A method for calculating ecological water demand target of river by zoning classification grading

Abstract

The application discloses a kind of partition classification hierarchical river ecological water demand target calculation method, the method includes the following steps: step 1, collecting research area data;Step 2, the river of research area is partitioned;Step 3, the river of research area is classified;Step 4, determine ecological protection object;Step 5, ecological water demand target hierarchical calculation.The method is disclosed in the application by considering the difference of river natural conditions and human development and utilization, the river of research area is scientifically partitioned and classified, and the ecological protection object of river is reasonably determined, the hierarchical system of ecological water demand including minimum ecological flow and suitable ecological flow is proposed, the water demand of river ecological environment and economic and social development is effectively considered, the real situation of river is objectively reflected, is helpful to the implementation of ecological water demand, provides technical support for river ecological water demand management and guarantee.

Description

Technical Field

[0001] This invention belongs to the field of ecological protection and restoration technology, and in particular relates to a method for calculating river ecological water demand targets based on regional classification and grading. Background Technology

[0002] The fundamental significance of conducting ecological water demand calculations for rivers lies in providing a scientific basis for achieving sustainable water resource management and maintaining the health and biodiversity of river ecosystems. Currently, there are numerous methods for calculating ecological water demand, including hundreds of methods across four categories: hydrological methods, hydraulic methods, habitat simulation methods, and holistic analysis methods. However, existing ecological water demand calculation methods typically employ a uniform standard for the entire watershed or region, failing to adequately consider regional heterogeneity, particularly lacking zoning and classification considerations for complex geographical environments and varying human activity intensities. Furthermore, traditional ecological water demand calculations overemphasize the demand from aquatic organisms, to some extent neglecting the water demand in areas with high human activity, making the calculation results difficult to implement. For example, the Tennant method, which has the lowest requirements for hydrological and hydraulic data, is favored and widely used. This method uses easily calculated multi-year average natural runoff as a basis, directly taking fixed percentages such as 10%, 20%, and 30% as ecological water demand targets, which is unsuitable for regions with vast areas and diverse climate and hydrological conditions.

[0003] Therefore, there is an urgent need to propose a method for calculating river ecological water demand that takes into account the differences in natural river conditions and human development and utilization, in order to overcome the shortcomings of existing calculation methods. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating river ecological water demand targets by region, category, and level, so as to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for calculating river ecological water demand targets based on regional classification and grading, the method comprising the following steps:

[0007] Step 1: Collect data for the study area: Collect daily precipitation data for many years in the study area, daily measured runoff and monthly natural runoff data of representative cross sections of rivers in the study area; collect water resources and water consumption data of rivers in the study area for many years in history;

[0008] Step 2: Divide the rivers in the study area into zones: Considering the need to maintain the integrity of the climate, geography and water system, the rivers in the study area are divided into zones using the water resource zoning method;

[0009] Step 3: Classify the rivers in the study area: Based on runoff recharge type and water inflow process, the rivers are divided into three types: no-flood type, summer-flood type, and spring-summer dual-flood type. Based on the collected water resource volume and water consumption data of the rivers in the study area, the average water resource development and utilization rate of the rivers is calculated, and the rivers are further divided into two types: high-development rivers and low-development rivers. Finally, the rivers are classified into six types: no-flood type × high-development river, no-flood type × low-development river, summer-flood type × high-development river, summer-flood type × low-development river, spring-summer dual-flood type × high-development river, and spring-summer dual-flood type × low-development river.

[0010] Step 4: Determine the ecological protection targets: Investigate the water supply and demand relationship between rivers and riparian vegetation, lakes and wetlands in different zones, and determine the types of riparian vegetation and lake wetlands that are ecological protection targets; Investigate the aquatic biological communities and species of rivers in different zones, select fish as indicator species, and determine the types of fish that are ecological protection targets.

[0011] Step 5: Calculation of ecological water demand targets by grade: For highly developed rivers, calculate the minimum ecological flow as the ecological water demand target for the river; for less developed rivers, calculate the appropriate ecological flow as the ecological water demand target for the river; calculate the ecological water demand target for each of the six river types.

