Ground water quality monitoring method based on high spatial resolution satellite

Abstract

The ground water quality monitoring method based on high-spatial-resolution satellites can efficiently and conveniently measure the water quality of the target water body. The ground water quality monitoring method includes: Step 1: Construct a ground water quality standard pool to obtain ground water quality data; the ground water quality standard pool includes: Standard Pool A for containing clear water, Standard Pool B for containing natural water, and Standard Pools C to E for containing three types of mixed water formed by mixing clear water and natural water with the proportion of clear water being n1, n2, and n3 respectively; Step 2: Obtain high-spatial-resolution remote sensing images and process them; Step 3: Conduct a correlation analysis on the remote sensing image data bands and the preset proportion values of the ground water quality standard pool to identify the remote sensing bands with high correlation; Step 4: Establish a water quality parameter inversion model and perform contrast inversion through the remote sensing bands with high correlation and the ground water quality data to obtain water quality data; Step 5: Based on the ground water quality data and the water quality data threshold, obtain water quality anomaly points.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface water quality monitoring, and particularly relates to a surface water quality monitoring method based on high-spatial-resolution satellites. Background Art

[0002] Compared with traditional water quality monitoring methods, water quality remote sensing has irreplaceable advantages such as rich data volume, periodicity, low cost, and large scale. At the same time, the large amount of data and spatio-temporal integrity brought by remote sensing can conveniently analyze and predict the spatio-temporal distribution changes of water quality, which helps to discover pollution sources and pollutant migration characteristics that are difficult to reveal by conventional methods. However, remote sensing technology still needs to rely on ground water quality data for inversion, which requires the construction of ground water quality monitoring means adapted to remote sensing technology. Currently, remote sensing technology uses data from ground monitoring stations, but the number of ground monitoring stations is small, the distribution is uneven, the construction cost is high, and the water quality detection method uses test tubes for multi-batch sampling. The large number of samples is easy to be confused, the sampling time and the batches of reagents used are often different, and at the same time, the water samples are not easy to preserve, generally having the disadvantages of time-consuming, laborious, introducing too many errors, and unstable results. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a surface water quality monitoring method based on high-spatial-resolution satellites, which can efficiently and conveniently measure the water quality of the target water body.

[0004] The surface water quality monitoring method based on high-spatial-resolution satellites provided by the present invention is characterized by comprising the following steps:

[0005] Step 1: Build a ground water quality standard pool through clear water, the natural water body to be measured, and mixed water of different proportions of the two to obtain ground water quality data; the ground water quality standard pool includes: standard pool A for containing clear water, standard pool B for containing natural water, and standard pools C, D, and E for containing three types of mixed water formed by mixing clear water and natural water with the proportions of clear water being n1, n2, and n3 respectively, and n1, n2, and n3 are different from each other; set water quality detection equipment to obtain the water quality data in standard pool B;

[0006] Step 2: Obtain high-spatial-resolution remote sensing images of lakes, reservoirs, and rivers, and then preprocess and crop the collected data;

[0007] Step 3: Perform a correlation analysis on the remote sensing image data bands obtained in Step 2 and the preset proportional values of the ground water quality standard pool in Step 1 to identify remote sensing bands with high correlation;

[0008] Step 4: Establish a water quality parameter inversion model, and compare and invert the highly correlated remote sensing bands obtained in Step 3 with the ground water quality data obtained in Step 1 to obtain the water quality data of the entire lake reservoir and river

[0009] Step 5: Based on the water quality data of the entire lake reservoir and river obtained in Step 4 and the preset water quality data threshold, obtain water quality anomaly points, thereby identifying areas where the pollutant concentration exceeds the standard.

[0010] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In Step 1, each standard pool is equipped with a valve; the revisit period of the satellite for acquiring remote sensing images is used as the pool water update period to remix and update the water bodies in each standard pool.

[0011] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In Step 1, the length and width of each standard pool should be not less than three times the resolution of the remote sensing image.

[0012] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In Step 1, there are more than three standard pools for containing mixed water, and at least three of these standard pools for containing mixed water have different proportions of clear water.

[0013] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In Step 1, n1 = 1 / 2, n2 = 2 / 3, n3 = 1 / 3.

