Artificial rainwater collection irrigation method for broken hillside cultivated land in stony desertification area

Abstract

An artificial rainwater collection irrigation method for broken hillside cultivated land in a stony desertification area comprises the steps that data such as broken bed rock surface trend and cultivated land distribution are measured in the field; calculating some important parameters by analyzing multi-year meteorological data: the mode of the number of rainwater collection cycles every year, the mode of rainfall in a rainfall period, the mode of illumination duration in an illumination period and the mode of single rainfall intensity; an artificial rainwater collecting surface is arranged, the material, the structure and the angle of the artificial rainwater collecting surface all have certain particularity, a confluence system is constructed, a low-position water collecting pool and a high-position water storage pool form an irrigation system, and the rainwater collecting area, the inner diameter of a confluence pipe, the storage battery capacitance, the photovoltaic panel area and the water pump power are calculated based on the important parameters; rainwater is collected in the main rainfall period in one year, and irrigation is conducted in the dry season. The system is particularly suitable for irrigation of broken hillside cultivated land in a stony desertification area with poor lithiasis ditch integrity, and irrigation requirements, a water collecting surface, a confluence path, a water collecting pool, a water storage tank and light energy can be integrally matched.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to the utilization of rainwater resources in fragmented mountain farmland, specifically a method for artificial rainwater harvesting and irrigation of fragmented mountain slope farmland in karst rocky desertification areas. Background Technology

[0002] In karst rocky desert regions, arable land resources are predominantly mountainous and hilly, with relatively little flat land. For example, in Guizhou Province, my country, mountains and hills account for 92.5% of the province, commonly described as "nine parts mountains, half part water, and half part farmland." The province's arable land is characterized by high slopes, scattered distribution, difficult irrigation, and shallow soil. Although the region receives an average annual rainfall of 1000 mm, 70% of the rain is concentrated between April and October, resulting in significant seasonal variations in water use. Furthermore, the unique geological structure of karst creates a rich dual-water system of surface and underground water, which, combined with the shallow soil, leads to rapid seepage and loss of surface rainwater, causing frequent surface soil drought due to engineering-induced water shortages. The main rivers in the region are distributed in deep mountain valleys, and the significant elevation differences result in high agricultural water costs. For a long time, rainfed agriculture has been the primary source of irrigation water for agricultural production in the region.

[0003] For general rainwater harvesting in mountainous farmland, existing technologies utilize existing impermeable surfaces such as roads, rooftops, and paved surfaces as the main rainwater collection points and runoff paths, which has solved the rainwater collection problem to some extent. However, these methods have limitations in meeting the irrigation needs of farmland on karst slopes. In karst desertification areas, these impermeable surfaces are usually located in villages and other areas with concentrated human activity, far from farmland. Using collected rainwater for farmland irrigation faces a mismatch between rainfall and irrigation volume, and excessively long rainwater transport paths result in high energy consumption, making it ineffective in meeting the actual needs of farmland irrigation. The applicant team's patent application CN202310585486.9, "A Low-Carbon Rainwater Collection and Irrigation Method for Karst Slopes with Karst Karst Cliffs," published in earlier technology development, proposes using karst cliffs in karst areas as rainwater collection surfaces and runoff paths, achieving the goal of nearby rainwater collection and irrigation in farmland. It also proposes high-level water storage through photovoltaic power supply. However, this method also has limitations in practical applications.

[0004] First, in areas with steep slopes, high degree of fragmentation, poor integrity of karst gullies formed by exposed bedrock, or no exposed bedrock in the context of broken mountainous terrain, using karst gullies as rainwater collection surfaces and confluence paths presents practical difficulties such as large leakage during the rainwater collection and confluence process, limited water storage resources, or even a lack of usable rainwater collection surfaces and confluence paths.

[0005] Secondly, due to the region's abundant rainfall in summer and autumn, and continuous rainy weather in winter and spring, the rain collection surface and runoff path must be able to quickly collect rainwater under heavy rainfall and effectively collect rainwater even under rainy conditions. The relatively rough material of the karst gullies makes adjustments to their structure, angle, and position difficult. Therefore, improvements are needed to the smoothness of the rain collection device's material, its flow guiding and confluence structure, and its installation angle to increase rainwater collection efficiency, improve rainwater flow, and reduce losses.

[0006] Third, in the process of photovoltaic water pumping, it is necessary to analyze the matching relationship between solar energy storage and rainwater accumulation, taking into account regional climate characteristics. While previous studies have mentioned the concept of using photovoltaics for high-level water storage, karst rocky desert areas are frequently affected by quasi-stationary fronts, resulting in frequent cloudy and damp weather. Therefore, it is crucial to clarify how to match solar resources with rainwater accumulation to achieve effective rainwater harvesting in fractured slope farmland. Currently, there are no mature technical solutions for the setup and control of photovoltaic systems that can save energy as much as possible while ensuring high-level rainwater storage, reducing the area of ​​photovoltaic panels used, and achieving effective utilization of karst climate resources and high energy efficiency. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies and the need for further optimization of the catchment surface and runoff path construction in fragmented mountain farmland in karst rocky desert areas. This invention provides an artificial rainwater harvesting irrigation method for fragmented mountain slope farmland in rocky desertification areas, constructing a rainwater harvesting surface and runoff path with high runoff coefficient, convenient construction, and low cost, thereby further improving rainwater harvesting efficiency. Simultaneously, it is necessary to combine the various configuration elements of the rainwater harvesting surface with regional irrigation needs and climate characteristics to achieve integrated matching of irrigation needs, catchment surface, runoff path, water collection tank, water storage tank, and solar energy. This invention achieves its purpose through the following technical solutions:

[0008] A method for artificial rainwater harvesting and irrigation of farmland on broken hillsides in rocky desertification areas includes the following steps:

[0009] Step 1: Field survey: Conduct a field survey of the exposed bedrock on the broken hillside farmland in the rainwater harvesting and irrigation area. Use drones to measure the slope, orientation, farmland distribution, and farmland area of ​​the broken bedrock surface to determine the area for laying artificial rainwater harvesting surfaces.

