Prediction Method of Appropriate Ecological Water Level Based on Binary Response Relationship between Water Quality and Water Level

Abstract

The present invention discloses a method for predicting suitable ecological water levels based on the binary response relationship between water quality and water levels, including: (1) dividing the annual time periods according to the changing trends of hydrological elements and water quality elements; (2) determining the water level range and the monthly water level change rate that meet the set water quality target according to the total amount of retained pollutants, the pollutant assimilation capacity, and the water level-water quality empirical formula; (3) calculating the natural water level regime using the IHA-RVA method; and modifying the natural water level regime according to the water level range and the water level-water quality response relationship to obtain the suitable ecological water levels that meet the set water quality target. The suitable ecological water levels calculated by the invention can not only meet the requirements of the lake ecosystem for the water body size, but also reflect the requirements of the lake ecosystem for water quality, providing reference and basis for the ecological regulation and water resources management of flowing-through lakes.

Description

Technical Field

[0001] The present invention relates to a method for predicting suitable ecological water levels based on the binary response relationship between water quality and water levels, and belongs to the technical field of water level prediction. Background Art

[0002] With global warming and the rapid development of social economy, many lakes in China have problems such as area shrinkage, water quality deterioration, and ecological degradation. Water level is an important indicator reflecting the hydrological situation and lake planning and management of lakes. Its spatio-temporal variation process will have a profound impact on the lake ecosystem and is the key to solving the above problems. The research on lake ecological water levels is divided into two aspects: the minimum ecological water level and the suitable ecological water level. The minimum ecological water level is the water level red line that meets the basic needs of the lake ecosystem. It can often protect the functions and structures of the lake ecosystem from being severely damaged in the short term, but long-term maintenance will lead to the degradation or even collapse of the lake basin ecosystem; and the minimum ecological water level is mostly a fixed hydrological characteristic value, which is difficult to reflect the requirements of the lake system for water levels at different time nodes. Therefore, determining the suitable ecological water level to maintain the sustainable and healthy development of the lake ecosystem has become a new hot spot in lake ecological research.

[0003] At present, domestic and foreign scholars mostly refer to the IHA-RVA method to calculate the natural water level situation of lakes, so as to determine the suitable ecological water level requirements of lakes. However, the IHA-RVA method focuses on restoring the natural water level situation in historical data and shows the water volume requirements of the lake ecosystem under less human intervention. Large-scale flowing-through lakes often undertake multiple functions such as flood control, water supply, and shipping. Intense human activities have changed the ecological environment of large-scale flowing-through lakes in China, and the increase in pollution loads has caused varying degrees of deterioration of water quality conditions. Pollution phenomena such as heavy metal enrichment and cyanobacteria blooms occur frequently, damaging the sustainable and healthy development of the lake ecosystem. The suitable ecological water level calculated only by the IHA-RVA method is difficult to comprehensively reflect the requirements of the healthy development of biological communities for the living environment, and it is necessary to include water quality factors in the consideration scope of deriving the suitable ecological water level of flowing-through lakes.

[0004] At present, domestic scholars have carried out a large number of studies on the water level-water quality correlation of flowing-through lakes, but the research on the suitable ecological water level considering the water quality requirements of flowing-through lakes is still relatively rare. The management department mostly uses the minimum ecological water level as the ecological water demand index for flowing-through lakes. At the same time, due to the large inflow and outflow of water in flowing-through lakes, the practical application effects of some mature experience in existing water quality regulation, such as increasing the inflow of water during specific periods to improve the water quality of the lake area, are not good. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for predicting suitable ecological water levels based on the binary response relationship between water quality and water levels.

[0006] To achieve the above object, the present invention provides a method for predicting suitable ecological water levels based on the binary response relationship between water quality and water levels, including: (1) dividing the annual time periods according to the changing trends of hydrological elements and water quality elements;

[0007] (2) determining the water level range and the monthly water level change rate that meet the set water quality target according to the total amount of retained pollutants, the pollutant assimilation capacity, and the water level-water quality empirical formula;

[0008] (3) calculating the natural water level regime using the IHA-RVA method;

[0009] Modifying the natural water level regime according to the water level range and the water level-water quality response relationship to obtain the suitable ecological water level that meets the set water quality target.

