Underground water resource bearing capacity evaluation method considering water quality

Abstract

The invention relates to an underground water resource bearing capacity evaluation method considering water quality, and belongs to the technical field of resources and environments, and the method comprises the following steps: constructing an underground water resource bearing capacity evaluation index system considering water quality; groundwater quality investigation is carried out, and data required by evaluation are obtained; determining an index weight based on an analytic hierarchy process; calculating the membership degree of each index, and determining the membership degree of the water quality index through a classification worst membership degree principle; and carrying out groundwater resource bearing capacity evaluation based on GIS software. The problem that in the prior art, an underground water resource bearing capacity evaluation method is insufficient in consideration of underground water quality is solved; the water quality parameters are divided into general water chemical indexes and toxicological indexes, so that the exaggeration of the severe degree of the water quality is avoided; the problem of mapping a plurality of water quality parameters to a single evaluation index is solved through a worst membership principle, so that the influence of the water quality condition on the groundwater resource bearing capacity can be reflected more truly.

Description

Technical Field

[0001] The present invention belongs to the technical field of resources and environment, and can be used to evaluate the spatio-temporal variation characteristics of the regional groundwater resource carrying capacity. More specifically, it relates to a method for evaluating the groundwater resource carrying capacity considering water quality. Background Art

[0002] Groundwater is an important water supply source in China. In the northern region of China, 65% of domestic water, 50% of industrial water, and 33% of agricultural water rely on groundwater. In the southern region, due to its advantages such as stable water volume and strong water resource preservation ability, groundwater plays a huge role in coping with extreme drought climate, rapid urbanization, and industrialization. However, the overexploitation of groundwater will also induce environmental problems such as water resource depletion, land subsidence, and groundwater pollution. The sustainable utilization of groundwater resources in China requires strengthening planning and management, which depends on the scientific assessment of water resource supply capacity. Water resource carrying capacity is a basic measure for evaluating water resource security, which refers to the maximum ability of water resources to supply water for industrial and agricultural production, people's livelihood, and ecological environment protection under certain economic and technological levels and social production conditions. The groundwater resource carrying capacity can be regarded as an extension of the water resource carrying capacity in terms of groundwater.

[0003] The construction of the index system is the core of the evaluation of the groundwater resource carrying capacity. Social economy, water resources, and water ecology related indicators are the main contents of the index systems used in most current studies. However, the resource attribute of water is jointly determined by water quantity and water quality, that is, groundwater that does not meet the water quality standard does not have the value of water supply. The development and utilization of groundwater in China generally face water quality problems. The proportion of monitoring points with groundwater quality meeting the Class I - III water quality standards in the Yangtze River and Yellow River basins is only 52.53% and 14.03% respectively, and the proportion of the area with excessive shallow groundwater quality in the whole country is as high as 59.49%. These data mean that the evaluation of the groundwater resource carrying capacity in China needs to focus on water quality issues.

[0004] Currently, only a few studies on the groundwater resource carrying capacity incorporate water quality related indicators into the evaluation index system. Some studies use indirect indicators such as sewage discharge and sewage treatment rate to characterize the groundwater quality status, which cannot directly reflect the impact of water quality on the groundwater resource carrying capacity. Other studies use parameters such as water quality compliance rate and multiple times of exceeding the single index to characterize the groundwater quality status. If the groundwater quality is characterized by a single index, there will be a problem that the representativeness of the index is doubtful due to the lack of a unified standard for the selection of water quality parameters. If it is characterized by the water quality compliance rate, due to the large differences in health hazards among different water quality parameters, the "one-size-fits-all" evaluation method for all indicators may overestimate the severity of water quality and underestimate the groundwater resource carrying capacity.

[0005] Generally speaking, the existing evaluation methods for the bearing capacity of groundwater resources inadequately consider groundwater quality and cannot adapt to the current reality of generally poor groundwater quality in China. There is an urgent need to propose an evaluation method for the bearing capacity of groundwater resources that can truthfully reflect the impact of water quality. Summary of the Invention

[0006] To solve the above problems, the present invention proposes an evaluation method for the bearing capacity of groundwater resources considering water quality. The present invention confirms that groundwater quality has an important impact on the bearing capacity of regional groundwater resources, and there are differences in the impact of different water quality parameters on the bearing capacity of groundwater resources due to different human health hazards. By collecting groundwater samples to obtain measured groundwater quality data, it avoids the problem that the use of indirect indicators such as sewage discharge and sewage treatment rate cannot truthfully reflect the impact of water quality conditions on the bearing capacity of groundwater resources. By classifying water quality parameters into general hydrochemical indicators and toxicological indicators, it avoids the problem of exaggerating the severity of water quality using "one-size-fits-all" type indicators such as water quality compliance rate and single-index exceeding multiple. The specific technical solutions are as follows:

[0007] An evaluation method for the bearing capacity of groundwater resources considering water quality, comprising the following steps:

[0008] Step 1: Construct an evaluation index system for the bearing capacity of groundwater resources considering water quality;

[0009] Step 2: Conduct a groundwater quality survey in the evaluation area to obtain the data required for the evaluation of the bearing capacity of groundwater resources;

[0010] Step 3: Determine the index weights based on the expert investigation method and the analytic hierarchy process;

[0011] Step 4: Calculate the membership degree of each index based on the membership function, and calculate the membership degree of water quality indicators through the principle of the worst membership degree of different types;

[0012] Step 5: Grid the membership degree data based on GIS software and conduct an evaluation of the bearing capacity of groundwater resources.

