Sponge green land rainwater interception method based on local garden plants

Abstract

The present application relates to the technical field of sponge city construction, and in particular to a sponge green land rainwater interception method based on native garden plants, which comprises the following steps: screening native arbor, shrub, grass and vine compound communities suitable for different regional hydrological conditions and performing three-dimensional configuration; designing multi-stage ecological interception units coordinated with the root system distribution of the plant community; constructing a native plant-microorganism synergistic purification module; and setting a rainwater circulation regulation and control system based on real-time hydrological data. The present application utilizes the strong adaptability and ecological advantages of native plants, combined with targeted engineering design, to increase the rainwater interception rate by 35%-50%, and the COD removal rate of purified rainwater is more than 60%, while reducing the construction and operation and maintenance costs, improving the regional ecological stability, and being suitable for urban parks, residential areas, road green spaces and other scenes in different climate zones, and having significant economic, ecological and social benefits.

Description

Technical Field

[0001] This invention relates to the technical fields of sponge city construction, urban water system safety assurance, and nature-based solutions, specifically a sponge green space rainwater interception and retention method based on native garden plants. Background Technology

[0002] With the acceleration of urbanization, the area of ​​urban hard surface coverage is constantly increasing, leading to a significant increase in rainwater runoff and making problems such as urban flooding, water shortage, and water environment deterioration increasingly prominent. Sponge city construction is an effective way to solve these problems. Its core is to build a rainwater management system that integrates infiltration, retention, storage, purification, utilization, and drainage. Sponge green space, as an important component of sponge cities, has multiple functions such as rainwater interception, purification, and water conservation.

[0003] Currently, sponge green space rainwater interception technology mostly adopts a combination of engineering measures and plant configuration. However, existing technologies have many key shortcomings, and the related technical points are mostly isolated, failing to form a systematic and collaborative design. First, the plant selection and engineering structure lack compatibility. Existing technologies either use exotic plants with poor adaptability, or although they mention the selection of native plants, they do not optimize the engineering structure parameters according to the root growth characteristics of native plants. As a result, the plant roots cannot fully play their role in soil fixation and infiltration, and the engineering structure may also restrict plant growth, ultimately resulting in unstable rainwater retention effect. Second, the design of the cascade interception system is crude. Although the existing technology discloses the layout ideas of multi-stage treatment facilities, it does not take into account the interception and buffering characteristics of native plants in the design of facility size, materials and arrangement. As a result, the rainwater retention time is short and the infiltration efficiency is not high. Third, the purification modules are not targeted enough. The "plant-microbe synergy" mentioned in the existing technology is mostly a generalized description. It does not screen specific microbial combinations that coexist with the roots of native plants, nor does it specify inoculation parameters, resulting in limited rainwater purification effect and water quality that is difficult to meet the requirements for reuse. Fourth, the control system has a single function. Existing intelligent control systems mostly target only the single parameter of water level and have not achieved dual closed-loop dynamic control of water level and water quality. This can easily lead to problems such as overflow waste, insufficient water storage, or substandard reuse of rainwater. Fifth, the ecological advantages of native plants have not been fully explored. Existing technologies have not formed a complete collaborative system of "native plants - engineering facilities - microorganisms - intelligent regulation", which makes it impossible to give full play to the core advantages of native plants, such as strong stress resistance and good compatibility with local ecosystems, resulting in high operation and maintenance costs and limited applicability.

[0004] For example, existing sponge city green space rainwater harvesting systems use vegetated swales, water storage ponds, and introduced turfgrass. Due to the poor adaptability of the plants and the lack of coordinated design with the project, the interception and purification effects are not ideal. Although some ecological retention ditch systems use a combination of substrate layer and plants, the substrate layer formula is not adapted to the root system of native plants and there is no targeted microbial synergy module, resulting in large fluctuations in treatment effect.

[0005] Native garden plants are plant groups that have adapted to local climate, soil, and hydrological conditions through long-term natural selection. They possess advantages such as flood tolerance, drought tolerance, strong resistance to diseases and pests, and ease of maintenance. Furthermore, their extensive root systems effectively improve soil permeability and enhance soil stabilization, while simultaneously forming a stable synergistic purification system with local microorganisms. Therefore, developing an integrated sponge green space rainwater interception and retention method centered on native garden plants, integrating engineering adaptation, microbial synergy, and dual-parameter control of water level and water quality, to achieve efficient rainwater interception, deep purification, and resource utilization, is of great significance for overcoming existing technological limitations and improving the ecological function and economic benefits of sponge green spaces. Summary of the Invention

[0006] To address the problems of poor plant adaptability, insufficient synergy between engineering and plants, limited rainwater purification effect, low precision of regulation, and low utilization rate of native plants in existing sponge green space rainwater interception and storage technologies, this invention provides a sponge green space rainwater interception and storage method based on native garden plants. Through an integrated technical solution of stratified configuration of native plant communities, multi-level engineering interception, tiered rainwater purification, and cyclic regulation, this method achieves efficient rainwater interception, deep purification, and resource utilization, thereby improving the ecological stability and economic benefits of urban sponge green spaces and reducing construction and operation and maintenance costs.

[0007] The technical solution adopted by this invention to solve its technical problem is: a sponge green space rainwater interception and retention method based on native garden plants, comprising the following steps: (1) Screening and three-dimensional configuration of native plant communities: Based on the climate type and soil hydrological conditions of the target area, select native trees, shrubs, herbs and vines that are resistant to waterlogging and drought and have well-developed root systems to construct a composite community with an upper tree shade layer, a middle shrub buffer layer, a lower herb cover layer and a vine climbing layer. Among them, native tree species with a diameter at breast height of 8-15cm are selected for trees, the spacing between shrubs is 0.8-1.5m, the herb coverage rate is not less than 90%, and the vines are arranged to climb along the structure of the water retention project. (2) Construction of multi-level ecological interception and storage units: Ecological retention ditch, infiltration pond, and grassed ditch-storage pond combination unit are set up in sequence along the direction of rainwater runoff. The bottom of the ecological retention ditch is covered with a modified substrate layer with a thickness of 30-50cm that is compatible with the root system of native herbs. The infiltration pond is set with a porous infiltration medium column that works in synergy with the root system of shrubs. The slope of the bottom of the grassed ditch is controlled at 1%-3%. The end is connected to the storage pond. The inner wall of the storage pond is covered with an ecological coating and planted with aquatic native plants. (3) Construction of native plant-microorganism synergistic purification module: Inoculate functional microbial agents that coexist with the roots of native plants in ecological retention ditches and infiltration ponds to form a synergistic purification system of plant roots and microbial film; (4) Rainwater circulation regulation: A water level sensor and a water quality monitoring device are installed in the water storage tank. Based on the real-time monitoring of water level and water quality data, the purified rainwater is recycled for green space irrigation or landscape water replenishment through a variable frequency pump. When the rainfall exceeds the storage capacity, the excess rainwater is introduced into the urban rainwater pipe network through the overflow pipe.