[0010] Preferably, step (1) specifically includes:

[0011] Obtaining the hydrological elements and water quality elements of the lake over a period of time, and calculating the multi-year monthly average out-lake water volume, the annual average out-lake water volume, the multi-year monthly average in-lake pollutant concentration, and the multi-year monthly average total in-lake pollutant amount;

[0012] Dividing the annual time periods according to the annual changing trends of the hydrological elements and water quality elements.

[0013] Preferably, the hydrological elements include the lake water level, the in-lake flow rate, and the out-lake flow rate;

[0014] The water quality elements include the lake pollutant concentration and the in-lake pollutant concentration;

[0015] The annual time periods include the water level fluctuation period, the water level rising period, and the water level falling period.

[0016] Preferably, step (2) includes:

[0017] Selecting the multi-year monthly water level change rates with occurrence frequencies of x and y as the thresholds of the monthly water level change rate, where x > y, and x and y are constants, and using the lake water level change rate to measure the total amount of retained pollutants:

[0018] ΔHZ′ i =P x (ΔZ′) (1),

[0019] ΔLZ′ i =P y (ΔZ′) (2),

[0020] In the formula, ΔHZ′ i is the upper limit of the monthly water level change rate, ΔLZ′ i is the lower limit of the monthly water level change rate; P x (ΔZ′) is the multi-year monthly water level change rate of the lake with occurrence frequency x, Py (ΔZ′) is the monthly water level change rate of the lake with the occurrence frequency y over the years.

[0021] Preferably, in step (2), determining the water level range that meets the set water quality target includes:

[0022] Calculating the pollutant assimilation capacity of the lake using the Dillon model;

[0023] Based on the average monthly outflow from the lake and the total monthly inflow of pollutants over the years, calculating the lower limit of the appropriate water level month by month:

[0024]

[0025]

[0026] Q a = Q × 12 / n (5)

[0027] In the formula, W is the pollutant assimilation capacity of total nitrogen in the lake; ρ s is the control target concentration of total nitrogen; Z is the average depth of the lake; Q a is the average annual outflow from the lake; A is the area of the lake; V is the storage capacity of the lake; R p is the retention coefficient of total nitrogen in the lake; Q is the outflow from the lake in the calculated month; n is the number of months in the calculated month;

[0028] Based on the water level of the lake and the lake pollutant concentration for a selected period of time, plotting the scatter diagram of lake water level - water quality for different periods and fitting the water level - water quality empirical formula;

[0029] Based on the water level - water quality empirical formula, calculating the water level range that meets the set water quality target.

[0030] Preferably, in step (2), determining the monthly water level change rate that meets the set water quality target includes:

[0031] Using the monthly average water level Z ave , i and the average daily water level change rate ΔZ of several days j as the calculation indexes of the appropriate ecological water level, i = 1 - 12, j = 1 - 365;

[0032] Selecting the calculation indexes with occurrence frequencies of x and y as the RVA threshold to determine the monthly water level change rate of the lake that meets the set water quality target in different periods.

[0033] Preferably, in step (3), calculating the natural water level regime using the IHA - RVA method;

[0034] According to the water level range and the water level - water quality response relationship, correcting the natural water level regime to obtain the appropriate ecological water level, including:

[0035] During the water level fluctuation period, replace the natural water level regime that does not meet the set water quality target with the water level interval that meets the set water quality target.

[0036] Based on the water level-water quality response relationship, monthly water level thresholds are corrected for the natural water level regime during the water level fluctuation period.

[0037] The calculation formula for the water level-water quality response relationship is:

[0038]

[0039]

[0040] In the formula: HZ′ i is the upper limit of the appropriate ecological water level for the i-th month during the corrected water level fluctuation period; LZ′ i is the lower limit of the appropriate ecological water level for the i-th month during the corrected water level fluctuation period; HZ wq is the upper limit of the water level that meets the set water quality target; LZ wq is the lower limit of the water level that meets the set water quality target; HZ i is the upper limit of the appropriate ecological water level for the i-th month during the water level fluctuation period before correction; LZ i is the lower limit of the appropriate ecological water level for the i-th month during the water level fluctuation period before correction.

