation Area, the Hetao Irrigation Area in Inner Mongolia, the Xiliaohe River Basin and the Maowusu Desert; and semi-humid areas with precipitation greater than 400 mm and less than 800 mm, including the Guanzhong Plain and the Haihe River Basin Plain. By comparing and analyzing the dependence calculated in the eight case areas, we can obtain the support role of regional groundwater to vegetation ecology under different precipitation gradients, such as Figure 7 As shown in the figure, the curve of groundwater support for vegetation with increasing rainfall shows that in areas with greater rainfall, the more water required for vegetation comes from precipitation, resulting in a smaller role of groundwater in supporting vegetation ecology. On the contrary, in areas with less precipitation, groundwater, as the main source of vegetation water demand, has a greater supporting role for vegetation.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas, characterized in that: The following steps are involved: S1. Determine the Normalized Difference Vegetation Index (NDVI) of the study area; S2. Determine the groundwater depth GD in the study area; S3. Determine the land use and land cover data LUCC in the study area; S4. Determine the precipitation in the study area; S5. Determine the relationship curve between NDVI and GD in the study area; S6. Determine the quantitative formula for the supporting effect of GD on NDVI in the study area. The specific method is: According to the relationship curve between NDVI and GD, the maximum and minimum NDVI values ​​in the study area are determined, that is, NDVI max With NDVI min , using NDVI max With NDVI min , we can get the quantitative formula of GD's supporting effect on NDVI: S7. Determine the extent to which groundwater supports vegetation diversity under different precipitation conditions.

2. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 1 is characterized in that: The method for determining the NDVI of the study area in S1 is: obtain the annual NDVI data of the study area through the MODIS data published on the official website of the Geospatial Data Cloud, and draw the spatial distribution of NDVI in different areas.

3. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 1 is characterized in that: The method for determining the GD of the study area in S2 is: construct multiple groundwater level monitoring points in the study area, collect groundwater level data of different periods in the area, and use the inverse distance weighted method to perform interpolation analysis on the groundwater level data.

4. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 1, characterized in that: The method for determining the LUCC of the study area in S3 is: determining the land use and coverage characteristics of the study area according to the data, and determining the vegetation types at different locations.

5. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 1, characterized in that: The method for determining the precipitation in the study area in S4 is: obtaining the actual annual precipitation in the study area through the meteorological station data in the study area.

6. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 1, characterized in that: The method for determining the relationship curve between NDVI and GD in the study area in S5 is: by analyzing the grid data of NDVI and GD, determining the GD value corresponding to the NDVI value on each cell, and drawing the relationship curve between NDVI and GD.

7. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 1, characterized in that: The method for determining the degree of support of groundwater to vegetation diversity under different precipitation conditions in S7 is: by selecting areas under different precipitation conditions for analysis, determining the supporting role of groundwater to vegetation ecology in different areas, and comparing and analyzing the degree of support of groundwater to vegetation diversity under different precipitation conditions.

8. The method for quantifying the supporting effect of groundwater on vegetation in different precipitation areas according to claim 7, characterized in that: The regions under different precipitation conditions include arid regions, semi-arid regions and semi-humid regions.

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