CN109508507B - A method of using wind direction to assist shallow lake water environment improvement - Google Patents

Abstract

The invention discloses a method for assisting improvement of a water environment of a shallow lake by utilizing wind direction, which comprises the following steps of 1: comprises the steps of 11, hydrological situation evaluation, 12, water quality evaluation; step 2, investigating pollution sources; step 3, constructing a water environment mathematical model: step 31, hydrodynamic model simulation; step 32, simulating a water quality model; step 33, ecological simulation: simulating chlorophyll a in the ecological environment of a shallow lake to be improved in water environment; and 4, wind direction auxiliary water environment improvement calculation: the method comprises the steps of 41, lake area division, 42, lake area hydrodynamic model simulation, 43 and optimal wind direction finding. The invention aims at the change condition of the current state water quality of shallow lakes based on the difference of wind directions, benefits and avoids harm, and is an innovation in the field of water environment.

Description

A method of using wind direction to assist in improving the water environment of shallow lakes

technical field

The invention relates to the field of water environment ecological protection and water conservancy projects, in particular to a method for using wind direction to assist in improving the water environment of shallow lakes.

Background technique

With the rapid growth of my country's urban population and the rapid development of industrial and agricultural production, the eutrophication of urban shallow lakes has become increasingly serious and has become a serious urban environmental ecological problem. Research on the occurrence mechanism, formation process and prevention measures of eutrophication will speed up urban The management and protection of water bodies are of great social and economic significance to ensure the sustainable development of cities.

Eutrophication of water body is a process in which the water body accepts excessive nitrogen, phosphorus and other nutrients, causing algae and other aquatic plants to multiply abnormally, resulting in a decrease in water transparency, a decrease in dissolved oxygen in water, deterioration of water quality, and a series of ecological structure damage and functional degradation of the water body. .

Urban water body is the main source of urban industrial and domestic water. Eutrophication increases the organic matter in the water body, breeds pathogenic bacteria, and produces harmful algae toxins, endangering the safety of drinking water. Urban water bodies have important urban ecological functions, and eutrophication will destroy their structures. Algae and other autotrophic plankton, after removing the limitation of nutrients such as phosphorus, multiply and cover the water surface in large numbers, blocking the transmission of light to the bottom of the water, hindering the photosynthesis of underwater plants and reducing the release of oxygen. When nutrients are exhausted, large areas will die, and when plant corpses are decomposed by microorganisms, a large amount of oxygen will be consumed. The results of the two effects will reduce the concentration of dissolved oxygen in water. The reduction of dissolved oxygen concentration will cause the death of aquatic animals, especially fish. In severe cases, anaerobic conditions are formed at the bottom of the water. Under the action of bacteria, sulfur is reduced to toxic sulfhydryl compounds. In addition, some algae emit a fishy smell, which makes the water smell unpleasant. The final development of eutrophication will reduce the storage capacity of the water body due to the accumulation of organic residues, destroy the ecological structure of the water body, break the biological chain, tend to single species, and degrade the function of the water body. Urban water body is an important place for urban cultural and natural landscape elements and leisure and entertainment. Eutrophic water body forms a green carpet, which makes the water quality muddy and the transparency reduced. Some algae emit odor. The process greatly reduces the sensory properties of the water body.

The eutrophication of urban shallow lakes has seriously endangered my country's urban water supply, ecological environment and sustainable development. The main cause of eutrophication is the excessive input of nitrogen and phosphorus, especially the limiting nutrient element phosphorus of aquatic plants. Phosphorus that enters the water body is hardly exchanged with the atmosphere, so the key to controlling eutrophication is to reduce the phosphorus in the water body. Since phosphorus pollution is mainly caused by point sources, the key to reducing phosphorus is to persist in treating it from the source, promote the prohibition of phosphorus in washing powder in cities, and carry out pipeline interception treatment of domestic and industrial sewage. At the same time, adopting bioremediation measures to release zooplankton and herbivorous fish into the water body is an effective method to inhibit the eutrophication of the water body and prevent the occurrence of algal blooms. Floating and planting valuable aquatic and terrestrial plants on the water surface can not only remove nutrients in the water, but also improve the ecology in the water, which is conducive to rebuilding the ecological balance and forming a natural circulation of the water body.