[0010] Step 2: Climate Parameter Calculation: Obtain multi-year meteorological data of the rainwater harvesting and irrigation area, analyze meteorological data, and obtain the annual main rainfall-sunlight alternation pattern. Consider each rainfall-sunlight period as a rainwater collection cycle m, and divide each cycle into rainfall periods m. l and duration of illumination m h The mode m of the number of rainwater collection cycles per year over many years. z The mode of rainfall Pz for each rainfall period and the mode of sunshine duration st for each sunshine period.n and the mode of single-event rainfall intensity during the main rainfall period z ;

[0011] Step 3: Artificial Rain Collection Surface Layout: The surface of the artificial rain collection surface consists of multiple parallel and alternating grooves and flanges. The grooves are oriented in the same direction as the slope of the fractured bedrock. The surface roughness RA value of the artificial rain collection surface is ≤8.0a. The lower surface of the artificial rain collection surface is fixedly connected to a load-bearing beam, which is supported by load-bearing piles fixed to the fractured bedrock. Multiple load-bearing piles form the support points of the artificial rain collection surface. The height of the load-bearing piles is adjusted so that the slope of the grooves in the rain collection surface is between 5-15°, and the slope of the artificial rain collection surface perpendicular to the grooves is also between 5-15°. The area of ​​the artificial rain collection surface is calculated using the following formula:

[0012]

[0013] In the formula, A is the artificial rain catchment area, in meters. 2 Q i It is the total irrigation demand for cultivated land in the region, in m 3 ;m z It is the mode of the number of rainwater collection cycles per year over many years, P z It is the mode of rainfall in each rainfall period;

[0014] Step 4: Installation of the manifold system: The manifold system consists of two parts: a rainwater collection pipe and a manifold. The rainwater collection pipe is a plastic half-pipe with grooves cut along the pipe's direction. The groove opening of the rainwater collection pipe connects to the lower edge of the groove in the artificial rainwater collection surface in the direction of flow guidance. The lower ends of all grooves are connected to the rainwater collection pipe. One end of the rainwater collection pipe is sealed, and the other end is connected to the manifold. The sealed end of the rainwater collection pipe is located at the high end of the vertical slope of the groove, and the end connected to the manifold is located at the low end of the vertical slope of the groove. The inner diameter of the manifold is calculated using the following formula:

[0015]

[0016] In the formula: I z It is the mode of single-event rainfall intensity during the main rainfall period over many years; α is the runoff generation coefficient, selected based on the catchment surface material; V is the pipe design flow velocity, ranging from 1 to 1.5 m / h; D is the inner diameter of the manifold, in meters;

[0017] Step 5: Construct a low-level collection tank: The low-level collection tank is used to collect and store rainwater from the artificial rainwater collection surface within a rainwater collection cycle. It is set below the artificial rainwater base surface or in a solution ditch below the height of the artificial rainwater collection surface, and the end of the manifold is connected to the low-level collection tank.

[0018] Step 6: Install the power supply system and water pump: The power supply system uses photovoltaic panels to generate electricity and batteries to store it. The batteries are connected to the water pump via wires to supply power to the pump. The water pump is installed in a low-level water collection tank, and a water level controller is installed in the low-level water collection tank to control the start and stop of the water pump.

[0019] Step 7: Constructing a high-level water storage tank: The high-level water storage tank is placed above all the farmland that needs irrigation in the rainwater collection and irrigation area, storing rainwater from one or more low-level water collection tanks. The inlet of the high-level water storage tank is connected to the output end of the water pump through a pipeline, and the outlet of the high-level water storage tank is connected to the irrigation pipe.

[0020] Step 8: Water Collection and Storage: During the rainfall period of a rainwater collection cycle in the main annual rainfall period, rainwater is collected using artificial rainwater collection surfaces and collected into a low-level collection tank through a runoff system. During the sunshine period of the same cycle, the rainwater in the low-level collection tank is pumped to a high-level storage tank. At the same time, during the sunshine period of the same cycle, electricity is generated by photovoltaic panels and stored in batteries for energy storage for the next cycle of water pumping. The above operation is repeated in all rainwater collection cycles until the end of the main rainfall period of the year.

[0021] Step 9: During the dry season, rainwater collected during the main rainfall period is transported through irrigation pipes to the farmland in the irrigation area for irrigation.

[0022] As an optimization of the photovoltaic function, in step six, the battery capacity, photovoltaic panel area, and water pump power are calculated using the following formulas:

[0023]

[0024] In the formula: C represents the rated storage capacity of the battery, Ah; Q l It is the volume of the low-level water collection tank, in meters. 3 ρ is the density of water, kg / m³ 3 , with a value of 1000; g is the gravitational acceleration, N / kg, with a value of 9.8; H is the water lifting height, m; β is the battery efficiency, with a reference value of 0.85 for colloidal gold batteries; a is the conversion between joules and watt-hours, with a value of 3600; v is the battery voltage, V;

[0025]

[0026] In the formula: A P The area of ​​the photovoltaic panel is expressed in meters (m). 2 ; d represents the power density per unit photovoltaic panel, W / m 2 ;st n δ is the mode of sunshine duration during each sunshine period in the major rainfall period over many years, in hours; δ is the working efficiency of the photovoltaic panel, with a reference value of 0.17 for monocrystalline silicon photovoltaic panels.

[0027]

[0028] In the formula: P represents the power of the water pump, W; λ is the working efficiency of the water pump, with a reference value of 0.6 for tributary pumps.

[0029] Further optimization involves determining the fractured hillside where the artificial rain collection surface will be laid, with a slope not exceeding 30°, in step one.

[0030] Furthermore, in step two, the multi-year meteorological data shall be no less than 40 years.