[0008] Specifically, the native trees mentioned in step (1) are selected from at least one of the following: Chinese tallow tree, weeping willow, and hackberry; the native shrubs are selected from at least one of the following: purple locust, willow, weigela, and dwarf hyacinth; the native herbs are selected from at least one of the following: bermudagrass, zoysia, miscanthus, and calamus; and the native vines are selected from at least one of the following: wisteria, trumpet creeper, and Virginia creeper.

[0009] Specifically, the cross-section of the ecological retention ditch is an inverted trapezoid, with an upper opening width of 1.5-2.5m, a lower opening width of 0.8-1.2m, a depth of 0.6-1.0m, and a ditch wall slope of 1:1.5-1:2.0.

[0010] Specifically, the improved substrate layer in step (2) is made of garden soil, leaf mold, river sand and biochar in a mass ratio of 4:3:2:1, wherein the biochar particle size is 2-5mm, and a permeable pipe network is pre-buried in the substrate layer with a permeable pipe spacing of 50-80cm.

[0011] Specifically, the porous permeable medium column mentioned in step (2) is made by mixing and pressing ceramsite, zeolite, and volcanic rock in a volume ratio of 3:2:1. The column has a diameter of 15-20cm, a height of 60-80cm, and a spacing of 1.2-1.8m. The column surface has through holes with a diameter of 2-3cm, and the through hole density is 4-6 holes / dm³. 2 .

[0012] Specifically, the functional microbial agent mentioned in step (3) includes Bacillus subtilis, Pseudomonas, and nitrifying bacteria, with a bacterial count ratio of 2:2:1, and an inoculation amount of 100-200 mL / m³. 2 Inoculation should be performed 15-20 days after the native plants are planted.

[0013] Specifically, the water level sensor in step (4) is set with three monitoring thresholds: high, medium, and low. The high threshold is 80% of the water storage tank volume, the medium threshold is 50%, and the low threshold is 20%. When the water level reaches the high threshold, the overflow device is activated; when it reaches the medium threshold, the recharge system is activated; when it reaches the low threshold, the recharge is stopped and the water replenishment device is activated. When the water quality monitoring data does not meet the standards, the circulating pump is activated to send the rainwater to the ecological retention ditch for secondary purification.

[0014] Specifically, the effective volume of the reservoir is 50-200 m³. 3 A water collection pit with a slope of 0.5%-1.0% is set at the bottom of the pool, and a sewage pipe is installed in the water collection pit.

[0015] Specifically, the native herbaceous plants planted in the grassed swales are controlled to be 20-40cm in height and are planted in strips at intervals along the direction of water flow, with a width of 0.5-1.0m.

[0016] Specifically, it also includes post-operation and maintenance steps: pruning and pest and disease control of native plants every quarter, testing and replacing the improved substrate layer and porous permeable medium column once a year, and regularly cleaning the sediment in the interception unit.

[0017] The beneficial effects of this invention are: Native plants and engineering structures work in synergy to significantly improve the stability and efficiency of rainwater retention: This invention selects native plants suitable for the target area and optimizes the structural parameters of multi-level retention units (such as substrate layer ratio, medium column size, and ditch slope) to achieve deep synergy between plant roots and engineering structures. This provides a favorable environment for plant growth while enhancing the retention effect of the engineering structure through root stabilization and infiltration. Rainwater retention rate is increased by 35%-50%, a significant improvement over existing isolated retention technologies. Furthermore, the survival rate of native plants reaches over 92%, avoiding the problem of easy death of introduced plants and ensuring long-term stable operation of the system.

[0018] Precise and synergistic purification significantly improves the quality of rainwater reuse: This invention selects specific functional microbial agents that coexist with the roots of native plants, clearly defining the combination ratio, inoculation amount, and inoculation timing of the agents to form a precise and synergistic purification system of "plant roots-microbial film," specifically removing pollutants such as COD, nitrogen, and phosphorus from rainwater. The COD removal rate reaches over 60%, the ammonia nitrogen removal rate over 55%, and the total phosphorus removal rate over 50%. The purified rainwater quality stably meets the reclaimed water reuse requirements of GB50014-2021 "Outdoor Drainage Design Standard," improving the purification effect by 25%-30% compared to existing generalized synergistic purification technologies.

[0019] This invention innovatively employs a dual closed-loop system of "three-threshold water level control + dynamic water quality feedback" to achieve efficient rainwater resource utilization. This system avoids overflow waste or insufficient water storage caused by single water level control, and ensures the quality of reused rainwater through a secondary purification mechanism when water quality fails to meet standards. The rainwater resource utilization rate can meet 30%-50% of the irrigation or landscape water replenishment needs of sponge green spaces, improving resource utilization by 20%-30% compared to existing intelligent control technologies.

[0020] The end-to-end collaborative design reduces operation and maintenance costs and expands the scope of application: The end-to-end collaborative system of "native plants - engineering facilities - microorganisms - intelligent regulation - post-operation and maintenance" constructed by this invention eliminates the need for frequent replanting of seedlings, spraying of chemical pesticides, or replacement of engineering components, reducing operation and maintenance costs by 45%-55%. At the same time, through targeted plant selection and parameter optimization, it can be adapted to different climate zones such as subtropical humid areas, temperate semi-humid areas, and arid and semi-arid areas, as well as various scenarios such as urban parks, residential areas, and roadside green spaces, with an applicability far exceeding that of existing sponge green space technologies that are targeted at a single area.

[0021] The invention unifies ecological and landscape values, enhancing regional ecological stability: The composite community of trees, shrubs, grasses, and vines constructed in this invention not only provides excellent landscape effects but also enriches the plant diversity of urban green spaces, provides habitats for local insects and birds, and strengthens the self-regulating capacity of the regional ecosystem. Compared to existing sponge green spaces with single plant configurations, this invention significantly improves ecological stability, achieving a unified triple value of stormwater management, water purification, and ecological restoration. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 The flowchart of the sponge green space rainwater interception method based on native garden plants provided by the present invention. Detailed Implementation

[0024] To make the technical solutions, technical features, objectives and effects of the present invention easier to understand, the present invention will be further described below in conjunction with specific embodiments.

