Design method for structural parameters of rainwater harvesting root zone supplementary irrigation device

Abstract

The invention provides a design method for structural parameters of a rainwater harvesting root domain supplementary irrigation device, which comprises the following steps of: simultaneously considering the rainwater harvesting surface area, the volume of a water storage tank and the design flow of a ceramic irrigation emitter, establishing a rainwater collection and utilization behavior calculation formula in the device under a daily scale, and calculating the structural parameters of the rainwater harvesting root domain supplementary irrigation device according to the formula. In combination with local day-by-day rainfall data, soil water holding capacity and a nursery stock root zone range, structural parameters including the rainwater collecting surface area, the water storage tank volume and the rated flow of a ceramic irrigation emitter are designed by taking the highest operation guarantee rate of an arid region rainwater collecting micropore ceramic root zone supplementary irrigation device as a target. The design method for the structural parameters of the rainwater-collecting micropore ceramic root domain supplementary irrigation device is provided for the first time, the rainwater utilization efficiency of rainwater-collecting root domain supplementary irrigation of afforestation seedlings in the arid region is improved, and then the seedling fruit rate and the preservation rate in afforestation engineering in the arid region are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of water-saving irrigation in arid forestry, relates to parameter design of a rain-collecting root zone supplementary irrigation device, and specifically relates to a design method for structural parameters of a rain-collecting root zone supplementary irrigation device. Background Art

[0002] Arid areas account for about 41% of the world's total land surface area and are an important part of the earth's terrestrial ecological system, supporting more than 38% of the world's population. In order to improve the ecological environment in arid areas, afforestation is usually adopted. However, due to the scarcity of water resources in arid areas and insufficient per capita water resources, how to ensure the survival of trees in arid areas under the condition of extreme water shortage is the most severe challenge facing afforestation projects.

[0003] In order to improve the ecological environment in arid areas, afforestation is usually adopted. At present, although rainwater harvesting irrigation technology, including water storage pit irrigation, rainwater collection deep infiltration and rainwater collection micro-irrigation, has achieved certain development and application, there are still problems such as low rainwater utilization efficiency and high equipment investment costs. For example, the soil is exposed in the water storage pit irrigation technology, the water evaporation is large, and surface runoff is easily formed during rainfall, which cannot meet the demand of seedlings for soil moisture; the rainwater collection deep infiltration technology uses ground film as rainwater collection material, and the ground film is easy to break in afforestation projects, resulting in reduced rainwater collection effect; the rainwater collection micro-irrigation technology requires the artificial construction of interception ditches or confluence channels, and the excavation of water cellars or reservoirs, and its investment cost and operation and management costs are high. Summary of the invention

[0004] In view of the defects and shortcomings of the prior art, the purpose of the present invention is to provide a method for designing the structural parameters of a rain-collecting root zone supplementary irrigation device to solve the technical problem of low rainwater utilization efficiency in the prior art when performing rain-collecting root zone supplementary irrigation on seedlings for afforestation in arid areas.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0006] A method for designing structural parameters of a rain-collecting root zone supplementary irrigation device, the method is used to design the structural parameters of the rain-collecting root zone supplementary irrigation device; the structural parameters of the rain-collecting root zone supplementary irrigation device include the rain-collecting surface area, the water storage tank volume, and the rated flow of the ceramic sprinkler; the method specifically comprises the following steps:

[0007] Step 1: Calculate the amount of rainwater collected by the rainwater collection root zone irrigation device on day t:

[0008] According to the rainwater collection area, the precipitation collection efficiency and the precipitation on the tth day, the rainwater collection amount of the rainwater collection root zone irrigation device on the tth day is calculated and obtained using Formula I; the formula I is as follows:

[0009]

[0010] Where:

[0011] R t is the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t, in m 3 .

[0012] P t is the precipitation on the tth day, in mm.

[0013] F t is the precipitation loss on the tth day, in mm.

[0014] A is the rainwater collection area, in m 2 .

[0015] E is the precipitation collection efficiency, in %.

[0016] Step 2: Calculate the overflow volume on day t:

[0017] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is less than or equal to the volume of the water storage tank, then the overflow rate on day t is 0 according to formula II-1.