[0041] Preferably, during the water level rising period and the water level falling period, the total amplitude of water level change is restricted by the upper limit of the water level that meets the set water quality target and the lower limit of the water level that meets the set water quality target. Based on the upper limit of the monthly water level change rate, the lower limit of the monthly water level change rate, and the calculated pollutant assimilation capacity of the lake, the water level change process is allocated.

[0042] The calculation formula for allocating the water level change process is as follows:

[0043]

[0044]

[0045] In the formula: HZ′ k is the upper limit of the appropriate ecological water level for the k-th month after correction; LZ′ k is the lower limit of the appropriate ecological water level for the k-th month after correction; HZ k is the upper limit of the appropriate ecological water level for the k-th month before correction; LZ k is the lower limit of the appropriate ecological water level for the k-th month before correction; HZ0 is the upper limit of the appropriate ecological water level after correction for the month before the water level change; LZ0 is the lower limit of the appropriate ecological water level after correction for the month before the water level change; LZ p is the upper limit of the appropriate ecological water level for the p-th month during the corrected water level fluctuation period calculated based on the calculation formula of the water level-water quality empirical relationship; LZr is the lower limit of the suitable ecological water level for the r-th month in the corrected water level fluctuation period calculated by the calculation formula based on the water level-water quality empirical relationship; LZ p is the lower limit of the water level calculated based on the pollution absorption capacity; j is the total number of months during the water level change; k = 1, 2,..., j - 1. An electronic device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the method described in any one of the above are implemented.

[0046] Preferably, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method described in any one of the above are implemented.

[0047] The beneficial effects achieved by the present invention:

[0048] 1. From three aspects of the total amount of retained pollutants, pollution absorption capacity, and water level-water quality empirical formula, the present invention quantifies the water level-water quality response relationship in different periods respectively, and obtains the water level interval that meets the lake water quality target.

[0049] 2. By introducing the water level-water quality response relationship in the design process of the suitable ecological water level, the present invention enhances the applicability of the designed suitable ecological water level and meets the water quality requirements of the lake ecosystem.

[0050] 3. The present invention provides a reference and basis for the ecological regulation and water resources management of large-scale flowing-through lakes, and has strong practicability and wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is the basin map of the second embodiment of the present invention;

[0052] Figure 2 is the schematic diagram of the suitable ecological water level in the corrected water level fluctuation period of the present invention;

[0053] Figure 3 is the schematic diagram of the suitable ecological water level in the corrected water level rising period of the present invention;

[0054] Figure 4 is the schematic diagram of the suitable ecological water level in the corrected water level falling period of the present invention;

[0055] Figure 5 is the monthly change trend chart of the inflow water volume, outflow water volume and lake water level of Hongze Lake;

[0056] Figure 6 is the schematic diagram of the five-day average water level change rate of Hongze Lake;;

[0057] Figure 7 is the relationship diagram between the inflow water volume and water level of Hongze Lake;

[0058] Figure 8 is the monthly change trend chart of water quality factors;

[0059] Figure 9 is the scatter plot of the water level during the normal water period and the compliance rate of water quality stations;

[0060] Figure 10 is the scatter plot of the water level during the water discharge period and the compliance rate of water quality stations;

[0061] Figure 11 is the scatter plot of the water level before the water storage period and the compliance rate of water quality stations;

[0062] Figure 12 is the scatter plot of the water level after the water storage period and the compliance rate of water quality stations;

[0063] Figure 13 is the schematic diagram of the suitable ecological water level calculated by the IHA-RVA method of the present invention;

[0064] Figure 14 is the suitable daily water level change rate chart calculated by the IHA-RVA method of the present invention;

[0065] Figure 15 is the interval chart of the suitable ecological water level after correction of the present invention. Detailed implementation mode

[0066] The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and cannot be used to limit the protection scope of the present invention.

