Lake risk prevention and control method based on water exchange and ecological restoration

Abstract

The application discloses a lake risk prevention and control method based on water exchange and ecological restoration, and comprises the following steps: evaluating water quality risk according to historical water quality data of a target lake, increasing water exchange amount of the target lake when the water quality risk exists, and performing water quality risk prevention and control; evaluating ecological risk of the target lake, and implementing wetland ecological restoration engineering on the target lake when the target lake has a certain degree of ecological risk; and the ecological risk evaluation of the target lake is performed by using superimposed water exchange working condition and shallow wetland habitat area loss. The application takes water quality risk prevention and control and ecological risk prevention and control as targets, can simultaneously realize the mitigation of water quality risk and ecological risk of the target lake, and has higher systematicness and operability, and can be applied to risk prevention and control of different lakes.

Description

Technical Field

[0001] This application belongs to the field of ecological governance technology, and specifically relates to a lake risk prevention and control method based on water exchange and ecological restoration. Background Technology

[0002] Lakes are an important component of river systems, possessing ecological functions such as flood control, water supply, navigation, and water purification. However, compared to rivers, lakes are more enclosed, with slower water flow, longer water exchange and renewal cycles, and weaker self-repair capabilities. Affected by a combination of natural and human activities, lake water pollution, eutrophication, and ecological degradation are prominent water-related ecological and environmental problems. Lake water pollution and ecological degradation have both natural attributes and are directly related to the scale of socio-economic development exceeding resource carrying capacity. For most lakes, their management primarily targets water pollutants, often exhibiting problems such as a single management model and insufficient systemic and holistic approaches. How to address both localized water pollution and overall water function decline based on practical experience has become a major challenge for the comprehensive management of lakes in the middle and lower reaches of the Yangtze River. Summary of the Invention

[0003] The purpose of this application is to provide a lake risk prevention and control method based on water exchange and ecological restoration. This application aims at both water quality risk prevention and control and ecological risk prevention and control, and carries out risk prevention and control of lakes in a more systematic way.

[0004] This application provides a lake risk prevention and control method based on water exchange and ecological restoration, including:

[0005] Water quality risk is assessed based on historical water quality data of the target lake. If a water quality risk is identified, the water exchange volume of the target lake is increased to mitigate the risk. The increased water exchange volume is determined using the following method:

[0006] Different water exchange rates were set, and the concentrations of major pollutants in the target lake were simulated under different water exchange rates. The water quality was evaluated based on the concentrations of major pollutants under each water exchange rate. The minimum water exchange rate corresponding to the water quality meeting the standard was taken as the increased water exchange rate. The water quality was evaluated as meeting the standard only when the concentrations of all major pollutants were not greater than the corresponding standard concentration thresholds.

[0007] Assess the ecological risk of the target lake; if the target lake has a certain degree of ecological risk, implement wetland ecological restoration projects for the target lake; the assessment of the ecological risk of the target lake includes:

[0008] Obtain the relationship curve between the shallow wetland habitat area and the water level of the target lake; based on the relationship curve, obtain the shallow wetland habitat area at the reference water level and the water level after water exchange, respectively. Using the shallow wetland habitat area at the reference water level as the reference area, calculate the decline rate of the shallow wetland habitat area at the water level after water exchange relative to the reference area; when the decline rate exceeds the preset decline rate threshold, it indicates that the target lake has a certain degree of ecological risk.

[0009] The reference water level is the historical daily average water level of the target lake during winter and spring; the water level after water exchange is the water level after the water exchange conditions are added to the current water level based on the amount of water exchange.

[0010] In some specific implementations, historical water quality data are taken from the national and / or provincial monitoring sections of the target lake.

[0011] In some specific implementations, water quality risk is assessed based on historical water quality data of the target lake, including:

[0012] The concentration values ​​of major pollutants in the target lake at different periods are obtained from historical water quality data. The concentration values ​​of each major pollutant are compared with the corresponding standard concentration thresholds, which are preset. When the concentration value of any pollutant is greater than its corresponding standard concentration threshold, it is assessed that there is a water quality risk.

[0013] In some specific implementations, the concentrations of the main pollutants in the target lake are simulated, including:

[0014] Take daily water level data of the target lake for more than 50 years and calculate the multi-year monthly average water level; obtain the lake volume value corresponding to the multi-year monthly average water level from the water level-lake volume curve of the target lake, that is, the multi-year monthly average lake volume.