[0031] Furthermore, in step three, each artificial rain collection surface has a reference length ≤ 8 mm, a thickness ≥ 2 mm, and a weight ≤ 800 g / m². 2 The grooves and flanges of the artificial rain collection surface are all composed of arcs, giving the surface of the artificial rain collection surface a wave-like structure.

[0032] Furthermore, in step three, the load-bearing pile is made of a mixture of crushed stone and mortar, and the bottom of the load-bearing pile is fixed together with the mortar and the broken bedrock; the load-bearing beam is made of miscellaneous tree trunks, and the diameter of the load-bearing beam is not greater than the diameter of the groove of the artificial rain collection surface. The artificial rain collection surface and the load-bearing beam are connected by screws, and waterproof glue is applied to the screws after fixing.

[0033] Furthermore, the material of the artificial rain collection surface is PVC plastic steel composite resin tile; the material of the water collection pipe is PVC pipe; the material of the manifold pipe is PVC pipe or PE pipe and needs to be buried underground; the low-level rain collection tank uses stainless steel water buckets or uses mortar to seal the solution trench water tank; the high-level water storage tank uses stainless steel or plastic material.

[0034] Furthermore, the low-level water collection tank is connected to an artificial rainwater harvesting surface, and its volume is calculated using the following formula:

[0035] Q l =A×P z

[0036] The low-level water collection tank is connected to multiple artificial rainwater collection surfaces, and its volume is calculated using the following formula:

[0037]

[0038] In the formula: A n It is the nth catchment area, m 2 .

[0039] Furthermore, the volume of the elevated water storage tank is calculated using the following formula:

[0040]

[0041] In the formula: Q h The volume of the elevated water storage tank is in meters. 3Q ln Let m be the volume of the nth low-level water collection tank. 3 .

[0042] The advantages and beneficial effects of this invention are:

[0043] The present invention provides an artificial rainwater harvesting and irrigation method for fragmented hillside farmland in desertified areas. This method is designed for fragmented mountain farmland, especially in areas with scattered farmland. It further supplements and optimizes existing technologies by optimizing the rainwater harvesting surface and runoff path through artificial measures to make up for the deficiencies in existing rainwater harvesting and irrigation methods for fragmented farmland in rocky desertified areas, thereby achieving efficient rainwater harvesting.

[0044] This invention combines various configuration elements of the rainwater harvesting surface with regional irrigation needs and climate characteristics to achieve integrated matching of irrigation needs, rainwater harvesting surface, runoff path, water collection pool, water storage tank, and solar energy. While achieving efficient rainwater harvesting, it effectively utilizes climate resources, reduces the area of ​​photovoltaic panels used, improves construction convenience, and balances economy and efficiency, making it highly practical. Attached Figure Description

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] Figure 1 This is a schematic diagram illustrating the implementation effect of the method of the present invention.

[0047] Figure 2 A schematic diagram of the inclination angle of the load-bearing piles for the rainwater collection surface: the longitudinal inclination angle is the angle of the water flow direction of the rainwater collection surface, which is the slope of the drainage direction of the rainwater collection surface groove; the transverse inclination angle is the slope perpendicular to the groove direction.

[0048] Figure 3 This is a schematic diagram of a rainwater collection surface load-bearing pile structure.

[0049] Figure 4 This is a schematic diagram of rainwater runoff under a wave-like structure on the rain collection surface.

[0050] Figure 5 This is a schematic diagram of the rainwater collection surface and the runoff system.

[0051] Figure 6 This is a schematic diagram of the complete structure of the rainwater collection surface.

[0052] Figure 7 Schematic diagram for meteorological parameter calculation: where V l and V h This indicates the water volume collected in the low-level water collection tank and the water volume stored in the high-level water storage tank for each cycle.

[0053] Figure 8 This is a map showing the current state of rocky desertification at the Renmu Community base in Xinren Township, Qianxi City, Guizhou Province, in Example 1.

[0054] Figure 9 Photograph of the rainwater catchment surface constructed in Xinren Township, Qianxi City, Guizhou Province, for Example 1.

[0055] Figure 10 This is a photograph of the pipeline of the manifold system constructed in Xinren Township, Qianxi City, Guizhou Province, for Example 1.

[0056] Figure 11 This is a photograph of a high-level water storage tank constructed in Xinren Township, Qianxi City, Guizhou Province, as shown in Example 1.

[0057] Figure 12 The monthly rainfall collected in the low-level water collection tank in Example 1.

[0058] Figure 13 The monthly rainwater collection volume of the high-level water storage tank in Example 1.

[0059] Attached diagram descriptions: 1. Load-bearing pile; 2. Load-bearing beam; 3. Artificial rainwater collection surface; 31. Groove; 32. Flange; 33. Sealing end; 4. Rainwater collection pipe; 5. Manifold; 6. Low-level water collection tank; 7. Water pump; 8. Storage battery; 9. Photovoltaic panel; 10. High-level water storage tank; 11. Irrigation pipe. Detailed Implementation

[0060] A method for artificial rainwater harvesting and irrigation of farmland on broken hillsides in rocky desertification areas includes the following steps:

[0061] Step 1: Field Survey. A field survey is conducted on the exposed bedrock on fractured hillside farmland within the rainwater harvesting area. Using drones, the slope, orientation, farmland distribution, and farmland area of ​​the fractured bedrock are measured to determine the area for artificial rainwater harvesting surfaces. Areas with higher degrees of bedrock fragmentation are selected for this purpose. A suitable slope is crucial for ensuring rapid rainwater flow on the harvesting surface; the slope should not exceed 30°. Slopes exceeding this range increase the difficulty and cost of construction. The farmland area is used to calculate irrigation demand. Irrigation demand is calculated using the farmland area obtained from the field survey and relevant data from irrigation quotas. Determining the irrigation demand is the basis for matching the subsequent rainwater harvesting system with irrigation quotas.