[0067] Embodiment 1

[0068] A method for deriving the suitable ecological water level for a flowing-through lake based on the binary response relationship between water quality and water level, comprising the steps of:

[0069] (1) Divide the annual time period according to the change trends of hydrological elements and water quality elements;

[0070] (2) Quantify the water level-water quality response relationship in different periods respectively from three aspects: the total amount of retained pollutants, the pollution absorption capacity and the water level-water quality empirical formula, and determine the water level interval A and the monthly water level change rate that meet the set water quality target based on this;

[0071] (3) Calculate the natural water level regime of the lake by the IHA-RVA method, and correct the natural water level regime according to the water level interval A to obtain the suitable ecological water level that meets the set water quality target (such as Class V water quality).

[0072] In the step (1), the annual time period is divided according to the change trends of hydrological elements and water quality elements:

[0073] The multi-year monthly average outflow of the lake, the multi-year monthly average concentration of pollutants entering the lake, and the multi-year monthly average total amount of pollutants entering the lake are obtained by using the hydrological elements of the lake for more than 30 years and the water quality elements for more than 5 years. The annual variation trends of the hydrological elements and water quality elements are analyzed respectively, and the annual time periods are divided based on this.

[0074] The hydrological elements include the lake water level, the inflow into the lake, and the outflow from the lake.

[0075] The water quality elements include the concentration of pollutants in the lake and the concentration of pollutants entering the lake.

[0076] The annual time periods include the water level fluctuation period, the water level rising period, and the water level falling period.

[0077] In step (2), from three aspects of the total amount of retained pollutants, the pollutant assimilation capacity, and the water level-water quality empirical formula, the water level-water quality response relationship in different periods is quantified respectively, and based on this, the water level interval A that meets the water quality target is determined, including:

[0078] (21) The total amount of retained pollutants is measured by the lake water level change rate. The multi-year monthly water level change rates with preset occurrence frequencies of 75% and 25% are selected as the thresholds of the monthly water level change rate. The calculation formula is as follows:

[0079] ΔHZ′ i =P 75％ (ΔZ′) (1)

[0080] ΔLZ′ i =P 25％ (ΔZ′) (2)

[0081] In the formula: ΔHZ′ i and ΔLZ′ i are the upper and lower limits of the monthly water level change rate of the lake, m / month; P 75％ (ΔZ′) and P 25％ (ΔZ′) are the multi-year monthly water level change rates of the lake with occurrence frequencies of 75% and 25%, m / month.

[0082] (22) The Dillon model is used to calculate the pollutant assimilation capacity of the lake, and based on the multi-year monthly average outflow of the lake and the multi-year monthly average total amount of pollutants entering the lake, the monthly appropriate water level lower limit is calculated. The calculation formula is:

[0083]

[0084]

[0085] Q a =Q×12 / n (5)

[0086] In the formula: W is the pollutant assimilation capacity of total nitrogen in the lake, t / a; ρs is the total nitrogen control target concentration, mg / L; Z is the average depth of the lake, m; Q a is the average annual outflow of the lake, m 3 ; A is the area of the lake, m 2 ; V is the storage capacity of the lake, m 3 ; R p is the retention coefficient of total nitrogen in the lake, a -1 ; Q is the outflow of the lake in the calculated month, m 3 ; n is the number of months in the calculated month.

[0087] (23) Using the lake water level and pollutant concentration data over 5 years, draw the lake water level - water quality scatter plot for different time periods, and fit the water level - water quality empirical formula;

[0088] Based on the water level - water quality empirical formula, calculate the water level range that meets the set water quality target.

[0089] In step (3) above, use the IHA - RVA method to calculate the natural water level regime of the lake, and correct the natural water level regime according to the water level range A to obtain the suitable ecological water level that meets the set water quality target, specifically including:

[0090] (1) Based on the daily water level data of Hongze Lake over the years, use the monthly average water level (Z ave，i , i = 1 - 12, m) and the five - day average daily water level change rate (ΔZ j , j = 1 - 365, m) as the calculation indicators for the suitable ecological water level, and select the calculation indicators with occurrence frequencies of 25% and 75% as the RVA thresholds to initially determine the requirements of the lake ecosystem for the lake water body size and water level change rate in different periods.