[0015] The multi-year monthly average lake volume is input into the MIKE21 model as the lake volume of the target lake. Then, the pollutant discharge and different water exchange volumes of the watershed where the target lake is located are input. The average pollutant concentration of the target lake under different amounts of exchange is calculated using the lake-reservoir uniform mixing attenuation model.

[0016] In some specific implementations, the relationship curve between the shallow wetland habitat area and water level of the target lake is obtained using the following method:

[0017] Remote sensing image data of the target lake at different water levels were acquired. The remote sensing image data were interpreted using the decision tree classification method to obtain the shallow wetland habitat area corresponding to different water levels. The shallow wetland habitat area and water level data were fitted to obtain the relationship curve between shallow wetland habitat area and water level.

[0018] In some specific embodiments, the reference water level and the water level after the exchange of water volume are determined using the following method:

[0019] Acquire long-term series water level data of the target lake for more than 50 years, and take time nodes. The water level data before and after the time nodes are historical water level data and current water level data, respectively. The time nodes are selected from the points of abrupt change in water level or the time when human interference has a significant impact.

[0020] Historical water level data for winter and spring are taken from historical water level data, and the daily average water level for winter and spring is calculated as a reference water level.

[0021] Based on the water exchange volume, the water exchange conditions are superimposed on the current water level. Combined with the inflow and outflow of the target lake and the water level-lake capacity curve, the water level after superimposing the water exchange conditions is calculated and recorded as the water level after water exchange.

[0022] Compared with the prior art, this application has the following features and beneficial effects:

[0023] This application first conducts a water quality risk assessment on the target lake. If the target lake has a water quality risk, the water quality risk is controlled by increasing the water exchange volume to improve the self-purification capacity of the target lake and thus alleviate the water quality risk. However, while increasing the water exchange volume can effectively alleviate the water quality risk, it will also increase the ecological risk to a certain extent. Therefore, based on the loss of shallow wetland habitat area after superimposed water exchange conditions, an ecological risk assessment is conducted on the target lake. If the target lake has a certain degree of ecological risk, ecological restoration projects are carried out on the target lake to alleviate the ecological risk.

[0024] This application aims to control both water quality risks and ecological risks, and can simultaneously mitigate the water quality and ecological risks of the target lake. The method in this application is more systematic and operable, and can be applied to risk control of different lakes. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the lake risk prevention and control method proposed in this application. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0027] The following is a detailed implementation of the lake risk prevention and control method based on water exchange and ecological restoration proposed in this application. The steps are as follows:

[0028] (1) Lake risk prevention and control targets water quality risk prevention and control and ecological risk prevention and control.

[0029] (2) Assess water quality risk based on historical water quality data of the target lake. If water quality risk exists, increase the water exchange volume of the target lake to carry out water quality risk prevention and control.

[0030] In this embodiment, historical data is taken from the target lake over the past 5-10 years, using water quality data from national or provincial monitoring sections of the target lake. Specifically, the concentration values ​​of major pollutants in the target lake at different periods are obtained from the water quality data. The concentration values ​​of each pollutant are compared with their corresponding standard concentration thresholds. The standard concentration thresholds for each pollutant are preset and can be adjusted according to actual needs. When the concentration value of any pollutant exceeds its corresponding standard concentration threshold, it is assessed as a water quality risk. The major pollutants are pre-selected, generally choosing pollutants with a significant impact on water bodies, such as phosphorus-containing and nitrogen-containing pollutants.

[0031] Increasing water exchange volume can reduce pollutant concentrations in a target lake; therefore, this application aims to mitigate water quality risks in the target lake by increasing water exchange volume. Specifically, the increased water exchange volume can be determined using the following method:

[0032] Different water exchange rates were set, and the MIKE21 model was used to simulate the concentration of major pollutants in the target lake under different water exchange rates. The water quality was assessed based on the concentration of major pollutants at each water exchange rate to determine whether the water quality met the standards. The minimum water exchange rate corresponding to water quality meeting the standards was taken as the increased water exchange rate. Water quality meeting the standards means that the concentration of all major pollutants is not greater than the corresponding standard concentration threshold; otherwise, the water quality does not meet the standards.

[0033] To facilitate understanding, the concentrations of the main pollutants in the simulated target lake will be described in further detail below.

