A method for evaluating regional health water balance based on WEP distributed hydrological model

Abstract

This invention discloses a regional healthy water balance assessment method based on the WEP distributed hydrological model, belonging to the field of water resources management. The method includes: constructing a WEP distributed hydrological model of the study area containing a river surface evaporation-leakage loss module and a groundwater evaporation module; constructing a healthy water balance index system and an evaluation index calculation model; using a combination of entropy weighting and empirical weighting methods, and introducing an adaptive combination coefficient solution strategy based on maximizing the sum of squared deviations, to determine the combined weights of the evaluation indicators; calculating the healthy water balance score, and determining the healthy water balance status of the calculation unit. This invention corrects the systematic bias of traditional models from a physical mechanism perspective, corrects the distortion of river water balance caused by neglecting dynamic feedback of water level-loss, significantly improves the systematic bias of runoff simulation during the dry season, and enables the model to maintain water balance closure under different flow levels, thus making the healthy water balance assessment results more scientific and reliable.

Description

Technical Field

[0001] This invention belongs to the field of water resources management technology, specifically relating to a regional healthy water balance assessment method based on the WEP distributed hydrological model. Background Technology

[0002] Regional healthy water balance refers to an ideal state maintained by a regional natural-social dual water cycle system under the dual driving forces of natural changes and human activities. It is closely related to the sound operation of the water cycle system, the stable succession of the ecosystem, and the sustainable use of water resources. Achieving regional healthy water balance is an important aspect and challenge of water conservancy work, and is of great significance to ensuring national water security and the sustained and stable development of the national economy and society.

[0003] The existing technologies for regional health water balance assessment have the following main shortcomings: (1) Lack of a quantifiable comprehensive assessment framework. Existing studies have mostly defined the concept of "healthy water balance" from a theoretical perspective, but a set of operational and quantifiable technical assessment systems based on multiple dimensions has not yet been formed. (2) Due to limitations in technical means, the acquisition of some key hydrological variables is spatially limited, which restricts the promotion and application of assessment methods. (3) Traditional assessment methods are mostly based on static statistical data, reflecting "results" rather than "processes", and are difficult to depict the dynamic health status of the region. (4) Existing distributed hydrological models ignore water loss caused by water level changes when calculating river confluence. This simplification is acceptable in conventional runoff simulation, but in the process of health water balance assessment, it will lead to an imbalance of water volume between variables such as river flow and groundwater level, which in turn leads to the distortion of assessment indicators such as "balance" and "sustainability". Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a regional health water balance assessment method based on the WEP distributed hydrological model, which can effectively solve the above-mentioned problems.

[0005] The technical solution adopted in this invention is as follows:

[0006] This invention provides a regional healthy water balance assessment method based on the WEP distributed hydrological model, comprising the following steps:

[0007] Step S1: Construct a WEP distributed hydrological model for the study area, including a river surface evaporation-seepage loss module and a groundwater evaporation module; the WEP distributed hydrological model simulates the water cycle elements of the study area and outputs key hydrological simulation data with physical consistency in the study area during the evaluation period;

[0008] Step S2: Construct a health balance indicator system comprising a target layer, a criterion layer, and an indicator layer; the target layer is the health balance assessment target; the criterion layer includes multiple evaluation dimensions; each evaluation dimension is provided with at least one evaluation indicator located in the indicator layer;

[0009] Step S3: Construct an evaluation index calculation model for each of the evaluation indicators; the evaluation index calculation model calculates the true value of the evaluation index in each calculation unit of the study area based on the key hydrological simulation data output by the WEP distributed hydrological model; according to the pre-established mapping relationship between the true value, level and score of the evaluation index, the score of the evaluation index in each calculation unit of the study area is obtained based on the true value of the evaluation index.

[0010] Step S4: Using a combination of entropy weighting method and empirical weighting method, and introducing an adaptive combination coefficient solution strategy based on maximizing the sum of squared deviations, the combination weight of each evaluation index is determined.

[0011] Step S5: Based on the combined weight of each evaluation index, the scores of each evaluation index in each calculation unit are weighted and summed to obtain the health balance score of the calculation unit. The health balance status of the calculation unit is determined by the health balance score.

[0012] The regional health water balance assessment method based on the WEP distributed hydrological model provided by this invention has the following advantages:

[0013] (1) A regional health level measurement and assessment framework was constructed. In view of the problem that the health water balance remains at the theoretical definition and lacks specific assessment methods, this invention starts from four dimensions: carrying capacity, sustainability, balance and stability, selects seven quantifiable core indicators, establishes a complete indicator system and calculation process, and provides a repeatable and verifiable quantitative assessment tool for the health status of the regional water cycle system.

[0014] (2) This invention relies on the WEP distributed hydrological model to simulate the water cycle process and outputs spatiotemporally continuous data with physical consistency. It can overcome the spatial limitations of ground monitoring equipment, enable the assessment to be extended to different time and spatial scales, significantly improve the representativeness and applicability of the assessment results, and has broad application prospects.

[0015] (3) The systematic bias of the traditional model is corrected from the perspective of physical mechanism. The improvement of the WEP model in this invention corrects the distortion of river water balance caused by ignoring the dynamic feedback of water level and loss without increasing the parameters to be calibrated. It significantly improves the systematic bias of runoff simulation during the dry season, so that the model can maintain water balance closure under different flow levels, thereby making the healthy water balance assessment results more scientific and reliable. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The score for per capita water resources availability in the Yellow River's important water source conservation area in 2020 is an embodiment of the present invention.

[0018] Figure 2 The score for the per-mu water resource possession rate in the important water source conservation area of ​​the Yellow River in 2020 is the embodiment of the present invention.

[0019] Figure 3 The score for the development and utilization rate of surface water resources in the important water conservation area of ​​the Yellow River in 2020 is the embodiment of the present invention.

[0020] Figure 4 The score for the development and utilization rate of groundwater resources in the important water conservation area of ​​the Yellow River in 2020 is the embodiment of the present invention.

[0021] Figure 5 The water balance index score of the Yellow River important water source conservation area in 2020 is the embodiment of the present invention.

[0022] Figure 6 The score for the ecological flow guarantee level of the Yellow River's important water source conservation area in 2020 is the embodiment of the present invention.