[0018] If the sum of the actual water storage capacity of the water tank on the t-1 day and the rainwater collected by the rainwater collecting root zone irrigation device on the t day is greater than the volume of the water tank, then based on the actual water storage capacity of the water tank on the t-1 day, the rainwater collected by the rainwater collecting root zone irrigation device on the t day and the volume of the water tank, Formula II-2 is used to calculate and obtain the overflow flow on the t day.

[0019] The formula II-1 and formula II-2 are shown below:

[0020]

[0021] Where:

[0022] O t is the overflow volume on day t, in m 3 .

[0023] S is the volume of the water tank, in m 3 .

[0024] S t-1 is the actual water storage capacity of the water tank on day t-1, in m 3 .

[0025] Step 3: Calculate the actual water supply on day t:

[0026] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is equal to 0, then the actual water supply on day t is 0 according to formula IV-1.

[0027] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root area irrigation device on day t is greater than 0 and less than or equal to the preset water supply on day t, formula IV-2 is used to calculate and obtain the actual water supply on day t.

[0028] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than the preset water supply on day t, the actual water supply on day t is obtained according to formula IV-3.

[0029] The formula IV-1, formula IV-2 and formula IV-3 are shown below:

[0030]

[0031] Where:

[0032] D t The preset water supply volume for day t, in m 3 .

[0033] D t ' is the actual water supply on day t, in m 3 .

[0034] Step 4: Calculate the actual water storage capacity of the water tank on day t:

[0035] If the sum of the actual water storage capacity of the water tank on day t-1 and the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t is less than or equal to the volume of the water tank, then formula III-1 is used to calculate and obtain the actual water storage capacity of the water tank on day t.

[0036] If the sum of the actual water storage capacity of the water tank on day t-1 and the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than the volume of the water tank, then formula III-2 is used to calculate and obtain the actual water storage capacity of the water tank on day t.

[0037] The formula III-1 and formula III-2 are shown below:

[0038]

[0039] Where:

[0040] S t is the water storage capacity of the device on day t, in m 3 .

[0041] The preset water supply volume on the tth day is calculated and obtained using formula VII; the formula VII is as follows:

[0042] D t =nQ t Formula VII.

[0043] Where:

[0044] n is the number of ceramic emitters connected to the water tank.

[0045] Q t is the rated flow rate of the ceramic sprinkler, i.e. the outflow rate of the ceramic sprinkler on day t, in mL h -1 .

[0046] The outflow rate of the ceramic emitter on the tth day is calculated and obtained by using formula VIII; the formula VIII is as follows:

[0047]

[0048] Where:

[0049] k is the water conductivity of ceramic material, unit is m day -1 .

[0050] a is the seepage area of ​​ceramic material, unit is m 2 .

[0051] lThe length of the seepage path of the ceramic material, in meters.

[0052] H t-1 is the working water head on the t-1th day, in m.

[0053] The present invention also has the following technical features:

[0054] Specifically, the method further includes:

[0055] Step 5: Calculate the actual total number of days during the total operation period of the rainwater collection root zone irrigation device that cannot meet the use requirements:

[0056] The preset total number of days during the total operation cycle of the rainwater collection root area irrigation device that cannot meet the usage requirements is assigned a value of 0.

[0057] If the actual water supply on the tth day is greater than the reference afforestation seedling water requirement, then according to Formula V-1, the actual total number of days during the total operating cycle of the rain-collecting root zone irrigation device that cannot meet the usage requirements is 0.

[0058] If the actual water supply on the tth day is less than or equal to the reference afforestation seedling water requirement, formula V-2 is used to calculate and obtain the actual total number of days during the total operating cycle of the rain-collecting root zone irrigation device that cannot meet the usage requirements.

[0059] The formula V-1 and formula V-2 are as follows:

[0060]

[0061] Where:

[0062] U' is the actual total number of days during the total operation cycle of the rainwater harvesting root zone irrigation device that cannot meet the usage requirements.

[0063] U is the preset total number of days during the total operation cycle of the rainwater harvesting root zone irrigation device that cannot meet the usage requirements.

[0064] ET c It is the water requirement of afforestation seedlings, in mm.