[0034] 2.1 Obtain daily water level data for the target lake over 50 years and calculate the multi-year monthly average water level; obtain the lake volume value corresponding to the multi-year monthly average water level from the water level-lake volume curve of the target lake, i.e., the multi-year monthly average lake volume of the target lake. The water level-lake volume curve is plotted with water level as the horizontal axis and lake volume as the vertical axis, and is used to represent the relationship between the water level and the lake volume of a lake.

[0035] 2.2 When performing the MIKE21 model simulation, the multi-year monthly average lake volume is input as the target lake volume. Then, based on the pollutant discharge volume of the watershed where the target lake is located and the input water exchange volume, the average pollutant concentration of the target lake under different exchange volumes is calculated. Specifically, the lake-reservoir uniform mixing attenuation model in the MIKE21 model can be used to calculate the average pollutant concentration. The pollutant discharge volume of the watershed is obtained from actual survey data.

[0036] (3) Assess the ecological risks of the target lake. If the target lake has a certain degree of ecological risk, implement wetland ecological restoration projects for the target lake to increase the exposed area of ​​shallow wetlands.

[0037] The specific implementation process of this step will be explained in detail below.

[0038] 3.1 Obtain the relationship curve between the shallow wetland habitat area and water level of the target lake.

[0039] Remote sensing image data of the target lake at different water levels were acquired. The remote sensing image data were interpreted using the decision tree classification method to obtain the shallow wetland habitat area corresponding to different water levels. The shallow wetland habitat area and water level data were fitted to obtain the relationship curve between the shallow wetland habitat area and water level.

[0040] 3.2 Based on the relationship curve between shallow wetland habitat area and water level, the shallow wetland habitat area under the reference water level and the water level after water exchange was obtained respectively, and an ecological risk assessment was conducted based on the change in shallow wetland habitat area.

[0041] Using the area of ​​shallow wetland habitat at a reference water level as the reference area, a decrease in the area of ​​shallow wetland habitat at the water level relative to the reference area after water exchange indicates an ecological risk. Specifically, the ecological risk level of the target lake is assessed by the rate of decrease in the area of ​​shallow wetland habitat at the water level after water exchange. In this embodiment, if the rate of decrease in the area of ​​shallow wetland habitat at the water level after water exchange is no more than 10%, the ecological risk is assessed as low; if the rate of decrease is in the range of [10%, 30%], the ecological risk is assessed as moderate; if the rate of decrease is in the range of (30%, 50%), the ecological risk is assessed as high; and if the rate of decrease exceeds 50%, the ecological risk is assessed as very high.

[0042] The water level after exchanging the above reference water level and water volume is determined using the following method:

[0043] Long-term water level data for the target lake over a period of more than 50 years are obtained, and Pettitt's test is used to identify water level abrupt changes. These abrupt changes are used as time nodes; water level data before these time nodes are considered historical water level data, and water level data after these time nodes are considered current water level data. In some specific implementations, times with significant human interference affecting the target lake can also be selected as time nodes. For example, taking Chaohu Lake as an example, the Chaohu Sluice Gate was built in 1962; therefore, 1962 is used as the time node, water level data from 1953 to 1962 are considered historical water level data, and water level data from 1963 to 2020 are considered current water level data.

[0044] Historical water level data for winter and spring is taken from historical water level data, and the daily average water level for winter and spring is calculated as the reference water level. Current water level data for winter and spring is taken from current water level data, and the daily average water level for winter and spring is calculated as the current water level. The water exchange condition is superimposed on the current water level according to the water exchange volume calculated in step (2), and the water level after superimposing the water exchange condition is calculated by combining the inflow and outflow of the target lake and the water level-lake capacity curve. This is recorded as the water level after water exchange.

[0045] 3.3 When the ecological risk is assessed as high or very high, i.e., the decline rate of shallow wetland habitat area below the current water level is not less than 30%, wetland ecological restoration projects shall be implemented for the target lake. The wetland ecological restoration project in this embodiment includes constructing cofferdams, dredging bottom sediment, micro-topography modification, raising the beach, stabilizing the beach, and protecting the beach, with the aim of further increasing the exposed area of ​​shallow wetlands.