[0014] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In Step 2, the resolution of the acquired high-spatial-resolution remote sensing image should not exceed 1 m.

[0015] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In Step 3, according to the natural water body and the proportion of clear water in the standard pool, the proportion of pollutant concentration in the standard pool can be obtained, and finally, through correlation analysis, remote sensing bands with higher adaptability and correlation with the proportion of pollutant concentration can be obtained.

[0016] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: Through correlation analysis, several bands with relatively high correlation degrees can be obtained. At least the top three bands are selected, or those bands with a correlation coefficient exceeding a certain value are selected.

[0017] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In step 3, a correlation analysis is performed on the remote sensing bands and the preset proportional values of the ground water quality standard pools. X1 is the remote sensing band matrix, and Y1 is the preset proportional value matrix of the pollutant concentration; through the correlation analysis, a correlation coefficient matrix R1 of each band and the preset proportional value matrix of the pollutant concentration is obtained:

[0018]

[0019] In the formula, the subscripts A to E are the standard pool numbers, and the superscripts I, II, III, IV, V, and VI are the band types. That is, the value of band I of standard pool A.

[0020]

[0021] R1 = [r Ⅰ r Ⅱ r Ⅲ r Ⅳ r Ⅴ r Ⅵ

[0022] Solve and select multiple bands with the top-ranked values in R1, or select those bands with a correlation coefficient exceeding a certain value as the remote sensing bands with high correlation.

[0023] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In step 4, the water quality index - spectral reflectance correlation model of the monitoring point is inversely calculated from the ground water quality standard pool data and the spectral reflectance data of the corresponding monitoring sites through an optimization model, and the multiple correlation coefficient R 2 is used to test the accuracy of the model. By performing a correlation statistical analysis on each band and band combination and the corresponding water quality index data, the optimal inversion bands and band combinations of each water quality index are determined, and an inversion regression model of the pollutant concentration is established respectively. The water quality parameter inversion model includes, but is not limited to, using the partial least squares method.

[0024] Preferably, the ground water quality monitoring method based on high-spatial-resolution satellites provided by the present invention may further have the following features: In step 5, based on the overall lake / reservoir and river water quality data obtained in step 4 and the water quality data threshold, the overall water quality situation and water quality distribution situation can also be identified and notified and warned. In step 5, the extracted results include the overall water quality situation, water quality distribution situation, and the results of abnormal point investigation, and can detect various pollutant situations, including but not limited to COD, total phosphorus, and total nitrogen.

[0025] Functions and effects of the invention

[0026] 1. The present invention saves time and effort and can effectively reduce the number of water quality detection stations required.

[0027] 2. This solution establishes a ground water quality standard pool, and multiple sets of data for different intervals can be obtained using a single set of water quality detection equipment, which is more conducive to establishing the correlation between wavebands and pollutant concentrations.

[0028] 3. Compared with the instability of results caused by possible factors such as different sampling times and different batches of reagents in traditional methods, the results obtained by the present invention are more stable and effective.

[0029] 4. The present invention can identify remote sensing wavebands with high correlation and better applicability.

[0030] 5. The present invention can obtain the overall water quality status of lakes, reservoirs and rivers.

[0031] 6. The present invention can effectively detect anomalies, and has a monitoring and early warning effect on large-scale pollution or abnormal leakage.

[0032] 7. The present invention can effectively reduce costs and reduce the use of water quality monitoring reagents.

[0033] In summary, the present invention can measure the water quality of target water bodies more efficiently, conveniently and quickly, which is beneficial to large-scale water quality monitoring. At the same time, it can effectively reduce costs, reduce the number of water quality detection experiments, detect pollution abnormal points, and is conducive to the early warning of sudden pollution events and the investigation of pollution sources. The method of the present invention is convenient to build, easy to maintain, has good effects and high efficiency, and is very suitable for large-scale promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flowchart of the ground water quality monitoring method based on high spatial resolution satellites according to an embodiment of the present invention;

[0035] Figure 2 is a schematic diagram of the location of the ground water quality standard pool according to an embodiment of the present invention;

[0036] Figure 3 is a simulated satellite map according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following describes in detail the ground water quality monitoring method based on high spatial resolution satellites according to the present invention with reference to the accompanying drawings.