[0013] Further, the specific steps of Step 1 include the following sub-steps:

[0014] S101, starting from three dimensions of ecological protection, agricultural production, and urban construction, comprehensively considering factors such as groundwater resources, groundwater ecology, groundwater quality, and water use efficiency to construct an evaluation index system for the bearing capacity of groundwater resources. The specific indicators include groundwater resource modulus, groundwater recharge modulus, groundwater resource development and utilization rate, groundwater level depth, aquifer depth, available water volume for farmland irrigation, rainfall, compliance rate of farmland irrigation water quality, average water consumption per mu for farmland irrigation, available water volume for urban construction, concentration of general hydrochemical indicators in groundwater, concentration of toxicological indicators in groundwater, per capita daily domestic water consumption, and water consumption per 10,000 yuan of industrial added value;

[0015] S102. Determine the water quality parameters included in the concentrations of general hydrochemical indicators and toxicological indicators of groundwater in the index system. Specifically, the general hydrochemical indicators of groundwater include pH, Na, Al, NH4 + , Cl - , SO4 2- , COD, TDS, total hardness, chromaticity, turbidity, Mn, Cu, Zn, Fe, S, and the toxicological indicators of groundwater include NO3 - , F, NO2 - , cyanide, Cr, I, Se, As, Hg, Pb, Cd.

[0016] S103. Determine the positive and negative attributes of each evaluation indicator. A positive indicator indicates that the higher the value of the indicator, the higher the groundwater resource carrying capacity, and the opposite is true for a negative indicator. Specifically, the positive indicators include groundwater resource modulus, groundwater recharge modulus, aquifer depth, available water volume for farmland irrigation, rainfall, passing rate of farmland irrigation water quality, available water volume for urban construction, and the negative indicators include groundwater resource development and utilization rate, groundwater level depth, average water consumption per mu of farmland irrigation, concentration of general hydrochemical indicators of groundwater, concentration of toxicological indicators of groundwater, per capita daily domestic water consumption, and water consumption per 10,000 yuan of industrial added value.

[0017] Further, the specific steps of step 2 include the following sub-steps:

[0018] S201. Determine the area for groundwater resource carrying capacity evaluation. Collect as many groundwater samples as possible in the selected area. While collecting the samples, use a pH meter to measure the pH of the groundwater, and use a portable spectrophotometer to measure the concentrations of NH4 + , COD, chromaticity, turbidity, S, NO2 - , cyanide and other volatile indicator concentrations in some groundwater samples. Some groundwater samples are filtered through a 0.45μm filter membrane and then taken in glass bottles, and some groundwater samples are filtered through a 0.45μm filter membrane, acidified with high-purity concentrated nitric acid, and then taken in glass bottles;

[0019] S202. Use an ion chromatograph to measure the concentrations of Cl - , SO4 2- , NO3 - , F - in the unacidified samples, use an inductively coupled plasma emission spectrometer to measure the concentrations of Na, total hardness, Al, Mn, Fe in the acidified samples, use an inductively coupled plasma mass spectrometer to measure the concentrations of Cr, I, Se, As, Hg, Pb, Cd, Cu, Zn in the acidified samples, and use an analytical balance to measure the TDS of the unacidified samples by the gravimetric method;

[0020] S203. Calculate the passing rate of farmland irrigation water quality of groundwater in the evaluation area based on the groundwater quality measurement results. The calculation formula is as follows:

[0021]

[0022] F j = max(F ij )

[0023]

[0024] In the formula, F ij is the exceeding multiple of the i-th water quality parameter of the j-th groundwater sample; C ij is the concentration of the i-th water quality parameter of the j-th groundwater sample; S i is the limit value of the i-th water quality parameter. The specific value can be referred to the "Standard for Farmland Irrigation Water Quality" (GB 5048-2021); F j is the maximum exceeding multiple of the j-th sample; F is the number of qualified groundwater samples in the evaluation area; f is the passing rate of farmland irrigation water quality of groundwater in the evaluation area; the farmland irrigation water quality parameters used in the present invention include pH, COD, Cl - , S, TDS, Pb, Cd, Cr, Hg, As;

[0025] S204. Collect non-water quality index data and organize all data into two categories: panel data and well location data; the panel data is based on administrative regions and specifically includes groundwater resource modulus, groundwater recharge modulus, groundwater resource development and utilization rate, available water volume for farmland irrigation, rainfall, passing rate of farmland irrigation water quality, average water consumption per mu of farmland irrigation, available water volume for urban construction, average daily water consumption per capita, and water consumption per 10,000 yuan of industrial added value; the well location data is based on groundwater monitoring wells and includes groundwater level depth, aquifer depth, concentration of general hydrochemical indexes of groundwater, and concentration of toxicological indexes of groundwater; the specific water quality parameters included in the concentration of general hydrochemical indexes of groundwater and the concentration of toxicological indexes of groundwater are the same as those described in sub-step S102.

