Ecological flow staging regulation method based on dynamic threshold

Abstract

The present application relates to the technical field of hydrology and ecological hydraulics, and particularly relates to an ecological flow staging regulation method based on dynamic threshold value. The present application firstly constructs a dynamic ecological flow threshold value interval varying with months based on long sequence runoff data, with the ecological base flow as the lower limit value and the Lyon method calculation value as the upper limit value; then according to the real-time water month, the threshold value range is automatically matched, and the discharge flow is determined according to the three-stage rule of "discharging the upper limit when the water is sufficient, discharging the water when the water is moderate, and discharging the lower limit when the water is insufficient"; finally, the dynamic threshold value is embedded as a rigid constraint in the reservoir regulation diagram for forced execution. The present application realizes the change of ecological flow from "static quota" to "dynamic threshold value", releases more water resources for water supply and power generation in the wet season, and strictly guarantees the ecological base flow bottom line in the dry season, which safeguards the differentiated needs of river ecological system while avoiding excessive occupation of beneficial reservoir capacity, and realizes the scientific balance of ecological protection and water resource utilization.

Description

Technical Field

[0001] This invention relates to the field of hydrology and ecohydraulics technology, specifically to a method for phased regulation of ecological flow based on dynamic thresholds. Background Technology

[0002] While reservoirs fulfill their beneficial objectives such as flood control, water supply, and power generation, they often significantly disrupt the natural hydrological rhythms of downstream rivers. Traditional reservoir management typically uses a fixed threshold (e.g., 10% of the multi-year average flow) or a minimum ecological base flow to determine ecological flow. This "static quota" approach ignores the natural alternation of wet and dry seasons throughout the year, resulting in low ecological flow during the wet season, failing to meet high ecological water demands, and high ecological flow during the dry season, unreasonably encroaching on beneficial reservoir capacity. Furthermore, existing management maps often focus on flood control and water supply, with ecological targets frequently existing as suggested or reference values, lacking rigid constraints. Ecological flow during the dry season is easily squeezed out, making it difficult to achieve synergistic optimization of ecological protection and water resource utilization.

[0003] Therefore, there is a need for an ecological flow regulation method that can reflect natural hydrological rhythms, dynamically adapt to the ecological needs of different water periods, and be organically integrated with reservoir scheduling maps. Summary of the Invention

[0004] (1) Technical solution This invention provides a method for phased regulation of ecological flow based on dynamic thresholds, comprising the following steps: Step 1: Based on long-series runoff data, using ecological baseflow as the lower limit and Lyon method calculation as the upper limit, construct a dynamic ecological flow threshold range that varies with the month. Step 2: Based on the real-time water inflow month, automatically match the corresponding threshold range for each period and determine the target value of the discharge flow rate according to the interval; Step 3: Embed the dynamic ecological flow threshold range as a rigid constraint into the reservoir scheduling diagram to enforce the ecological objectives in each scheduling zone; Preferably, the ecological flow in step one is determined using the Tennant method or 10% of the multi-year average flow.

[0005] Preferably, the Lyon method calculation value in step one is determined according to the following piecewise function:

[0006] Q i Let be the multi-year median flow rate for month i, in m³ / s; Let be the average monthly flow rate for month i, in m³ / s; The flow rate is the multi-year average, in m³ / s; i represents the month.

[0007] Preferably, in step one, the ecological base flow is used as the lower limit of the ecological flow threshold; when the value calculated by the Lyon method is higher than the ecological base flow, the calculated value is used as the upper limit; when the calculated value is lower than the ecological base flow, the upper limit is used as the ecological base flow, that is, the upper and lower limits are equal at this time.

[0008] Preferably, the specific rules for determining the target value of the downstream ecological flow in step two are as follows: If the current inflow is greater than or equal to the upper limit for the current month, then the upper limit will be released. If the current inflow rate is between the lower limit and the upper limit, then the water will be discharged according to the inflow rate. If the current inflow rate is less than or equal to the lower limit for the current month, then the lower limit will be released.

[0009] Preferably, the rigid constraint in step three means that in the increased water supply area, normal water supply area and reduced water supply area of ​​the scheduling diagram, priority is given to ensuring the release of the dynamic ecological flow threshold, and then the water supply scheduling rules are executed according to the remaining reservoir capacity.