[0091] (2) Divide the annual time period into a water level fluctuation period, a water level rising period, and a water level falling period according to the lake water level change trend. As Figure 2 shown, in the water level fluctuation period, directly replace the suitable ecological water level threshold that does not meet the set water quality target with the calculated water level range that meets the set water quality target, and correct the monthly water level threshold of the IHA - RVA calculation result in the water level fluctuation period based on the water level - water quality response relationship;

[0092] The calculation formula of the water level - water quality response relationship is as follows:

[0093]

[0094]

[0095] In the formula: HZ′ i is the upper limit of the suitable ecological water level in the i - th month of the corrected water level fluctuation period, m; LZ′ iThe lower limit of the appropriate ecological water level in the i-th month during the corrected water level fluctuation period, m; HZ wq The upper limit of the water level to meet the set water quality target, m; LZ wq The lower limit of the water level to meet the set water quality target, m; HZ i The upper limit of the appropriate ecological water level in the i-th month during the water level fluctuation period before correction, m; LZ i The lower limit of the appropriate ecological water level in the i-th month during the water level fluctuation period before correction, m.

[0096] For the water level rising period and the water level falling period, Equations (6)-(7) should be used to limit the total water level change range by the upper limit of the water level to meet the set water quality target and the lower limit of the water level to meet the set water quality target, and then allocate the water level change process according to the upper limit of the monthly water level change rate on a five-day average, the lower limit of the monthly water level change rate, and the calculated lake pollution absorption capacity, as Figure 3 and 4 shown. The calculation formula for allocating the water level change process is as follows:

[0097]

[0098]

[0099] In the formula: HZ′ k The upper limit of the appropriate ecological water level in the k-th month after correction, m; LZ′ k The lower limit of the appropriate ecological water level in the k-th month after correction, m; HZ k The upper limit of the appropriate ecological water level in the k-th month before correction, m; LZ k The lower limit of the appropriate ecological water level in the k-th month before correction, m; HZ0 is the upper limit of the appropriate ecological water level after correction in the month before the water level change, m; LZ0 is the lower limit of the appropriate ecological water level after correction in the month before the water level change, m; LZ p The upper limit of the appropriate ecological water level in the p-th month during the corrected water level fluctuation period calculated by the calculation formula based on the water level-water quality empirical relationship, m; LZ r The lower limit of the appropriate ecological water level in the r-th month during the corrected water level fluctuation period calculated by the calculation formula based on the water level-water quality empirical relationship, m; LZ p The lower limit of the water level calculated based on the pollution absorption capacity, m; j is the total number of months during the water level change; k = 1, 2,..., j - 1.

[0100] Calculating the natural water level regime using the IHA-RVA method, calculating the lake pollution absorption capacity using the Dillon model, and fitting the water level-water quality empirical formula based on the historical data of the lake water level and lake pollutant concentration all belong to the prior art, and will not be elaborated in detail in this embodiment.

[0101] Example 2

[0102] This paper selects Hongze Lake as an implementation case. Hongze Lake is located at the junction of the middle and lower reaches of the Huaihe River, with a catchment area of ​​15.8km 2 , the fourth largest freshwater lake in China. As a water-transfer lake, Hongze Lake has a strong throughput capacity and a short water exchange cycle. Since the 1990s, the pollution of Hongze Lake has gradually become serious, and the water quality has deteriorated. Although it has improved in recent years, it is still in a state of mild eutrophication. At present, the water quality of Hongze Lake is mostly inferior Class V, and total nitrogen is the main pollutant. Without considering the total nitrogen, the water quality of Hongze Lake can reach Class III standards. The water body of Hongze Lake mainly relies on surface runoff for replenishment. Its main rivers entering the lake are the Huaihe River, Xinbian River, Huaihongxin River, Chihe River, Xinsui River, Laosui River and Xuhong River. The main rivers out of the lake are the river channel, the Subei Irrigation Main Canal and the sea channel. Among them, the Huaihe River is the main source of water in Hongze Lake and the main source of total nitrogen entering the lake. The geographical location of Hongze Lake and the distribution of rivers entering and leaving the lake and water quality monitoring points are as follows Figure 1 shown.