[0026] Further, the specific steps of step 3 include the following sub-steps:

[0027] S301. Make and distribute an expert questionnaire, collect the scoring opinions of experts on the relative importance of each index, and organize the importance scores into the form of a judgment matrix;

[0028] S302. Calculate the maximum eigenvalue and eigenvector of the judgment matrix. The calculation formula is as follows:

[0029]

[0030] In the formula: A refers to the judgment matrix; is the geometric mean of the elements in each row of the judgment matrix; n is the number of indicators in the judgment matrix; aij is the element in the i-th row and j-th column, taking values between 1 and n; ω i is the value after normalization, which is the eigenvector of the judgment matrix; λ max is the maximum eigenvalue;

[0031] S303. Conduct a consistency test on the judgment matrix. The test formula is as follows:

[0032]

[0033] In the formula, n is the number of indicators in the judgment matrix; C R is the consistency ratio; C I is the consistency index; R I is the random consistency index, which is taken according to the value of n. When n is between 1 and 9, they are 0, 0, 0.58, 0.90, 1.12, 1.24, 1.32, 1.41, 1.45 respectively.

[0034] When C R <0.1, the judgment matrix passes the consistency test. At this time, the ω obtained in sub-step S303 i is the weight of each indicator in the judgment matrix. If the consistency test fails, it is necessary to reconstruct the judgment matrix until the consistency test is satisfied.

[0035] S304. Calculate the comprehensive weight of each indicator based on the weights of the criterion layer and the indicators within the criterion layer. The calculation formula is as follows:

[0036] W i =ω j ×ω i

[0037] In the formula: W i is the final weight of the i-th indicator; ω j is the weight of the criterion layer to which the i-th indicator belongs; ω i is the weight of the i-th indicator in the corresponding criterion layer.

[0038] Furthermore, step 4 specifically includes the following sub-steps:

[0039] S401. Divide each indicator into 5 evaluation levels (V1 - 5). V1, V2, V3, V4, and V5 represent that the groundwater resource carrying capacity corresponding to the indicator gradually decreases. The threshold for the evaluation level division is determined based on the expert survey method. Among them, the concentration of general hydrochemical indicators and toxicological indicators of groundwater are divided into all water quality parameters selected in sub-step S102;

[0040] S402. Calculate the membership degrees of each index data for the 5 evaluation levels based on the membership function. For positive indexes, the following membership degree calculation formula is available:

[0041] When :

[0042]

[0043] When

[0044]

[0045] Except and the membership degrees of the other 3 levels are 0;

[0046] When :

[0047]

[0048] Except the membership degrees of the other 4 levels are 0;

[0049] When :

[0050]

[0051] Except and the membership degrees of the other 3 levels are 0;

[0052] When :

[0053]

[0054] where t is the evaluation level, t = 1, 2, 3, 4, 5; r i (t) is the membership degree of the t-th level; ri is the actual data of the i-th index, is the upper limit value of the t-th evaluation level, is the lower limit value of the t-th evaluation level, is the average value of the t-th evaluation level.

[0055] For reverse indexes, after calculating according to the above formula, reverse the obtained membership degrees, that is, swap the membership degrees of V1 and V5, swap the membership degrees of V2 and V4, and keep the membership degree of V3 unchanged.

[0056] Specifically, the membership degrees of the general hydrochemical index concentration and the toxicological index concentration of groundwater must first calculate the membership degrees of all water quality parameters described in step S102 of the above method, and then calculate the membership degree attribution of the two according to the worst membership degree principle. The calculation formula is as follows:

[0057]

[0058] r i = c q

[0059] In the formula, to are the membership degree values of the pth water quality parameter for 5 evaluation levels; d p is the judgment value of the worst membership degree; q is the serial number of the water quality parameter with the worst membership degree; r i is the membership degree of the general hydrochemical index concentration or the toxicological index concentration of groundwater.

[0060] S403. Organize all membership degrees into two categories: panel data and well location data. The specific indicators are the same as those in sub-step S204, but at this time, the well location data only includes the general hydrochemical index concentration and the toxicological index concentration of groundwater, and is not subdivided into water quality parameters.

[0061] Furthermore, step 5 specifically includes the following sub-steps:

[0062] S501. Use GIS software to convert the membership degrees of each indicator into raster data. Among them, the membership degrees of the panel data are directly assigned to the administrative region, and the membership degrees of the well location data are spatially interpolated by IDW for the membership degrees after projecting the geographical coordinates of the groundwater monitoring wells. A total of 60 raster data of membership degrees are obtained for 14 evaluation indicators;

[0063] S502. Use GIS software to conduct an evaluation of the groundwater resource carrying capacity. The calculation formula is as follows:

[0064] b j = W i × r ij

[0065] F = b j × a j

[0066] In the formula, F is the comprehensive score of the groundwater resource carrying capacity; b j is the fuzzy comprehensive evaluation matrix of the jth indicator; W i is the weight of the ith indicator obtained in sub-step S304; r ij is the membership degree of each indicator sorted out in S501, presented in the form of raster data; a jis the score for the j-th evaluation level, where a1 = 0.1, a2 = 0.3, a3 = 0.5, a4 = 0.7, a5 = 0.9.