[0012] Furthermore, the selection criteria for the representative river section in step 1 are as follows: based on the distribution of the river's ecological protection objects, select the section with a long series of measured runoff data within the river section where the ecological protection objects are distributed as the representative river section.

[0013] Furthermore, the method of dividing the rivers in the study area into zones based on water resource zoning described in step 2 is as follows: the zones are divided according to the national water resource zoning system, including 10 primary water resource zones, 80 secondary water resource zones, and 210 tertiary water resource zones.

[0014] Furthermore, the specific process for classifying rivers into three types—no-flood, summer-flood, and spring-summer dual-flood—based on runoff supply type and inflow process, as described in step 3, is as follows: The criteria for determining a no-flood river are: based on the river's multi-year average daily runoff process, if there is no significant rise in water level for more than three consecutive days, the river is considered a no-flood river; if the daily flow increases by more than 50% relative to the previous day's flow, the river is considered to have experienced a significant rise in water level. The criteria for determining a summer-flood river are: based on the river's multi-year average daily runoff process, if floods with a recurrence period of 5 years or more occur concentrated in summer (June to September), the river is considered a summer-flood river. The criteria for determining a spring-summer dual-flood river are: based on the river's multi-year average daily runoff process, if floods with a recurrence period of 5 years or more occur in both spring (March to April) and summer (June to September), the river is considered a spring-summer dual-flood river.

[0015] The specific process of further classifying rivers into two types, high-development rivers and low-development rivers, is as follows: when the average water resource development and utilization rate of a river is >40%, it is classified as a high-development river; when the average water resource development and utilization rate of a river is ≤40%, it is classified as a low-development river.

[0016] Furthermore, the types of riparian vegetation and lake wetlands described in step 4 as objects of ecological protection include native riparian tree and shrub communities that rely on groundwater or periodic river flooding, wetland vegetation communities that serve as hydrological indicators, and seasonal lake wetlands that provide important habitats for migratory waterbirds; the types of fish described as objects of ecological protection include rare and endemic fish species at various levels, migratory fish species that require specific spawning grounds, feeding grounds, or overwintering grounds to complete their life history, and sensitive fish species that have special requirements for dissolved oxygen and water temperature.

[0017] Furthermore, the specific process for calculating the ecological water demand target of each of the six river types as described in step 5 is as follows:

[0018] (1) For flood-free × high-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the flow required to maintain the minimum riparian vegetation area and the minimum lake and wetland area.

[0019] The ecological base current is calculated using the Qp method. Specifically, based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0020] The ecological flow required to maintain the minimum riparian vegetation area and the minimum lake wetland area is calculated using the area quota method, as follows:

[0021] (1)

[0022] In the formula, The ecological flow required to maintain the minimum riparian vegetation area and the minimum lake and wetland area is m³ / s; n is the number of ecological protection objects. Let hm be the minimum area of ​​the i-th ecological protection target, namely riparian vegetation and lake wetlands. 2 ; For the ecological water demand quota of the i-th ecological protection object, m 3 / hm 2 ;T i Let be the ecological water demand time for the i-th ecological protection object, in seconds;

[0023] Among them, the historical comparison method was used to determine the minimum area of ​​riparian vegetation and lake wetlands. Specifically, land use remote sensing image data from the 1980s and 1990s were collected to determine the annual average area of ​​riparian vegetation and lake wetlands, and 50% of this average was taken as the minimum area of ​​riparian vegetation and lake wetlands.

[0024] (2) For flood-free × low-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the flow required to maintain a suitable riparian vegetation area and a suitable lake and wetland area.

[0025] Ecological base current is calculated using the Qp method: Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0026] The ecological flow required to maintain suitable riparian vegetation area and suitable lake and wetland area is calculated using the area quota method. The calculation formula is as follows:

[0027] (2)

[0028] In the formula, The ecological flow required to maintain a suitable riparian vegetation area and a suitable lake and wetland area is m³ / s; n is the number of ecological protection objects. Let hm be the suitable area of ​​the i-th ecological protection target, namely riparian vegetation and lake wetlands. 2 ; For the ecological water demand quota of the i-th ecological protection object, m 3 / hm 2 ;T i Let be the ecological water demand time for the i-th ecological protection object, in seconds;

[0029] The suitable area of ​​riparian vegetation and lake wetlands was determined by using the historical comparison method. Specifically, land use remote sensing image data from the 1980s and 1990s were collected to determine the annual average area of ​​riparian vegetation and lake wetlands, which were then used as the suitable area of ​​riparian vegetation and lake wetlands.

