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CN-116882121-B - Water quality model parameter calibration method based on equivalent pollution source thought

CN116882121BCN 116882121 BCN116882121 BCN 116882121BCN-116882121-B

Abstract

The invention discloses a water quality model parameter calibration method based on an equivalent pollution source idea, which fully utilizes real-time water quality monitoring data, and equivalent an upstream section pollutant concentration value sequence to known pollutant total amount through curve fitting and integral ideas, and simultaneously instantaneously putting a distribution source on a certain space range as a pollution source of a downstream section, simulating and calculating the pollutant concentration value sequence of the downstream section, determining a value range and a step length of a parameter to be calibrated through an empirical formula, performing traversal combination, and determining a final calibration result through comparing the error between the simulation of the downstream section and the actually measured pollutant concentration value sequence. By designing a water pollution scene, the parameter calibration condition under the condition of pollution discharge at the upstream is calculated and analyzed, and the feasibility and the accuracy of the method are verified. The invention provides a water quality model parameter calibration method based on an equivalent pollution source idea, which has the characteristics of reasonable, accurate and various calibration results by fully combining river actual measurement data.

Inventors

  • LI JINYE
  • WANG WENJING
  • GAO RAN

Assignees

  • 中国计量大学

Dates

Publication Date
20260505
Application Date
20230310

Claims (8)

  1. 1. A water quality model parameter calibration method based on an equivalent pollution source idea is characterized by comprising the following steps: Step 1, acquiring basic data of a river channel region to be rated, modeling a flow diffusion model through two-dimensional river pollutants, and determining parameters to be rated; step 2, on-line monitoring equipment is equidistantly distributed in a river channel area to be rated to monitor the water quality condition in real time; step 3, when the monitoring data of a certain online monitoring device is continuously and three times more than 20% of the previous monitoring value, judging that pollution occurs, determining the online monitoring device as water quality abnormal equipment, and simultaneously acquiring data of the water quality abnormal equipment and the nearest equipment downstream of the water quality abnormal equipment to obtain two groups of pollutant concentration value sequences; And 4, using an integral idea to equivalent the pollutant concentration value sequence of the upstream section to a distribution source which is the total quantity of known pollutants and is simultaneously and instantaneously put in a certain space range, using the distribution source as a pollution source of the downstream section, superposing countless instantaneous distribution sources which are equivalent to the distribution source of the downstream section through an integral form, and simulating to calculate the pollutant concentration value sequence of the downstream section, wherein the step of equivalent the pollutant concentration value sequence of the upstream section to the pollutant source of the downstream section is as follows: step 4.1, converting the time sequence into a space sequence according to the time and flow velocity relation, wherein the calculation formula is as follows: n=t n ×u x (1) n i ＝t i ×u x (2) In the formula (1), n is the total space length, t n is the total monitoring time length, u x is the parallel river bank flow velocity, n i is the space sequence interval, and t i is the monitoring frequency; step 4.2, fitting the converted sequence graph with a curve, and determining that the relation function of the concentration and the distance is; and 4.3, superposing a plurality of equivalent instantaneous concentrated sources into a simulated pollutant concentration value sequence of a downstream section in an integral form, wherein the calculation formula of superposition concentration at x is as follows: in the formula (3), C (x, t) is the concentration of pollutants at the moment x of t in mg/L, f (x) is a relation function of concentration and distance, n is the total length of space of an upstream section, x is the length of a river point from an instantaneous point source in the parallel direction of a river flow direction, m is the distance between two devices, y is the length of the river point from the instantaneous point source in the vertical direction of the river flow direction, m is the time from the instantaneous pollution, s is the time node to be calculated, h is the river depth, m is the diffusion coefficient in the x and y directions, D x 、D y is the diffusion coefficient in the x and y directions, m 2 /s;u x is the parallel river bank flow velocity, m/s is the vertical river bank flow velocity, m/s is the degradation coefficient, and k is the degradation coefficient in 1/D; Step 5, determining the value range and the step length of the parameters to be calibrated through an empirical formula, and traversing the combination of the parameters in the value range; Step 6, establishing an objective function with minimum error between the simulation of the downstream section and the actually measured pollutant concentration value sequence; Step 7, traversing parameter combinations in a parameter range to be calibrated to perform numerical simulation and calculating an objective function value; And 8, sorting the objective function values, and finally determining a group of parameter combinations as a rating result according to the objective function values and the river channel conditions.
  2. 2. The method for calibrating parameters according to claim 1, wherein the depth/width of the river to be calibrated is 1/30 or less.
  3. 3. The method of claim 1, wherein in step 1, the basic data of the river area to be calibrated includes river depth h, river width b, parallel river bank flow velocity u x , vertical river bank flow velocity u y , and the parameters to be calibrated are a transverse diffusion coefficient D x , a vertical diffusion coefficient D y and a degradation coefficient k.
  4. 4. The parameter calibration method according to claim 1, wherein in the step2, the on-line monitoring devices are arranged in the parallel river bank direction, the spacing distance of the arranged on-line monitoring devices is less than or equal to 200m, and the monitoring frequency is less than or equal to the spacing distance/parallel river bank flow rate.
  5. 5. The method of parameter calibration according to claim 1, wherein in step 3, data of two real-time online water quality monitoring devices in a same sampling period is used for parameter calibration, the initial time of the sampling period is the first monitoring time when the continuous three times of monitoring data of the upstream device are all greater than 20% of the last monitoring value, and the end time is the last monitoring time when the continuous three times of monitoring data of the downstream device are all less than 20% of the last monitoring value.
  6. 6. The method of claim 1, wherein in step 5, D y and k are calculated by using an empirical formula and river actual conditions, the range of D y and k is determined to be [ 0.1D y * ,10D y *],[ 0.1k*,10k* ],D y * and k are calculated values of actual data determined according to the empirical formula, and D x is determined to be the range of tested values [10 and 20].
  7. 7. The method of calibrating parameters according to claim 1, wherein in step 6, the objective function is a sum of deviations of the simulated pollutant concentration value sequence and the measured pollutant concentration value sequence of the downstream section calculated by using the pollutant diffusion model, and the objective function is as follows: in the formula (4), f (y, y * ) is an objective function, y is a theoretical calculation value of the concentration of the pollutant, y * is a concentration observation value, and m is the number of the observation values.
  8. 8. The method of claim 7, wherein in step 8, the objective function values are sorted in ascending order to determine the parameter combination sequence, and the final parameter combination is determined in combination with the actual condition of the river to be calibrated.