[0067] S503. Based on the comprehensive score, the groundwater resource carrying capacity is divided into 5 levels: low, F ∈ [0, 0.2); relatively low, F ∈ [0.2, 0.4); medium, F ∈ [0.4, 0.6); relatively high, F ∈ [0.6, 0.8); high, F ∈ [0.8, 1).

[0068] The present invention solves the problem that the existing evaluation method for groundwater resource carrying capacity insufficiently considers the groundwater quality. By conducting groundwater quality surveys to obtain real water quality data, by classifying water quality parameters into two categories: general hydrochemical indicators and toxicological indicators, it avoids exaggerating the severity of water quality, and by using the worst membership degree principle, it solves the problem of mapping multiple water quality parameters to a single evaluation index, and thus can more truly reflect the impact of water quality conditions on the groundwater resource carrying capacity. Given the generally poor groundwater quality in China, the present invention has good application prospects in the planning and management of groundwater resources in China. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 The flowchart of the method of the present invention.

[0070] Figure 2 The distribution of groundwater sample survey points in the embodiment.

[0071] Figure 3 The evaluation result of the groundwater resource carrying capacity score in the embodiment.

[0072] Figure 4 The evaluation result of the groundwater resource carrying capacity level in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0073] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all 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 protection scope of the present invention.

[0074] This embodiment provides an evaluation method for groundwater resource carrying capacity considering water quality, as Figure 1 shown, and specifically includes the following steps:

[0075] (1) Construct an evaluation index system for the carrying capacity of groundwater resources considering water quality. In this embodiment, starting from three criterion layers of ecological protection, agricultural production, and urban construction, an evaluation index system for the carrying capacity of groundwater resources consisting of 14 specific indicators is constructed by comprehensively considering factors such as groundwater resources, groundwater ecology, groundwater quality, and water use efficiency, and the positive and negative attributes of all indicators are determined. The finally determined index system is shown in Table 1.

[0076] Table 1 Evaluation Index System for the Carrying Capacity of Groundwater Resources Considering Water Quality

[0077]

[0078]

[0079] Among them, the concentration of general hydrochemical indicators (C11) and the concentration of toxicological indicators (C12) in groundwater belong to multi-parameter indicators. Specifically, the general hydrochemical indicators in groundwater include pH, Na, Al, NH4 + , Cl - , SO4 2- , COD, TDS, total hardness, chromaticity, turbidity, Mn, Cu, Zn, Fe, S, and the toxicological indicators in groundwater include NO3 - , F, NO2 - , cyanide, Cr, I, Se, As, Hg, Pb, Cd.

[0080] (2) Investigate the groundwater quality status of the selected study area. In this embodiment, a certain irrigation area in the south of China is selected as a typical study area, 119 groups of groundwater samples are collected around the study area, and the determination of water quality parameters is carried out. The specific sampling points for the groundwater investigation are as Figure 2 shown.

[0081] Pump out the groundwater in the monitoring well using a water pump. After pumping for 10 minutes, use a pH meter to measure the pH value of the groundwater on-site, and use a portable spectrophotometer to measure the concentrations of volatile indicators such as NH4 + , COD, chromaticity, turbidity, S, NO2 - , cyanide, etc. in the groundwater on-site.

[0082] Subsequently, collect samples for the determination of the remaining water quality parameters. Filter the groundwater samples using a 0.45 μm water system filter membrane, and divide the filtered samples into 2 200 mL sampling bottles. One of them is acidified to a pH less than 2.0 using high-purity concentrated nitric acid. The samples are transported and stored in a refrigerated and light-proof manner at 4 °C until determination.

[0083] Use an ion chromatograph to measure Cl - , SO4 2- , NO3 - , F- For the concentrations of Na, total hardness, Al, Mn, and Fe in the acidified samples, an inductively coupled plasma optical emission spectrometer was used for determination. For the concentrations of Cr, I, Se, As, Hg, Pb, Cd, Cu, and Zn in the acidified samples, an inductively coupled plasma mass spectrometer was used for determination. The TDS of the non-acidified samples was determined by the gravimetric method using an analytical balance.

[0084] (3) Calculate the passing rate of the farmland irrigation water quality of the groundwater within the evaluation area based on the groundwater quality determination results. First, divide all the groundwater sample collection points according to county-level administrative regions, and then calculate the passing rate of the farmland irrigation water quality of each administrative region through the following formula:

[0085]

[0086] F j = max(F ij )

[0087]

[0088] In the formula, F ij is the exceeding multiple of the i-th water quality parameter of the j-th groundwater sample; C ij is the concentration of the i-th water quality parameter of the j-th groundwater sample; S i is the limit value of the i-th water quality parameter, and the specific value can be referred to the "Farmland Irrigation Water Quality Standard" (GB 5048 - 2021); F j is the maximum exceeding multiple of the j-th sample; F is the number of qualified groundwater samples within the evaluation area; f is the passing rate of the farmland irrigation water quality of the groundwater within the evaluation area; the farmland irrigation water quality parameters used in the present invention include pH, COD, Cl - , S, TDS, Pb, Cd, Cr, Hg, As;

[0089] (4) Collect and collate data. Collect data such as the groundwater resource modulus (C1), groundwater recharge modulus (C2), groundwater resource development and utilization rate (C3), available water volume for farmland irrigation (C6), rainfall (C7), average water consumption per mu of farmland irrigation (C9), available water volume for urban construction (C10), per capita daily domestic water consumption, and water consumption per 10,000 yuan of industrial added value (C14) from the publicly available "Water Resources Bulletin" and "Social and Economic Development Statistical Yearbook" of each place. Collect the data of the aquifer depth (C5) from geological borehole data. When sampling groundwater, simultaneously measure the groundwater level of the monitoring well to obtain the data of the groundwater level depth (C4).