[0062] Q i =A c ×I m (1)

[0063] In the formula, A c It is the area of ​​arable land, in meters. 2 ;I m This represents the irrigation requirement per unit area for m types of crops. 3 / km 2 ; This can be found in the national or local standards for irrigation water quotas. Q i It is the total irrigation demand for cultivated land in the region, in m 3 .

[0064] Step 2: Climate Parameter Calculation: Obtain meteorological data for at least the past 40 years for the rainwater harvesting irrigation area, analyze meteorological data including regional rainfall, sunshine duration, etc., and obtain the annual main rainfall period (April to October) rainfall-sunshine alternation distribution pattern (e.g., Figure 7 This period exhibits an alternating pattern of rainfall-sunshine-rainfall-sunshine. Each rainfall-sunshine period is considered a rainwater collection cycle m, and each cycle is divided into rainfall periods m. l and duration of illumination m h The mode m of the number of rainwater collection cycles per year over many years. z The mode of rainfall Pz for each rainfall period and the mode of sunshine duration st for each sunshine period. n and the mode of single-event rainfall intensity during the main rainfall period z The mode is calculated as follows:

[0065]

[0066] In the formula, Mo is the mode, L is the lower bound of the mode group, U is the upper bound of the mode group, and f is the lower bound of the mode group. m It is the group number containing the mode, f m-1 It is the next lower group of the group containing the mode, f m+1 It is the number of adjacent groups above the group containing the mode, and w is the group interval of the group containing the mode.

[0067] For example, by statistically analyzing relevant climate data from various meteorological stations in Guizhou Province from 1980 to 2024, a table of relevant climate parameter values ​​for each district and county in Guizhou Province was calculated. Alternatively, parameters can be calculated using the above method after obtaining point meteorological data from remote sensing data.

[0068] Table 1

[0069]

[0070]

[0071] Step 3: Artificial rainwater collection surface 3 layout: Before installation, it is necessary to combine the slope and direction of the broken and exposed bedrock obtained from the field survey to determine the layout location of the rainwater collection surface and the direction of the collected water flow. The direction of the collected rainwater flow (the direction of the groove of the rainwater collection surface) is set according to the slope and direction of the exposed bedrock.

[0072] Equipment layout as follows Figures 1-6 As shown, the surface of the artificial rain collection surface 3 consists of multiple parallel and alternating grooves 31 and flanges 32. The orientation of the grooves 31 is consistent with the slope direction of the fractured bedrock. In this embodiment, the artificial rain collection surface 3 is selected with the following surface roughness requirements: reference length ≤ 8 and RA value ≤ 8.0a, thickness ≥ 2mm, and weight ≤ 800g / m.2 The grooves 31 and flanges 32 of the artificial rain collection surface 3 are both composed of arc shapes, giving the surface of the artificial rain collection surface 3 a wavy structure. The area of ​​the artificial rain collection surface 3 is calculated using the following formula:

[0073]

[0074] In the formula, A is the artificial rain catchment area, in meters. 2 Q i It is the total irrigation demand for cultivated land in the region, in m 3 ;m z It is the mode of the number of rainwater collection cycles per year over many years, P z This is the mode of rainfall for each rainfall period, and the unit is converted to meters during calculation;

[0075] When rainwater is collected by multiple catchment surfaces, the total catchment area simultaneously satisfies the following formula:

[0076]

[0077] In the formula, A n It is the area of ​​the nth catchment surface, m 2 .

[0078] The lower surface of the artificial rain collection surface 3 is fixedly connected to the load-bearing beam 2. The load-bearing beam 2 is supported by load-bearing piles 1 fixed on the broken bedrock. Multiple load-bearing piles 1 form the support points of the artificial rain collection surface 3. The height of the load-bearing piles 1 is adjusted so that the slope of the artificial rain collection surface in the groove direction is 5-15°, and the slope of the artificial rain collection surface perpendicular to the groove direction is also 5-15°.

[0079] The load-bearing pile 1 is made of a mixture of crushed stone and mortar. The bottom of the load-bearing pile 1 is fixed together with the broken bedrock by mortar. The load-bearing beam 2 can be made from locally sourced miscellaneous tree trunks. The diameter of the load-bearing beam 2 is not larger than the diameter of the groove 31 of the artificial rain collection surface. The artificial rain collection surface 3 and the load-bearing beam 2 are connected by screws, and waterproof adhesive is applied to the screws after fixing. The load-bearing beam has a load-bearing capacity of not less than 100 kg / beam. When multiple artificial rain collection surfaces need to be laid, each adjacent rain collection surface should be laid with the upper water level rain collection surface overlapping the lower water level rain collection surface. The intersection of the two rain collection surfaces should not be less than 10 cm, and the gap at the intersection should be sealed with waterproof adhesive.

[0080] As long as the smoothness is suitable for artificial rain collection surfaces, various impermeable materials can be selected, with PVC plastic-steel composite resin tiles (commonly known as aluminum formwork tiles) being the preferred choice. The following are test data. Comparisons of rain collection surfaces made of different materials are shown below:

[0081] To select suitable rainwater harvesting surface materials, simulated rainfall experiments were conducted to analyze the performance of aluminum formwork roofing sheets, corrugated steel roofing sheets, and asphalt shingles. A 5-square-meter structure with a 10° inclination was constructed, simulating runoff coefficients under four rainfall intensities: 5 mm / h, 15 mm / h, 30 mm / h, and 45 mm / h. The results are shown in Table 2. Aluminum formwork roofing sheets and corrugated steel roofing sheets showed significantly higher runoff coefficients than asphalt shingles under all four rainfall intensities. Structurally and structurally, aluminum formwork roofing sheets and corrugated steel roofing sheets were also superior to asphalt shingles. In terms of wind resistance in outdoor applications, aluminum formwork roofing sheets, being heavier than corrugated steel roofing sheets, were superior; therefore, aluminum formwork roofing sheets were the preferred choice.