[0010] Preferably, the scheduling rules for each region are as follows: Increase water supply area: When the reservoir water level is between the increased water supply line and the flood control dispatch line, the water supply volume of the water plant can be increased; Normal water supply area: When the reservoir water level is between the increased water supply line and the normal water supply line, water supply can be scheduled according to the maximum water supply capacity; Reduce water supply area: When the reservoir water level is between the normal water supply line and the restricted water supply line, a strategy of reducing water supply shall be adopted, and the water supply volume shall be reduced by no less than 50% of the designed water supply volume.

[0011] (2) Beneficial effects The present invention proposes a phased regulation method for ecological flow based on dynamic thresholds. Compared with existing technologies, the present invention has the following advantages: 1. The dynamic threshold range is consistent with the trend of natural runoff. During the wet season, more water resources are released for water supply / power generation, while during the dry season, the ecological base flow is strictly guaranteed, thus achieving the resonance between ecological water demand and water inflow process.

[0012] 2. By setting reasonable upper and lower limits, the problem of traditional fixed thresholds excessively encroaching on beneficial storage capacity during the dry season or insufficient ecological flow during the wet season is avoided, thus finding the best balance between "protecting the ecology" and "protecting the economy".

[0013] 3. By directly embedding dynamic ecological thresholds into the reservoir scheduling map, the soft state of ecological targets being "adjustable or not" is changed, ensuring that ecological flow is not squeezed out during the dry season.

[0014] 4. By observing changes in reservoir capacity in different zones through the scheduling diagram (such as increasing the reduction of water supply zones or restricting the expansion of water supply zones), the impact of ecological constraints on water supply capacity can be intuitively assessed, facilitating scheduling decisions. Attached Figure Description

[0015] Figure 1 This is a graph showing the dynamic ecological flow threshold results of a reservoir in Embodiment 1 of the present invention; Figure 2 This is the original water supply scheduling diagram of a reservoir according to Embodiment 1 of the present invention; Figure 3 This is a reservoir water supply scheduling diagram after adding a dynamic threshold according to Embodiment 1 of the present invention; Figure 4 This is a diagram showing the changes before and after the water supply scheduling of a reservoir according to Embodiment 1 of the present invention. Detailed Implementation Example 1

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, a specific embodiment of a reservoir is used below, and the invention will be further described in detail with reference to the accompanying drawings. This embodiment is only used to explain the invention and does not constitute a limitation on the scope of protection.

[0017] 1. A reservoir dam site section has long-sequence runoff data. The ecological base flow is calculated to be 0.082 m³ / s using the Tennant method.

[0018] 2. Lyon method ecological flow threshold:

[0019] The monthly median flow obtained from years of statistical analysis is used as a certain proportion as the recommended ecological flow value for that month, resulting in the monthly ecological flow thresholds for the dam site, as follows: Table 1. Monthly Ecological Flow Thresholds at the Dam Site month April May June July August September October November December January February March Lyon method ecological flow threshold 1.47 2.27 2.64 1.26 1.90 1.50 0.30 0.21 0.15 0.24 0.38 1.25 Ecological base flow 0.082 0.082 0.082 0.082 0.082 0.082 0.082 0.082 0.082 0.082 0.082 0.082 Multi-year average runoff 3.33 4.90 6.65 3.71 5.72 4.78 1.54 0.99 0.86 0.94 1.67 2.76 3. Dynamic ecological flow threshold: The ecological base flow is used as the lower limit of the ecological flow threshold; when the calculated threshold is higher than the ecological base flow, the calculated value is used as the upper limit. This forms a dynamic ecological flow process with upper and lower limit ranges.

[0020] 4. Based on the extended long-sequence runoff data of a certain reservoir, three representative years with a design water supply guarantee rate of 95% were selected. Based on the monthly inflow of each representative year, the dead storage capacity at the end of the March water supply period was calculated. Initially, calculations are performed month by month in reverse chronological order, up to the beginning of the water storage period in April. The basic equation is expressed as: (1) In the formula, For the first The representative year The reservoir's water storage at the end of the month was 104m³.3 ; For the first Monthly water supply volume: 104m³ 3 ; The duration is in seconds (s). For the first The representative year Monthly design inbound traffic, m 3 ·s -1 .

[0021] The reservoir water storage at the end of each month of each representative year is obtained by formula (1), and then converted into the corresponding reservoir water level according to the reservoir water level-storage capacity relationship curve, thus obtaining the monthly reservoir water level of each representative year. ( As a representative year, =1,2……12 months). Based on this, draw the reservoir scheduling line according to (2): (2) In the formula, To increase the water level in the water supply line, m; The normal water supply line level is measured in meters (m). This is determined by connecting the minimum reservoir water levels for each month of different representative years to form the lower envelope, which serves as the normal water supply line; and by connecting the maximum values ​​to form the upper envelope, which serves as the increased water supply line.