[0090] All data are sorted into two categories: panel data and well location data. Among them, the panel data is based on administrative regions and specifically includes the modulus of groundwater resources (C1), the modulus of groundwater recharge (C2), the utilization rate of groundwater resources (C3), the available water volume for farmland irrigation (C6), rainfall (C7), the compliance rate of farmland irrigation water quality (C8), the average water consumption per mu for farmland irrigation (C9), the available water volume for urban construction (C10), the average daily water consumption per capita for domestic use (C13), and the water consumption per 10,000 yuan of industrial added value (C14); the well location data is based on groundwater monitoring wells and includes the buried depth of the groundwater level (C4), the buried depth of the aquifer (C5), the concentration of general hydrochemical indexes of groundwater (C11), and the concentration of toxicological indexes of groundwater (C12). The specific water quality parameters included in the concentration of general hydrochemical indexes of groundwater (C11) and the concentration of toxicological indexes of groundwater (C12) are consistent with those in the above step (1).

[0091] (5) Distribute expert questionnaires to collect the scoring opinions of industry experts on the relative importance of each index, and organize the importance scores into a judgment matrix. In this embodiment, a total of 3 valid expert scoring forms are collected, and all experts have senior professional titles and have been engaged in relevant production and research work in this field for a long time. Since the evaluation index system of groundwater carrying capacity has 3 subsystems, there are a total of 4 judgment matrices, which respectively describe the relative importance between subsystems and the relative importance scores of different indexes within the 3 subsystems. The values in the scoring matrix are the averages of the scores given by 3 experts. The final judgment matrices of this embodiment are shown in Tables 2 - 5.

[0092] Table 2 Judgment Matrix for Calculating the Weights of the Criterion Layer

[0093] Ecological protection Agricultural production Urban construction Ecological protection 1 1 1 Agricultural production / 1 1 Urban construction / / 1

[0094] Table 3 Judgment Matrix for Calculating the Weights of the Ecological Protection Subsystem

[0095] C1 C2 C3 C4 C5 C1 1.00 1.00 2.33 1.17 1.50 C2 / 1.00 2.33 1.17 1.50 C3 / / 1.00 0.50 0.67 C4 / / / 1.00 1.33 C5 / / / / 1.00

[0096] Table 4 Judgment Matrix for Calculating the Weights of the Agricultural Production Subsystem

[0097] C6 C7 C8 C9 C6 1.00 0.83 2.67 1.50 C7 / 1.00 3.00 1.67 C8 / / 1.00 0.67 C9 / / / 1.00

[0098] Table 5 Judgment Matrix for Calculating the Weights of the Urban Construction Subsystem

[0099]

[0100]

[0101] (6) Calculate the weights of each index based on the following formula. First, calculate the maximum eigenvalue and eigenvector of the 4 judgment matrices. The calculation formulas are as follows:

[0102]

[0103] In the formula: A refers to the judgment matrix; is the geometric mean of the elements in each row of the judgment matrix; n is the number of indicators contained in the judgment matrix; a ij is the element in the i-th row and j-th column, taking values between 1 and n; ω i is the value after normalization processing, and is the eigenvector of the judgment matrix; λ max is the maximum eigenvalue;

[0104] Secondly, conduct a consistency test on the judgment matrix, and the test formula is as follows:

[0105]

[0106] In the formula, n is the number of indicators contained in the judgment matrix; C R is the consistency ratio; C I is the consistency index; R I is the random consistency index, taking values according to the size of n. When n is between 1 and 9, they are 0, 0, 0.58, 0.90, 1.12, 1.24, 1.32, 1.41, 1.45 respectively.

[0107] When C R <0.1, the judgment matrix passes the consistency test, and at this time ω i is the weight of each indicator in the judgment matrix. If the consistency test fails, the judgment matrix needs to be reconstructed until the consistency test is satisfied.

[0108] Finally, calculate the comprehensive weight of each indicator based on the weights of the criterion layer and the indicators within the criterion layer. The calculation formula is as follows:

[0109] W i =ω j ×ω i

[0110] In the formula: W i is the final weight of the i-th indicator; ω j is the weight of the criterion layer to which the i-th indicator belongs; ω i is the weight of the i-th indicator in the corresponding criterion layer.

[0111] The 4 judgment matrices in this embodiment all passed the consistency test, and the calculated indicator weights are shown in Table 6.

[0112] Table 6 Criterion layer relative importance scoring matrix

[0113]

[0114] Further, step 4 specifically includes the following sub-steps:

[0115] (7) Divide each index into 5 evaluation levels (V1 - 5) through the expert investigation method. V1, V2, V3, V4, and V5 represent the gradually decreasing groundwater resource carrying capacity corresponding to the index. Among them, the concentration of general groundwater hydrochemical index (C11) and the concentration of groundwater toxicological index (C12) are divided into the same as the water quality parameters selected in the previous step (1). The division method of the evaluation levels of each index finally determined in this embodiment is shown in Table 7. The units of each evaluation index are the same as those shown in Table 1. pH is a dimensionless parameter, and the units of the remaining water quality parameters are all mg / L.