[0030] (3) For summer flood type × high development rivers, the ecological water demand target includes the ecological base flow to maintain the basic morphology of the river and the minimum flow to maintain the growth needs of typical fish during the summer flood season;

[0031] Ecological base current is calculated using the Qp method: Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0032] The minimum flow required to sustain the growth of typical fish species during the summer flood season was calculated using habitat simulation. The calculation process is as follows:

[0033] ① Investigate research findings related to the growth of typical fish species or conduct field observations to clarify the range of water depth and flow velocity requirements of these fish species during the flood season;

[0034] ② Determine the river section to be studied, establish a two-dimensional hydraulic model of the river section, simulate the hydraulic conditions of the study area, and obtain the water depth and velocity distribution of the river section under different flow rates;

[0035] ③ Statistically determine the area where the water depth and flow velocity meet the needs of typical fish species under different flow rates as the fish habitat area, and establish a curve showing the relationship between flow rate and habitat area.

[0036] ④The flow rate corresponding to when the habitat area reaches 40% of the peak area is taken as the minimum flow rate;

[0037] (4) For summer flood type × low development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the appropriate flow to maintain the growth needs of typical fish during the summer flood season;

[0038] Ecological base current is calculated using the Qp method: Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0039] Similarly, the habitat simulation method is used to calculate the appropriate flow rate to maintain the growth requirements of typical fish species during the summer flood season. Steps ① to ③ of the calculation process are the same as those described above. The difference is that in step ④, the flow rate corresponding to when the habitat area reaches 60% of the peak area is taken as the appropriate flow rate.

[0040] (5) For rivers with spring and summer double floods and high development, calculate the minimum ecological flow as the target for river ecological water demand; among which, the minimum ecological flow includes the ecological base flow to maintain the basic shape of the river and the minimum flow to maintain the growth needs of the corresponding typical fish species during different periods of spring and summer floods.

[0041] (6) For rivers with spring and summer double floods × low development, calculate the appropriate ecological flow as the target for river ecological water demand; among which, the appropriate ecological flow includes the ecological base flow to maintain the basic shape of the river and the appropriate flow to maintain the growth needs of the corresponding typical fish species during different periods of spring and summer floods.

[0042] The minimum and suitable flow rates required to maintain the growth of typical fish species during different periods of the spring and summer flood seasons were calculated using the habitat simulation method.

[0043] The beneficial effects of this invention are as follows: The method described in this invention scientifically divides and classifies rivers in the study area by considering the differences in natural conditions and human development and utilization, and rationally determines the ecological protection objects of rivers. It proposes an ecological water demand classification system that includes minimum ecological flow and suitable ecological flow, which effectively takes into account the water demand of river ecological environment and economic and social development, objectively reflects the real condition of rivers, helps to implement ecological water demand, and provides technical support for river ecological water demand management and protection.

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the river zoning, classification, and grading process in the study area of ​​this invention;

[0046] Figure 2 This is a map showing the Yellow River basin water system and the location of Lijin, a representative cross-section, in Example 1;

[0047] Figure 3 This is a schematic diagram of the water resource development and utilization rate in the Yellow River Basin from 2020 to 2024, as shown in Example 1.

[0048] Figure 4 This is a graph showing the relationship between the Yellow River carp's flood season flow and habitat area, as shown in Example 1.

[0049] Figure 5 This is a schematic diagram of the ecological water demand process of the Yellow River in Example 1. Detailed Implementation

[0050] This invention discloses a method for calculating river ecological water demand targets based on regional classification and grading, such as... Figure 1 As shown, the method includes the following steps:

[0051] Step 1: Data Collection for the Study Area: Collect daily precipitation data (generally over 30 years) and daily measured runoff and monthly natural runoff data for representative river sections in the study area by consulting hydrological yearbooks and river hydrological data. Specifically, based on the distribution of river ecological protection objects, select river sections with long-term (over 30 years) measured runoff data as representative river sections within the distribution areas of these objects. Additionally, collect water resource quantity and water consumption data for the study area's rivers over several years (generally over 5 years) by consulting water resource bulletins.