[0025] like Figure 1 As shown, the sponge green space rainwater retention method based on native garden plants of the present invention includes the following specific steps: 1. Screening and three-dimensional configuration of native plant communities First, a comprehensive survey was conducted on the target area's climate type (e.g., subtropical, temperate, arid and semi-arid), soil physicochemical properties (pH value, organic matter content, permeability, water retention, etc.), and hydrological conditions (annual rainfall, rainfall intensity, groundwater level, runoff pathways, etc.). Based on the survey results, native plants with flood and drought tolerance, well-developed root systems, strong soil-fixing capabilities, and landscape value were selected, specifically including native trees, shrubs, herbs, and vines. Among them, the trees selected should be deep-rooted species such as maple, tallow tree, weeping willow, and hackberry, with a diameter at breast height of 8-15cm to ensure that their roots can penetrate deep into the soil and enhance soil permeability; the shrubs selected should be clump-forming species such as Amorpha fruticosa, willow, weigela, and Clerodendrum trichotomum, with a spacing of 0.8-1.5m to form a middle buffer zone to intercept some rainwater runoff; the herbaceous plants selected should be creeping or clump-forming herbs such as Bermuda grass, Zoysia japonica, Miscanthus sinensis, and Acorus calamus, with a coverage rate of not less than 90% to cover the ground surface and reduce rainwater erosion; the vines selected should be climbing plants such as wisteria, trumpet creeper, and Virginia creeper, which should be arranged to climb along the interception structure (such as ditch walls, pool walls, overflow pipe supports, etc.) to enhance the stability of the structure and at the same time use their root systems to enhance soil permeability.

[0026] In terms of configuration, a three-dimensional composite configuration mode is adopted, consisting of an upper layer of tree shade, a middle layer of shrub buffer, a lower layer of herbaceous cover, and a vine climbing layer. Trees are planted upstream of rainwater runoff and around the interception project to form a shade layer and reduce surface evaporation; shrubs are planted on both sides and the bottom edge of the ecological retention ditch and grassed ditch; herbaceous plants fully cover the surface of the interception unit and the substrate layer; vines are planted along the walls of the ecological retention ditch, the walls of the reservoir, and the overflow pipe supports to achieve multi-layer interception and buffering of rainwater runoff by the plant community.

[0027] 2. Construction of multi-level ecological water retention units Along the direction of rainwater runoff, ecological retention ditches, infiltration ponds, and grassed swales-reservoir combination units are set up in sequence to form a multi-level interception and storage system, which gradually slows down the rainwater flow rate and increases the rainwater infiltration and retention time.

[0028] (1) Ecological retention ditch: Located at the starting point of rainwater runoff, with an inverted trapezoidal cross-section, 1.5-2.5m wide at the top, 0.8-1.2m wide at the bottom, and 0.6-1.0m deep. The slope of the ditch wall is 1:1.5-1:2.0 to ensure that rainwater can flow in smoothly and that the ditch wall is stable. An improved substrate layer with a thickness of 30-50cm is laid at the bottom of the ditch. The improved substrate layer is composed of garden soil, leaf mold, river sand, and biochar in a mass ratio of 4:3:2:1. The biochar has a particle size of 2-5mm and has good adsorption and air permeability. It can adsorb pollutants in rainwater and provide a good environment for the root growth of native herbaceous plants. A permeable pipe network is pre-buried in the substrate layer. The permeable pipes are spaced 50-80cm apart and have a diameter of 50-80mm. Permeable holes with a diameter of 2-3mm are opened on the permeable pipes, and the hole density is 8-10 holes / dm. 2 This is used to quickly drain excess water from the substrate layer, preventing plant roots from rotting due to lack of oxygen. Native herbaceous plants (such as Bermuda grass and Zoysia japonica) are planted in the ecological retention trench, while vines (such as Virginia creeper) are planted on the trench walls.

[0029] (2) Infiltration Pool: Located downstream of the ecological retention ditch, connected to the ecological retention ditch via a diversion channel with a slope of 1%-2%. The infiltration pool is rectangular, 5-10m long, 3-5m wide, and 1.0-1.5m deep. The pool walls are constructed with ecological bricks, with humus filling the brick joints and vines (such as trumpet creeper) planted to reinforce the pool walls. Porous infiltration media columns are installed inside the pool. These columns are made by mixing and pressing ceramsite, zeolite, and volcanic rock in a volume ratio of 3:2:1. The columns have a diameter of 15-20cm, a height of 60-80cm, and a spacing of 1.2-1.8m. Through-holes with a diameter of 2-3cm are opened on the surface of the columns, with a density of 4-6 holes / dm². 2 This facilitates rainwater infiltration and microbial attachment. A 10-15cm thick layer of gravel with a particle size of 5-10mm is laid at the bottom of the infiltration tank to enhance infiltration performance. Native shrubs (such as Amorpha fruticosa and Salix babylonica) and aquatic herbs (such as Acorus calamus) are planted in the infiltration tank. The shrubs are planted between the infiltration medium columns, and the aquatic herbs are planted at the bottom edge of the tank.

[0030] (3) Grass swale-reservoir combination unit: Located downstream of the infiltration pond, the grass swale and the infiltration pond are connected by an overflow weir with a height of 0.5-0.8m to control the water level in the infiltration pond. The slope of the grass swale bottom is controlled at 1%-3%, with a U-shaped cross-section, an upper opening width of 1.2-2.0m, and a depth of 0.4-0.6m. A 5-10cm thick improved substrate layer (with the same formula as the substrate layer of the ecological retention swale) is laid at the bottom of the swale, and native herbaceous plants (such as Miscanthus sinensis) are planted. The herbaceous plants are planted in strips along the direction of water flow, with a width of 0.5-1.0m, to enhance the interception and purification effect of rainwater runoff. The end of the grass swale is connected to a reservoir. The effective volume of the reservoir is determined according to the rainfall and reuse requirements of the target area, ranging from 50-200m³.3 The inner wall of the reservoir is coated with an ecological coating (made from a mixture of cement, humus, and biochar in a mass ratio of 5:3:2) to enhance its adsorption capacity. Native aquatic plants (such as lotus and water lilies) are also planted within the coating. A sump with a slope of 0.5%-1.0% is installed at the bottom of the reservoir, containing a drain pipe to remove sediment from the bottom. A cover plate is installed on the top of the reservoir, with ventilation holes spaced 1-2 meters apart and 10-15 cm in diameter.

[0031] 3. Construction of a Synergistic Purification Module Based on Native Plants and Microorganisms Functional microbial agents that coexist with the roots of native plants are inoculated into ecological retention ditches and infiltration ponds to form a synergistic purification system of "plant roots-microbial film," enhancing the removal of pollutants such as COD, nitrogen, and phosphorus from rainwater. The functional microbial agents include Bacillus subtilis, Pseudomonas, and nitrifying bacteria, with a bacterial count ratio of 2:2:1. Bacillus subtilis secretes extracellular enzymes to decompose organic pollutants; Pseudomonas has a strong pollutant degradation capacity and can remove various toxic and harmful substances; nitrifying bacteria can convert ammonia nitrogen into nitrate nitrogen, achieving nitrogen removal. The inoculation amount is 100-200 mL / m². 2 Inoculation should be performed 15-20 days after the native plants are planted, at which time the plant roots have begun to grow, providing a carrier and nutrients for microorganisms. Inoculation is done by spraying; the inoculant is diluted 10 times and sprayed evenly onto the substrate surface and around the plant roots. After inoculation, the substrate humidity should be maintained at 60%-70% for 7-10 days to promote the formation of a stable microbial film on the root surface.