[0023] Figure 7 The water conservation coefficient score of the important water conservation area of ​​the Yellow River in 2020 is the embodiment of the present invention.

[0024] Figure 8 The healthy water balance score of the Yellow River's important water source conservation area in 2020 is shown in the embodiment of this invention.

[0025] Figure 9 The healthy water balance level of the Yellow River's important water source conservation area in 2020 is shown in the embodiment of the present invention.

[0026] Figure 10 This is a diagram of the health water balance evaluation index system according to an embodiment of the present invention;

[0027] Figure 11 This is a weighted diagram of health water balance indicators in an embodiment of the present invention;

[0028] Figure 12 This is a classification diagram of healthy water balance status according to an embodiment of the present invention;

[0029] Figure 13 This is a flowchart of the healthy water balance calculation in an embodiment of the present invention. Detailed Implementation

[0030] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0031] This invention aims to address the following technical problems in existing regional health water balance assessments: lack of a systematic quantitative assessment framework, spatial limitations in obtaining key hydrological variables, and assessments based primarily on static data that fail to reflect dynamic processes. To this end, this invention provides a regional health water balance assessment method based on the WEP distributed hydrological model. It constructs an indicator system from four dimensions: carrying capacity, sustainability, balance, and stability. By relying on model simulation to overcome the limitations of data acquisition, it achieves a dynamic quantitative assessment of the health status of the regional water cycle system, providing a scientific basis for water resource regulation.

[0032] This invention aims to address the problem of physical inconsistencies in key hydrological variables caused by the simplification of the model's own mechanisms when using distributed hydrological models to support regional health water balance assessments in existing technologies. Specifically, existing hydrological models, in solving river confluence problems, neglect the increase in water surface area caused by water level changes and its dynamic feedback on evaporation and seepage losses for the sake of computational simplicity. This simplification is acceptable in conventional runoff simulations, but in the context of health water balance assessments, it prevents the water balance between variables such as river flow and groundwater level output by the model from being closed, directly leading to systematic distortion of assessment indicators such as "balance" and "sustainability." Therefore, this invention provides a regional health water balance assessment method based on the WEP distributed hydrological model, constructing an indicator system from four dimensions: carrying capacity, sustainability, balance, and stability. It relies on an improved model to obtain physically consistent simulation data, enabling dynamic assessment of the health status of the regional water cycle system.

[0033] See Figure 1 This invention provides a regional healthy water balance assessment method based on the WEP distributed hydrological model, comprising steps S1 to S5:

[0034] Step S1: Construct a WEP distributed hydrological model for the study area, including a river surface evaporation-seepage loss module and a groundwater evaporation module; the WEP distributed hydrological model simulates the water cycle elements of the study area and outputs key hydrological simulation data with physical consistency in the study area during the evaluation period;

[0035] As one implementation method, a WEP distributed hydrological model for the study area was constructed and its performance was evaluated. Meteorological, hydrological, topographic, soil property, underlying surface, vegetation, social water consumption, and population density data of the study area were collected, and computational units were divided and spatially distributed. The model parameters were calibrated using flow data from key watershed hydrological stations, and the Nash efficiency coefficient and water balance error were used to evaluate the model performance.

[0036] Meteorological data includes daily precipitation, average temperature, wind speed, sunshine duration, relative humidity, and latitude, longitude, and elevation data of meteorological stations, which are obtained from the meteorological data center.

[0037] The hydrological data includes daily flow data from hydrological stations, basin boundaries, and actual water system data, obtained from the Yellow River Hydrological Yearbook.

[0038] The terrain data includes digital elevation data (DEM), which is obtained from a geospatial data cloud platform.

[0039] Soil data, including soil type, soil thickness, and soil texture (percentage content of clay, silt, and sand), were obtained through remote sensing data interpretation; soil physicochemical properties (saturated water content, field water holding capacity, hygroscopic coefficient, and maximum molecular water holding capacity) were obtained from soil databases.

[0040] The underlying surface data includes land use data, which is obtained through remote sensing data interpretation.

[0041] Vegetation data includes monthly leaf area index and vegetation cover data for forests, grasslands, and crops, obtained through remote sensing data interpretation.

[0042] Social water consumption data includes industrial, domestic, and agricultural water consumption, obtained from the Yellow River Water Resources Bulletin.

[0043] Furthermore, when using one-dimensional moving waves (slope confluence and river confluence) in the solution of river confluence in distributed hydrological models, the rise in river level is not considered. To address the problem of systematically overestimating river flow due to evaporation and seepage losses caused by water surface fluctuations, this invention explicitly adds a loss source term to the Saint-Venant continuity equation. Traditional distributed hydrological models, for the sake of simplified calculations, generally assume narrow river cross-sections and small variations in water depth, thus neglecting the increase in water surface area caused by water level fluctuations and its feedback effects on evaporation and seepage. This assumption is acceptable in traditional runoff simulations, but in regional healthy water balance assessments, small errors in river flow balance, accumulated over a long period, can interfere with the calculation of groundwater-surface water interaction fluxes, leading to distortions in indicators such as "balance" and "sustainability."

[0044] The river surface evaporation-seepage loss module provided by this invention is characterized as follows:

[0045]

[0046] In the formula: The cross-sectional area of ​​the water passage. For cross-sectional flow, For lateral inflow, For time, Distance along the river Evaporation loss per unit length of river surface Losses due to seepage within the unit of river chief;

[0047] Evaporation loss per unit length of river surface Considering the increase in water surface area caused by coupled water level changes, the calculation formula is as follows:

[0048]

[0049] In the formula: This represents the water level at the end of the time period. The initial water level for that period. The base angle of the isosceles trapezoidal cross section, The first unit conversion factor, Evaporation capacity of water surface The calculation formula is:

[0050]

[0051] In the formula: Net radiation, This refers to the heat flux transferred into the water. This is the derivative of saturated vapor pressure with respect to temperature. For saturated gas pressure difference, For aerodynamic impedance, air density, For the specific heat of air, As latent heat of vaporization, It is the water vapor pressure;

[0052] Unit River Chief Seepage Loss A segmented calculation method is adopted, taking into account the groundwater level. Riverbed elevation The relationship between the water level and the river level is calculated using the following formula:

[0053]

[0054] In the formula: The permeability coefficient of the riverbed material. For riverbed thickness, The elevation of the riverbed. Groundwater level, This is the conversion factor for the second unit.