[0038] <Embodiment>

[0039] As Figure 1 shown, the ground water quality monitoring method based on high spatial resolution satellites provided in this embodiment includes the following steps:

[0040] S1. Build a surface water quality standard pool by mixing natural water bodies and clean water in different proportions to obtain surface water quality data.

[0041] Building the surface water quality standard pool includes two steps. The first step is to build the pool and then fill the corresponding pools with water bodies of different concentration gradients. Its length and width should be no less than three times the resolution. In this embodiment, the length × width × height of the standard pool is set to: 3m × 3m × 1m.

[0042] As Figure 2 shown, five standard pools A - E are distributed on one side of River - Lake 1, and standard pools B - E are all connected to River - Lake 1 through the natural water body connection pipeline 2. Among them, standard pool A is filled with clean water, standard pool B is filled with natural water, 1 / n1 of standard pool C is natural water and the rest is clean water, 1 / n2 of standard pool D is natural water and the rest is clean water, 1 / n3 of standard pool E is natural water and the rest is clean water. To ensure that the natural water entering the standard pool is consistent with that in the natural water body 1, valves are installed at the inlet of the standard pool to pump in natural water, and the water in the pool is re - mixed and updated with the satellite revisit period as the cycle. The simulated satellite image is as Figure 3 shown. And a set of water quality detection equipment is arranged in standard pool B. In this embodiment, n1, n2, and n3 are taken as 1 / 2, 2 / 3, and 1 / 3 respectively.

[0043] S2. Obtain high - spatial - resolution remote sensing images of lakes, reservoirs, and rivers, and pre - process and crop the collected data.

[0044] Satellite remote sensing uses high - spatial - resolution remote sensing. The ground resolution of high - spatial - resolution remote sensing is less than 1m, which can improve the accuracy of water quality detection.

[0045] Image pre - processing includes radiometric calibration, atmospheric correction, and geometric correction. Radiometric calibration is to convert the brightness and gray - scale values of the image into absolute radiance. Atmospheric correction is the process of eliminating the radiation errors caused by the atmosphere and retrieving the true surface reflectance of the ground object. Geometric correction refers to correcting and eliminating the deformation of the geometric positions, shapes, sizes, orientations, etc. of various ground objects on the original image caused by factors such as the deformation of the photographic material, lens distortion, atmospheric refraction, earth curvature, earth rotation, and terrain undulation during the imaging of remote sensing images when they do not meet the expression requirements in the reference system through a series of mathematical models.

[0046] S3. Through the correlation analysis of the remote sensing image data bands obtained in S2 and the preset proportion values of the S1 surface water quality standard pool, identify the remote sensing bands with high correlation.

[0047] Perform a correlation analysis on the preset ratio values of remote sensing bands and the ground water quality standard pool. Let X1 be the remote sensing band matrix and Y1 be the preset ratio value matrix of pollutant concentrations. By performing a correlation analysis on them, obtain the correlation coefficient matrix R1 of each band and the preset ratio value matrix of pollutant concentrations, and select the three bands with the largest correlation coefficients among them.

[0048]

[0049] Among them, the subscripts A - E are the standard pool numbers, and the superscripts Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ, Ⅵ are the band types. For example is the value of band Ⅰ of standard pool A(3).

[0050]

[0051] R1 = [r Ⅰ r Ⅱ r Ⅲ r Ⅳ r Ⅴ r Ⅵ

[0052] The following gives the specific calculation:

[0053]

[0054] From S1, in this embodiment, n1 = 1 / 2, n2 = 2 / 3, n3 = 1 / 3. Therefore:

[0055]

[0056] R1 = [0.312 0.026 0.548 0.713 0.547 0.561]

[0057] Therefore, the selected bands are bands Ⅲ, Ⅳ, and Ⅵ.

[0058] S4. Establish a water quality parameter inversion model. Compare and invert the high - correlation remote sensing bands obtained in S3 with the ground water quality data obtained in S1 to obtain the water quality data of the entire lake - reservoir and river.