Description

Water quality model parameter calibration method based on equivalent pollution source thought Technical Field The invention relates to the field of water pollution tracing, in particular to a water quality model parameter calibration method based on an equivalent pollution source idea. Background In recent years, the economy develops rapidly, so that a plurality of water pollution problems are caused, the possibility of sudden water pollution accidents and the pollution intensity are gradually increased, the tracing of the water pollution accidents is realized, the pollution sources are positioned, the discharge amount and the time are determined, and therefore, the pollution sources are cut off in time or related measures are taken, and the prevention and control of the water pollution are very important. The existing water pollution tracing method is quite large, wherein the pure mathematical model simulation method is mainly used for solving reversely in a mathematical mode, related data are not easy to obtain, the feasibility is poor, the real-time monitoring method is purely used for finding anomalies in time, but the tracing efficiency is low, the deterministic theory-based tracing method is mainly used for establishing an optimization problem of minimum error between a water quality model simulation value and an actual measurement value of a monitoring station, and the method has certain timeliness and high efficiency, but because the water quality model parameters are influenced by the conditions of different rivers, the accuracy requirement on the water quality model parameters is high. The water quality model parameters are generally required to be determined through a theoretical formula, a tracing experiment method or an empirical formula or are obtained through model parameter calibration, and the theoretical formula and the empirical formula have certain uncertainty due to different characteristics of different rivers, so that the tracing experiment method and the later model parameters are not suitable for tracing sudden water pollution due to the fact that timeliness is lacking in the rating of the tracing experiment method and the later model parameters. The related literature and the patent are rated through consulting the parameters of the water quality model, the related patent (application (patent) person: jiangxi university, publication number: CN 108304675A) pays attention to the use steps of the differential evolution of the adaptive strategy, the related patent (an improved design method for optimizing the parameters of the water quality model by a hybrid genetic algorithm) (application (patent) person: nanjing university, publication number: CN 1900956A) pays attention to the improvement and implementation of the genetic algorithm and the timeliness of the parameter rating is not considered. Disclosure of Invention The invention aims to realize online calibration of parameters of a water quality model by processing upstream and downstream section data by utilizing water quality data acquired by real-time online water quality monitoring equipment, thereby improving the accuracy of the water quality model and further improving the tracing accuracy of a tracing method based on a deterministic theory. A water quality model parameter calibration method based on an equivalent pollution source idea is shown in a figure 1, and comprises the following steps: step 1, acquiring basic data of a river channel region to be calibrated, modeling a flow diffusion model through two-dimensional river pollutants, and determining parameters to be calibrated. And 2, equidistant arrangement of on-line monitoring equipment in the range of the river channel to be rated to monitor the water quality condition in real time. And 3, when pollution occurs, acquiring data by using water quality abnormal equipment and downstream nearest equipment to obtain two groups of pollutant concentration value sequences. And 4, using an integral idea to equivalent the pollutant concentration value sequence of the upstream section to the total known pollutant, using a distribution source which is instantaneously thrown in a certain space range as a pollutant source of the downstream section, superposing countless instantaneous distribution sources which are equivalent to the distribution source by an integral form, and simulating and calculating the pollutant concentration value sequence of the downstream section. And 5, determining values of k and D y through an empirical formula, so as to determine a range and a step length, and traversing the combination of the parameters in the value range. And 6, establishing an objective function with the minimum error between the simulation value and the actual measurement value sequence of the downstream section. And 7, traversing parameter combinations in the range of the parameter to be calibrated to perform numerical simulation and calculating an objective function value. And 8, so