[0055] Furthermore, to address the limitation of the WEP model in not considering groundwater replenishment through capillary upwelling to soil evaporation and vegetation transpiration, the calculation of groundwater evaporation is introduced into the existing evaporation structure. The specific equations are as follows:

[0056] The submersible evaporation module is characterized as follows:

[0057]

[0058] In the formula: Evaporation by diving Evaporation capacity of water surface For the depth of the diving, This is the extreme depth for underwater evaporation. and The parameters to be fitted are related to soil texture and vegetation cover.

[0059] Groundwater evaporation, as a replenishment of water, prioritizes meeting the transpiration needs of vegetation, with the remainder used for soil evaporation. The groundwater evaporation is directly deducted from the groundwater level, resulting in the updated groundwater balance equation:

[0060]

[0061] In the formula: This represents the groundwater level at the end of the time period. The initial groundwater level during the period. This represents the net lateral inflow. This represents the leakage rate from the upper layer. This refers to the depth of leakage. The amount of groundwater exchanged with rivers and gullies.

[0062] The innovative contribution of this invention to the WEP model lies in its breakthrough from the traditional distributed hydrological model's neglect of water loss caused by water level changes in river confluence. It proposes an improved method based on water level-driven, nonlinear, two-way coupling of evaporation and seepage. The technical challenge lies in the fact that hydrological changes simultaneously alter both the water surface area and the hydraulic gradient of seepage, and these two factors interact through the water balance equation.

[0063] This invention explicitly incorporates water level into formulas (2) and (4), enabling dynamic adjustment of evaporation and seepage losses in the river channel with water level. This ensures that the variables output by the model, such as river flow, groundwater level, and soil moisture content, maintain a closed-loop water balance consistency. This improvement does not increase the parameters to be calibrated but rather corrects the systematic bias caused by the simplification assumptions of the traditional model from a physical mechanism perspective. This solves the distortion problem that occurs when such biases are transmitted to healthy water balance indicators (especially the water budget balance index and the degree of ecological flow guarantee).

[0064] Step S2: Construct a health balance indicator system comprising a target layer, a criterion layer, and an indicator layer; the target layer is the health balance assessment target; the criterion layer includes multiple evaluation dimensions; each evaluation dimension is provided with at least one evaluation indicator located in the indicator layer;

[0065] As one implementation method, based on the concept of healthy water balance, an evaluation index system is constructed from four dimensions: carrying capacity, sustainability, balance, and stability. The criteria layer includes one or more evaluation dimensions from these four dimensions. Carrying capacity is the foundation of the system, objectively representing the potential of water resource endowment to support socio-economic development. Therefore, the evaluation indicators for the carrying capacity dimension include per capita water resource availability and per mu (unit of land area). Sustainability focuses on the intensity of human intervention and its impact on the long-term sustainability of resources. The evaluation indicators for the sustainability dimension include the development and utilization rate of surface water resources and the development and utilization rate of groundwater resources. Balance focuses on the equilibrium state of the water cycle process, measuring whether the input and output of regional water are matched in total amount. The evaluation indicators for the balance dimension include the water budget balance index. Stability measures the system's ability to maintain its key structures and functions when facing pressures such as climate change and human activities. The evaluation indicators for the stability dimension include the degree of ecological flow guarantee and the water conservation coefficient.

[0066] Step S3: Construct an evaluation index calculation model for each of the evaluation indicators; the evaluation index calculation model calculates the true value of the evaluation index in each calculation unit of the study area based on the key hydrological simulation data output by the WEP distributed hydrological model; according to the pre-established mapping relationship between the true value, level and score of the evaluation index, the score of the evaluation index in each calculation unit of the study area is obtained based on the true value of the evaluation index.

[0067] Specifically, this step uses single-index quantitative calculation. Based on the WEP model already constructed in S1, the key hydrological variables are output using the WEP model, and seven characterizing indicators that represent the health status of the regional water cycle system are statistically obtained. All indicators are calculated in units of calculation unit x.

[0068] The calculation models for each evaluation indicator are as follows:

[0069] ① Per capita water resources are defined as the total amount of water resources. Total population of the statistical area The ratio, its calculation model includes:

[0070] Total water resources The calculation formula is as follows:

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] The per capita water resources for:

[0077]

[0078] In the formula: Number the calculation unit; The surface water distribution coefficient; This is the groundwater distribution coefficient; Surface water resources, in mm; Groundwater resources, in mm; The total amount of water resources is expressed in m³. Rainfall, in mm; To calculate the area of ​​a unit, km 2 UH is the unit conversion factor, 1000; Surface irrigation volume, mm; The soil infiltration rate is expressed in mm. Surface seepage, in mm; Surface runoff, mm; The saturated slope yield is expressed in mm. Groundwater exchange rate in gullies, mm; The groundwater exchange rate in the river channel is expressed in mm. Evaporation rate (mm); Evaporation from the river surface, in mm; Vertical displacement due to gravity, in mm; This represents the net lateral recharge of groundwater, in mm; This refers to the per capita water resources available to each person, expressed in m³ / person. To count the total population of the region, in people;

[0079] ② The per-mu water resource availability is defined as the total water resources. and irrigated farmland area The ratio, its calculation model is as follows:

[0080]

[0081] In the formula: Water resources per mu (unit of land area), m³ / mu; The area of ​​irrigated farmland is measured in mu (a Chinese unit of area, approximately 0.165 acres).

[0082] ③ The surface water resource development and utilization rate is defined as the surface water supply volume With surface water resources The ratio, its calculation model includes:

[0083]

[0084]

[0085] In the formula: The rate of development and utilization of surface water resources is dimensionless. Surface water supply, in ten thousand m³; The quantity of surface water resources is in ten thousand m³.