[0082] Table 2

[0083] Rainfall intensity (mm / h) Aluminum formwork Corrugated steel sheets Asphalt shingles 5 0.82±0.01a 0.81±0.02a 0.58±0.03b 15 0.89±0.02a 0.88±0.01a 0.65±0.04b 30 0.97±0.01a 0.96±0.01a 0.75±0.02b 45 0.98±0.01a 0.97±0.01a 0.83±0.02b

[0084] Note: Lowercase letters in the same row indicate significance at the 0.05 confidence level.

[0085] The number of load-bearing piles should be selected based on the area of ​​the rainwater catchment surface and the terrain, and should not be less than 5m. 2 A single pile forms the support point for the rainwater collection surface. During construction, the plane formed by the multiple piles must have a certain slope. The slope in the direction of water flow in the rainwater collection surface should be between 5-15°. When the slope is less than 5°, rainfall with an intensity of less than 10 mm / h will have a slow flow rate, resulting in increased evaporation and water loss. When the slope is greater than 15°, rainfall with an intensity of more than 40 mm / h will have a too fast flow rate, resulting in overflow of the rainwater collection pipe and waste of rainwater. At the same time, the greater the slope, the smaller the effective rainwater collection surface.

[0086] The horizontal slope of the water flow direction is between 5-15°. This slope mainly determines the rapid transfer of rainwater along the slope from the wavy grooves of the rainwater collection surface into the rainwater collection pipe. When the slope is less than 5°, rainfall with an intensity greater than 40 mm / h will cause the rainwater collection pipe to overflow due to the large accumulation of rainwater, resulting in rainwater waste. When the slope is greater than 15°, the rainwater collection surface will have a large difference in different directions, increasing the construction difficulty and reducing the effective rainwater collection surface. The selection of the above rainwater collection surface angle also takes into account the damage of mountain winds to the rainwater collection surface. When the angle exceeds 15°, the probability of damage by gusts increases significantly.

[0087] Comparison of different tilt surface settings:

[0088] To compare the rainwater collection effect of the catchment surface (in the direction of water flow) at different tilt angles, a comparative experiment was conducted at a field base in Renmu Community, Xinren Township, Qianxi City, Guizhou Province, using different tilt surfaces. A single 10m section was constructed in an adjacent area. 2Six aluminum-coated roof tiles were used for rainwater collection. Six experimental groups were set up with slopes of 2°, 5°, 10°, 15°, 20°, and 25°. Each group of experiments was repeated five times under the same rainfall intensity. The ratio of collected rainfall to total rainfall was calculated for each experiment to compare the rainwater collection effect under different slope angles. It was found that when the slope was 2°, the rainwater collection effect was significantly lower than that of other slope treatment groups under all six rainfall intensities. When the slope was greater than 15°, the rainwater collection effect did not increase with increasing rainfall intensity but instead decreased. Only the treatment group between 5-15° showed relatively stable performance, and could collect rainwater well under both low-intensity and high-intensity rainfall.

[0089] Table 3

[0090]

[0091]

[0092] Note: Lowercase letters in the same row indicate significance at the 0.05 confidence level.

[0093] To compare the rainwater collection effect of a catchment surface (inclined perpendicular to the water flow direction) at different inclination angles, a comparative experiment was conducted at a field base in Renmu Community, Xinren Township, Qianxi City, Guizhou Province. A single 10m section was constructed in an adjacent area. 2 Six aluminum-coated roof tiles were used for rainwater collection. Six experimental groups were set up with slopes of 2°, 5°, 10°, 15°, 20°, and 30°. Each group of experiments was repeated five times under the same rainfall intensity. The ratio of collected rainfall to total rainfall was calculated for each experiment to compare the rainwater collection effect under different slope angles. It was found that when the slope was 2°, the rainwater collection effect was significantly lower than that of other slope treatment groups under all six rainfall intensities. When the slope was greater than 15°, the rainwater collection effect did not increase with increasing rainfall intensity but instead decreased. Only the treatment group between 5-15° showed relatively stable performance, and could collect rainwater well under both low-intensity and high-intensity rainfall.

[0094] Table 4

[0095]

[0096] Note: Lowercase letters in the same row indicate significance at the 0.05 confidence level.

[0097] Step 4: Installation of the manifold system: The manifold system consists of two parts: rainwater collection pipe 4 and manifold pipe 5. The rainwater collection pipe 4 is a plastic half-pipe with a groove along the direction of the pipe. The groove of the rainwater collection pipe 4 is connected to the lower edge of the artificial rainwater collection surface 3 in the direction of the flow. The lower ends of all grooves 31 are connected to the rainwater collection pipe 4. One end of the rainwater collection pipe 4 is blocked, and the other end is connected to the manifold pipe 5. The blocked end 33 is located at the high end of the vertical slope of the groove, and the end connected to the manifold pipe is located at the low end of the vertical slope of the groove.

[0098] Derivation of manifold diameter calculation:

[0099] The calculation of the manifold diameter depends on the rainfall intensity, the runoff coefficient of the catchment surface, the design flow velocity, and the catchment area.

[0100] First, the flow rate of the manifold is calculated:

[0101] Q = I z ×A×α (6)

[0102] In the formula: Q is the design pipeline flow rate, m 3 / h; A is the area of ​​the catchment surface, m 2 ;I z The mode of single rainfall intensity (m / h) during the regional rainy season (April-October) over many years was obtained by statistically analyzing regional rainfall data over the past 50 years. α is the runoff generation coefficient, selected based on the catchment surface material.

[0103] Secondly, the relationship between flow velocity, cross-sectional area, and flow rate in the manifold:

[0104] Q = A 截 ×V(7)

[0105]

[0106] Combining formulas (7) and (8), we can solve for D to obtain formula (9):

[0107]

[0108] In the above formulas (7), (8) and (9), Q is the design flow rate of the confluence pipe, m 3 / h;A 截 It is the cross-sectional area of ​​the manifold, in meters. 2 V is the design flow velocity of the pipeline, m / h; its value is 1-1.5; D is the inner diameter of the manifold, m.