[0052] Step 2: Zoning the Rivers in the Study Area: Considering the maintenance of climatic, geographical, and water system integrity, the rivers in the study area are zoned using water resource zoning methods to facilitate the rational determination of ecological protection targets and the unified management of river ecological water demand objectives. Currently, a relatively mature and widely accepted water resource zoning system has been established nationwide, including 10 primary water resource zones, 80 secondary water resource zones, and 210 tertiary water resource zones. Some counties and cities have further divided the area into several quaternary water resource zones based on their own water resource management practices. Each water resource zone has basically consistent natural resources, socio-economic conditions, and river development and utilization conditions. Therefore, this study chooses to conduct a zoning study on river ecological baseflow targets based on existing water resource zoning results.

[0053] Step 3: Classify the rivers in the study area: Based on the runoff supply type and water inflow process, the rivers are classified into three types: no-flood type, summer-flood type, and spring-summer dual-flood type.

[0054] Rivers with no flood season are primarily fed by groundwater or have evenly distributed rainfall throughout the year, resulting in gradual changes in runoff over time. The criteria for determining this type are: based on the river's multi-year average daily runoff, if there are no significant flood events lasting more than three consecutive days, the river is considered a river with no flood season. A significant flood is defined as a daily flow increasing by more than 50% compared to the previous day's flow. Rivers with summer floods are primarily fed by summer rainfall or glacial meltwater, with runoff concentrated in summer (June to September). The criteria for determining this type are: based on the river's multi-year average daily runoff, if floods with a return period of 5 years or more occur concentrated in June to September, the river is considered a summer flood river. Rivers with both spring and summer floods are fed by both spring snowmelt and summer rainfall, with flood events occurring in spring (March to April) and summer (June to September). The criteria for determining this type are: based on the river's multi-year average daily runoff, if floods with a return period of 5 years or more occur in both spring (March to April) and summer (June to September), the river is considered a spring and summer double-flood river.

[0055] Based on historical water resource volume and water consumption data collected from the study area over many years, the average water resource development and utilization rate of the rivers was calculated. Rivers were further classified into two types—highly developed rivers and lowly developed rivers—based on whether the average water resource development and utilization rate exceeded 40%. Specifically, rivers with an average water resource development and utilization rate > 40% were classified as highly developed rivers, while those with an average rate ≤ 40% were classified as lowly developed rivers.

[0056] Taking into account the river's replenishment type, inflow process, and degree of water resource development and utilization, rivers are ultimately classified into six types: flood-free × high-development rivers, flood-free × low-development rivers, summer flood × high-development rivers, summer flood × low-development rivers, spring and summer double flood × high-development rivers, and spring and summer double flood × low-development rivers.

[0057] Step 4: Identify ecological protection targets: Investigate the water supply and demand relationship between rivers and riparian vegetation, lakes and wetlands in different zones, and select riparian vegetation and lake wetlands that are sensitive to changes in water volume and have high ecological function importance as ecological protection targets. These include native riparian tree and shrub communities that rely on groundwater or periodic river flooding (such as river valley forests), wetland vegetation communities with hydrological indicators (such as reed marshes and sedge wetlands), and seasonal lake wetlands that provide important habitats for migratory waterbirds. Investigate the aquatic biological communities and species in rivers in different zones, select fish as indicator species, and select typical fish as ecological protection targets, including rare and endemic fish of various levels, migratory fish that need specific spawning grounds, feeding grounds or overwintering grounds to complete their life history, and sensitive fish that have special requirements for dissolved oxygen and water temperature.

[0058] Step 5: Calculation of Ecological Water Demand Targets by Category: For highly developed rivers, calculate the minimum ecological flow as the river's ecological water demand target. For less developed rivers, calculate the appropriate ecological flow as the river's ecological water demand target. Furthermore, based on the six river types, the calculation of river ecological water demand targets is further refined.