[0032] 4. Rainwater circulation regulation A water level sensor and a water quality monitoring device are installed in the reservoir. The water level sensor has three monitoring thresholds: high, medium, and low (high threshold is 80% of the reservoir volume, medium threshold is 50%, and low threshold is 20%). The water quality monitoring device monitors indicators such as COD, ammonia nitrogen, and total phosphorus in rainwater in real time. The monitoring data is transmitted to the controller via a data acquisition module. The controller implements intelligent regulation of rainwater circulation based on the monitoring data: when the rainfall is heavy and the water level in the reservoir reaches the high threshold, the controller activates the solenoid valve on the overflow pipe to divert excess rainwater into the urban rainwater pipe network; when the water level drops to the medium threshold, the variable frequency pump is activated to reuse the purified rainwater for green space irrigation or landscape water replenishment through the water supply network; when the water level drops to the low threshold, the recharge is stopped and the water replenishment device (connected to the urban tap water or reclaimed water network) is activated to ensure sufficient water storage in the reservoir; when the water quality monitoring data shows that the pollutant concentration exceeds the reuse standard, the controller activates the circulation pump to pump the rainwater in the reservoir to the ecological retention ditch for secondary purification until the water quality meets the standard.

[0033] 5. Post-maintenance Native plants are pruned and treated for pests and diseases quarterly. Pruned branches are shredded and mixed into the improved substrate layer for resource recycling. Pest and disease control employs biological methods (such as releasing parasitic wasps and spraying biological pesticides) to avoid pollution of the ecological environment by chemical pesticides. The improved substrate layer and porous permeable media columns are tested annually. When the permeability of the substrate layer decreases by more than 30% or the adsorption capacity of the media columns reaches saturation, a portion of the substrate or media column is replaced (replacement ratio is 30%-50%). Sediments within the interception units are cleaned regularly. Ecological retention ditches and vegetated swales are cleaned every six months, while infiltration ponds and reservoirs are cleaned annually. The cleaned sediment is dried, sieved, and then mixed with humus for green space improvement.

[0034] Example

[0035] Example 1: Rainwater interception and retention project in urban parks in subtropical humid regions This example is applied to a city park in a subtropical humid region. The area receives 1200-1500 mm of rainfall annually, concentrated between June and August. The soil type is red soil, with a pH of 5.5-6.5 and an organic matter content of 1.5%-2.5%. The target sponge green space area is 500 m². 2 The demand for rainwater reuse is for irrigation water (average daily water consumption of 5m³). 3 ).

[0036] 1. Screening and three-dimensional configuration of native plant communities Based on the climate and soil conditions of the area, the following native plants were selected: *Pterocarya stenoptera* and *Salix babylonica* (diameter at breast height 10-12 cm) were chosen as trees; *Amorpha fruticosa* and *Weigela florida* (spacing 1.0-1.2 m) were chosen as shrubs; *Cynodon dactylon* and *Zoysia japonica* were chosen as herbs; and *Parthenocissus tricuspidata* and *Campsis grandiflora* were chosen as vines. Planting method: *Pterocarya stenoptera* and *Salix babylonica* were planted upstream of the rainwater runoff and around the ecological retention ditch, with a spacing of 3-4 m, forming an upper shade layer, with a planting quantity of 20 plants; *Amorpha fruticosa* and *Weigela florida* were planted on both sides of the ecological retention ditch and around the infiltration pond, forming a middle buffer zone, with a planting quantity of 50 plants; *Cynodon dactylon* and *Zoysia japonica* were planted throughout the ecological retention ditch, grassed swales, and green space surface, with a mixing ratio of 1:1 and a coverage rate of 95%; *Parthenocissus tricuspidata* and *Campsis grandiflora* were planted along the walls of the ecological retention ditch and the reservoir walls, with a planting density of 0.5 plants / m.

[0037] 2. Construction of multi-level ecological water retention units (1) Ecological retention ditch: Located at the rainwater collection point at the park entrance, with an inverted trapezoidal cross-section, 2.0m wide at the top, 1.0m wide at the bottom, and 0.8m deep, with a slope of 1:1.8. A 40cm thick improved substrate layer (garden soil: leaf mold: river sand: biochar = 4:3:2:1) is laid at the bottom of the ditch, with biochar particles of 3-4mm in diameter. A permeable pipe network is pre-buried in the substrate layer, with a pipe diameter of 65mm, a spacing of 60cm, and permeable holes of 2.5mm in diameter on the permeable pipes, with a hole density of 9 holes / dm. 2 The ecological retention ditch is planted with a mixture of Bermuda grass and Zoysia japonica, and the ditch walls are planted with Virginia creeper.

[0038] (2) Infiltration Pool: Located downstream of the ecological retention ditch, connected by a diversion channel with a slope of 1.5%. The infiltration pool is rectangular, 8m long, 4m wide, and 1.2m deep. The pool walls are constructed of ecological bricks, with humus filling the joints, and planted with trumpet creeper. Porous infiltration media columns are installed inside the pool. The columns are 18cm in diameter, 70cm high, and spaced 1.5m apart. Through-holes with a diameter of 2.5cm are opened on the surface of the columns, with a density of 5 through-holes / dm³. 2 A 12cm thick layer of gravel (6-8mm in diameter) is laid at the bottom of the infiltration pool. Fifteen Amorpha fruticosa plants and 20 clumps of sweet flag are planted inside the infiltration pool. The Amorpha fruticosa plants are planted between the infiltration medium columns, and the sweet flag is planted along the edge of the pool bottom.

[0039] (3) Grassed swale-reservoir combination unit: The grassed swale is located downstream of the infiltration pond and connected by an overflow weir with a height of 0.6m. The grassed swale has a 2% slope at the bottom, a U-shaped cross-section, a top width of 1.6m, and a depth of 0.5m. An 8cm thick improved substrate layer (with the same formula as the ecological retention swale) is laid at the bottom of the swale, and Miscanthus sinensis is planted in strips at intervals along the water flow direction with a width of 0.8m. The end of the grassed swale is connected to a reservoir with an effective volume of 120m³. 3 The inner wall is coated with an ecological coating (cement: humus: biochar = 5:3:2), and planted with lotus (10 plants) and water lilies (15 clumps). The bottom of the reservoir is equipped with a sump pit with a slope of 0.8%, and a DN100 sewage pipe is installed in the sump pit. The top of the reservoir is covered with a reinforced concrete cover plate, with 12cm ventilation holes spaced 1.5m apart.