[0086] ④ The groundwater resource development and utilization rate is defined as the groundwater supply volume With groundwater resources The ratio, its calculation model is as follows:

[0087]

[0088] In the formula: The rate of development and utilization of groundwater resources is dimensionless. The groundwater supply volume is in tens of thousands of cubic meters. The exploitable amount of groundwater resources, in tens of thousands of cubic meters;

[0089] ⑤ The water balance index reflects the balance of the water cycle process and is used to determine whether the system is in a state of sustainable metabolic equilibrium or metabolic deficit. Its calculation model is as follows:

[0090]

[0091]

[0092]

[0093] In the formula: Income-expenditure imbalance; Rainfall, in mm; Inflow volume, 10,000 m³; The outflow volume is in ten thousand m³. The volume of water to be diverted is 10,000 m³. To adjust the water volume, 10,000 m³; The amount of water input by humans, in tens of thousands of cubic meters; Human-generated water output, in tens of thousands of cubic meters; The infiltrated water volume is in tens of thousands of cubic meters. The amount of seepage water is in tens of thousands of cubic meters. Evaporation rate, mm; The total inflow volume is expressed in m³. The total outflow volume is expressed in m³. The total amount of water resources is expressed in m³.

[0094] ⑥ The degree of ecological flow guarantee emphasizes that the hydrological conditions necessary to maintain the structural stability and functional health of the river ecosystem must be met. Its calculation model is as follows:

[0095]

[0096] In the formula: To ensure the level of ecological flow protection; The minimum daily average flow rate from April to September, in m³ / s; The average flow rate over many years is from April to September, in m³ / s; The minimum daily average flow rate from October to March of the following year, in m³ / s; The average flow rate over many years is from October to March of the following year, in m³ / s;

[0097] ⑦ The water conservation coefficient is defined as the ratio of water conservation capacity to precipitation, and its calculation model is as follows:

[0098]

[0099]

[0100] In the formula: The water conservation coefficient is dimensionless. Water conservation capacity, mm; The source terms include precipitation, snowmelt, and irrigation water, in mm; Surface runoff, mm; Evapotranspiration from non-vegetation areas, in mm.

[0101] In this step, the mapping relationship between the pre-established evaluation index's actual value, level, and score is as follows:

[0102] Per capita water resources are divided into five levels: AWP < 500, severe water shortage; 500 ≤ AWP < 1000, water shortage; 1000 ≤ AWP < 1700, water pressure exists; 1700 ≤ AWP < 3000, no water pressure exists; 3000 ≤ AWP, water abundance exists. Scores are assigned as 0, 40, 60, 80, and 100 points respectively on a percentage scale.

[0103] According to the characteristics of the Yellow River Basin, the average water resources possession per mu is divided into 6 levels: MWP < 300, 300 ≤ MWP < 600, 600 ≤ MWP < 900, 900 ≤ MWP < 1200, 1200 ≤ MWP < 1500, 1500 ≤ MWP, and the corresponding scores are 0, 20, 40, 60, 80, and 100 respectively;

[0104] Referring to the surface water resources development and utilization rate, referring to the "Specifications for River and Lake Health Assessment" (SL / T 793-2025), the surface water resources development and utilization rate is divided into 6 levels: WURI < 40%, 40% ≤ WURI < 50%, 50% ≤ WURI < 67%, 67% ≤ WURI < 75%, 75% ≤ WURI < 90%, 90% ≤ WURI, and the corresponding scores are 100, 80, 50, 20, 10, and 0 respectively;

[0105] The classification standard for the development and utilization rate of groundwater resources refers to that of surface water resources. The development and utilization rate of groundwater resources is divided into 6 levels: WGRI < 40%, 40% ≤ WGRI < 50%, 50% ≤ WGRI < 67%, 67% ≤ WGRI < 75%, 75% ≤ WGRI < 90%, 90% ≤ WGRI, and the corresponding scores are 100, 80, 50, 20, 10, and 0 respectively;

[0106] The water balance index is divided into 6 levels: V_IOB < -0.6, -0.6 < V_IOB < -0.4, -0.4 ≤ V_IOB < -0.2, -0.2 ≤ V_IOB < -0.05, -0.05 ≤ V_IOB < 0, 0 ≤ V_IOB, and the corresponding scores are 0, 20, 40, 60, 80, and 100 respectively;

[0107] The degree of ecological flow guarantee can refer to the "Specifications for River and Lake Health Assessment" (SL / T 793-2025). The degree of ecological flow guarantee is divided into 5 levels, and the corresponding scores are 0, 20, 40, 80, and 100 respectively;

[0108] The water conservation coefficient is divided into 7 levels: WACC < 0.05, 0.05 ≤ WACC < 0.1, 0.1 ≤ WACC < 0.2, 0.2 ≤ WACC < 0.3, 0.3 ≤ WACC < 0.4, 0.4 ≤ WACC < 0.5, 0.5 ≤ WACC, and the corresponding scores are 0, 40, 80, 100, 80, 40, and 0 respectively.

[0109] Step S4, determination of the combined weight of multiple methods: To avoid subjectivity or one-sidedness of a single weight determination method, the present invention uses a combination of an objective weighting method (entropy weight method) and an empirical weighting method (expert scoring method) to determine the index weights, realizing the integration of data fluctuation laws and prior knowledge.

[0110] Specifically, a combination of entropy weighting and empirical weighting methods is adopted, and an adaptive combination coefficient solution strategy based on maximizing the sum of squared deviations is introduced to determine the combination weight of each evaluation index.

[0111] Step S41, Objective Weighting Method: The index weights are calculated using the entropy weighting method. First, the data is standardized using the maximum-minimum normalization method to eliminate the influence of dimensions. Then, the weight ratio and information entropy value of each index are calculated to obtain the information entropy redundancy. Finally, the objective weights of each index are calculated.

[0112] As shown in formulas (23) and (24), based on the positive and negative characteristics of each evaluation indicator, the maximum-minimum normalization method is used to standardize the true values ​​of each evaluation indicator:

[0113]

[0114]

[0115] in: Indicates the first The evaluation indicators in the first The actual values ​​of the evaluation indicators for each computing unit; , This indicates the number of computing units in the study area; Indicates the first The evaluation indicators in the first Standardized values ​​of evaluation indicators for each computing unit;

[0116] For per capita water resources, per mu of water resources, water revenue and expenditure balance index, ecological flow guarantee degree and water source conservation coefficient, which are positive indicators, the formula (23) is used for standardization.

[0117] For the development and utilization rates of surface water resources and groundwater resources, which are negative indicators, the standardization process is carried out using formula (24).