[0103] (1) Dividing the time periods within the year according to the changing trends of hydrological and water quality elements

[0104] Considering the characteristics of Hongze Lake, the present invention selects total nitrogen as the pollutant of Hongze Lake and uses Class V water quality as the water quality target for calculation. The hydrological data from 1988 to 2018 and the water quality data from 2013 to 2018 are used to calculate the average value and draw a trend chart, as shown in Figure 2. Figure 5 The monthly water inflow into the lake varies from 8.0 to 8.65 billion m 3 , the whole year can be divided into three periods of water volume changes: from January to June, the amount of water entering Hongze Lake is relatively small, and the overall trend is fluctuating; the amount of water entering the lake reaches a peak in July, and then it shows a downward trend from August to September, but the total amount is large, accounting for 65.9% of the annual water inflow from July to September; the amount of water entering the lake drops sharply from October to December, and the amount of water entering the lake in December is less than half of that in October. According to the five-day water level change rate, the whole year can be divided into four periods: from January to April, the water level of Hongze Lake fluctuates slightly between 13 and 13.14m; from May to June, due to the need for flood prevention during the flood season, the water level of Hongze Lake drops rapidly; after July, the water level of the lake rises rapidly with the inflow of water during the flood season; after the flood season ends, the water level rises slowly from October to December. Figure 6 The five-day average water level change rate is shown in Figure 2. Figure 7 As shown in the figure, the relationship between the water inflow and water level of Hongze Lake is a time series cycle curve, which can be divided into four stages with obvious characteristics.

[0105] The trend of water quality factors is shown in the figure below: Figure 8As shown in the figure, according to the total nitrogen concentration and total nitrogen amount entering the lake, the annual variation of the pollution load in Hongze Lake can be divided into four periods. The monthly average total nitrogen concentration entering Hongze Lake ranges from 1.96 to 3.75 mg / L, and the annual variation is as follows: the concentration fluctuates between 3.37 and 3.75 mg / L from January to April; the concentration shows a slight downward trend from May to June; due to the rapid increase in the water volume entering the lake during the flood season from July to September, the total nitrogen concentration drops significantly, and it is only 1.75 mg / L in September; the total nitrogen concentration rebounds significantly from October to December. The annual variation range of the monthly average total nitrogen amount entering Hongze Lake for many years is from 3170.44 to 12301.92 t. The amount of water entering the lake during the flood season is much larger than that during the non-flood season. The annual variation trend mainly shows a single-peak change with July as the boundary, first increasing and then decreasing, and there is a slight rebound in October.

[0106] Based on the hydrological situation of Hongze Lake and the annual variation trend of the total nitrogen load (as shown in the following table), the whole year is divided into four periods: normal water period (from January to April), water discharge period (from May to June), pre-impoundment period (from July to September), and post-impoundment period (from October to December), and the water level-water quality response relationship is quantified respectively.

[0107]

[0108] (2) Quantify the water level-water quality response relationship in different periods respectively from three aspects: the total amount of retained pollutants, the pollutant assimilation capacity, and the water level-water quality empirical formula, and based on this, determine the monthly water level change rate and water level interval A that meet the water quality target.

[0109] (1) The calculated range of the appropriate monthly water level change rate of Hongze Lake is from -0.79 m to 1.12 m, as shown below.

[0110]

[0111]

[0112] (2) Based on the Class V water quality standard, the pollutant assimilation capacity and the lower water level limit of Hongze Lake calculated according to the Dillion model are as shown below. Among them, the normal water period is 11.08 m, the water discharge period is 12.39 m, and the post-impoundment period is 12.9 m.