[0116] Table 7 Division method of evaluation levels for each index

[0117]

[0118]

[0119] (8) Calculate the membership degrees of each index data to the 5 evaluation levels based on the membership function. For positive indexes, there is the following membership degree calculation formula:

[0120] When :

[0121]

[0122] When

[0123]

[0124] The membership degrees of other levels are 0;

[0125] When :

[0126]

[0127] The membership degrees of other levels are 0;

[0128] When :

[0129]

[0130] The membership degrees of other levels are 0;

[0131] When :

[0132]

[0133] Among them, t is the evaluation level, t = 1, 2, 3, 4, 5; r i(t) is the membership degree of the t-th level; ri is the actual data of the i-th index, is the upper limit value of the t-th evaluation level, is the lower limit value of the t-th evaluation level, is the average value of the t-th evaluation level.

[0134] For reverse indexes, after calculating according to the above formula, the obtained membership degrees are reversed, that is, the membership degrees of V1 and V5 are swapped, the membership degrees of V2 and V4 are swapped, and the membership degree of V3 remains unchanged.

[0135] In particular, for the membership degrees of the general hydrochemical index concentration (C11) and the toxicological index concentration (C12) of groundwater, the membership degrees of all water quality parameters described in step (1) of the above calculation method shall be calculated first, and then the membership degree attribution of the two shall be calculated according to the worst membership degree principle. The calculation formula for the worst membership degree is as follows:

[0136]

[0137] r i = c q

[0138] In the formula, to are the membership degree values of the p-th water quality parameter for 5 evaluation levels; d p is the judgment value of the worst membership degree; q is the serial number of the water quality parameter with the worst membership degree; r i is the membership degree of the general hydrochemical index concentration or the toxicological index concentration of groundwater.

[0139] (9) Conduct an evaluation of the groundwater resource carrying capacity. First, organize all membership degree data into two categories: panel data and well location data. The division of panel data and well location data is the same as that described in step (4), but at this time, only the worst membership degrees of the general hydrochemical index concentration (C11) and the toxicological index concentration (C12) of groundwater are taken, and they are not subdivided into water quality parameters.

[0140] Subsequently, use ArcGIS software to convert the membership degrees of each index into raster data. Among them, the membership degrees of panel data are directly assigned to county-level administrative regions, and the membership degrees of well location data are spatially interpolated by IDW for the membership degrees after projecting with the geographical coordinates of groundwater monitoring wells. Each index has 5 raster data of membership degree spatial distribution, and a total of 70 raster data of membership degrees are obtained for 14 evaluation indexes.

[0141] Finally, use the raster calculator of ArcGIS software to conduct an evaluation of the groundwater resource carrying capacity. The calculation formula is as follows:

[0142] b j = Wi × ij

[0143] F=b j ×a j

[0144] Where, F is the comprehensive score of groundwater resources carrying capacity; b j is the fuzzy comprehensive evaluation matrix of the jth index; W i is the weight of the ith indicator shown in Table 6; r ij is the degree of membership of each indicator, presented in the form of raster data; a j are the scores of the j-th evaluation level, a1=0.1, a2=0.3, a3=0.5, a4=0.7, a5=0.9.

[0145] Figure 3 and Figure 4 The figure shows the groundwater resource carrying capacity score and rating results of this implementation. As can be seen from the figure, the groundwater resource carrying capacity scores of different regions in this embodiment are between 0.549 and 0.757, which are at medium and high carrying capacity levels. The groundwater resource carrying capacity score is generally based on administrative regions, but there are also slight differences between the same administrative regions, reflecting the joint impact of panel data and well location data on the groundwater resource carrying capacity. In addition, the weights of the general water chemical index concentration of groundwater (C11) and the toxicological index concentration of groundwater (C12) are 0.033 and 0.115, respectively, indicating that the impact of the groundwater toxicological index concentration (C12) on the groundwater resource carrying capacity is 3.5 times that of the general water chemical index concentration (C11) of groundwater, which is consistent with the relatively serious health hazards of toxicological indicators. Obviously, the beneficial effects of the present invention include: by using the measured groundwater quality data, the effect of truthfully reflecting the impact of water quality conditions on the carrying capacity of groundwater resources is achieved; by dividing water quality parameters into general hydrochemical indicators and toxicological indicators, the problem of exaggerating the severity of water quality due to the use of "one-size-fits-all" indicators such as water quality compliance rate and single indicator excess multiples is avoided.

[0146] The above describes in detail the preferred implementation of this patent, but this patent is not limited to the above implementation. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of this patent.