[0109] Finally, substituting formula (6) into formula (9) yields the final manifold diameter calculation formula (10):

[0110]

[0111] Rainwater collection pipes are made of rigid materials, with PVC pipes being the preferred choice; manifolds can be made of either rigid PVC pipes or flexible PE pipes. The pipes need to be buried underground to prevent damage in high-temperature or freezing environments in the field.

[0112] Step 5: Constructing a Low-Level Rainwater Collection Tank 6: The low-level rainwater collection tank 6 is used for collecting and storing rainwater from the artificial rainwater collection surface 3 within a rainwater collection cycle. It is located below the artificial rainwater collection surface 3 or in a solution trench below the height of the artificial rainwater collection surface 3. The end of the manifold 5 is connected to the low-level rainwater collection tank 6. The low-level rainwater collection tank can be made of stainless steel buckets, or a suitable solution trench can be sealed with mortar to form a low-level water tank. The low-level water collection tank can be connected to one rainwater collection surface or multiple rainwater collection surfaces. The volume of the low-level water collection tank 6 connected to an artificial rainwater collection surface 3 is calculated according to the following formula:

[0113] Q l =A×P z (11) The low-level water collection tank 6 is connected to multiple artificial rainwater collection surfaces 3. The volume is calculated according to the following formula:

[0114]

[0115] In the formula: A n It is the nth catchment area, m 2 .

[0116] Step 6: Install the power supply system and water pump: The power supply system uses photovoltaic panels 9 to generate electricity and batteries 8 to store electricity. The batteries 8 are connected to the water pump 7 via wires to supply power to the water pump 7. The water pump 7 is installed in the low-level water collection tank 6, and a water level controller is installed in the low-level water collection tank 6 to control the start and stop of the water pump 7. The battery capacity, photovoltaic panel area, and water pump power are calculated according to the following formula:

[0117]

[0118] In the formula: C represents the rated storage capacity of the battery, Ah; Q l It is the volume of the low-level water collection tank, in meters. 3 ρ is the density of water, kg / m³ 3 , with a value of 1000; g is the gravitational acceleration, N / kg, with a value of 9.8; H is the water lifting height, m; β is the battery efficiency, with a reference value of 0.85 for colloidal gold batteries; a is the conversion between joules and watt-hours, with a value of 3600; v is the battery voltage, V;

[0119]

[0120] In the formula: A P The area of ​​the photovoltaic panel is expressed in meters (m). 2 ; d represents the power density per unit photovoltaic panel, W / m 2 ;st n δ is the mode of sunshine duration during each sunshine period in the major rainfall period over many years, in hours; δ is the working efficiency of the photovoltaic panel, with a reference value of 0.17 for monocrystalline silicon photovoltaic panels.

[0121]

[0122] In the formula: P represents the power of the water pump, W; λ is the working efficiency of the water pump, with a reference value of 0.6 for DC pumps;

[0123] Step 7: Constructing a high-level water storage tank 10: The high-level water storage tank 10 is placed above all the farmland that needs irrigation in the rainwater collection and irrigation area, storing rainwater from one or more low-level water collection tanks 6. The inlet of the high-level water storage tank 10 is connected to the output end of the water pump 7 through a pipeline, and the outlet of the high-level water storage tank 10 is connected to an irrigation pipe 11. The high-level water storage tank can be made of stainless steel or plastic, or it can be a stainless steel frame with a rain collection cloth inside.

[0124] The volume of the elevated water storage tank 10 is calculated using the following formula:

[0125]

[0126] In the formula: Q h The volume of the elevated water storage tank is in meters. 3 Q ln Let m be the volume of the nth low-level water collection tank. 3 .

[0127] Step 8: Water Collection and Storage: During the rainfall period of a rainwater collection cycle during the main annual rainfall period, rainwater is collected by artificial rainwater collection surface 3 and collected into low-level collection tank 6 through a runoff system. During the sunshine period of the same cycle, the rainwater in the low-level collection tank 6 is pumped by water pump 7 to high-level storage tank 10 to empty the low-level collection tank 6. At the same time, during the sunshine period of the same cycle, electricity is generated by photovoltaic panels 9 and stored in batteries 8 for water pumping and energy storage in the next cycle. The above operation is repeated in all rainwater collection cycles until the end of the main rainfall period of the year.

[0128] Step 9: When irrigation is needed, the rainwater collected during the main rainfall period is transported through irrigation pipe 11 to the cultivated land in the irrigation area for irrigation.

[0129] Example 1

[0130] Based on the above embodiments, the present invention was specifically tested in Renmu Community, Xinren Township, Qianxi City, Guizhou Province.

[0131] The total cultivated land area of ​​the Renmu Village base in Xinren Township is 150 mu, but it is scattered among the rocky karst gullies, with the largest single plot measuring 1.4 mu. Figure 8The area is characterized by typical fractured mountainous terrain, with an average annual rainfall of around 1100 mm. Rapeseed is the main crop during winter and spring, while corn is the main crop during summer and autumn. According to Guizhou Province's local irrigation quota standards, the annual irrigation requirement is 180 cubic meters per mu (approximately 120 cubic meters per hectare) under an 80% hydrological year. Given the poor integrity and high degree of fragmentation of the rock surfaces in the karst gullies, artificial rainwater harvesting surfaces are used for rainwater collection.

[0132] Based on the rainwater harvesting surface formulas (1) and (2) of this invention, an artificial rainwater harvesting surface of 33,750 square meters is required. In the verification experiment, mainly to verify the feasibility of the technology, three artificial rainwater harvesting surfaces were actually constructed on the site, with areas of 60, 80, and 85 square meters respectively. Figure 9 ).

[0133] By querying regional climate data over the past 50 years, it was found that the median rainfall intensity during the rainy season (April-October) is 18 mm / h, and the design flow velocity is 60 m / h. Using the calculation formula (10) for the manifold diameter in this invention, the manifold diameters of the three artificial rain collection surfaces are calculated to be 15 cm, 17 cm, and 17 cm respectively. Figure 10 ).