[0113]

[0114] (3) Use the water levels in the normal water period, water discharge period, pre-impoundment period, post-impoundment period of Hongze Lake from 2013 to 2018 and the compliance rate of water quality stations to draw scatter plots in different periods, as Figures 9 - 12As shown, during the early stage of water storage, the water quality shows a tendency to improve with the rising water level, but the correlation is poor. In the remaining periods, the water quality is significantly negatively correlated with the water level. After removing some abnormally fluctuating water level data, the SPSS software is used to calculate the correlation between the water level and the proportion of water quality stations reaching the standard in these three periods and fit the empirical relationship formula. The results are as follows.

[0115]

[0116] (4) By comprehensively considering the water intake capacity and the water level requirements calculated from the water level - water quality empirical formula, the water level range A that meets the set water quality target is that the water level is lower than 12.99 m during the normal water period, 12.39 - 12.63 m during the water discharge period, and 12.90 - 13.04 m during the late stage of water storage.

[0117] (3) Based on the IHA - RVA method, the natural water level regime of the lake is calculated, and the natural water level regime is corrected according to the water level range A to obtain the suitable ecological water level that meets the set water quality target.

[0118] (1) The thresholds of the suitable ecological water level and the suitable daily water level change rate calculated based on IHA - RVA are shown in Figure 13 and Figure 14 respectively. The suitable ecological water level change range of Hongze Lake is 11.97 - 13.41 m, and the suitable daily water level change range is - 0.06 m - 0.05 m. As Figure 13 shown, during the non - flood season, the water level change amplitude of Hongze Lake is small, and during the flood season, the water level of Hongze Lake shows a trend of first decreasing and then increasing; as Figure 14 shown, the large - amplitude water level changes of Hongze Lake mainly occur from May to August. Among them, the water level shows a decreasing trend from May to June and an increasing trend from July to August, and the water level fluctuation amplitude in the remaining periods of the year is small.

[0119] (2) The monthly suitable ecological water level intervals corrected according to the water level - water quality empirical formula and the water intake capacity requirements are shown in Figure 15 respectively. The water level intervals for each month are: 12.92 - 12.99 m, 12.79 - 12.99 m, 12.84 - 12.99 m, 12.86 - 12.99 m, 12.71 - 12.89 m, 12.39 - 12.63 m, 11.97 - 12.93 m, 12.50 - 13.07 m, 12.65 - 13.26 m, 12.90 - 13.04 m, 12.90 - 13.04 m, 12.90 - 13.04 m.

[0120] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0121] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0122] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0123] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for predicting the appropriate ecological water level based on the binary response relationship between water quality and water level, characterized in that Including: (1) Divide the annual time periods according to the changing trends of hydrological elements and water quality elements; (2) Select the multi-year monthly water level change rates with occurrence frequencies of x and y as the thresholds of the monthly water level change rate, where x > y, and x and y are constants. Use the lake water level change rate to measure the total amount of retained pollutants: ΔHZ′ i = P x (ΔZ′) (1), ΔLZ′ i = P y (ΔZ′)(2), where ΔHZ′ i is the upper limit of the monthly water level change rate, and ΔLZ′ i is the lower limit of the monthly water level change rate; P x (ΔZ′) is the multi-year monthly water level change rate of the lake with the occurrence frequency x, and P y (ΔZ′) is the multi-year monthly water level change rate of the lake with the occurrence frequency y; Use the Dillon model to calculate the pollutant assimilation capacity of the lake; Based on the multi-year monthly average lake outflow and the multi-year monthly average total amount of pollutants entering the lake, calculate the lower limit of the appropriate water level month by month; Q a = Q × 12 / n (5) Where, W is the pollution absorption capacity of total nitrogen in the lake; ρ s is the total nitrogen control target concentration; Z is the average depth of the lake; Q a is the annual average outflow of the lake; A is the lake area; V is the lake storage capacity; R p is the retention coefficient of total nitrogen in the lake; Q is the outflow of the lake in the calculated month; n is the number of months in the calculated month; Based on the lake water level and lake pollutant concentration for a selected period of time, draw the lake water level-water quality scatter plot for different periods and fit the water level-water quality empirical formula; Modify the natural water level regime according to the water level interval and the water level-water quality response relationship to obtain the appropriate ecological water level, including: During the water level fluctuation period, use the water level interval that meets the set water quality target to replace the set natural water level regime that does not meet the set water quality target; Based on the water level-water quality response relationship, perform monthly water level threshold correction on the natural water level regime during the water level fluctuation period; The calculation formula of the water level-water quality response relationship is: Where: HZ′ i is the upper limit of the suitable ecological water level for the i-th month during the corrected water level fluctuation period; LZ′ i is the lower limit of the suitable ecological water level for the i-th month during the corrected water level fluctuation period; HZ wq is the upper limit of the water level to meet the set water quality target; LZ wq is the lower limit of the water level to meet the set water quality target; HZ i is the upper limit of the suitable ecological water level for the i-th month during the water level fluctuation period before correction; LZ i is the lower limit of the suitable ecological water level for the i-th month during the water level fluctuation period before correction; Based on the total amount of retained pollutants, the pollutant assimilation capacity, and the water level-water quality empirical formula, determine the water level interval and the monthly water level change rate that meet the set water quality target; (3) Use the IHA-RVA method to calculate the natural water level regime; Modify the natural water level regime according to the water level interval and the water level-water quality response relationship to obtain the appropriate ecological water level that meets the set water quality target.