[0065] Step 6: Calculate the safe operation guarantee rate of the rainwater collection root area irrigation device:

[0066] According to the total number of days in the total operation cycle of the rain-collecting root zone supplementary irrigation device and the actual total number of days in which the rain-collecting root zone supplementary irrigation device cannot meet the use requirements within the total operation cycle, the safe operation guarantee rate of the rain-collecting root zone supplementary irrigation device is calculated and obtained using formula VI; the formula VI is as follows:

[0067]

[0068] Where:

[0069] DOR is the device safe operation guarantee rate, in %.

[0070] N is the total number of days of the total operation cycle of the rain-collecting root zone irrigation device.

[0071] When the actual water supply on the t day is greater than the water demand of the afforestation seedlings on that day, the rain-collecting root zone irrigation device is in a safe operating state; when the actual water supply on the t day is less than or equal to the water demand of the afforestation seedlings on that day, the rain-collecting root zone irrigation device is not in a safe operating state.

[0072] Specifically, the working water head on the t-1th day is calculated and obtained using Formula IX; the Formula IX is as follows:

[0073]

[0074] Where:

[0075] A t is the bottom area of ​​the water tank, in m 2 .

[0076] d is the burial depth of the ceramic emitter, in meters.

[0077] Specifically, the water requirement of the afforestation seedlings is calculated and obtained using Formula X; the Formula X is as follows:

[0078] ET c =K c ×ET0 formula Ⅹ.

[0079] Where:

[0080] K c is the crop coefficient; K c The value of is 0.6.

[0081] ET0 is the reference crop evapotranspiration, in mm.

[0082] Specifically, the rain-collecting root zone irrigation device comprises a water tank, a rain-collecting tray is installed in the water tank, a ceramic sprinkler is arranged below the water tank, and the ceramic sprinkler and the water tank are connected by a hose; the bottom of the water tank, the ceramic sprinkler and the hose are all buried under the ground; the top surface of the rain-collecting tray is the rain-collecting surface, and the rain-collecting surface is exposed on the ground where the device is used; plants are planted on the ground where the device is used, and the water tank and the rain-collecting tray are mounted outside the bottom of the plants.

[0083] Specifically, the water tank comprises a main water tank shell, and a water tank bottom plate is integrally arranged at the bottom end of the main water tank shell; a pair of water tank shell extension plates are integrally arranged in the water tank main shell, and the water tank shell extension plates are arranged along the radial direction of the water tank bottom plate, and the pair of water tank shell extension plates are arranged in parallel and opposite to each other; a water tank center cylinder is integrally arranged at the center of the water tank bottom plate, and the notch of the water tank center cylinder is just opposite to the notch of the main water tank shell, and the space surrounded by the water tank center cylinder is coaxial with the center hole of the water tank bottom plate; the water tank center cylinder and the water tank shell extension plate are integrally arranged, and the gap between the pair of water tank shell extension plates and the space surrounded by the water tank center cylinder are connected and together constitute a water tank opening.

[0084] Specifically, the notch of the rain collecting tray is just opposite to the notch of the main shell of the water tank, the central opening of the rain collecting tray is the rain collecting plate mounting port, and the rain collecting tray is mounted on the central tube of the water tank through the rain collecting plate mounting port; the rain collecting tray includes a plurality of upwardly protruding rain collecting prisms, the plurality of rain collecting prisms are evenly arranged along the circumferential direction, the rain collecting prisms are inclined along the radial direction and the radial outer ends thereof are higher than the radial inner ends; the connection between two adjacent rain collecting prisms is recessed downward to form a rain collecting groove; a long through hole is opened on the rain collecting tray around the rain collecting plate mounting port, and the long through hole is a confluence inlet.

[0085] Specifically, a pair of soil retaining plates are integrally arranged at the edge of the rain collecting tray, and the gap between the pair of soil retaining plates is the notch of the rain collecting tray.

[0086] Specifically, the ceramic emitter includes an emitter lower shell, which is a hollow flat cylindrical structure. An emitter upper shell is installed in the emitter lower shell. An emitter water inlet is provided on the top of the emitter upper shell. The emitter water inlet is connected to a water storage tank through a hose. The open bottom end of the emitter lower shell is an emitter water outlet. A water seepage sheet is installed in the emitter lower shell, and the water seepage sheet is located between the emitter upper shell and the emitter water outlet.