Claims

1. An evaluation method for the bearing capacity of groundwater resources considering water quality, characterized in that It includes the following steps: Step 1: Construct an evaluation index system for the bearing capacity of groundwater resources considering water quality; Step 2: Conduct a groundwater quality survey in the evaluation area to obtain the data required for the evaluation of the bearing capacity of groundwater resources; Step 3: Determine the index weights based on the expert investigation method and the analytic hierarchy process; Step 4: Calculate the membership degree of each index based on the membership function, and calculate the membership degree of water quality indexes through the principle of the worst membership degree of classification; Step 5: Rasterize the membership degree data based on GIS software and conduct an evaluation of the bearing capacity of groundwater resources.

2. The groundwater resource carrying capacity evaluation method considering water quality according to claim 1, characterized in that, The specific steps of Step 1 include the following sub-steps: S101. Construct an evaluation index system for the bearing capacity of groundwater resources considering water quality from three criterion levels of ecological protection, agricultural production, and urban construction. The ecological protection criterion level includes the groundwater resource modulus, groundwater recharge modulus, groundwater resource development and utilization rate, groundwater level depth, and aquifer depth; the agricultural production criterion level includes the available water volume for farmland irrigation, rainfall, the compliance rate of farmland irrigation water quality, and the average water consumption per mu of farmland irrigation; the urban construction criterion level includes the available water volume for urban construction, the concentration of general hydrochemical indexes of groundwater, the concentration of toxicological indexes of groundwater, the daily per capita domestic water consumption, and the water consumption per 10,000 yuan of industrial added value. S102, determine the water quality parameters included in the concentrations of general hydrochemical indicators and toxicological indicators of groundwater in the indicator system. The general hydrochemical indicators of groundwater include pH, Na, Al, NH4 + , Cl - , SO4 2- , COD, TDS, total hardness, chromaticity, turbidity, Mn, Cu, Zn, Fe and S. The toxicological indicators of groundwater include NO3 - , F, NO2 - , cyanide, Cr, I, Se, As, Hg, Pb and Cd; S103. Determine the positive and negative attributes of the evaluation indexes determined in Steps S101 and S102. A positive index indicates that the higher the index value, the higher the bearing capacity of groundwater resources, and the opposite is true for a negative index.

3. The evaluation method of the bearing capacity of groundwater resources considering water quality according to claim 1, characterized in that, The specific steps of Step 2 include the following sub-steps: S201, determine the area for the evaluation of the groundwater resources carrying capacity, collect groundwater samples within the selected area, and use a pH meter and a portable spectrophotometer to measure the pH, NH4 + , COD, chromaticity, turbidity, S, NO2 - , the concentrations of labile indicators such as cyanide in the groundwater samples. Then, filter a part of the samples through a 0.45-μm filter membrane, directly bottle them in glass bottles for one part, and acidify and bottle the other part with high-purity concentrated nitric acid; S202, measure the concentrations of Cl, SO4, NO3, and F in the unacidified sample using an ion chromatograph, measure the concentrations of Na, total hardness, Al, Mn, and Fe in the acidified sample using an inductively coupled plasma optical emission spectrometer, measure the concentrations of Cr, I, Se, As, Hg, Pb, Cd, Cu, and Zn in the acidified sample using an inductively coupled plasma mass spectrometer, and measure the TDS of the unacidified sample using an analytical balance by the gravimetric method; - 、SO4 2- 、NO3 - 、F - in the acidified sample using an inductively coupled plasma optical emission spectrometer, measure the concentrations of Cr, I, Se, As, Hg, Pb, Cd, Cu, and Zn in the acidified sample using an inductively coupled plasma mass spectrometer, and measure the TDS of the unacidified sample using an analytical balance by the gravimetric method; S203. Calculate the compliance rate of farmland irrigation water quality of groundwater in the evaluation area according to the groundwater quality measurement results, and the calculation formula is as follows: F j = max(F ij ) In the formula, F ij is the exceeding multiple of the i-th water quality parameter of the j-th groundwater sample; C ij is the concentration of the i-th water quality parameter of the j-th groundwater sample; S i is the limit value of the i-th water quality parameter, and the specific value refers to the "Irrigation Water Quality Standard GB 5048-2021"; F j is the maximum exceeding multiple of the j-th sample; F is the number of qualified groundwater samples in the evaluation area; f is the passing rate of the irrigation water quality of groundwater in the evaluation area; among them, the irrigation water quality parameters include pH, COD, Cl - , S, TDS, Pb, Cd, Cr, Hg and As; S204. Collect non-water quality index data and organize all data into two categories: panel data and well location data; the panel data is based on administrative regions and includes the groundwater resource modulus, groundwater recharge modulus, groundwater resource development and utilization rate, available water volume for farmland irrigation, rainfall, the compliance rate of farmland irrigation water quality, the average water consumption per mu of farmland irrigation, available water volume for urban construction, the daily per capita domestic water consumption, and the water consumption per 10,000 yuan of industrial added value; the well location data is based on groundwater monitoring wells and includes the groundwater level depth, aquifer depth, the concentration of general hydrochemical indexes of groundwater, and the concentration of toxicological indexes of groundwater; the specific water quality parameters included in the concentration of general hydrochemical indexes of groundwater and the concentration of toxicological indexes of groundwater are the same as those in sub-step S102.