However, if the impact of wind direction on the water environment can be considered, it will help improve the water environment of shallow lakes to a certain extent.

Contents of the invention

The technical problem to be solved in the present invention is to provide a method for improving the water environment of shallow lakes by using wind direction to assist in improving the water environment of shallow lakes based on the above-mentioned deficiencies in the prior art. It will be an innovation in the field of water environment to change the state of water quality and seek advantages and avoid disadvantages.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A method for using wind direction to assist in improving the water environment of shallow lakes, comprising the following steps.

Step 1, hydrological regime and water quality assessment, includes the following two steps.

Step 11, assessing the hydrological situation, for the lakes or rivers within the watershed range of the shallow lake whose water environment needs to be improved, the following two methods are used to evaluate the hydrological situation.

a) For the lakes or rivers where the hydrological stations with flow records are located, directly use the hydrological data automatically recorded by the hydrological stations for the past three years to analyze the hydrological data, and finally get the surface of the respective lakes or rivers under different rainfall guarantee rates run-off.

b) For lakes or rivers without hydrological stations, collect rainfall data for more than 30 years within the watershed of shallow lakes, and calculate the P-III curve for the watershed to obtain the discharge of each lake or river.

Step 12, water quality assessment: For the watersheds involved in the shallow lakes whose water environment needs to be improved, collect 3-5 years of water quality monitoring data within the scope of small watersheds, and conduct full index evaluation.

Step 2. Pollution source investigation: Calculate the discharge of pollutants from industries, sewage plants, population, aquaculture, and planting within the basin of shallow lakes where the water environment needs to be improved in the past two years, and conduct sub-regional statistics.

Step 3, water environment mathematical model construction: perform numerical simulation on shallow lakes, including hydrodynamic model simulation, water quality model simulation and ecological simulation; the specific simulation methods are as follows:

Step 31, hydrodynamic model simulation: the upstream is the flow control boundary condition, and the downstream is the water level control boundary condition; the actual measured flow rate of the lake or river channel corresponding to the upstream of the shallow lake in step 1 or the converted surface runoff is used as the upstream boundary; The water levels of several tributaries downstream of the shallow lake are used as downstream boundary conditions.

Step 32, water quality model simulation: use the pollutant discharge amount investigated in step 2 as the pollution source; substitute the water quality evaluation data of one year in the water quality evaluation results in step 12 into the water quality model for calculation.

Step 33, ecological simulation: Simulate the chlorophyll a in the ecological environment of the shallow lake whose water environment needs to be improved. Determined to obtain the relevant parameters of the model, wherein the model includes the hydrodynamic model and water quality model constructed in step 31 and step 32; after the utilization rate is determined, the model parameters are calculated for the model in other periods, and when the model calculation is consistent with the measured data, Then it is considered that the calibration of the model is successful, referred to as the calibration model, and the calibration model will be used to predict the concentration of chlorophyll a at a certain time in the future.

Step 4, wind direction assisted water environment improvement calculation: In the hydrodynamic model constructed in step 31, under the condition that other conditions remain unchanged and only the wind direction is changed, the influence of different wind directions on the water quality concentration in shallow lakes is studied. The influence of water quality concentration includes water quality Concentration field distribution and changes in water quality concentration until the best wind direction to disturb the water quality is found. In the best wind direction, the water quality is optimal; the best way to find the wind direction is as follows:

Step 41, dividing the lake area: dividing the shallow lake whose water environment needs to be improved into several different lake areas.

Step 42, lake area hydrodynamic model simulation: For each lake area divided in step 41, firstly, according to the north wind 0°, northeast wind 45°, east wind 90°, southeast wind 135°, south wind 180°, southwest wind 225°, west wind 270°, northwest wind 315°, that is, starting from the north wind, the hydrodynamic model calculation is carried out according to the increase of 45° respectively.

Step 43, find the best wind direction: if the water quality concentrations in different lake areas are relatively consistent, the lake water quality is considered to be relatively uniform, and the wind direction at this time is the best wind direction; if the water quality in different lake areas is relatively close, but there are still some differences, then in Within the range of 45° before and after the degree corresponding to this wind direction, the simulation is carried out with a wind direction interval of 15° to find the best wind direction.