2. The appropriate ecological water level prediction method based on the water quality-water level binary response relationship according to claim 1, wherein Step (1) specifically includes: Obtain the hydrological elements and water quality elements of the lake for a period of time, and calculate the multi-year monthly average lake outflow, annual average lake outflow, multi-year monthly average pollutant concentration entering the lake, and multi-year monthly average total amount of pollutants entering the lake; Divide the annual time periods according to the annual changing trends of the hydrological elements and water quality elements.

3. The appropriate ecological water level prediction method based on the water quality-water level binary response relationship according to claim 2, characterized in that The hydrological elements include lake water level, inflow into the lake, and outflow from the lake; The water quality elements include lake pollutant concentration and pollutant concentration entering the lake; The annual time periods include the water level fluctuation period, the water level rising period, and the water level falling period.

4. The appropriate ecological water level prediction method based on the water quality-water level binary response relationship according to claim 3, characterized in that, Step (2), determining the monthly water level change rate that meets the set water quality target, includes: Using the monthly average water level Z ave，i and the average daily water level change rate ΔZ for several days j as the calculation index of the suitable ecological water level, where i = 1 to 12 and j = 1 to 365; Select the calculation indicators with occurrence frequencies of x and y as the RVA thresholds to determine the monthly water level change rate of the lake that meets the set water quality target for different periods.

5. The suitable ecological water level prediction method based on the water quality-water level binary response relationship according to claim 1, characterized in that During the water level rising period and the water level falling period, use the upper limit of the water level of the set water quality target and the lower limit of the water level of the set water quality target to limit the total water level change range, and based on the upper limit of the monthly water level change rate, the lower limit of the monthly water level change rate, and the calculated pollutant assimilation capacity of the lake, allocate the water level change process; The calculation formula for allocating the water level change process is as follows: Where: HZ′ k is the upper limit of the suitable ecological water level in the k-th month after correction; LZ′ k is the lower limit of the suitable ecological water level in the k-th month after correction; HZ k is the upper limit of the suitable ecological water level in the k-th month before correction; LZ k is the lower limit of the suitable ecological water level in the k-th month before correction; HZ0 is the upper limit of the suitable ecological water level after correction in the month before the water level change; LZ0 is the lower limit of the suitable ecological water level after correction in the month before the water level change; LZ p is the upper limit of the suitable ecological water level in the p-th month of the corrected water level fluctuation period calculated by the calculation formula based on the water level-water quality empirical relationship; LZ r is the lower limit of the suitable ecological water level in the r-th month of the corrected water level fluctuation period calculated by the calculation formula based on the water level-water quality empirical relationship; LZ p is the lower limit of the water level calculated based on the pollution carrying capacity; j is the total number of months during the water level change; k = 1, 2,..., j - 1.

6. An electronic device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method described in any one of claims 1 to 5.

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