[0118] Step S42: Using formula (25), calculate the weight ratio and information entropy value of each evaluation indicator, thereby obtaining the information entropy redundancy, and finally obtaining the objective weight of each evaluation indicator:

[0119]

[0120] in: Indicates the number of evaluation indicators; The entropy weight method determines the first Objective weights of evaluation indicators;

[0121] Step S43: Using the experience-based weighting method, the experience weights of each evaluation indicator are determined through expert scoring.

[0122]

[0123] in: Experts indicated their opinion on the first Scoring of each evaluation indicator; Indicates the first The empirical weight of each evaluation indicator;

[0124] Step S44: Determine the combination coefficients of objective weights and empirical weights using the principle of maximizing the sum of squared deviations.

[0125]

[0126]

[0127]

[0128]

[0129] in: Indicates the first The combined weights of the evaluation indicators; The contribution coefficient representing the objective weight; Indicates the first The evaluation indicators in the first The score of each calculation unit; Indicates the first The overall score of each calculation unit; This represents the average score of all calculation units. This represents the sum of squared deviations across all computational units; A function that maximizes the sum of squared deviations;

[0130] By maximizing the sum of squared deviations of all computational units, the optimal value of λ is automatically searched, such that the first... The comprehensive weighting of the evaluation indicators can best distinguish the health balance status of different calculation units.

[0131] Therefore, the innovative contribution of this invention in combined weighting lies not in simply using the entropy weighting method and the expert scoring method simultaneously, but in proposing an "adaptive combined coefficient solution strategy based on maximizing the sum of squared deviations." Traditional methods typically set λ=0.5 manually or rely on trial and error based on experience, resulting in arbitrary weight combinations. This invention automatically searches for the optimal λ value by maximizing the sum of squared deviations of the comprehensive scores of all computing units, enabling the final index weights to distinguish the health balance status of different computing units to the greatest extent.

[0132] Step S5, Determining the health balance status: Based on the combined weight of each evaluation index, the scores of each evaluation index in each calculation unit are weighted and summed to obtain the health balance score of the calculation unit. The health balance status of the calculation unit is determined by the health balance score.

[0133] Step S51, Determination of healthy fluid balance:

[0134] Using formula (31), calculate the first... Health balance score of each calculation unit :

[0135]

[0136] For larger-scale study areas, the health balance score for that study area is obtained by area-weighted aggregation:

[0137]

[0138] in: Indicates the first The area of ​​each computing unit occupies the study area The proportion of the total area This indicates the health balance score of the study area;

[0139] Step S52: Based on the health water balance score of the study area, the health status of the regional water cycle system is divided into 5 levels: 90~100 points is Level I, steady-state coordination; 80~90 points is Level II, metastable fluctuation; 60~80 points is Level III, critical stress; 50~60 points is Level IV, imbalance state; 0~50 points is Level V, severe imbalance.

[0140] The present invention has the following advantages:

[0141] (1) A regional health level measurement and assessment framework was constructed. In view of the problem that the health water balance remains at the theoretical definition and lacks specific assessment methods, this invention starts from four dimensions: carrying capacity, sustainability, balance and stability, selects seven quantifiable core indicators, establishes a complete indicator system and calculation process, and provides a repeatable and verifiable quantitative assessment tool for the health status of the regional water cycle system.

[0142] (2) This invention relies on the WEP distributed hydrological model to simulate the water cycle process and outputs spatiotemporally continuous data with physical consistency. It can overcome the spatial limitations of ground monitoring equipment, enable the assessment to be extended to different time and spatial scales, significantly improve the representativeness and applicability of the assessment results, and has broad application prospects.

[0143] (3) The systematic bias of the traditional model is corrected from the perspective of physical mechanism. The improvement of the WEP model in this invention corrects the distortion of river water balance caused by ignoring the dynamic feedback of water level and loss without increasing the parameters to be calibrated. It significantly improves the systematic bias of runoff simulation during the dry season, so that the model can maintain water balance closure under different flow levels, thereby making the healthy water balance assessment results more scientific and reliable.

[0144] The following example, using the Yellow River's important water conservation area, illustrates a practical application of this invention:

[0145] like Figure 4 As shown, a regional healthy water balance assessment method based on the WEP distributed hydrological model includes the following steps:

[0146] S1. A WEP distributed hydrological model for the Yellow River's important water source conservation area was constructed, and its performance was evaluated. Meteorological, hydrological, topographic, soil, underlying surface, vegetation, social water consumption, and population density data for the Yellow River's important water source conservation area from 1956 to 2021 were collected and organized, dividing the area into 3246 sub-basins and 15272 contour zones. Monthly runoff data from the Tangnaihai, Lanzhou, Huaxian, and Heishiguan hydrological stations were used to evaluate the model's performance. The evaluation results showed that the Nash efficiency coefficient was above 0.70, and the water balance error was within 10%, indicating that the WEP model can be used to simulate water cycle elements in the Yellow River's important water source conservation area. This embodiment adopted an improved WEP model that includes a river surface evaporation-seepage loss module and a groundwater evaporation module.

[0147] S2, Construction of a Healthy Water Balance Indicator System. The healthy water balance evaluation indicator system consists of four categories of secondary indicators, each of which contains one or two tertiary indicators, for a total of seven indicators: per capita water resource availability, per mu (unit of land area) water resource availability, surface water resource development and utilization rate, groundwater resource development and utilization rate, water revenue and expenditure balance index, ecological flow guarantee level, and water source conservation coefficient.

[0148] S3, Single-Indicator Quantitative Calculation. Using the key hydrological variables output from the WEP (Weighted Ecosystem Protection Area) of the Yellow River's important water source conservation zone constructed in S1, seven indicators characterizing the region's healthy water balance status were statistically obtained. All indicators were calculated using the calculation unit x. Taking the 2020 calculation results as an example, the results are shown below. Figures 1-7 .

[0149] Figure 1 The score represents the per capita water resources availability in the important water conservation areas of the Yellow River in 2020. Figure 1The data shows that most areas above Lanzhou have a per capita water resource score of 100, the central urban area has a score between 40 and 60, a small number of areas in the Weihe River tributary and the Yihe River basin have a score of 100, most areas have a score below 60, and some areas in the lower reaches of the Yihe River have a score of 0, indicating extremely scarce water resources.