In step 12, after the evaluation of all indicators, the non-standard projects are screened out, and then the water quality process evaluation, standard-exceeding rate evaluation and standard-exceeding multiple evaluation are carried out for the screened non-standard projects according to Ku Fengping in the past 3 to 5 years.

In step 12, the evaluation standard for all index evaluation is "Surface Water Environmental Quality Standard (GB3838-2002)".

In step 4, by changing the wind speed, find the best wind direction under different wind speeds.

In step 11, the analysis of the hydrological data of the hydrological station includes the analysis of the change trend of the water level and the analysis of the flow and velocity characteristics.

The invention has the following beneficial effects: based on the difference in wind direction, it will be an innovation in the field of water environment to change the current water quality of shallow lakes, seek advantages and avoid disadvantages. In addition, depending on the observation of the wind direction, it is possible to judge which wind direction is conducive to the improvement of the water environment and which wind direction is not conducive to the improvement of the water environment, saving capital investment in water environment improvement, and building an eco-environment-friendly society.

Description of drawings

Figure 1 shows a schematic diagram of the total phosphorus concentration field in Lake Xuanwu.

Figure 2 shows a schematic diagram of the total nitrogen concentration field in Lake Xuanwu.

Figure 3 shows the change of total phosphorus in different lake areas in Xuanwu Lake with wind direction.

Figure 4 shows the change of total nitrogen with wind direction in different lake areas in Xuanwu Lake.

Detailed ways

The present invention will be further described in detail with respect to specific preferred embodiments.

A method for using wind direction to assist in improving the water environment of shallow lakes, comprising the following steps.

Step 1, hydrological regime and water quality assessment, includes the following two steps.

Step 11, assessing the hydrological situation, for the lakes or rivers within the watershed range of the shallow lake whose water environment needs to be improved, the following two methods are used to evaluate the hydrological situation.

a) For the lakes or rivers where the hydrological stations with flow records are located, directly use the hydrological data automatically recorded by the hydrological stations for the past three years to analyze the hydrological data, and finally get the surface of the respective lakes or rivers under different rainfall guarantee rates run-off.

The analysis of the above-mentioned hydrological data preferably includes the analysis of water level variation trend and the analysis of flow and flow velocity characteristics.

b) For lakes or rivers without hydrological stations, collect rainfall data for more than 30 years within the watershed of shallow lakes, and calculate the P-III curve for the watershed to obtain the discharge of each lake or river.

Step 12, water quality assessment: For the watersheds involved in the shallow lakes whose water environment needs to be improved, collect 3-5 years of water quality monitoring data within the scope of small watersheds (including lakes, rivers or land, etc.), preferably in accordance with the "Surface Water Environmental Quality Standards ( GB3838-2002)" conducts full-index evaluation, after the full-index evaluation, screens out the non-standard projects, and then conducts the water quality process evaluation, standard-exceeding rate evaluation and standard-exceeding multiple evaluation for the screened non-standard projects according to Kufengping in the past 3 to 5 years .

Step 2. Pollution source investigation: the statistical yearbooks and statistical bulletins on national economic and social development in the past two years within the basin of shallow lakes where the water environment needs to be improved. The census data and environmental statistical data are calculated according to their respective calculation methods for the pollutant discharge of industries, sewage plants, population, aquaculture, and planting industries, and statistics are made by region.

Step 3, water environment mathematical model construction: perform numerical simulation on shallow lakes, including hydrodynamic model simulation, water quality model simulation and ecological simulation; the specific simulation methods are as follows:

Step 31, hydrodynamic model simulation: the upstream is the flow control boundary condition, and the downstream is the water level control boundary condition; the actual measured flow rate of the lake or river channel corresponding to the upstream of the shallow lake in step 1 or the converted surface runoff is used as the upstream boundary; The water levels of several tributaries downstream of the shallow lake are used as downstream boundary conditions.

Step 32, water quality model simulation: use the pollutant discharge amount investigated in step 2 as the pollution source; substitute the water quality evaluation data of one year in the water quality evaluation results in step 12 into the water quality model for calculation.