[0059] Using the data of the ground water quality standard pool and the spectral reflectance data of the corresponding monitoring stations, an optimized model such as the partial least squares method is used to invert the water quality index - the spectral reflectance correlation model of the monitoring points, and the multiple correlation coefficient R 2 is used to test the accuracy of the model. That is, by performing a correlation statistical analysis on each band and band combination and the corresponding water quality index data, the best inversion bands and band combinations of each water quality index are determined, and the inversion regression models of pollutant concentrations are established respectively.

[0060] The steps of the partial least squares method are as follows: ​

[0061] 1. Establish an independent variable group (taking the case where the correlation coefficients in Bands III, IV, and VI are the largest):

[0062]

[0063] In the formula, the subscript A is the standard cell number, and the superscripts III, IV, and VI are the band types. For example, is the value of Band III of the standard cell A(3).

[0064] 2. Establish a dependent variable group

[0065] Regular water quality tests need to be carried out on the standard cell B to obtain:

[0066]

[0067] In the formula, C COD , C TP , C TN are the measured values of COD, TP, and TN of natural water.

[0068] 3. Standardize X and Y into E0 and F0, and obtain the rank h of X.

[0069] 4. Find the unit eigenvector ω1 corresponding to the largest eigenvalue of the matrix , and the corresponding component t1:

[0070] t1 = E0ω1

[0071]

[0072]

[0073] 5. Find the unit eigenvector ω2 corresponding to the largest eigenvalue of the matrix , and the corresponding component t2:

[0074] t2 = E1ω2

[0075]

[0076] 6. Repeat the steps until the unit eigenvector ω corresponding to the largest eigenvalue of the matrix h , and the corresponding component t h are obtained.

[0077] 7. The ordinary least squares regression equation of F0 on t1,..., t h is:

[0078]

[0079] The specific calculation is given below:

[0080] After measurement, C TN is 1.8 mg / L.

[0081]

[0082] Y = [0 1.8 0.9 1.2 0.6]

[0083] Y = 2.20 + 0.000486*X Ⅲ - 0.00411*X Ⅳ + 0.00342X Ⅵ

[0084] In the formula, Y is the total nitrogen value, X Ⅲ is the value of the III band at the calculation point, X Ⅳ is the value of the IV band at the calculation point, X Ⅵ is the value of the VI band at the calculation point.

[0085] According to the relationship between the obtained pollutant concentration values and the bands, the pollutant concentration values of the entire lake and reservoir can be calculated.

[0086] S5. Based on the water quality data of the entire lake and reservoir and the rivers obtained in S4, and the set water quality data threshold, the abnormal points are investigated and reported.

[0087] In this embodiment, the set water quality data threshold is: the pollutant concentration reaches five times the surrounding pollutant concentration and the pollutant concentration meets the surface water class V standard.

[0088] Therefore, the abnormal points are the points where the pollutant concentration is more than five times higher than the surrounding pollutant concentration and exceeds the surface water class V standard. After discovering the abnormal points, their causes can be reported for investigation, that is, the following conditions are met: y i,k > 5×y i,j &y i,k > x i , where y i,k is the concentration of pollutant i at point K (i = 1, 2, 3, which are COD, total phosphorus, and total nitrogen respectively), y i,j is the concentration of pollutant i at point J (point J meets the condition D < 3×d, where D is the distance between point J and point K, and d is the satellite spatial resolution), x i is the surface water class V standard concentration corresponding to the pollutant (x1 = 40 mg / L, x2 = 0.4 mg / L, x3 = 2.0 mg / L).

[0089] The above embodiments are only illustrative examples of the technical solution of the present invention. The method for monitoring ground water quality based on high-spatial-resolution satellites involved in the present invention is not limited solely to the content described in the above embodiments, but is subject to the scope defined by the claims. Any modifications, supplements, or equivalent replacements made by those skilled in the art to which the present invention pertains based on this embodiment are within the scope protected by the claims of the present invention.