[0134] By querying regional climate data over the past 50 years, it was found that the mode of single rainfall during the rainy season (April-October) is 21.5 mm. Based on the calculation formula (12) of the low-level water collection tank of this invention, the volume of the low-level water collection tank is calculated to be 4.8375 cubic meters. A 5-cubic-meter stainless steel tank is used as the low-level water collection tank during installation.

[0135] The design process uses the volume and elevation of the low-level water collection tank and the battery voltage to derive the design. The water pumping elevation is 70 meters and the battery voltage is 12V. Based on the battery volume derivation formula (13), photovoltaic panel area derivation formula (14), and water pump power derivation formula (15) in this invention, the battery capacity is calculated to be 93.4Ah. In actual construction, a 100Ah battery is selected. The photovoltaic panel area is 1.85 square meters, but 2 square meters is actually selected. The calculated power of the water pump is 210.5W, but a 350W DC water pump is actually selected.

[0136] The elevated water storage tank is mainly used to collect and store water from all the low-level water tanks in the area for irrigation needs. At this site, based on the average number of rainfall events during the rainy season (April-July) over the past 50 years (37 times), and according to the elevated water storage tank volume derivation formula (16) in this invention, the volume of the elevated water storage tank is calculated to be 178.9875 cubic meters. The volume constructed during construction is 180 cubic meters. Figure 11 ).

[0137] Further analysis of data from April 2023 to April 2024 at the aforementioned base revealed that the low-level catchment pond collected a total of 235.55 m³ of rainwater during the rainy season (April-October) within a 225 square meter catchment area.3 The total amount of rainwater collected during the non-rainy season (November to March) is 32.73 m³. 3 The total amount of rainwater collected throughout the year was 268.28 m³. 3 ( Figure 12 The elevated water storage tank collects a total of 209.61 m³ of rainwater during the rainy season (April-October) throughout the year. 3 The system's rainwater harvesting efficiency is 88.9%, and the total amount of rainwater collected during the non-rainy season (November to March) is 21.22 m³. 3 The system's rainwater harvesting efficiency is 64.8%, and the total annual rainwater collected is 230.83 m³. 3 The system's rainwater harvesting efficiency is 86%. Figure 13 By comparing and analyzing the measured irrigation data from the Guizhou Provincial Irrigation Experimental Center Station, which planted the same crop varieties during the same period, it was found that under an 80% irrigation guarantee rate for the three types of irrigation, the annual water collection can meet the irrigation needs of 1.54 mu of rapeseed or 1.78 mu of corn. This indicates that the method can store rainwater during the rainy season for irrigation during the dry season, thus resolving the time mismatch between rainwater resources and crop water needs in karst areas.

[0138] Finally, it should be noted that the above description is only used to illustrate the technical solutions of the present invention and is not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A method for artificial rainwater harvesting and irrigation of farmland on fragmented hillsides in rocky desertification areas, characterized in that: Specifically, the following steps are included: Step 1: Field survey: Field survey the exposed bedrock on the broken hillside farmland in the rainwater harvesting and irrigation area. The slope, orientation, farmland distribution and farmland area of ​​the broken bedrock surface are measured by drone to determine the area for laying artificial rainwater harvesting surface (3). Step 2: Climate Parameter Calculation: Obtain multi-year meteorological data of the rainwater harvesting and irrigation area, analyze meteorological data, and obtain the annual main rainfall-sunlight alternation pattern. Consider each rainfall-sunlight period as a rainwater collection cycle m, and divide each cycle into rainfall periods m. l and duration of illumination m h The mode m of the number of rainwater collection cycles per year over many years. z The mode of rainfall Pz for each rainfall period and the mode of sunshine duration st for each sunshine period. n and the mode of single-event rainfall intensity during the main rainfall period z ; Step 3: Arrangement of artificial rain collection surface (3): The surface of artificial rain collection surface (3) consists of multiple parallel and alternately arranged grooves (31) and flanges (32). The direction of the grooves (31) is consistent with the slope direction of the fractured bedrock. The surface roughness RA value of artificial rain collection surface (3) is ≤8.0a. The lower surface of artificial rain collection surface (3) is fixedly connected to the load-bearing beam (2). The load-bearing beam (2) is supported by load-bearing piles (1) fixed on the fractured bedrock. Multiple load-bearing piles (1) constitute the support points of artificial rain collection surface (3). The height of the load-bearing piles (1) is adjusted so that the slope of the grooves of artificial rain collection surface is 5-15° and the slope of artificial rain collection surface perpendicular to the groove direction is also 5-15°. The area of ​​artificial rain collection surface (3) is calculated according to the following formula: In the formula, A is the artificial rain catchment area, in meters. 2 Q i It is the total irrigation demand for cultivated land in the region, in m 3 ; m z It is the mode of the number of rainwater collection cycles per year over many years, P z It is the mode of rainfall in each rainfall period; Step 4: Installation of the manifold system: The manifold system consists of two parts: a rainwater collection pipe (4) and a manifold pipe (5); the rainwater collection pipe (4) is a plastic half-pipe with a groove along the direction of the pipe. The groove of the rainwater collection pipe (4) is connected to the lower edge of the groove in the direction of the flow of the artificial rainwater collection surface (3). The lower ends of all grooves (31) are connected to the rainwater collection pipe (4). One end of the rainwater collection pipe (4) is sealed, and the other end is connected to the manifold pipe (5). The sealed end (33) of the rainwater collection pipe (4) is located at the high end of the vertical slope of the groove, and the end connected to the manifold pipe is located at the low end of the vertical slope of the groove. The inner diameter of the manifold pipe (5) is calculated according to the following formula: In the formula: I z It is the mode of single-event rainfall intensity during the main rainfall period over many years; α is the runoff generation coefficient, selected based on the catchment surface material; V is the pipe design flow velocity, ranging from 1 to 1.5 m / h; D is the inner diameter of the manifold, in meters; Step 5: Constructing a low-level water collection tank (6): The low-level water collection tank (6) is used for the collection and storage of rainwater from the artificial rain collection surface (3) within a rainwater collection cycle. It is set in a solution ditch below the artificial rain base surface (3) or below the height of the artificial rain collection surface (3). The end of the manifold (5) is connected to the low-level water collection tank (6). Step 6: Install the power supply system and water pump: The power supply system uses photovoltaic panels (9) to generate electricity and batteries (8) to store electricity. The batteries (8) are connected to the water pump (7) through wires to supply power to the water pump (7). The water pump (7) is installed in the low-level water collection tank (6). At the same time, a water level controller is installed in the low-level water collection tank (6) to control the start and stop of the water pump (7). Step 7: Constructing a high-level water storage tank (10): The high-level water storage tank (10) is placed above all the farmland that needs irrigation in the rainwater collection and irrigation area, storing rainwater from one or more low-level water collection tanks (6). The inlet of the high-level water storage tank (10) is connected to the output end of the water pump (7) through a pipeline, and the outlet of the high-level water storage tank (10) is connected to the irrigation pipe (11). Step 8: Water collection and storage: During the rainfall period of a rainwater collection cycle during the main rainfall period of the year, rainwater is collected by artificial rainwater collection surface (3) and collected into a low-level collection tank (6) through a runoff system. During the sunshine period of the same cycle, the rainwater in the low-level collection tank (6) is pumped to a high-level storage tank (10) by a water pump (7). At the same time, during the sunshine period of the same cycle, electricity is generated by photovoltaic panels (9) and stored in batteries (8) for water pumping and energy storage in the next cycle. The above operation is repeated in all rainwater collection cycles until the end of the main rainfall period of the year. Step 9: During the dry season, rainwater collected during the main rainfall period is transported through irrigation pipes (1) to the cultivated land in the irrigation area for irrigation.