[0040] 3. Construction of a Synergistic Purification Module Based on Native Plants and Microorganisms The functional microbial agent selected is Bacillus subtilis (1×10⁻⁶ bacteria). 9 CFU / mL), Pseudomonas (bacterial count 1×10⁻⁶) 9 CFU / mL), nitrifying bacteria (1×10⁻⁶) 9 The three components (CFU / mL) were mixed in a volume ratio of 2:2:1. Inoculation was carried out 18 days after the transplanting of native plants, with an inoculation volume of 150 mL / m². 2Dilute the bacterial agent 10 times and spray it evenly onto the surface of the substrate layer in the ecological retention trench and infiltration pond, as well as around the plant roots, using a spraying device. After inoculation, maintain the substrate layer humidity at 65% for 8 consecutive days, and spray water regularly to keep it moist during this period.

[0041] 4. Rainwater circulation regulation A submersible water level sensor (measuring range 0-2m, accuracy 0.01m) and an online water quality monitor (monitoring indicators: COD, ammonia nitrogen, total phosphorus, accuracy 0.1mg / L) are installed in the reservoir. The data acquisition module transmits the monitoring data to the PLC controller. The high water level threshold is set to 96m. 3 (80% of the reservoir volume), with a median threshold of 60m³. 3 (50%), Low threshold is 24m 3 (20%). When rainfall is heavy during the rainy season, the water level in the reservoir reaches 96m. 3 When the water level drops to 60m, the controller activates the solenoid valve on the overflow pipe to direct excess rainwater into the city's stormwater drainage network; when the water level drops to 60m... 3 At that time, start the variable frequency pump (flow rate 5m³ / h). 3 / h), the purified rainwater is transported to the park's green space irrigation system through a PE water transmission network (110mm diameter); when the water level drops to 24m 3 When the pump stops, start the water replenishment device (connected to the city's reclaimed water network) to replenish water to 60m³. 3 When water quality monitoring data shows COD > 50 mg / L, ammonia nitrogen > 5 mg / L, or total phosphorus > 0.5 mg / L, start the circulation pump (flow rate 3 m³ / L). 3 The rainwater is pumped to an ecological retention ditch for secondary purification until the water quality meets the standards ( / h).

[0042] 5. Post-maintenance Plants are pruned quarterly. The pruning height for maple and weeping willow is controlled at 6-8m, for purple locust and weigela at 1.2-1.5m, and for bermudagrass and zoysia at 5-8cm. Pest and disease control involves releasing parasitic wasps (to control aphids) and spraying matrine biological pesticides (to control moth larvae). The improved substrate layer and porous permeable media columns are tested annually in spring. When the permeability of the ecological retention ditch substrate layer decreases by 35%, 40% of the substrate layer is replaced. When the adsorption capacity of the permeable media column reaches saturation (detected by COD adsorption tests), 40% of the media column is replaced. Sediment in the ecological retention ditch and vegetated ditch is cleaned every six months, and sediment in the infiltration pond and reservoir is cleaned annually in winter. The cleaned sediment is dried, sieved, and then mixed with humus at a 1:2 ratio for park green space improvement.

[0043] After one year of operation, the monitoring results of this embodiment showed that the rainwater retention rate reached 48%, which is 42% higher than that of traditional sponge green space; the COD removal rate of the purified rainwater reached 68%, the ammonia nitrogen removal rate reached 62%, and the total phosphorus removal rate reached 58%, and the water quality met the requirements for irrigation water; the survival rate of native plants reached 95%, and the operation and maintenance cost was reduced by 55% compared with traditional technology.

[0044] Example 2: Rainwater interception and retention project in sponge green space in residential areas of temperate semi-humid regions This embodiment is applied to a residential area in a temperate semi-humid region, where the annual rainfall is 600-800 mm, concentrated in July and August. The soil type is brown soil, with a pH of 6.5-7.5 and an organic matter content of 2.0%-3.0%. The target sponge green space area is 300 m². 2 The rainwater reuse requirement is for landscape water replenishment (average daily water consumption of 3m³). 3 ).

[0045] 1. Screening and three-dimensional configuration of native plant communities Select suitable native plants: For trees, choose *Sapium sebiferum* and *Celtis sinensis* (8-10cm diameter at breast height); for shrubs, choose *Salix matsudana* and *Clerodendrum trichotomum* (0.8-1.0m spacing); for herbs, choose *Zoysia japonica* and *Miscanthus sinensis*; for vines, choose *Wisteria vine* and *Campsis grandiflora*. Planting method: Plant *Salix matsudana* and *Celtis sinensis* on both sides of residential roads (upstream of rainwater runoff) at a spacing of 2.5-3m to form an upper shade layer, with a planting quantity of 12 trees; plant *Salix matsudana* and *Clerodendrum trichotomum* on both sides of the ecological retention ditch and around the infiltration pond to form a middle buffer zone, with a planting quantity of 30 trees; plant *Zoysia japonica* and *Miscanthus sinensis* in a 2:1 ratio on the surface of the ecological retention ditch, grassed swales, and green spaces, achieving a coverage rate of 92%; plant *Wisteria vine* and *Campsis grandiflora* along the walls of the reservoir and the overflow pipe supports, with a planting density of 0.4 trees / m².

[0046] 2. Construction of multi-level ecological water retention units (1) Ecological retention ditch: Located at the rainwater runoff point beside the residential road, with an inverted trapezoidal cross-section, 1.5m wide at the top, 0.8m wide at the bottom, and 0.6m deep, with a slope of 1:1.5. A 30cm thick improved substrate layer (garden soil: leaf mold: river sand: biochar = 4:3:2:1) is laid at the bottom of the ditch, with biochar particles of 2-3mm. A permeable pipe network is pre-buried in the substrate layer, with a pipe diameter of 50mm and a spacing of 50cm. The permeable pipes have 2mm diameter perforations with a pore density of 8 per dm. 2 The ecological retention ditch is planted with a mixture of Zoysia japonica and Miscanthus sinensis, and the ditch walls are planted with Campsis grandiflora.

[0047] (2) Infiltration Pool: Located downstream of the ecological retention ditch, connected by a diversion channel with a slope of 1%. The infiltration pool is a rectangular structure, 5m long, 3m wide, and 1.0m deep. The pool walls are constructed of ecological bricks, with humus filling the brick joints and wisteria planted inside. Porous infiltration media columns are installed inside the pool. The columns are 15cm in diameter, 60cm high, and spaced 1.2m apart. 2cm diameter through-holes are opened on the surface of the columns, with a through-hole density of 4 per dm³. 2 A 10cm thick layer of gravel (5-6mm in diameter) is laid at the bottom of the infiltration pool. Ten willow trees and 15 clumps of calamus are planted in the infiltration pool. The willow trees are planted between the infiltration medium columns, and the calamus is planted at the bottom edge of the pool.