[0087] Compared with the prior art, the present invention has the following beneficial technical effects:

[0088] (I) The present invention proposes for the first time that by calculating the rainwater collection and utilization behavior in the device on a daily scale under different rainwater collection surface areas, water storage tank volumes, and rated flow rates of ceramic emitters, and taking the highest guarantee rate of safe operation of the device as the goal, the structural parameter design of the rainwater collection microporous ceramic root zone supplementary irrigation device in arid forests can be achieved. The present invention fills the gap in the structural parameter design of the rainwater collection root zone supplementary irrigation device, and helps to improve the rainwater utilization efficiency of rainwater collection root zone supplementary irrigation for afforestation seedlings in arid areas.

[0089] (II) Since the present invention takes into account the daily rainfall distribution in the area where the device is used, the parameter design result is more accurate, which helps to improve the seedling fruit yield and preservation rate in the afforestation project in arid areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 This is the installation diagram of the rainwater collecting root zone irrigation device.

[0091] Figure 2 This is a schematic diagram of the structure of the water tank.

[0092] Figure 3 It is a structural schematic diagram of the rain collection tray.

[0093] Figure 4 It is a structural schematic diagram of a ceramic water emitter (exploded view).

[0094] Figure 5 This is a schematic diagram of the structure of a ceramic water emitter.

[0095] Figure 6 The calculation flow chart of the design method of the structural parameters of the rainwater harvesting root zone irrigation device.

[0096] Figure 7 This is the distribution map of the applied standard precipitation index in the mining area of ​​Wuda District, Wuhai City from 2002 to 2020.

[0097] Figure 8 The effects of different water storage tank volumes and rainwater collection areas on the safe operation guarantee rate of the device in drought years, normal years and wet years are demonstrated.

[0098] The meanings of the numbers in the figure are: 1-water storage tank, 2-rainwater collection tray, 3-ceramic sprinkler, 4-hose, 5-ground, 6-plants.

[0099] 101 - main shell of water tank, 102 - bottom plate of water tank, 103 - extension plate of water tank shell, 104 - central tube of water tank, 105 - opening of water tank, 106 - buckle.

[0100] 201-rain collecting plate installation opening, 202-rain collecting prism, 203-rain collecting trough, 204-confluence inlet, 205-soil retaining plate.

[0101] 301-the lower shell of the sprinkler, 302-the upper shell of the sprinkler, 303-the water inlet of the sprinkler, 304-the water outlet of the sprinkler, 305-the water seepage sheet, 306-the water stop gasket, 307-the inner thread of the lower shell of the sprinkler, 308-the outer thread of the upper shell of the sprinkler.

[0102] The technical solution of the present invention is further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0103] The technical idea of ​​the present invention is as follows: the present invention simultaneously considers the rainwater collection surface area of ​​the rainwater collection tray (2), the volume of the water storage tank (1), and the ceramic sprinkler (3), and establishes a calculation formula for rainwater collection and utilization behavior in the device on a daily scale. According to this formula, after the daily rainfall data, soil physical property parameters, and seedling species to be planted at the given device use site are taken as the highest safe operation guarantee rate of the rainwater collection microporous ceramic root zone irrigation device in dry years, normal years, and wet years, the structural parameters including the rainwater collection surface area, the volume of the water storage tank, and the rated flow of the ceramic sprinkler are designed.

[0104] The calculation formulas for rainwater collection and utilization behavior in the device on a daily scale include the following formulas I, II, III and IV:

[0105]

[0106] Where: R t is the amount of rainwater collected by the rainwater collecting root zone irrigation device on the tth day; P t is the precipitation on day t; F t is the precipitation loss on the tth day; A is the rainwater collection area; E is the precipitation collection efficiency; O t is the overflow volume on day t; S is the volume of the water tank; S t-1 is the actual water storage capacity of the water tank on day t-1; D t Preset water supply for day t; D t ' is the actual water supply on day t; S t is the water storage capacity of the device on day t.

[0107] It should be noted that all components used in the present invention, unless otherwise specified, are components known in the art.