[0150] Figure 2 The score represents the per-mu water resource availability in the important water conservation areas of the Yellow River in 2020. Figure 2 This indicates that the per-mu water resources in the areas above Lanzhou are differentiated. The area above Lijiaxia Reservoir scores 100, while the downstream area near the central urban area of ​​Lanzhou scores around 20. Most areas in the Weihe River tributary and the Yihe River basin are in a state of severe water shortage, with a score of 0. The southern area of ​​the Weihe River tributary has a per-mu water resources exceeding 1000 m³ / mu, and the source area of ​​the Yihe River and a small area in the south have a per-mu water resources exceeding 500 m³ / mu, with a score above 60.

[0151] Figure 3 The score represents the surface water resource development and utilization rate in the Yellow River's important water source conservation area in 2020. Figure 3 The data shows that the water resource development and utilization rate is relatively high in the central urban areas above Lanzhou, the northern part of the Weihe River's southern tributary, and the urban agglomeration in the lower reaches of the Yihe and Luohe Rivers (surface water development and utilization rate greater than 70%), with some areas exceeding 90%, while the remaining majority of areas have a water resource development and utilization rate of less than 20%. The overall score for surface water resource development and utilization rate is between 80 and 90 in most areas, while the central urban areas, with their high water consumption, have surface water resource scores between 0 and 10.

[0152] Figure 4 The score represents the development and utilization rate of groundwater resources in the important water conservation area of ​​the Yellow River in 2020. Figure 4 This indicates that, except for a few areas that scored 0, the overall groundwater development and utilization rate was relatively low. Therefore, most areas scored high, with the entire conservation area scoring around 98.

[0153] Figure 5 The water balance index score for the important water source conservation areas of the Yellow River in 2020. Figure 5 The results indicate that the water balance index score for the entire conservation area ranges from 80 to 100. Influenced by precipitation and the degree of water resource development and utilization, the water balance index score fluctuates, with lower scores in some years. Spatially, the water balance index score shows a slight deficit in the area above Lanzhou, particularly in the Yellow River source region, with scores between 40 and 60. The Weihe River's southern tributaries and the source region of the Yihe and Luohe Rivers also experience water deficits in some years, with scores between 20 and 40.

[0154] Figure 6 The score for the ecological flow guarantee level of the Yellow River's important water source conservation area in 2020. Figure 6 The data shows that the overall ecological flow guarantee level in the water conservation area is relatively high, with the vast majority of areas exceeding 80% of the annual ecological flow guarantee level.

[0155] The dynamic flow guarantee is relatively good.

[0156] A high water conservation coefficient indicates that the region has a strong ability to regulate and store precipitation, but the amount of water supplied to downstream areas is reduced, resulting in a low water conservation coefficient. This makes it difficult to store water to meet local water demand. Therefore, the water conservation coefficient should be within a reasonable range. Figure 7 The water conservation coefficient score for the important water conservation areas of the Yellow River in 2020. Figure 7 The most suitable water conservation coefficient is mainly distributed in the central part of the area above Lanzhou, the central part of the Weihe River's southern tributary, the source area of ​​the Yihe River, and a small amount of downstream areas. The more suitable water conservation coefficient is close to the most suitable water conservation coefficient distribution. Overall, the water conservation coefficient score of the conservation area fluctuates between 60 and 70 points.

[0157] S4. Weighting determined by a combination of multiple methods. To avoid the subjectivity or bias of a single weighting method, this invention combines the entropy weighting method with expert scoring to determine the indicator weights, ultimately determining the indicator weights. Specifically, the weights are as follows: per capita water resource availability rate is 0.0152, per mu (unit of land area) water resource availability rate is 0.1456, surface water resource development and utilization rate is 0.3004, groundwater resource development and utilization rate is 0.0967, water balance index is 0.0770, ecological flow guarantee level is 0.3150, and water conservation coefficient is 0.0501.

[0158] S5, Determination of Healthy Water Balance Status. The scores of each indicator in S3 are weighted and summed with the weights determined in S4 to obtain the healthy water balance status of the sub-basin. A weighted summation yields the overall healthy water balance status of the region. Taking the 2020 assessment results as an example, the healthy water balance status of the Yellow River's important water source conservation area is shown below. Figures 8-9 .

[0159] Figure 8 The score for the healthy water balance of the Yellow River's important water source conservation areas in 2020; Figure 8The data shows that the water balance in the Yellow River source area, Qilian Mountains, and Qinling Mountains is stable and coordinated, with relatively good water resource endowment and suitable water conservation capacity. The water balance in the middle and lower reaches of the Weihe River's southern tributaries and the upper reaches of the Yihe and Luohe Rivers is in a metastable and fluctuating state. The lower reaches of the Yihe and Luohe Rivers are in a state of severe imbalance, with high water resource development intensity and low per capita and per mu water resource availability. At the same time, some parts of the central urban area of ​​Lanzhou City are in a state of imbalance and severe imbalance due to low per capita water resource availability, high degree of surface water resource development and utilization, and weak water conservation capacity. The water resource development and utilization intensity and low water conservation capacity in the source area of ​​the Weihe River's southern tributaries make its water balance fragile and highly susceptible to fluctuations in precipitation, resulting in a better water balance in wet years and a worse water balance in dry years.

[0160] Figure 9 The level of healthy water balance in the important water conservation areas of the Yellow River in 2020; Figure 9 The data shows that most areas in the water conservation area are in good health, with a healthy water balance state of "steady-state coordination" and "substable fluctuations". Only the central urban area of ​​Lanzhou, Dingxi City, Guanzhong Basin, Longmen Town and other places have a "severe imbalance".