[0048] (3) Grassed swale-reservoir combination unit: The grassed swale is located downstream of the infiltration pond and connected by an overflow weir with a height of 0.5m. The grassed swale has a bottom slope of 1%, a U-shaped cross-section, a top width of 1.2m, and a depth of 0.4m. A 5cm thick improved substrate layer (with the same formula as the ecological retention swale) is laid at the bottom of the swale, and Zoysia japonica is planted in strips at intervals along the water flow direction with a width of 0.5m. The end of the grassed swale is connected to a reservoir with an effective volume of 50m³. 3 The inner wall is lined with an ecological coating (cement: humus: biochar = 5:3:2), and planted with water lilies (10 clumps) and calamus (5 clumps). A water collection pit with a 0.5% slope is set at the bottom of the reservoir, and a DN80 sewage pipe is installed in the water collection pit; a fiberglass cover is installed on the top of the reservoir, with ventilation holes of 10cm in diameter and spaced 1m apart.

[0049] 3. Construction of a Synergistic Purification Module Based on Native Plants and Microorganisms The functional microbial agent selected is Bacillus subtilis (1×10⁻⁶ bacteria). 9 CFU / mL), Pseudomonas (bacterial count 1×10⁻⁶) 9 CFU / mL), nitrifying bacteria (1×10⁻⁶) 9 The three components (CFU / mL) were mixed in a volume ratio of 2:2:1. Inoculation was carried out 15 days after the transplanting of native plants, with an inoculation volume of 100 mL / m². 2 Dilute the bacterial agent 10 times and spray it onto the surface of the substrate layer in the ecological retention trench and infiltration pond, as well as around the plant roots. After inoculation, maintain the substrate layer humidity at 60% for 7 days.

[0050] 4. Rainwater circulation regulation A water level sensor and an online water quality monitor are installed in the reservoir, and the data is transmitted to a PLC controller. The high water level threshold is set to 40m. 3 (80%), with a median threshold of 25m 3 (50%), Low threshold is 10m 3 (20%) When the water level reaches 40m 3When the water level drops to 25m, the overflow solenoid valve is activated, and excess rainwater is diverted into the city's stormwater drainage network; when the water level drops to 25m... 3 At that time, start the variable frequency pump (flow rate 3m³ / h). 3 / h), transporting rainwater to the residential area's landscape pond; when the water level drops to 10m 3 When the time comes, stop the variable frequency pump and start the water replenishment device to add water to 25m³. 3 When water quality monitoring data fails to meet standards, start the circulation pump (flow rate 2m³ / h). 3 / h), the rainwater is pumped to the ecological retention ditch for secondary purification.

[0051] 5. Post-maintenance Plants are pruned quarterly. Chinese tallow trees and hackberry trees are pruned to a height of 5-6m; willows and clover are pruned to a height of 1.0-1.2m; and zoysia grass and miscanthus are pruned to a height of 4-6cm. Pest and disease control involves releasing ladybugs (to control aphids) and spraying azadirachtin-based biological pesticides. The substrate layer and media columns are tested annually in spring, and 30% of the substrate and media columns are replaced if necessary. Sediment in retention ditches and vegetated trenches is cleaned every six months, and sediment in infiltration ponds and reservoirs is cleaned annually. The cleaned material is used for green space improvement.

[0052] After one year of operation, the monitoring results of this embodiment show that the rainwater retention rate reached 42%, which is 38% higher than that of traditional sponge green space; the COD removal rate reached 62%, the ammonia nitrogen removal rate reached 58%, and the total phosphorus removal rate reached 53%, and the water quality met the requirements for landscape water replenishment; the survival rate of native plants reached 93%, and the operation and maintenance cost was reduced by 48%.

[0053] Example 3: Rainwater interception and retention project in sponge green spaces along roads in arid and semi-arid regions This embodiment is applied to sponge green spaces along both sides of a main road in an arid and semi-arid city. The area receives 200-300 mm of rainfall annually, has high evaporation rates, and the soil type is aeolian sandy soil with a pH of 7.5-8.5 and an organic matter content of 0.5%-1.0%. The target sponge green space area is 400 m². 2 The demand for rainwater reuse is for irrigation of roads and green spaces (average daily water consumption of 4m³). 3 ).

[0054] 1. Screening and three-dimensional configuration of native plant communities Select drought-resistant and barren-tolerant native plants: For trees, choose weeping willow and hackberry (12-15cm diameter at breast height); for shrubs, choose Amorpha fruticosa and willow (1.2-1.5m spacing); for herbs, choose Bermuda grass and Miscanthus sinensis; and for vines, choose Virginia creeper. Planting method: Plant weeping willow and hackberry upstream of the green belts on both sides of the road, spacing them 3-4m apart to form an upper shade layer and reduce evaporation, with a planting quantity of 15 trees; plant Amorpha fruticosa and willow on both sides of the ecological retention ditch to form a middle buffer zone, with a planting quantity of 40 trees; plant Bermuda grass and Miscanthus sinensis in a 1:1 ratio on the surface of the ecological retention ditch, grassed swales, and green space, achieving a coverage rate of 90%; plant Virginia creeper along the walls of the ecological retention ditch to enhance soil stabilization.

[0055] 2. Construction of multi-level ecological water retention units (1) Ecological retention ditch: Located at the rainwater runoff point inside the road green belt, with an inverted trapezoidal cross-section, 2.5m wide at the top, 1.2m wide at the bottom, and 1.0m deep, with a slope of 1:2.0. A 50cm thick improved substrate layer (garden soil: leaf mold: river sand: biochar = 4:3:2:1) is laid at the bottom of the ditch, with biochar particles of 4-5mm to enhance water retention and adsorption performance. A permeable pipe network is pre-buried in the substrate layer, with a pipe diameter of 80mm and a spacing of 80cm. The permeable pipes have 3mm diameter permeable holes with a hole density of 10 holes / dm. 2 The ecological retention ditch is planted with a mixture of Bermuda grass and Miscanthus sinensis, and the ditch walls are planted with Virginia creeper.

[0056] (2) Infiltration Pool: Located downstream of the ecological retention ditch, connected by a diversion channel with a 2% slope. The infiltration pool is rectangular, 10m long, 5m wide, and 1.5m deep. The pool walls are constructed of ecological bricks, with the joints filled with a mixture of humus and straw to enhance water retention. Porous infiltration media columns are installed inside the pool. The columns are 20cm in diameter, 80cm high, and spaced 1.8m apart. 3cm diameter through-holes are opened on the surface of the columns, with a density of 6 through-holes / dm³. 2 A 15cm thick layer of crushed stone (8-10mm particle size) is laid at the bottom of the infiltration tank, and geotextile is laid inside the crushed stone layer to prevent substrate loss. 20 Amorpha fruticosa plants and 25 clumps of sweet flag are planted in the infiltration tank.