[0046] Example

[0047] Taking Chaohu Lake as an example, assessments indicate that it currently faces both water quality and ecological risks. The method described in this application will be used to implement risk control measures for Chaohu Lake. After implementation, the water quality of Chaohu Lake can be stabilized at Class III, mitigating the water quality risks. Simultaneously, wetland ecological restoration projects will promote the exposure of shallow wetland habitats in Chaohu Lake, further mitigating its ecological risks.

[0048] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of this application, all of which fall within the scope of protection of this application.

Claims

1. A lake risk prevention and control method based on water exchange and ecological restoration, characterized in that, include: Water quality risk is assessed based on historical water quality data of the target lake. If a water quality risk is identified, the water exchange volume of the target lake is increased to mitigate the risk. The increased water exchange volume is determined using the following method: Different water exchange rates were set, and the concentrations of major pollutants in the target lake were simulated under different water exchange rates. The water quality was evaluated based on the concentrations of major pollutants under each water exchange rate. The minimum water exchange rate corresponding to the water quality meeting the standard was taken as the increased water exchange rate. The water quality was evaluated as meeting the standard only when the concentrations of all major pollutants were not greater than the corresponding standard concentration thresholds. Assess the ecological risks of the target lake; if the target lake has a certain degree of ecological risk, implement wetland ecological restoration projects for the target lake. The assessment of the ecological risk of the target lake includes: Obtain the relationship curve between the shallow wetland habitat area and the water level of the target lake; based on the relationship curve, obtain the shallow wetland habitat area at the reference water level and the water level after water exchange, respectively. Using the shallow wetland habitat area at the reference water level as the reference area, calculate the decline rate of the shallow wetland habitat area at the water level after water exchange relative to the reference area; when the decline rate exceeds the preset decline rate threshold, it indicates that the target lake has a certain degree of ecological risk. The reference water level is the historical daily average water level of the target lake during winter and spring; the water level after water exchange is the water level after superimposing the water exchange conditions on the current water level according to the water exchange volume. The concentrations of the main pollutants in the simulated target lake include: Take daily water level data of the target lake for more than 50 years and calculate the multi-year monthly average water level; obtain the lake volume value corresponding to the multi-year monthly average water level from the water level-lake volume curve of the target lake, that is, the multi-year monthly average lake volume. The multi-year monthly average lake volume is input into the MIKE21 model as the lake volume of the target lake. Then, the pollutant discharge and water exchange volume of the watershed where the target lake is located are input. The average pollutant concentration of the target lake under different amounts of exchange volume is calculated using the lake-reservoir uniform mixing and attenuation model. The curve showing the relationship between the shallow wetland habitat area and water level of the target lake was obtained using the following method: Remote sensing image data of the target lake at different water levels were acquired. The remote sensing image data were interpreted using the decision tree classification method to obtain the shallow wetland habitat area corresponding to different water levels. The shallow wetland habitat area and water level data were fitted to obtain the relationship curve between shallow wetland habitat area and water level. The reference water level and the water level after the water volume exchange are determined using the following method: Acquire long-term series water level data of the target lake for more than 50 years, and take time nodes. The water level data before and after the time nodes are historical water level data and current water level data, respectively. The time nodes are selected from the points of abrupt change in water level or the time when human interference has a significant impact. Historical water level data for winter and spring are taken from historical water level data, and the daily average water level for winter and spring is calculated as a reference water level. Based on the water exchange rate, the water exchange conditions are superimposed on the current water level. Combined with the inflow and outflow of the target lake and the water level-lake capacity curve, the water level after superimposing the water exchange conditions is calculated and recorded as the water level after water exchange. The wetland ecological restoration project includes constructing dikes, dredging bottom sediment, micro-topography modification, beach elevation, beach stabilization, and beach protection.

2. The lake risk prevention and control method based on water exchange and ecological restoration as described in claim 1, characterized in that: The historical water quality data used are water quality data from national and / or provincial control sections of the target lake.

3. The lake risk prevention and control method based on water exchange and ecological restoration as described in claim 1, characterized in that: The assessment of water quality risk based on historical water quality data of the target lake includes: The concentration values ​​of major pollutants in the target lake at different periods are obtained from historical water quality data. The concentration values ​​of each major pollutant are compared with the corresponding standard concentration thresholds, which are preset. When the concentration value of any pollutant is greater than its corresponding standard concentration threshold, it is assessed that there is a water quality risk.

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