Step 33, ecological simulation: Simulate the chlorophyll a in the ecological environment of the shallow lake whose water environment needs to be improved. Determined to obtain the relevant parameters of the model, wherein the model includes the hydrodynamic model and water quality model constructed in step 31 and step 32; after the utilization rate is determined, the model parameters are calculated for the model in other periods, and when the model calculation is consistent with the measured data, Then it is considered that the calibration of the model is successful, referred to as the calibration model, and the calibration model will be used to predict the concentration of chlorophyll a at a certain time in the future.

Step 4, wind direction assisted water environment improvement calculation: In the hydrodynamic model constructed in step 31, under the condition that other conditions remain unchanged and only the wind direction is changed, the influence of different wind directions on the water quality concentration in shallow lakes is studied. The influence of water quality concentration includes water quality Concentration field distribution and changes in water quality concentration until the best wind direction to disturb the water quality is found. In the best wind direction, the water quality is optimal; the best way to find the wind direction is as follows:

Step 41, dividing the lake area: dividing the shallow lake whose water environment needs to be improved into several different lake areas.

In the present invention, taking Xuanwu Lake as an example for description, for example, Xuanwu Lake is divided into Northeast Lake, Southeast Lake, Northwest Lake and Southwest Lake. Alternatively, other divisions are also possible.

Step 42, lake area hydrodynamic model simulation: For each lake area divided in step 41, firstly, according to the north wind 0°, northeast wind 45°, east wind 90°, southeast wind 135°, south wind 180°, southwest wind 225°, west wind 270°, northwest wind 315°, that is, starting from the north wind, the hydrodynamic model calculation is carried out according to the increase of 45° respectively.

Taking the calculation results of Xuanwu Lake in Nanjing as an example, at a wind speed of 1m/s, according to the wind direction, north wind (0°), northeast wind (45°), east wind (90°), southeast wind (135°), south wind (180°) °), southwest wind (225°), west wind (270°), northwest wind (315°) respectively calculated the concentration field and concentration value of total phosphorus and total nitrogen, and the calculation results are shown in Figures 1 to 4, and the results show There is no significant change in the concentration difference in each lake area under different wind conditions. When the southwest wind blows, the water quality concentration of the whole lake is relatively uniform, and the southwest wind is the best wind direction.

In Figure 3 and Figure 4, NE lake is the water quality concentration of the Northeast Lake, SE Lake is the water quality concentration of the Southeast Lake, NW Lake is the water quality concentration of the Northwest Lake, SW Lake is the water quality concentration of the Southwest Lake, and ave. is the average water quality concentration of the whole lake.

Step 43, find the best wind direction: if the water quality concentrations in different lake areas are relatively consistent, the lake water quality is considered to be relatively uniform, and the wind direction at this time is the best wind direction; if the water quality in different lake areas is relatively close, but there are still some differences, then in Within the range of 45° before and after the degree corresponding to this wind direction, the simulation is carried out with a wind direction interval of 15° to find the best wind direction.

Step 44, by changing the wind speed, according to steps 41 to 43, to find the best wind direction under different wind speeds.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be carried out to the technical solutions of the present invention. These equivalent transformations All belong to the protection scope of the present invention.

Claims (5)

1. A method for assisting water environment improvement of shallow lakes by utilizing wind direction is characterized by comprising the following steps: the method comprises the following steps:

step 1, evaluating the hydrological situation and water quality, which comprises the following two steps:

step 11, evaluating the hydrological situation, namely evaluating the hydrological situation of lakes or river channels in the range of the basin related to the shallow lakes to be improved in water environment by adopting the following two methods:

a) Directly analyzing hydrological data of nearly three years, which are automatically recorded by the hydrological station, of the lake or the river where the hydrological station with the flow record is located, and finally obtaining surface runoff of the respective lake or river under the conditions of different rainfall guarantee rates;

b) For lakes or rivers without hydrologic stations, collecting rainfall data of more than 30 years in the basin range of shallow lakes, and carrying out P-III curve calculation on the basin to obtain the flow of each lake or river;