[0022] To ensure water supply security, the original water supply schedule, which no longer includes ecological objectives, will now reserve 15 days' worth of water supply (1.05 million m³) below the normal water supply line. 3 As an emergency reserve; after introducing dynamic ecological targets, 15 days' worth of water supply (1.05 million m³) will be reserved each month. 3 ) and ecological base flow (105,000 m³) 3 As an emergency water supply and ecological reserve for next month, the reservoir capacity corresponding to the normal water supply line is set at [value missing]. The corresponding reservoir capacity for the emergency water supply line is: (3) If the emergency water supply line level calculated according to formula (3) is lower than the dead water level, the normal water supply line needs to be appropriately raised so that the emergency water supply line is not lower than the dead water level. After correction, the increased water supply line is re-determined based on the new normal water supply line, and finally the corrected increased water supply line and normal water supply line are obtained.

[0023] 4. Reasonableness Analysis: From Figure 1 It can be seen that the ecological flow threshold of the Lyon method is basically consistent with the trend of the multi-year average runoff at the dam site. Both show a pattern of higher flow during the flood season (April to September) and lower flow during the dry season (October to March), which can better reflect the hydrological rhythm of the basin's annual alternation between wet and dry seasons.

[0024] This invention achieves a scientific balance between ecological protection and water resource utilization by constructing a dynamic ecological flow threshold. Based on hydrological rhythms, the invention uses the ecological baseflow as the lower limit and the Lyon method calculation value as the upper limit to form a dynamic threshold range that varies with the month. This scheme synchronizes ecological water demand with natural water inflow: during the wet season, more water resources are released for water supply (power generation), while during the dry season, the ecological baseflow baseline is guaranteed.

[0025] 5. Results Verification Reservoir scheduling maps are an important basis for guiding the daily operation of reservoirs and can coordinate the water use competition between different water supply targets. Therefore, the impact of dynamic ecological flow thresholds on reservoir scheduling is verified through reservoir scheduling maps.

[0026] Original reservoir scheduling diagram: Original water supply scheduling diagram of a certain reservoir ( Figure 2 With water supply as the core objective, the reservoir was originally designed to supply 70,000 tons of water per day to a certain town. A zoned water supply system was adopted, dividing the reservoir into three areas: an increased water supply zone, a normal water supply zone, and a reduced water supply zone. The scheduling rules for each area are as follows: (1) Increase the water supply area R: When the reservoir water level is between the increased water supply line and the flood control dispatch line, the water supply of the water plant can be increased; (2) Normal water supply area T: When the reservoir water level is between the increased water supply line and the normal water supply line, water supply can be scheduled according to the maximum water supply capacity; (3) Restricted (reduced) water supply area Q: When the reservoir water level is between the normal water supply line and the restricted water supply line, the water supply strategy is reduced in this area, and the water supply is generally reduced by no less than 50% of the designed water supply.

[0027] Table 2. Characteristics of the original scheduling partitions Scheduling partitions serial number <![CDATA[Original annual storage capacity range (10,000 m 3 )]]> Scheduling rules Increase water supply area R1 5479.02~10416.17 Increase water supply Normal water supply area T1 3352.90~5479.02 Normal water supply Restricted water supply area Q1 2254.02~3352.90 Water supply restricted (reduced) Table 3 Comparison of reservoir capacity changes in scheduling zones after adding dynamic ecological thresholds Scheduling partitions serial number <![CDATA[Full-year storage capacity range after adding dynamic ecological threshold (10,000 m 3 ).]]> <![CDATA[Change amount compared to the original schedule (10,000 m 3 )]]> Change rate compared to the original schedule (%) Increase water supply area R2 5981.35~10416.17 -661.28 -13.39% Normal water supply area T2 4002.52~5981.35 -502.69 -23.64% Restricted water supply area Q2 2254.02~4002.52 1163.97 +105.92% From Table 2 and Figure 2 It is evident that the original scheduling map only divided the scheduling zones based on the water supply guarantee rate, without incorporating any ecological objectives. Each scheduling zone was solely guided by water supply tasks, lacking a systematic consideration of the ecological water demand of downstream river channels. In years with low water levels during the dry season, reservoirs were prone to an operational situation of "prioritizing water supply while neglecting ecological protection," making it difficult to meet the differentiated needs of the river ecosystem at different water periods.