[0108] In accordance with the above technical scheme, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical scheme of this application fall within the protection scope of the present invention.

[0109] Embodiment 1:

[0110] This embodiment provides a rainwater collection root zone irrigation device, such as Figure 1 As shown, it includes a water tank 1, a rain collecting tray 2 is installed in the water tank 1, a ceramic sprinkler 3 is arranged below the water tank 1, and the ceramic sprinkler 3 and the water tank 1 are connected through a hose 4; the bottom of the water tank 1, the ceramic sprinkler 3 and the hose 4 are all buried under the ground 5; the top surface of the rain collecting tray 2 is the rain collecting surface, and the rain collecting surface is exposed on the ground 5 where the device is used; plants 6 are planted on the ground where the device is used, and the water tank 1 and the rain collecting tray 2 are set outside the bottom of the plants 6.

[0111] As a specific solution of this embodiment, Figure 2 As shown, the water tank 1 includes a water tank main shell 101, which is a cylindrical structure with a notch. The bottom end of the water tank main shell 101 is integrally provided with a water tank bottom plate 102, which is a circular plate structure with a notch and a center hole. A pair of water tank shell extension plates 103 are integrally provided in the water tank main shell 101, and the water tank shell extension plates 103 are arranged along the radial direction of the water tank bottom plate 102. The pair of water tank shell extension plates 103 are arranged parallel to each other. The water tank bottom plate 102 A water tank central tube 104 is integrally arranged at the center, and the water tank central tube 104 is a cylindrical structure with a notch, and the notch of the water tank central tube 104 is just opposite to the notch of the water tank main shell 101, and the space surrounded by the water tank central tube 104 is coaxial with the center hole of the water tank bottom plate 102; the water tank central tube 104 and the water tank shell extension plate 103 are integrated, and the gap between a pair of water tank shell extension plates 103 and the space surrounded by the water tank central tube 104 are connected and together constitute a water tank opening 105.

[0112] As a specific solution of this embodiment, Figure 2 As shown, a buckle 106 is provided at the upper edge of the main shell 101 of the water storage tank.

[0113] As a specific solution of this embodiment, Figure 3 As shown, the rain collecting tray 2 is a circular structure similar to a folding fan with a notch, the notch of the rain collecting tray 2 is just opposite to the notch of the main shell 101 of the water storage tank, the central opening of the rain collecting tray 2 is a rain collecting plate mounting opening 201, and the rain collecting tray 2 is sleeved on the central tube 104 of the water storage tank through the rain collecting plate mounting opening 201; the rain collecting tray 2 includes a plurality of upwardly protruding rain collecting prisms 202, the plurality of rain collecting prisms 202 are evenly arranged along the circumferential direction, the rain collecting prisms 202 are inclined along the radial direction and the radial outer ends thereof are higher than the radial inner ends; the connection between two adjacent rain collecting prisms 202 is recessed downward to form a rain collecting groove 203; a long through hole similar to a circular fan is provided on the rain collecting tray 2 around the rain collecting plate mounting opening 201, and the long through hole is a confluence inlet 204.

[0114] As a specific solution of this embodiment, Figure 3 As shown, a pair of soil retaining plates 205 are integrally provided at the edge of the rain collecting tray 2 , and the gap between the pair of soil retaining plates 205 is the notch of the rain collecting tray 2 .

[0115] As a specific solution of this embodiment, Figure 4 and Figure 5 As shown, the ceramic emitter 3 is a button-type microporous ceramic emitter known in the prior art; the ceramic emitter 3 comprises an emitter lower shell 301, which is a hollow flat cylindrical structure, an emitter upper shell 302 is installed in the emitter lower shell 301, an emitter water inlet 303 is arranged on the top of the emitter upper shell 302, the emitter water inlet 303 is connected to the water storage tank 1 through a hose 4, and the open bottom end of the emitter lower shell 301 is an emitter water outlet 304; a water seepage sheet 305 is installed in the emitter lower shell 301, and the water seepage sheet 305 is located between the emitter upper shell 302 and the emitter water outlet 304.