step 12, water quality evaluation: collecting water quality monitoring data within a small watershed range from 3 to 5 years for watersheds related to shallow lakes with water environments to be improved, and performing full-index evaluation;

step 2, pollution source investigation: calculating the pollutant discharge amount of the nearly 2 years industry, sewage plant, population, breeding industry and planting industry in the basin range of the shallow lake to be improved in the water environment, and carrying out regional statistics;

step 3, constructing a water environment mathematical model: performing numerical simulation on the shallow lake, wherein the simulation content comprises hydrodynamic model simulation, water quality model simulation and ecological simulation; the specific simulation method comprises the following steps:

step 31, hydrodynamic model simulation: the upstream is a flow control boundary condition, and the downstream is a water level control boundary condition; taking the measured flow over the years of the lake or river corresponding to the upstream of the shallow lake in the step 1 or the converted surface runoff as an upstream boundary;

taking the water levels of a plurality of branches at the downstream of the shallow lake as a downstream boundary condition;

step 32, water quality model simulation: taking the pollutant discharge amount obtained by investigation in the step 2 as a pollution source; substituting the water quality evaluation data of the whole year in the water quality evaluation result in the step 12 into the water quality model for calculation;

step 33, ecological simulation: simulating chlorophyll a in the ecological environment of a shallow lake to be improved in water environment, wherein the simulation method comprises the following steps: applying the concentration data of chlorophyll a in the shallow lake at the same moment to model calculation at the moment, and calibrating the model to obtain relevant parameters of the model, wherein the model comprises a hydrodynamic model and a water quality model which are constructed in the steps 31 and 32; calculating the models in other periods by using the model parameters after the calibration, and when the model calculation is consistent with the actually measured data, determining that the model calibration is successful, namely a calibration model for short, wherein the calibration model can be used for predicting the concentration of chlorophyll a at a certain time in the future;

and 4, wind direction auxiliary water environment improvement calculation: in the hydrodynamic model constructed in step 31, under the condition that other conditions are unchanged and only the wind direction is changed, the influence of different wind directions on the water quality concentration in the shallow lake is researched, wherein the water quality concentration influence comprises the distribution of a water quality concentration field and the change of the water quality concentration, until the optimal wind direction for disturbing the water quality is found, and the water quality is optimal in the optimal wind direction; the optimal wind direction finding method comprises the following steps:

step 41, lake area division: dividing a shallow lake with a water environment to be improved into a plurality of different lake areas;

step 42, lake region hydrodynamic model simulation: for each lake area divided in step 41, performing hydrodynamic model calculation according to the difference of 45 degrees from north wind, 0 degree from east wind, 45 degrees from east wind, 90 degrees from east wind, 135 degrees from east wind, 180 degrees from south wind, 225 degrees from west wind, 270 degrees from west wind, and 315 degrees from west wind, namely starting from north wind;

step 43, finding the optimal wind direction: if the water quality concentrations of different lake areas are relatively consistent, the lake water quality is considered to be relatively uniform, and the wind direction is the optimal wind direction; if the water quality of different lake areas is different, the simulation is carried out at 15-degree wind direction intervals in the range of 45 degrees before and after the corresponding degree of the wind direction, and the optimal wind direction is found.

2. The method for assisting the improvement of the water environment of the shallow lake by utilizing the wind direction as claimed in claim 1, wherein: in step 12, after the full index evaluation, the non-standard items are screened out, and then the screened non-standard items are subjected to water quality process evaluation, overproof rate evaluation and overproof multiple evaluation for nearly 3 to 5 years according to the kunfeng.

3. The method for assisting in improving the water environment of the shallow lake by utilizing the wind direction as claimed in claim 2, wherein: in the step 12, the evaluation standard of the whole index evaluation is 'surface water environmental quality standard GB 3838-2002'.

4. The method for assisting the improvement of the water environment of the shallow lake by utilizing the wind direction as claimed in claim 1, wherein: in step 4, the optimal wind direction under different wind speeds is searched by changing the wind speed.

5. The method for assisting the improvement of the water environment of the shallow lake by utilizing the wind direction as claimed in claim 1, wherein: in step 11, the hydrological data analysis of the hydrological station comprises water level change trend analysis and flow speed characteristic analysis.

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