Claims

1. A method for monitoring ground water quality based on high spatial resolution satellites, characterized in that, It includes the following steps: Step 1: Build a surface water quality standard pool with clear water, the natural water body to be measured, and mixed water of different proportions of the two to obtain surface water quality data. The surface water quality standard pool includes: Standard Pool A for containing clear water, Standard Pool B for containing natural water, and Standard Pools C, D, and E for containing three types of mixed water formed by mixing clear water and natural water with the proportion of clear water being n1, n2, and n3 respectively, and n1, n2, and n3 are different from each other. Set up water quality detection equipment to obtain the water quality data in Standard Pool B; Step 2: Obtain high-spatial-resolution remote sensing images of lakes, reservoirs, and rivers, and preprocess and crop the collected data; Step 3: Through correlation analysis of the remote sensing image data bands obtained in Step 2 and the preset proportion values of the surface water quality standard pool in Step 1, identify the remote sensing bands with high correlation; Step 4: Establish a water quality parameter inversion model, and perform contrast inversion through the remote sensing bands with high correlation obtained in Step 3 and the surface water quality data obtained in Step 1 to obtain the water quality data of the entire lake, reservoir, and river; Step 5: Based on the water quality data of the entire lake, reservoir, and river obtained in Step 4 and the water quality data threshold, obtain water quality anomaly points, thereby identifying areas where the pollutant concentration exceeds the standard; Among them, in Step 3, when performing correlation analysis on the remote sensing bands and the preset proportion values of the surface water quality standard pool, X1 is the remote sensing band matrix, and Y1 is the preset proportion value matrix of the pollutant concentration; through performing correlation analysis on it, obtain the correlation coefficient matrix R1 of each band and the preset proportion value matrix of the pollutant concentration: In the formula, the subscripts A to E are the standard cell numbers, and the superscripts I, II, III, IV, V, VI are the band types, which is the value of band I of standard cell A; R1＝[r Ⅰ r Ⅱ r Ⅲ r Ⅳ r Ⅴ r Ⅵ ] Solve and select multiple bands with the top-ranked values in R1, or select those bands with a correlation coefficient exceeding a certain value as the remote sensing bands with high correlation; In step 4, the water quality standard pool data and the spectral reflectance data of the corresponding monitoring sites are used to inversely calculate the water quality indexes of the monitoring points through an optimized model - a spectral reflectance correlation model, and the multiple correlation coefficient R 2 is used to test the accuracy of the model. By conducting a correlation statistical analysis on each band and band combination with the corresponding water quality index data, the optimal inversion bands and band combinations for each water quality index are determined, and the inversion regression models for pollutant concentrations are established respectively.

2. The surface water quality monitoring method based on high-spatial-resolution satellites according to claim 1, wherein: Among them, In Step 1, each standard pool is equipped with a valve; use the revisit period of the satellite for obtaining remote sensing images as the pool water update period to remix and update the water bodies in each standard pool.

3. The method for monitoring ground water quality based on high-spatial-resolution satellites according to claim 1, wherein: Among them, In Step 1, the length and width of each standard pool should be not less than three times the resolution of the remote sensing image.

4. The surface water quality monitoring method based on high-spatial-resolution satellites according to claim 1, wherein: Among them, In Step 1, there are more than three standard pools for containing mixed water, and at least three of these standard pools for containing mixed water have different proportions of clear water.

5. The method for monitoring surface water quality based on high-spatial-resolution satellites according to claim 1, wherein: In Step 1, n1 = 1 / 2, n2 = 2 / 3, n3 = 1 / 3.

6. The method for monitoring surface water quality based on high-spatial-resolution satellites according to claim 1, wherein: Among them, In Step 2, the resolution of the obtained high-spatial-resolution remote sensing image should not exceed 1m.

7. The surface water quality monitoring method based on high-spatial-resolution satellites according to claim 1, wherein: Among them, In Step 3, according to the proportion of natural water and clear water in the standard pool, the pollutant concentration proportion in the standard pool can be obtained, and then through correlation analysis, several bands with high adaptability and correlation with the pollutant concentration proportion are obtained, at least select the top three bands, or select those bands with a correlation coefficient exceeding a certain value.

8. The ground water quality monitoring method based on high spatial resolution satellites according to claim 1, wherein: Among them, In step 5, based on the water quality data of the entire lake reservoir and river obtained in step 4 and the water quality data threshold, the overall water quality situation and the water quality distribution situation can also be identified.

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