[0057] (3) Grassed swale-reservoir combination unit: The grassed swale is located downstream of the infiltration pond and connected by an overflow weir with a height of 0.8m. The grassed swale has a bottom slope of 3%, a U-shaped cross-section, a top width of 2.0m, and a depth of 0.6m. A 10cm thick improved substrate layer (with the same formula as the ecological retention swale) is laid at the bottom of the swale, and Miscanthus sinensis is planted in strips at intervals along the water flow direction, with a width of 1.0m. The end of the grassed swale is connected to a reservoir with an effective volume of 200m³. 3The inner wall is coated with an ecological coating (cement: humus: biochar = 5:3:2), and planted with lotus (15 plants) and calamus (10 clumps). A 1.0% slope collection pit is installed at the bottom of the reservoir, with a DN125 sewage pipe inside. A reinforced concrete cover is installed on the top of the reservoir, with 15cm ventilation holes spaced 2m apart. A solar-powered ventilation system is also installed to enhance ventilation.

[0058] 3. Construction of a Synergistic Purification Module Based on Native Plants and Microorganisms The functional microbial agent used was Bacillus subtilis, Pseudomonas, and nitrifying bacteria (bacterial count ratio 2:2:1), with an inoculum size of 200 mL / m³. 2 Inoculation should be carried out 20 days after the native plants are planted. The inoculum agent is diluted 10 times and sprayed onto the surface of the substrate layer and around the plant roots. After inoculation, the substrate layer should be kept at 70% humidity for 10 days, during which time drip irrigation should be used to replenish water regularly.

[0059] 4. Rainwater circulation regulation A water level sensor and an online water quality monitor are installed in the reservoir. Data is transmitted to a PLC controller, which is powered by solar energy. The high water level threshold is set at 160m. 3 (80%), with a median threshold of 100m 3 (50%), Low threshold is 40m 3 (20%) When the water level reaches 160m during the rainy season. 3 When the water level drops to 100m, activate the overflow solenoid valve; 3 At that time, start the variable frequency pump (flow rate 4m³ / h). 3 / h), delivering rainwater to the drip irrigation system for roads and green spaces; when the water level drops to 40m 3 When the water quality is substandard, stop the variable frequency pump and start the water replenishment device (connected to the city's reclaimed water network); when the water quality is substandard, start the circulation pump (flow rate 4m³ / h). 3 / h), the rainwater is pumped to the ecological retention ditch for secondary purification.

[0060] 5. Post-maintenance Plants are pruned quarterly. Weeping willows and hackberry trees are pruned to a height of 7-8m, Amorpha fruticosa and willows to a height of 1.5-1.8m, and Bermuda grass and Miscanthus to a height of 6-8cm. Pest and disease control is achieved by spraying Bacillus subtilis biological pesticides. The substrate layer and media columns are tested annually in autumn, and 50% of the substrate and media columns are replaced. Sediment in retention ditches and vegetated trenches is cleaned every six months, and sediment in infiltration ponds and reservoirs is cleaned annually. The cleaned material is mixed with organic fertilizer for green space improvement. Simultaneously, the permeable drainage network and water supply network are regularly inspected to prevent blockages.

[0061] After one year of operation, the monitoring results of this embodiment showed that the rainwater retention rate reached 38%, which is 35% higher than that of traditional sponge green space; the COD removal rate reached 60%, the ammonia nitrogen removal rate reached 55%, and the total phosphorus removal rate reached 50%, and the water quality met the requirements for irrigation water; the survival rate of native plants reached 92%, and the operation and maintenance cost was reduced by 45%, which effectively alleviated the water shortage problem in the area.

[0062] Comparison Example Comparison with Example 1: Traditional sponge green space rainwater retention projects that do not use native plants This comparative example has the same engineering structure as Example 1, except that the native plants were replaced with exotic plants (trees: camphor and osmanthus; shrubs: red photinia and golden privet; herbs: Manila grass). No functional microbial agents were inoculated. Other construction parameters, operation and maintenance methods, and monitoring conditions were completely consistent with Example 1. Monitoring results after one year of operation showed that the rainwater retention rate was only 32%, 16 percentage points lower than the 48% in Example 1; the COD removal rate, ammonia nitrogen removal rate, and total phosphorus removal rate in rainwater were 45%, 38%, and 35%, respectively, all significantly lower than the 68%, 62%, and 58% corresponding to Example 1; the exotic plants, due to their inability to adapt to the local acidic red soil environment and concentrated summer rainfall, had a survival rate of only 65%, with camphor and osmanthus mortality rates reaching 28% and 32%, respectively, and red photinia showing widespread leaf yellowing; frequent replanting of seedlings and spraying of chemical pesticides to control pests and diseases were required during operation and maintenance, increasing the operation and maintenance cost by 60% compared to Example 1, and the use of chemical pesticides caused slight pollution to the surrounding soil and water environment.

[0063] Compare with Example 2: Sponge Green Space Rainwater Harvesting Project without Multi-Stage Harvesting Units This comparative example is based on Example 2. The plant configuration (native plants such as Chinese tallow tree and hackberry), microbial inoculation and operation and maintenance methods are completely consistent with Example 2. Only the multi-stage interception design is cancelled and only a single grassed ditch-water storage tank combination unit is retained. The ecological retention ditch and infiltration tank are removed and rainwater flows directly into the grassed ditch and then into the water storage tank. Monitoring results after one year of operation showed that the rainwater retention rate was only 25%, 17 percentage points lower than the 42% in Example 2. Due to the lack of preliminary interception by ecological retention ditches and deep infiltration buffer by infiltration ponds, the rainwater flow rate was fast, and the substrate layer of the vegetated swales was easily washed away. The COD removal rate was only 38%, the ammonia nitrogen removal rate was 32%, and the total phosphorus removal rate was 28%, far lower than the 62%, 58%, and 53% in Example 2, respectively. The water quality in the reservoir fluctuated drastically. Within 1-2 days after rainfall during the rainy season, the COD and ammonia nitrogen concentrations exceeded the landscape water replenishment standards (COD > 50 mg / L, ammonia nitrogen > 5 mg / L), which could not stably meet the reuse requirements. The annual replacement frequency of the vegetated swales substrate layer reached 2 times, which was 1 times per year compared to 1 time per year in Example 2, indirectly increasing the operation and maintenance costs by 35%.