[0059] (1) For flood-free × high-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the flow required to maintain the minimum riparian vegetation area and the minimum lake wetland area.

[0060] Among them, the Qp method is used to calculate the ecological base flow: based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence (referred to as "natural Q90 monthly average flow") is calculated as the ecological base flow.

[0061] The ecological flow required to maintain the minimum riparian vegetation area and the minimum lake wetland area is calculated using the area quota method, as follows:

[0062] (1)

[0063] In the formula, The ecological flow required to maintain the minimum riparian vegetation area and the minimum lake and wetland area is m³ / s; n is the number of ecological protection objects. Let hm be the minimum area of ​​the i-th ecological protection object (riparian vegetation, lake wetland). 2 ; For the ecological water demand quota of the i-th ecological protection object, m 3 / hm 2 ;T i Let s be the ecological water demand time for the i-th ecological protection object.

[0064] Among them, the historical comparison method was used to determine the minimum area of ​​riparian vegetation and lake wetlands. Specifically, land use remote sensing image data from the 1980s and 1990s were collected to determine the annual average area of ​​riparian vegetation and lake wetland, and 50% of this average (based on previous research experience) was taken as the minimum area of ​​riparian vegetation and lake wetlands.

[0065] (2) For flood-free × low-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the flow required to maintain a suitable riparian vegetation area and a suitable lake and wetland area.

[0066] Ecological base current is calculated using the Qp method: Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0067] The ecological flow required to maintain suitable riparian vegetation area and suitable lake and wetland area is calculated using the area quota method. The calculation formula is as follows:

[0068] (2)

[0069] In the formula, The ecological flow required to maintain a suitable riparian vegetation area and a suitable lake and wetland area is m³ / s; n is the number of ecological protection objects. Let hm be the suitable area for the i-th ecological protection object (riparian vegetation, lake wetland). 2 ; For the ecological water demand quota of the i-th ecological protection object, m 3 / hm 2 ;T i Let s be the ecological water demand time for the i-th ecological protection object.

[0070] The suitable areas for riparian vegetation and lake wetlands were determined using a historical comparison method. Land use remote sensing imagery data from the 1980s and 1990s were collected to determine the annual average area of ​​riparian vegetation and lake wetlands, which were then used as the suitable areas for riparian vegetation and lake wetlands.

[0071] (3) For summer flood type × high development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the minimum flow to maintain the growth needs of typical fish during the summer flood season.

[0072] Ecological base current is calculated using the Qp method: Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0073] The minimum flow required to sustain the growth of typical fish species during the summer flood season was calculated using habitat simulation. The calculation process is as follows:

[0074] ① Investigate research findings related to the growth of typical fish species or conduct field observations to clarify the range of water depth and flow velocity requirements of these fish species during the flood season;

[0075] ② Determine the river section to be studied, establish a two-dimensional hydraulic model of the river section, simulate the hydraulic conditions of the study area, and obtain the water depth and velocity distribution of the river section under different flow rates;

[0076] ③ Statistically determine the area where the water depth and flow velocity meet the needs of typical fish species under different flow rates as the fish habitat area, and establish a curve showing the relationship between flow rate and habitat area.

[0077] ④ The minimum flow rate is defined as the flow rate corresponding to when the habitat area reaches 40% of the peak area (based on previous research experience).

[0078] (4) For summer flood type × low development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the appropriate flow to maintain the growth needs of typical fish during the summer flood season.

[0079] Ecological base current is calculated using the Qp method: Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural dry month runoff sequence is calculated as the ecological base current.

[0080] Similarly, the habitat simulation method was used to calculate the appropriate flow rate to maintain the growth needs of typical fish species during the summer flood season. Steps ① to ③ of the calculation process were the same as those described above. The difference was that in step ④, the flow rate corresponding to when the habitat area reached 60% of the peak area (based on previous research experience) was taken as the appropriate flow rate.

[0081] (5) For rivers with spring and summer double floods and high development, calculate the minimum ecological flow as the target for river ecological water demand. The minimum ecological flow includes the ecological base flow to maintain the basic shape of the river and the minimum flow to maintain the growth needs of the corresponding typical fish species during different periods of spring and summer floods.