[0116] As a specific solution of this embodiment, Figure 4 and Figure 5 As shown, two water-stopping washers 306 are installed outside the upper housing 302 of the emitter, and the water-stopping washers 306 are arranged between the upper housing 302 of the emitter and the lower housing 301 of the emitter.

[0117] As a specific solution of this embodiment, Figure 4 and Figure 5 As shown, the inner wall of the emitter lower shell 301 is provided with an emitter lower shell internal thread 307 , and the outer wall of the emitter upper shell 302 is provided with an emitter upper shell external thread 308 , which matches the emitter lower shell internal thread 307 .

[0118] Embodiment 2:

[0119] This embodiment provides a method for designing the structural parameters of a rainwater collecting root zone supplementary irrigation device, which is used to design the structural parameters of the rainwater collecting root zone supplementary irrigation device of embodiment 1. Figure 7 As shown, the method specifically comprises the following steps:

[0120] Step 1: Calculate the amount of rainwater collected by the rainwater collection root zone irrigation device on day t:

[0121] According to the rainwater collection area, precipitation collection efficiency and precipitation on the tth day, the rainwater collection amount of the rainwater collection root zone irrigation device on the tth day is calculated and obtained using formula I; formula I is as follows:

[0122]

[0123] Where:

[0124] R t is the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t, in m 3 .

[0125] P t is the precipitation on the tth day, in mm, and the value is obtained from the China Meteorological Data Network.

[0126] F t is the precipitation loss on the tth day, in mm, and the value is obtained through the China Meteorological Data Network.

[0127] A is the rainwater collection area, in m 2 .

[0128] E is the precipitation collection efficiency, in %. In this embodiment, the value of E is 0.78.

[0129] Step 2: Calculate the overflow volume on day t:

[0130] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is less than or equal to the volume of the water storage tank, then the overflow rate on day t is 0 according to formula II-1.

[0131] If the sum of the actual water storage capacity of the water tank on the t-1 day and the rainwater collected by the rainwater collecting root zone irrigation device on the t day is greater than the volume of the water tank, then based on the actual water storage capacity of the water tank on the t-1 day, the rainwater collected by the rainwater collecting root zone irrigation device on the t day and the volume of the water tank, Formula II-2 is used to calculate and obtain the overflow flow on the t day.

[0132] The formula II-1 and formula II-2 are shown below:

[0133]

[0134] Where:

[0135] O t is the overflow volume on day t, in m 3 .

[0136] S is the volume of the water tank, in m 3 .

[0137] S t-1 is the actual water storage capacity of the water tank on day t-1, in m 3 .

[0138] Step 3: Calculate the actual water supply on day t:

[0139] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is equal to 0, then the actual water supply on day t is 0 according to formula IV-1.

[0140] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root area irrigation device on day t is greater than 0 and less than or equal to the preset water supply on day t, formula IV-2 is used to calculate and obtain the actual water supply on day t.

[0141] If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than the preset water supply on day t, the actual water supply on day t is obtained according to formula IV-3.

[0142] The formula IV-1, formula IV-2 and formula IV-3 are shown below:

[0143]

[0144] Where:

[0145] D t The preset water supply volume for day t, in m 3 .

[0146] D t ' is the actual water supply on day t, in m 3 .

[0147] Step 4: Calculate the actual water storage capacity of the water tank on day t:

[0148] If the sum of the actual water storage capacity of the water tank on day t-1 and the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t is less than or equal to the volume of the water tank, then formula III-1 is used to calculate and obtain the actual water storage capacity of the water tank on day t.

[0149] If the sum of the actual water storage capacity of the water tank on day t-1 and the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than the volume of the water tank, then formula III-2 is used to calculate and obtain the actual water storage capacity of the water tank on day t.

[0150] The formula III-1 and formula III-2 are shown below:

[0151]

[0152] Where:

[0153] S t is the water storage capacity of the device on day t, in m 3 .

[0154] Step 5: Calculate the actual total number of days during the total operation period of the rainwater collection root zone irrigation device that cannot meet the use requirements:

[0155] The preset total number of days during the total operation cycle of the rainwater collection root area irrigation device that cannot meet the usage requirements is assigned a value of 0.