[0161] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for assessing regional healthy water balance based on the WEP distributed hydrological model, characterized in that, Includes the following steps: Step S1: Construct a WEP distributed hydrological model for the study area, including a river surface evaporation-seepage loss module and a groundwater evaporation module; the WEP distributed hydrological model simulates the water cycle elements of the study area and outputs key hydrological simulation data with physical consistency in the study area during the evaluation period. Step S2: Construct a health balance indicator system comprising a target layer, a criterion layer, and an indicator layer; the target layer is the health balance assessment target; the criterion layer includes multiple evaluation dimensions; each evaluation dimension is provided with at least one evaluation indicator located in the indicator layer; Step S3: Construct an evaluation index calculation model for each of the evaluation indicators; the evaluation index calculation model is based on the key hydrological simulation data output by the WEP distributed hydrological model to calculate the true value of the evaluation index in each calculation unit of the study area. Based on the pre-established mapping relationship between the actual values, levels, and scores of the evaluation indicators, the score of the evaluation indicator in each calculation unit in the study area is obtained based on the actual values ​​of the evaluation indicators. Step S4: Using a combination of entropy weighting method and empirical weighting method, and introducing an adaptive combination coefficient solution strategy based on maximizing the sum of squared deviations, the combination weight of each evaluation index is determined. Step S5: Based on the combined weight of each evaluation index, the scores of each evaluation index in each calculation unit are weighted and summed to obtain the health balance score of the calculation unit. The health balance status of the calculation unit is determined by the health balance score.

2. The regional health water balance assessment method based on the WEP distributed hydrological model according to claim 1, characterized in that, The river surface evaporation-seepage loss module is characterized as follows: ； In the formula: The cross-sectional area of ​​the water passage. For cross-sectional flow, For lateral inflow, For time, Distance along the river Evaporation loss per unit length of river surface Losses due to seepage within the unit of river chief; Evaporation loss per unit length of river surface Considering the increase in water surface area caused by coupled water level changes, the calculation formula is as follows: ； In the formula: This represents the water level at the end of the time period. The initial water level for that period. The base angle of the isosceles trapezoidal cross section, The first unit conversion factor, Evaporation capacity of water surface The calculation formula is: ； In the formula: Net radiation, This refers to the heat flux transferred into the water. This is the derivative of saturated vapor pressure with respect to temperature. For saturated gas pressure difference, For aerodynamic impedance, air density, For the specific heat of air, As latent heat of vaporization, It is the water vapor pressure; Unit River Chief Seepage Loss A segmented calculation method is adopted, taking into account the groundwater level. Riverbed elevation The relationship between the water level and the river level is calculated using the following formula: ； In the formula: The permeability coefficient of the riverbed material. For riverbed thickness, The elevation of the riverbed. Groundwater level, This is the conversion factor for the second unit.

3. The regional health water balance assessment method based on the WEP distributed hydrological model according to claim 1, characterized in that, The submersible evaporation module is characterized as follows: ； In the formula: Evaporation by diving Evaporation capacity of water surface For the depth of the diving, This is the extreme depth for underwater evaporation. and The parameters to be fitted are related to soil texture and vegetation cover. Groundwater evaporation, as a replenishment of water, prioritizes meeting the transpiration needs of vegetation, with the remainder used for soil evaporation. The groundwater evaporation is directly deducted from the groundwater level, resulting in the updated groundwater balance equation: ； In the formula: This represents the groundwater level at the end of the time period. The initial groundwater level during the period. This represents the net lateral inflow. This represents the leakage rate from the upper layer. This refers to the depth of leakage. The amount of groundwater exchanged with rivers and gullies.

4. The regional health water balance assessment method based on the WEP distributed hydrological model according to claim 1, characterized in that, The criteria layer includes one or more evaluation dimensions among carrying capacity, sustainability, balance, and stability. The evaluation indicators set for the carrying capacity evaluation dimension include per capita water resources and per mu of water resources. The evaluation indicators set for the sustainability evaluation dimension include the development and utilization rate of surface water resources and the development and utilization rate of groundwater resources. The evaluation indicators set for the balance evaluation dimension include the water revenue and expenditure balance index. The evaluation indicators set for the stability evaluation dimension include the degree of ecological flow guarantee and the water source conservation coefficient.

5. A regional health water balance assessment method based on the WEP distributed hydrological model according to claim 4, characterized in that, The calculation models for each evaluation indicator are as follows: ① Per capita water resources are defined as the total amount of water resources. Total population of the statistical area The ratio, its calculation model includes: Total water resources The calculation formula is as follows: ； ； ； ； ； The per capita water resources for: ； In the formula: Number the calculation unit; The surface water distribution coefficient; This is the groundwater distribution coefficient; Surface water resources, in mm; Groundwater resources, in mm; The total amount of water resources is expressed in m³. Rainfall, in mm; To calculate the area of ​​a unit, km 2 UH is the unit conversion factor, 1000; Surface irrigation volume, mm; The soil infiltration rate is expressed in mm. Surface seepage, in mm; Surface runoff, mm; The saturated slope yield is expressed in mm. Groundwater exchange rate in gullies, mm; The groundwater exchange rate in the river channel is expressed in mm. Evaporation rate (mm); Evaporation from the river surface, in mm; Vertical displacement due to gravity, in mm; This represents the net lateral recharge of groundwater, in mm; This refers to the per capita water resources available to each person, expressed in m³ / person. To count the total population of the region, in people; ② The per-mu water resource availability is defined as the total water resources. and irrigated farmland area The ratio, its calculation model is as follows: ； In the formula: Water resources per mu (unit of land area), m³ / mu; The area of ​​irrigated farmland is measured in mu (a Chinese unit of area, approximately 0.165 acres). ③ The surface water resource development and utilization rate is defined as the surface water supply volume With surface water resources The ratio, its calculation model includes: ； ； In the formula: The rate of development and utilization of surface water resources is dimensionless. Surface water supply, in ten thousand m³; Surface water resources, in ten thousand m³; ④ The groundwater resource development and utilization rate is defined as the groundwater supply volume With groundwater resources The ratio, its calculation model is as follows: ； In the formula: The rate of development and utilization of groundwater resources is dimensionless. The groundwater supply volume is in tens of thousands of cubic meters. The exploitable amount of groundwater resources, in tens of thousands of cubic meters; ⑤ The water balance index reflects the balance of the water cycle process and is used to determine whether the system is in a state of sustainable metabolic equilibrium or metabolic deficit. Its calculation model is as follows: ； ； ； In the formula: Income and expenditure imbalance; Rainfall, in mm; Inflow volume, 10,000 m³; The outflow volume is in ten thousand m³. The volume of water to be transferred in is 10,000 m³. To adjust the water volume, 10,000 m³; The amount of water input by humans, in tens of thousands of cubic meters; Human-generated water output volume, in tens of thousands of cubic meters; The infiltration volume is in ten thousand m³. The amount of seepage water is in tens of thousands of cubic meters. Evaporation rate, mm; The total inflow volume is expressed in m³. The total outflow volume is expressed in m³. The total amount of water resources is expressed in m³. ⑥ The degree of ecological flow guarantee emphasizes that the hydrological conditions necessary to maintain the structural stability and functional health of the river ecosystem must be met. Its calculation model is as follows: ； In the formula: To ensure the level of ecological flow protection; The minimum daily average flow rate from April to September, in m³ / s; The average flow rate over many years is from April to September, in m³ / s; The minimum daily average flow rate from October to March of the following year, in m³ / s; The average flow rate over many years is from October to March of the following year, in m³ / s; ⑦ The water conservation coefficient is defined as the ratio of water conservation capacity to precipitation, and its calculation model is as follows: ； ； In the formula: The water conservation coefficient is dimensionless. Water conservation capacity, mm; The source terms include precipitation, snowmelt, and irrigation water, in mm; Surface runoff, mm; Evapotranspiration from non-vegetation areas, in mm.