[0082] (6) For rivers with spring and summer double floods and low development, calculate the appropriate ecological flow as the target for the river's ecological water demand. The appropriate ecological flow includes the ecological base flow to maintain the basic shape of the river and the appropriate flow to maintain the growth needs of the corresponding typical fish species during different periods of the spring and summer floods.

[0083] The minimum and suitable flow rates required to maintain the growth of typical fish species during different periods of the spring and summer floods were calculated using the habitat simulation method, and the calculation process was the same as above.

[0084] Example 1

[0085] This embodiment is a specific application example of the above method.

[0086] This embodiment addresses the needs of ecological protection and high-quality development in the Yellow River Basin. It selects the Yellow River Basin as the study area and uses the Lijin section, the control section at the Yellow River outlet, as the representative section to perform regional, categorized, and graded ecological water demand calculations.

[0087] The Yellow River is one of the ten first-level water resource zones, and is a core area for national economic and social development and a key area for river health restoration. Figure 2 As shown. Daily measured runoff and monthly natural runoff data for the Lijin section of the Yellow River from 1980 to 2024 were collected. The flood occurrence process was calculated, and it was determined to be a summer flood type river. The water resource development and utilization rate of the Yellow River basin from 2020 to 2024 was calculated, with an average of 69.3%, far exceeding 40%, thus classifying it as a highly developed river. Figure 3 As shown. The ecological water demand of the Yellow River is calculated based on a comprehensive assessment, categorized as a summer flood season × a high-development river.

[0088] According to aquatic life survey data from the lower reaches of the Yellow River, the Yellow River carp has been overfished, resulting in a continuous decline in its population and a severe shortage of replacement populations. Individuals are also showing significant signs of miniaturization and premature aging. Considering its native species status, ecological value, endangered status, and economic value, the carp was selected as a typical fish species for assessing the ecological water demand of the lower Yellow River section.

[0089] Determination of ecological water demand classification at the Lijin section of the Yellow River:

[0090] (1) According to the fact that the Yellow River is a summer flood type × high development river, the ecological water demand is calculated based on the minimum ecological flow. Among them, the minimum ecological flow includes the ecological base flow and the minimum flow required for carp to grow during the summer flood season.

[0091] (2) Based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency of the annual dry month runoff sequence was calculated using the Qp method as the ecological base flow. The calculated ecological base flow at the Lijin section of the Yellow River is 246 m³ / s.

[0092] (3) Hydrodynamic simulation was conducted on an 18km stretch of the Yellow River upstream and downstream of the Lijin section. A curve showing the relationship between the suitable habitat area and flow rate for carp was plotted. The flow rate corresponding to when the habitat area reaches 40% of its peak area was determined. Figure 4 As shown. Calculations show that the minimum flow rate at the Lijin section of the Yellow River during the flood season should reach 620 m³ / s.

[0093] (4) In summary, the ecological water demand of the Lijin section of the Yellow River is determined to be 246 m³ / s from October to May and 620 m³ / s from June to September. Figure 5 As shown.