4. The evaluation method of the bearing capacity of groundwater resources considering water quality according to claim 1 is characterized in that, The specific steps of Step 3 include the following sub-steps: S301. Make and distribute an expert questionnaire, collect the scoring opinions of experts on the relative importance of each index, and organize the importance scores into a judgment matrix; S302. Calculate the maximum eigenvalue and eigenvector of the judgment matrix, and the calculation formula is as follows: Where: A refers to the judgment matrix; is the geometric mean of the elements in each row of the judgment matrix; n is the number of indicators contained in the judgment matrix; a ij is the element in the i-th row and j-th column, taking values between 1 and n; ω i is the value after normalization processing, which is the eigenvector of the judgment matrix; λ max is the maximum eigenvalue; S303. Conduct a consistency test on the judgment matrix, and the test formula is as follows: Wherein, n is the number of indicators contained in the judgment matrix; C R is the consistency ratio; C I is the consistency index; R I is the random consistency index, which is taken according to the size of n. When n is between 1 and 9, they are 0, 0, 0.58, 0.90, 1.12, 1.24, 1.32, 1.41, 1.45 respectively; When C R < 0.1, the judgment matrix passes the consistency test, and at this time, ω i obtained in sub-step S303 is the weight of each index in the judgment matrix; If the consistency test fails, it is necessary to reconstruct the judgment matrix until the consistency test is satisfied; S304. Calculate the comprehensive weight of each index based on the weights of the criterion level and the indexes within the criterion level, and the calculation formula is as follows: W i = ω j × ω i Where: W i is the final weight of the i-th index; ω j is the weight of the i-th index in the criterion layer; ω i is the weight of the i-th index in the corresponding criterion layer.

5. The evaluation method for the bearing capacity of groundwater resources considering water quality according to claim 1, characterized in that The specific steps of Step 4 include the following sub-steps: S401. Divide each indicator into 5 evaluation levels. V1, V2, V3, V4, and V5 represent the gradually decreasing groundwater resource carrying capacity corresponding to the indicators. The threshold for the evaluation level division is determined based on the expert survey method. Among them, the concentrations of general hydrochemical indicators and toxicological indicators of groundwater are divided into all water quality parameters selected in sub-step S102. S402. Calculate the membership degrees of each indicator data to the 5 evaluation levels based on the membership function. For positive indicators, the following membership degree calculation formula is adopted: When : When Except and the membership degrees of the other three levels are 0; When (where \(i = 2, 3, 4\)): Except The membership degrees of the other four levels are 0; When : Except and the membership degrees of the other three levels are 0; When : where t is the evaluation level, t = 2, 3, 4; r i (t) is the membership degree of the t-th level; r i is the actual data of the i-th index, is the upper limit value of the t-th evaluation level, is the lower limit value of the t-th evaluation level, is the average value of the t-th evaluation level. For reverse indicators, after calculating according to the above formula, the obtained membership degrees are reversed, that is, the membership degrees of V1 and V5 are swapped, the membership degrees of V2 and V4 are swapped, and the membership degree of V3 remains unchanged. S403. Organize all membership degrees into two categories: panel data and well location data. The specific indicators are the same as those in sub-step S204. However, at this time, the well location data only includes the concentrations of general hydrochemical indicators and toxicological indicators of groundwater, and is not subdivided into water quality parameters.

6. The groundwater resources carrying capacity evaluation method considering water quality according to claim 5, characterized in that: The membership degrees of the concentrations of general hydrochemical indicators and toxicological indicators of groundwater must first be based on the membership degrees of all water quality parameters in step S102, and then the membership degree attribution of the two is calculated according to the worst membership degree principle. The calculation formula is as follows: r i ＝c q Wherein, to are the membership degree values of the p-th water quality parameter for 5 evaluation grades; d p is the judgment value of the worst membership degree; q is the serial number of the water quality parameter with the worst membership degree; r i is the membership degree of the concentration of general hydrochemical indexes or toxicological indexes of groundwater.

7. The evaluation method of groundwater resources carrying capacity considering water quality according to claim 1, characterized in that, Step 5 specifically includes the following sub-steps: S501. Use GIS software to convert the membership degrees of each indicator into raster data. Among them, the membership degrees of panel data are directly assigned to administrative regions, and the membership degrees of well location data are spatially interpolated by IDW for the membership degrees after projecting the geographical coordinates of groundwater monitoring wells. A total of 60 raster data of membership degrees are obtained for 14 evaluation indicators. S502. Use GIS software to conduct an evaluation of the groundwater resource carrying capacity. The calculation formula is as follows: b j = W i × r ij F = b j × a j Wherein, F is the comprehensive score of the groundwater resource carrying capacity; b j is the fuzzy comprehensive evaluation matrix of the j-th index; W i is the weight of the i-th index obtained in sub-step S304; r ij is the membership degree of each index sorted out in S501, presented in the form of raster data; a j is the score of the j-th evaluation level, a1 = 0.1, a2 = 0.3, a3 = 0.5, a4 = 0.7, a5 = 0.

9.

8. The evaluation method for the bearing capacity of groundwater resources considering water quality according to claim 7, characterized in that, Step 5 also includes: S503. Based on the comprehensive score, divide the groundwater resource carrying capacity into 5 levels: low F ∈ [0, 0.2), relatively low F ∈ [0.2, 0.4), medium F ∈ [0.4, 0.6), relatively high F ∈ [0.6, 0.8), high F ∈ [0.8, 1).

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