[0028] From Table 3 and Figure 3 It can be seen that after adding dynamic ecological thresholds (R2, T2, Q2), compared with the original scheduling, the reservoir capacity of the increased water supply area and the normal water supply area is reduced by 13.39% and 23.64% respectively, and the restricted water supply area is expanded by 105.92%.

[0029] Depend on Figure 4 Compared to the original scheduling diagram, the addition of dynamic thresholds to the scheduling diagram not only resulted in an overall upward adjustment of the scheduling zones' boundaries, but also altered the zone structure. Specifically, for example, in October, raising the water supply line by 6.68m corresponded to an increase in regulating reservoir capacity of approximately 3.29 million m³; raising the normal water supply line by 7.04m corresponded to an increase in reservoir capacity of approximately 2.62 million m³. 3 Similar to November and December, although the magnitude of the rise varied, the shadow persisted. This characteristic of "storing during wet seasons and replenishing during dry seasons" in reservoir capacity redistribution contrasts sharply with the original water supply area pattern in the dispatching map, achieving an adaptive redistribution of dispatched reservoir capacity between wet and dry seasons.

[0030] The embodiments described above are merely preferred embodiments of the present invention, and are described in a relatively specific and detailed manner. However, the present invention is not limited to these embodiments. It should be noted that for those skilled in the art, any modifications made without departing from the spirit of the present invention fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for phased regulation of ecological flow based on dynamic thresholds, characterized in that, Includes the following steps: Step 1: Based on long-series runoff data, using ecological baseflow as the lower limit and Lyon method calculation as the upper limit, construct a dynamic ecological flow threshold range that varies with the month. Step 2: Based on the real-time water inflow month, automatically match the corresponding threshold range for each period and determine the target value of the discharge flow rate according to the interval; Step 3: Embed the dynamic ecological flow threshold range as a rigid constraint into the reservoir scheduling diagram to enforce the ecological objectives in each scheduling zone.

2. The method for phased regulation of ecological flow based on dynamic thresholds according to claim 1, characterized in that, The ecological flow in step one is determined using the Tennant method or 10% of the multi-year average flow.

3. The method for phased regulation of ecological flow based on dynamic thresholds according to claim 1, characterized in that, The Lyon method calculation value in step one is determined according to the following piecewise function: ； Q i Let be the multi-year median flow rate for month i, in m³ / s; Let be the average monthly flow rate for month i, in m³ / s; The flow rate is the multi-year average, in m³ / s; i represents the month.

4. The method for phased regulation of ecological flow based on dynamic thresholds according to claim 1, characterized in that, In step one, the ecological base flow is used as the lower limit of the ecological flow threshold; when the value calculated by the Lyon method is higher than the ecological base flow, the calculated value is used as the upper limit; when the calculated value is lower than the ecological base flow, the upper limit is used as the ecological base flow, that is, the upper and lower limits are equal at this time.

5. The method for phased regulation of ecological flow based on dynamic thresholds according to claim 1, characterized in that, The specific rules for determining the target value of the downstream ecological flow in step two are as follows: If the current inflow is greater than or equal to the upper limit for the current month, then the upper limit will be released. If the current inflow rate is between the lower limit and the upper limit, then the water will be discharged according to the inflow rate. If the current inflow rate is less than or equal to the lower limit for the current month, then the lower limit will be released.

6. The method for phased regulation of ecological flow based on dynamic thresholds according to claim 1, characterized in that, The rigid constraint mentioned in step three refers to prioritizing the release of dynamic ecological flow thresholds in the increased water supply zone, normal water supply zone, and reduced water supply zone of the scheduling diagram, and then executing the water supply scheduling rules according to the remaining reservoir capacity.

7. The method for phased regulation of ecological flow based on dynamic thresholds according to claim 6, characterized in that, The scheduling rules for each region are as follows: Increase water supply area: When the reservoir water level is between the increased water supply line and the flood control dispatch line, the water supply volume of the water plant can be increased; Normal water supply area: When the reservoir water level is between the increased water supply line and the normal water supply line, water supply can be scheduled according to the maximum water supply capacity; Reduce water supply area: When the reservoir water level is between the normal water supply line and the restricted water supply line, a strategy of reducing water supply shall be adopted, and the water supply volume shall be reduced by no less than 50% of the designed water supply volume.

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