[0094] Finally, it should be noted that the above description is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for calculating river ecological water demand targets based on regional classification and grading, characterized in that, The method includes the following steps: Step 1: Collect data for the study area: Collect daily precipitation data for many years in the study area, daily measured runoff and monthly natural runoff data of representative cross sections of rivers in the study area; collect water resources and water consumption data of rivers in the study area for many years in history; Step 2: Divide the rivers in the study area into zones: Considering the need to maintain the integrity of the climate, geography and water system, the rivers in the study area are divided into zones using the water resource zoning method; Step 3: Classify the rivers in the study area: Based on runoff recharge type and water inflow process, the rivers are divided into three types: no-flood type, summer-flood type, and spring-summer dual-flood type. Based on the collected water resource volume and water consumption data of the rivers in the study area, the average water resource development and utilization rate of the rivers is calculated, and the rivers are further divided into two types: high-development rivers and low-development rivers. Finally, the rivers are classified into six types: no-flood type × high-development river, no-flood type × low-development river, summer-flood type × high-development river, summer-flood type × low-development river, spring-summer dual-flood type × high-development river, and spring-summer dual-flood type × low-development river. Step 4: Determine the ecological protection targets: Investigate the water supply and demand relationship between rivers and riparian vegetation, lakes and wetlands in different zones, and determine the types of riparian vegetation and lake wetlands that are ecological protection targets; Investigate the aquatic biological communities and species of rivers in different zones, select fish as indicator species, and determine the typical fish types that are ecological protection targets. Step 5: Calculation of Ecological Water Demand Targets by Category: For highly developed rivers, calculate the minimum ecological flow as the river's ecological water demand target; for less developed rivers, calculate the appropriate ecological flow as the river's ecological water demand target; calculate the river's ecological water demand target according to the six river types: For flood-free × highly developed rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the flow required to maintain the minimum riparian vegetation area and the minimum lake and wetland area. For flood-free × low-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic shape of the river and the flow required to maintain a suitable riparian vegetation area and a suitable lake and wetland area. For summer flood-type × high-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic morphology of the river and the minimum flow to maintain the growth requirements of typical fish species during the summer flood season. For summer flood-type × low-development rivers, the ecological water demand targets include the ecological base flow to maintain the basic morphology of the river and the appropriate flow to maintain the growth needs of typical fish species during the summer flood season. For rivers with spring and summer double floods and high development, the minimum ecological flow is calculated as the target for the river's ecological water demand. The minimum ecological flow includes the ecological base flow to maintain the basic shape of the river and the minimum flow to maintain the growth needs of typical fish species during different periods of the spring and summer floods. For rivers with spring and summer double floods and low development, the appropriate ecological flow is calculated as the target for the river's ecological water demand. The appropriate ecological flow includes the ecological base flow to maintain the basic shape of the river and the appropriate flow to maintain the growth needs of typical fish species during different periods of the spring and summer floods.

2. The method for calculating river ecological water demand targets by region, category, and grade according to claim 1, characterized in that, The selection criteria for the representative river section in step 1 are as follows: based on the distribution of the ecological protection objects of the river, select the section with a long series of measured runoff data within the river section where the ecological protection objects are distributed as the representative river section.

3. The method for calculating river ecological water demand targets by region, classification, and grading according to claim 1, characterized in that, The method of dividing the rivers in the study area into zones based on water resources zoning in step 2 is as follows: the zones are divided according to the national water resources zoning system, including 10 primary water resources zones, 80 secondary water resources zones, and 210 tertiary water resources zones.

4. The method for calculating river ecological water demand targets by region, classification, and grading according to claim 1, characterized in that, The specific process for classifying rivers into three types—no-flood, summer-flood, and spring-summer dual-flood—based on runoff supply type and inflow process, as described in step 3, is as follows: The criteria for determining a no-flood river are: based on the river's multi-year average daily runoff process, if there is no significant rise in water level for more than three consecutive days, the river is considered a no-flood river; if the daily flow increases by more than 50% relative to the previous day's flow, the river is considered to have experienced a significant rise in water level. The criteria for determining a summer-flood river are: based on the river's multi-year average daily runoff process, if floods with a recurrence period of 5 years or more occur concentrated in the summer months (June to September), the river is considered a summer-flood river. The criteria for determining a spring-summer dual-flood river are: based on the river's multi-year average daily runoff process, if floods with a recurrence period of 5 years or more occur in both the spring months (March to April) and the summer months (June to September), the river is considered a spring-summer dual-flood river. The specific process of further classifying rivers into two types, high-development rivers and low-development rivers, is as follows: when the average water resource development and utilization rate of a river is >40%, it is classified as a high-development river; when the average water resource development and utilization rate of a river is ≤40%, it is classified as a low-development river.

5. The method for calculating river ecological water demand targets by region, classification, and grading according to claim 1, characterized in that, The types of riparian vegetation and lake wetlands described in step 4 as ecological protection objects include native riparian tree and shrub communities that rely on groundwater or periodic river flooding, wetland vegetation communities that serve as hydrological indicators, and seasonal lake wetlands that provide important habitats for migratory waterbirds; the typical fish types described as ecological protection objects include rare and endemic fish species at various levels, migratory fish species that require spawning grounds, feeding grounds, or overwintering grounds to complete their life cycle, and sensitive fish species that have requirements for dissolved oxygen and water temperature.