2. The method for artificial rainwater harvesting and irrigation of farmland on broken slopes in rocky desertification areas according to claim 1, characterized in that: In step six, the battery capacity, photovoltaic panel area, and water pump power are calculated using the following formulas: In the formula: C represents the rated storage capacity of the battery, Ah; Q l It is the volume of the low-level water collection tank, in meters. 3 ; ρ is the density of water, kg / m³ 3 , with a value of 1000; g is the gravitational acceleration, N / kg, with a value of 9.8; H is the water lifting height, m; β is the battery efficiency, with a reference value of 0.85 for colloidal gold batteries; a is the conversion between joules and watt-hours, with a value of 3600; v is the battery voltage, V; In the formula: A P The area of ​​the photovoltaic panel is expressed in meters (m). 2 ;d represents the power density per unit photovoltaic panel, W / m2;st n δ is the mode of sunshine duration during each sunshine period in the major rainfall period over many years, in hours; δ is the working efficiency of the photovoltaic panel, with a reference value of 0.17 for monocrystalline silicon photovoltaic panels. In the formula: P represents the power of the water pump, W; λ is the working efficiency of the water pump, with a reference value of 0.6 for tributary pumps.

3. The method for artificial rainwater harvesting and irrigation of farmland on broken hillsides in rocky desertification areas according to claim 1, characterized in that: In step one, the broken hillside to which the artificial rain collection surface is laid is determined, with a slope not exceeding 30°.

4. The method for artificial rainwater harvesting and irrigation of farmland on broken slopes in rocky desertification areas according to claim 1, characterized in that: In step two, the multi-year meteorological data shall be no less than 40 years.

5. The method for artificial rainwater harvesting and irrigation of farmland on broken hillsides in rocky desertification areas according to claim 1, characterized in that: In step three, each artificial rain collection surface (3) has a reference length ≤ 8, a thickness ≥ 2mm, and a weight ≤ 800g / m². 2 The groove (31) and flange (32) of the artificial rain collection surface (3) are both composed of arcs, so that the surface of the artificial rain collection surface (3) presents a wave structure.

6. The method for artificial rainwater harvesting and irrigation of farmland on broken slopes in rocky desertification areas according to claim 1, characterized in that: In step three, the load-bearing pile (1) is made of a mixture of crushed stone and mortar. The bottom of the load-bearing pile (1) is fixed together with the broken bedrock by mortar. The load-bearing beam (2) is made of miscellaneous tree trunks. The diameter of the load-bearing beam (2) is not greater than the diameter of the groove (31) of the artificial rain collection surface. The artificial rain collection surface (3) and the load-bearing beam (2) are connected by screws, and waterproof glue is applied to the screws after fixing.

7. The method for artificial rainwater harvesting and irrigation of farmland on broken slopes in rocky desertification areas according to claim 1, characterized in that: The material of the artificial rain collection surface (3) is PVC plastic steel composite resin tile; the material of the water collection pipe (4) is PVC pipe; the material of the manifold (5) is PVC pipe or PE pipe and needs to be buried underground; the low-level rain collection pool (6) is made of stainless steel water bucket or mortar-sealed solution ditch pool; the high-level water storage pool (10) is made of stainless steel or plastic material.

8. The method for artificial rainwater harvesting and irrigation of farmland on broken slopes in rocky desertification areas according to claim 1, characterized in that: The low-level water collection tank (6) is connected to an artificial rainwater collection surface (3), and its volume is calculated according to the following formula: Q l =A×P z The low-level water collection tank (6) is connected to multiple artificial rainwater collection surfaces (3), and its volume is calculated according to the following formula: In the formula: A n It is the nth catchment area, m 2 .

9. The method for artificial rainwater harvesting and irrigation of farmland on broken hillsides in rocky desertification areas according to claim 1, characterized in that: The volume of the elevated water storage tank (10) is calculated using the following formula: In the formula: Q h The volume of the elevated water storage tank is in meters. 3 Q ln Let m be the volume of the nth low-level water collection tank. 3 .

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