6. The regional health water balance assessment method based on the WEP distributed hydrological model according to claim 1, characterized in that, The mapping relationship between the pre-established evaluation indicators' actual values, levels, and scores is as follows: The per capita water resource possession is divided into 5 levels: AWP < 500, a severe water shortage level; 500 ≤ AWP < 1000, a water shortage state; 1000 ≤ AWP < 1700, there is water resource pressure; 1700 ≤ AWP < 3000, there is no water resource pressure; 3000 ≤ AWP, a state of abundant water resources; The scores are determined as 0, 40, 60, 80, and 100 points respectively according to the percentage system; The per mu water resource possession is divided into 6 levels: MWP < 300, 300 ≤ MWP < 600, 600 ≤ MWP < 900, 900 ≤ MWP < 1200, 1200 ≤ MWP < 1500, 1500 ≤ MWP, and the corresponding scores are 0, 20, 40, 60, 80, and 100 respectively; The surface water resource development and utilization rate is divided into 6 levels: WURI < 40%, 40% ≤ WURI < 50%, 50% ≤ WURI < 67%, 67% ≤ WURI < 75%, 75% ≤ WURI < 90%, 90% ≤ WURI, and the corresponding scores are 100, 80, 50, 20, 10, and 0 respectively; The groundwater resource development and utilization rate is divided into 6 levels: WGRI < 40%, 40% ≤ WGRI < 50%, 50% ≤ WGRI < 67%, 67% ≤ WGRI < 75%, 75% ≤ WGRI < 90%, 90% ≤ WGRI, and the corresponding scores are 100, 80, 50, 20, 10, and 0 respectively; The water balance index is divided into 6 levels: V_IOB < -0.6, -0.6 < V_IOB < -0.4, -0.4 ≤ V_IOB < -0.2, -0.2 ≤ V_IOB < -0.05, -0.05 ≤ V_IOB < 0, 0 ≤ V_IOB, and the corresponding scores are 0, 20, 40, 60, 80, and 100 respectively; The ecological flow guarantee degree is divided into 5 levels, and the corresponding scores are 0, 20, 40, 80, 100 respectively; The water conservation coefficient is divided into 7 levels: WACC < 0.05, 0.05 ≤ WACC < 0.1, 0.1 ≤ WACC < 0.2, 0.2 ≤ WACC < 0.3, 0.3 ≤ WACC < 0.4, 0.4 ≤ WACC < 0.5, 0.5 ≤ WACC, and the corresponding scores are 0, 40, 80, 100, 80, 40, and 0 respectively.

7. The regional health water balance assessment method based on the WEP distributed hydrological model according to claim 1, characterized in that, Step S4 includes: Step S41, according to the positive and negative characteristics of each evaluation index, use the maximum-minimum normalization method to standardize the true value of the evaluation index of each evaluation index: ； ； in: Indicates the first The evaluation indicators in the first The actual values ​​of the evaluation indicators for each computing unit; , This indicates the number of computing units in the study area; Indicates the first The evaluation indicators in the first Standardized values ​​of evaluation indicators for each computing unit; For the per capita water resource possession, the per mu water resource possession, the water balance index, the ecological flow guarantee degree, and the water conservation coefficient, which are positive indicators, use formula (23) for standardization; For the surface water resource development and utilization rate and the groundwater resource development and utilization rate, which are negative indicators, use formula (24) for standardization; Step S42: Using formula (25), calculate the weight ratio and information entropy value of each evaluation indicator, thereby obtaining the information entropy redundancy, and finally obtaining the objective weight of each evaluation indicator: ； in: Indicates the number of evaluation indicators; The entropy weight method determines the first Objective weights of evaluation indicators; Step S43: Using the experience-based weighting method, the experience weights of each evaluation indicator are determined through expert scoring. ； in: Experts indicated their opinion on the first Scoring of each evaluation indicator; Indicates the first The empirical weights of the evaluation indicators; Step S44: Determine the combination coefficients of objective weights and empirical weights using the principle of maximizing the sum of squared deviations. ； ； ； ； in: Indicates the first The combined weights of the evaluation indicators; The contribution coefficient representing the objective weight; Indicates the first The evaluation indicators in the first The score of each calculation unit; Indicates the first The overall score of each calculation unit; This represents the average score of all calculation units. This represents the sum of squared deviations across all computational units; A function that maximizes the sum of squared deviations; By maximizing the sum of squared deviations of all computational units, the optimal value of λ is automatically searched, such that the first... The comprehensive weighting of the evaluation indicators can best distinguish the health balance status of different calculation units.

8. The regional health water balance assessment method based on the WEP distributed hydrological model according to claim 7, characterized in that, Step S5 specifically includes: Step S51, Determination of healthy fluid balance: Using formula (31), calculate the first... Health balance score of each calculation unit : ； For larger-scale study areas, the health balance score for that study area is obtained by area-weighted aggregation: ； in: Indicates the first The area of ​​each computing unit occupies the study area The proportion of the total area This indicates the health balance score of the study area; Step S52: Based on the health water balance score of the study area, the health status of the regional water cycle system is divided into 5 levels: 90~100 points is Level I, steady-state coordination; 80~90 points is Level II, metastable fluctuation; 60~80 points is Level III, critical stress; 50~60 points is Level IV, imbalance state; 0~50 points is Level V, severe imbalance.

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