6. The method for calculating river ecological water demand targets by region, classification, and grading according to claim 1, characterized in that, In step 5, for flood-free × high-development rivers, the ecological base flow is calculated using the Qp method. Specifically, based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural driest month runoff sequence is calculated as the ecological base flow. The ecological flow required to maintain the minimum riparian vegetation area and the minimum lake wetland area is calculated using the area quota method, as follows: In the formula, The ecological flow required to maintain the minimum riparian vegetation area and the minimum lake and wetland area is m³ / s; n is the number of ecological protection objects. Let hm be the minimum area of ​​the i-th ecological protection target, namely riparian vegetation and lake wetlands. 2 ; For the ecological water demand quota of the i-th ecological protection object, m 3 / hm 2 ; Let be the ecological water demand time for the i-th ecological protection object, in seconds; Among them, the historical comparison method was used to determine the minimum area of ​​riparian vegetation and lake wetlands. Specifically, land use remote sensing image data from the 1980s and 1990s were collected to determine the annual average area of ​​riparian vegetation and lake wetlands, and 50% of this average was taken as the minimum area of ​​riparian vegetation and lake wetlands. For flood-free × low-development rivers, the Qp method is used to calculate the ecological base flow: based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural driest month runoff sequence is calculated as the ecological base flow. The ecological flow required to maintain suitable riparian vegetation area and suitable lake and wetland area is calculated using the area quota method. The calculation formula is as follows: In the formula, The ecological flow required to maintain a suitable riparian vegetation area and a suitable lake and wetland area is m³ / s; n is the number of ecological protection objects. Let hm be the suitable area of ​​the i-th ecological protection target, namely riparian vegetation and lake wetlands. 2 ; For the ecological water demand quota of the i-th ecological protection object, m 3 / hm 2 ; Let be the ecological water demand time for the i-th ecological protection object, in seconds; The suitable area of ​​riparian vegetation and lake wetlands was determined by using the historical comparison method. Specifically, land use remote sensing image data from the 1980s and 1990s were collected to determine the annual average area of ​​riparian vegetation and lake wetlands, which were then used as the suitable area of ​​riparian vegetation and lake wetlands. For summer flood type × high development rivers, the Qp method is used to calculate the ecological base flow: based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural driest month runoff sequence is calculated as the ecological base flow. The minimum flow required to sustain the growth of typical fish species during the summer flood season was calculated using habitat simulation. The calculation process is as follows: ① Investigate research findings related to the growth of typical fish species or conduct field observations to clarify the range of water depth and flow velocity requirements of these fish species during the flood season; ② Determine the river section to be studied, establish a two-dimensional hydraulic model of the river section, simulate the hydraulic conditions of the study area, and obtain the water depth and velocity distribution of the river section under different flow rates; ③Statistically determine the area where the water depth and flow velocity meet the needs of typical fish under different flow rates as the fish habitat area, and establish a curve showing the relationship between flow rate and habitat area. ④The flow rate corresponding to when the habitat area reaches 40% of the peak area is taken as the minimum flow rate; For summer flood type × low development rivers, the Qp method is used to calculate the ecological base flow: based on the collected monthly natural runoff data of representative river sections, the monthly average flow at 90% frequency in the annual natural driest month runoff sequence is calculated as the ecological base flow. Similarly, the habitat simulation method is used to calculate the appropriate flow rate to maintain the growth requirements of typical fish species during the summer flood season. Steps ① to ③ of the calculation process are the same as those described above. The difference is that in step ④, the flow rate corresponding to when the habitat area reaches 60% of the peak area is taken as the appropriate flow rate. For both spring-summer dual-flood type × high-development rivers and spring-summer dual-flood type × low-development rivers, the minimum and suitable flow rates required to maintain the growth of corresponding typical fish species during different periods of the spring and summer floods are calculated using the habitat simulation method.

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