[0156] If the actual water supply on the tth day is greater than the reference afforestation seedling water requirement, then according to Formula V-1, the actual total number of days during the total operating cycle of the rain-collecting root zone irrigation device that cannot meet the usage requirements is 0.

[0157] If the actual water supply on the tth day is less than or equal to the reference afforestation seedling water requirement, formula V-2 is used to calculate and obtain the actual total number of days during the total operating cycle of the rain-collecting root zone irrigation device that cannot meet the usage requirements.

[0158] The formula V-1 and formula V-2 are as follows:

[0159]

[0160] Where:

[0161] U' is the actual total number of days during the total operation cycle of the rainwater harvesting root zone irrigation device that cannot meet the usage requirements.

[0162] U is the preset total number of days during the total operation cycle of the rainwater harvesting root zone irrigation device that cannot meet the usage requirements.

[0163] ET c It is the water requirement of afforestation seedlings, in mm.

[0164] Step 6: Calculate the safe operation guarantee rate of the rainwater collection root area irrigation device:

[0165] According to the total number of days in the total operation cycle of the rain-collecting root zone supplementary irrigation device and the actual total number of days in which the rain-collecting root zone supplementary irrigation device cannot meet the use requirements within the total operation cycle, the safe operation guarantee rate of the rain-collecting root zone supplementary irrigation device is calculated and obtained using formula VI; the formula VI is as follows:

[0166]

[0167] Where:

[0168] DOR is the device safe operation guarantee rate, in %.

[0169] N is the total number of days of the total operation cycle of the rain-collecting root zone irrigation device.

[0170] When the actual water supply on the t day is greater than the water demand of the afforestation seedlings on that day, the rain-collecting root zone irrigation device is in a safe operating state; when the actual water supply on the t day is less than or equal to the water demand of the afforestation seedlings on that day, the rain-collecting root zone irrigation device is not in a safe operating state.

[0171] As a specific solution of this embodiment, the preset water supply volume on the tth day is calculated and obtained using formula VII; the formula VII is as follows:

[0172] D t =nQ t Formula VII.

[0173] Where:

[0174] n is the number of ceramic sprinklers connected to the water tank. In this embodiment, the value of n is 2, that is, each water tank is connected to two ceramic sprinklers.

[0175] Q t is the rated flow rate of the ceramic sprinkler, that is, the outflow rate of the ceramic sprinkler on the tth day, in m 3 day -1 .

[0176] As a specific solution of this embodiment, according to Darcy's law, the outflow rate of the ceramic emitter on the tth day is calculated and obtained using Formula VIII; the Formula VIII is as follows:

[0177]

[0178] Where:

[0179] k is the discharge coefficient of the ceramic emitter, in m day -1 ;

[0180] a is the seepage area of ​​the ceramic emitter, unit is m 2 ; In this embodiment, the value of a is 0.00126.

[0181] l is the length of the seepage path of the ceramic emitter, in meters. In this embodiment, the value of l is 2.

[0182] H t-1 is the working water head on day t-1, in m;

[0183] As a specific solution of this embodiment, the working water head on the t-1th day is calculated and obtained using Formula IX; the Formula IX is as follows:

[0184]

[0185] Where:

[0186] A t is the bottom area of ​​the water tank, in m 2 In this embodiment, A t The value of is 0.04.

[0187] d is the burial depth of the ceramic emitter, in meters. In this embodiment, the value of d is 0.15.

[0188] As a specific solution of this embodiment, the water requirement of the afforestation seedlings is calculated and obtained using Formula X; the Formula X is as follows:

[0189] ET c =Kc ×ET0 formula Ⅹ.

[0190] Where:

[0191] K c is the crop coefficient. In this embodiment, K c The value of is 0.6.

[0192] ET0 is the reference crop evapotranspiration, in mm;

[0193] Effect verification of Example 2:

[0194] The application site of the rainwater collection root zone irrigation device in Example 2 is located in the mining area of ​​Wuda District, Wuhai City. The mining area has an altitude of 1181-1257m, an average annual precipitation of 156.8mm, and an average annual surface evaporation of 3206mm. It belongs to a typical arid climate. There are 12 mines in the area with a total area of ​​29.6873km 2 .