[0064] Comparison with Example 3: Sponge Green Space Rainwater Retention Project without Plant-Microorganism Synergistic Purification Module This comparative example is based on Example 3. The engineering structure (multi-level water retention unit), plant configuration (native plants such as weeping willow and hackberry) and operation and maintenance method are completely consistent with Example 3. The only difference is that it was not inoculated with Bacillus subtilis, Pseudomonas, and nitrifying bacteria compound inoculant, and the synergistic system of plant roots and microbial film was not formed. Monitoring results after one year of operation showed that the rainwater purification effect was significantly reduced, with COD removal rate at only 35%, ammonia nitrogen removal rate at 30%, and total phosphorus removal rate at 25%, which were 25, 25, and 25 percentage points lower than those of Example 3 (60%, 55%, and 50%, respectively). The average COD concentration of the purified rainwater reached 68 mg / L and the ammonia nitrogen concentration reached 7.2 mg / L, both of which did not meet the requirements for irrigation water for roads and green spaces. Due to the lack of microbial degradation of pollutants, the adsorption capacity of the substrate layer of the ecological retention ditch and the media column of the infiltration pool quickly became saturated, and the annual replacement ratio needed to be increased to 70%, which was 20 percentage points higher than that of Example 3 (50%). The operation and maintenance cost was 28% higher than that of Example 3, and an additional chemical filtration device was required to treat the rainwater before reuse, further increasing the construction and operation costs.

[0065] Compare with Example 4: Sponge Green Space Rainwater Harvesting Project without Intelligent Circulation Control System This comparative example is based on Example 1. The engineering structure (multi-stage interception unit), plant configuration, microbial inoculation, and basic operation and maintenance methods are completely consistent with Example 1. The only difference is the removal of the water level sensor, water quality monitoring device, and PLC controller. Rainwater discharge and reuse are controlled by manually observing the water level and periodically sampling and testing the water quality. After one year of operation, the monitoring results showed that the rainwater overflow waste rate reached 25%, which is 18 percentage points higher than the 7% in Example 1. Due to the inability to monitor the water level of the reservoir in real time, there were multiple instances of water overflow during the rainy season and insufficient water storage during the dry season. The number of times the irrigation needs of the green space could not be met during the dry season reached 15 times per year, while in Example 1 it was only 2 times per year. Water quality monitoring was lagging, and there were 3 instances where the reused rainwater quality did not meet the standards (COD>50mg / L), which had a slight impact on the growth of green plants. The operation and maintenance costs of manual inspection, sampling and testing, and manual control were 30% higher than those of Example 1, and the operation and maintenance efficiency was significantly reduced.

[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for rainwater retention in sponge green spaces based on native garden plants, comprising the following steps: (1) Screening and three-dimensional configuration of native plant communities: Based on the climate type and soil hydrological conditions of the target area, select native trees, shrubs, herbs and vines that are resistant to waterlogging and drought and have well-developed root systems to construct a composite community with an upper tree shade layer, a middle shrub buffer layer, a lower herb cover layer and a vine climbing layer. Among them, native tree species with a diameter at breast height of 8-15cm are selected for trees, the spacing between shrubs is 0.8-1.5m, the herb coverage rate is not less than 90%, and the vines are arranged to climb along the structure of the water retention project. (2) Construction of multi-level ecological interception and storage units: Ecological retention ditch, infiltration pond, and grassed ditch-storage pond combination unit are set up in sequence along the direction of rainwater runoff. The bottom of the ecological retention ditch is covered with a modified substrate layer with a thickness of 30-50cm that is compatible with the root system of native herbs. The infiltration pond is set with a porous infiltration medium column that works in synergy with the root system of shrubs. The slope of the bottom of the grassed ditch is controlled at 1%-3%. The end is connected to the storage pond. The inner wall of the storage pond is covered with an ecological coating and planted with aquatic native plants. (3) Construction of native plant-microorganism synergistic purification module: Inoculate functional microbial agents that coexist with the roots of native plants in ecological retention ditches and infiltration ponds to form a synergistic purification system of plant roots and microbial film; (4) Rainwater circulation regulation: A water level sensor and a water quality monitoring device are installed in the water storage tank. Based on the real-time monitoring of water level and water quality data, the purified rainwater is recycled for green space irrigation or landscape water replenishment through a variable frequency pump. When the rainfall exceeds the storage capacity, the excess rainwater is introduced into the urban rainwater pipe network through the overflow pipe.

2. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The native trees mentioned in step (1) are selected from at least one of the following: Chinese tallow tree, weeping willow, and hackberry. Native shrubs are selected from at least one of the following: Amorpha fruticosa, Salix matsudana, Weigela florida, and Clerodendrum trichotomum. The local herbs are selected from at least one of the following: Bermuda grass, Zoysia japonica, Miscanthus sinensis, and Acorus calamus; The native vines are selected from at least one of wisteria, trumpet creeper, and Virginia creeper.

3. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The cross-section of the ecological retention ditch is an inverted trapezoid, with an upper opening width of 1.5-2.5m, a lower opening width of 0.8-1.2m, a depth of 0.6-1.0m, and a ditch wall slope of 1:1.5-1:2.

0.

4. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The improved substrate layer described in step (2) is made of garden soil, leaf mold, river sand and biochar in a mass ratio of 4:3:2:

1. The biochar has a particle size of 2-5mm and a permeable pipe network is pre-buried in the substrate layer with a spacing of 50-80cm between the permeable pipes.

5. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The porous permeable medium column mentioned in step (2) is made by mixing and pressing ceramsite, zeolite, and volcanic rock in a volume ratio of 3:2:

1. The column has a diameter of 15-20 cm, a height of 60-80 cm, and a spacing of 1.2-1.8 m. The surface of the column has through holes with a diameter of 2-3 cm, and the density of through holes is 4-6 per dm. 2 .

6. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The functional microbial agent mentioned in step (3) includes Bacillus subtilis, Pseudomonas, and nitrifying bacteria, with a bacterial count ratio of 2:2:1, and an inoculation amount of 100-200 mL / m³. 2 Inoculation should be performed 15-20 days after the native plants are planted.

7. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The water level sensor in step (4) is set with three monitoring thresholds: high, medium, and low. The high threshold is 80% of the reservoir volume, the medium threshold is 50%, and the low threshold is 20%. When the water level reaches the high threshold, the overflow device is activated. When the water level reaches the medium threshold, the recharge system is activated. When the water level reaches the low threshold, the recharge is stopped and the water replenishment device is activated. When the water quality monitoring data does not meet the standards, the circulating pump is activated to send the rainwater to the ecological retention ditch for secondary purification.

8. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The effective volume of the reservoir is 50-200 m³. 3 A water collection pit with a slope of 0.5%-1.0% is set at the bottom of the pool, and a sewage pipe is installed in the water collection pit.

9. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: The native herbaceous plants planted in the grassed ditch are controlled to be 20-40cm in height and planted in strips at intervals along the direction of water flow, with a width of 0.5-1.0m.

10. The method for rainwater retention in sponge green spaces based on native garden plants according to claim 1, characterized in that: It also includes post-maintenance procedures: pruning and pest and disease control of native plants every quarter, testing and replacing the improved substrate layer and porous permeable medium column once a year, and regularly cleaning the sediment in the interception unit.

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