[0195] like Figure 1 As shown, when in use, the rain collecting tray 2 is flush with the soil surface, and the water storage tank 1 is buried 20 cm into the soil; the ceramic sprinkler 3 is connected to the water storage tank 1 with a hose 4, the burial depth d of the ceramic sprinkler is 5 cm, and the precipitation collection efficiency E is 0.78.

[0196] The soil of the application site of the rainwater collection root zone irrigation device is sandy loam, and the field water holding capacity is 0.17cm 3 cm -3 , the wilting coefficient is 0.10cm 3 cm -3 , saturated hydraulic conductivity is 106.1cm day -1 Scots pine is a common tree used in local afforestation projects. It is drought-resistant and heat-resistant. The maximum root length of the seedling is 40cm and the horizontal width is 20cm.

[0197] (1) Selection of characteristic precipitation years: The standard precipitation index is an important parameter that reflects the precipitation characteristics of different regions. The lower the standard precipitation index, the lower the total precipitation in that year and the higher the degree of drought. The standard precipitation index can be calculated using the following formula Ⅺ:

[0198]

[0199] Where:

[0200] SPI is the Standardized Precipitation Index.

[0201] X p It is the total monthly precipitation in mm.

[0202] X m It is the multi-year average monthly precipitation, in mm.

[0203] σ is the standard deviation of the total monthly precipitation over many years.

[0204] The SPI value represents the amount of local precipitation resources. It is divided into seven situations according to the size of the SPI value, namely extremely wet (>2.00), very wet (1.50 to 1.99), relatively wet (1.00 to 1.49), normal (-0.99 to 0.99), relatively dry (-1.49 to -1.00), very dry (-1.99 to -1.50) and extremely dry (<-2.00). The years corresponding to the lowest, medium and highest SPI are selected as dry years, normal years and wet years.

[0205] Figure 7 The distribution pattern of the standard precipitation index in the application area from 2002 to 2020 is shown. Figure 7 As can be seen in the graph, the highest and lowest SPI values ​​(-1.23 and 199, respectively) were observed in 2005 and 2018. In addition, the SPI value in 2004 was 0.24, which is close to the average SPI value.

[0206] Therefore, 2005, 2004, and 2018 were selected as dry, normal, and wet years, respectively.

[0207] (2) Determination of rated flow rate of ceramic sprinkler: Figure 5 As shown in the figure, when the flow coefficient of the ceramic sprinkler is between 0.1 and 0.3 cm h -1 When the flow coefficient of the ceramic emitter is greater than 0.3 cm h -1 When the device operation reliability of different representative years decreases rapidly with the increase of the ceramic emitter flow coefficient.

[0208] Therefore, the rainwater collection root zone irrigation device should use a ceramic emitter with a flow coefficient of 0.3 cm h -1 The rated flow rate is calculated by formula VIII to be 6 mL h -1 The ceramic sprinkler is suitable for the afforestation project in Wuda mining area.

[0209] (3) Determination of rainwater collection area A and water storage tank volume S: -1 ) under the condition that Figure 8As shown in the figure, the influence of different water storage tank volumes and rainwater collection areas on the safe operation guarantee rate of the device in dry years, normal years and wet years. When the water storage tank volume S is less than 25L, the operation reliability of the device in dry years, normal years and wet years increases with the increase of the water storage tank volume S. When the water storage tank volume S is greater than 25L, the operation reliability of the device in different rainwater collection areas in dry years, normal years and wet years can be maintained at 100%.

[0210] Therefore, when the rainwater collection area is 0.5m 2 The water tank capacity is 25L, and the device operation reliability is above 90%, which can be used as the device structural parameters for the afforestation project in Wuda mining area.

Claims

1. A method for designing structural parameters of a rainwater collecting root zone irrigation device, characterized in that: The method is used to design the structural parameters of a rain-collecting root zone supplementary irrigation device; the structural parameters of the rain-collecting root zone supplementary irrigation device include the rain-collecting surface area, the water storage tank volume, and the rated flow of the ceramic sprinkler; The method specifically comprises the following steps: Step 1: Calculate the amount of rainwater collected by the rainwater collection root zone irrigation device on day t: According to the rainwater collection area, the precipitation collection efficiency and the precipitation on the tth day, the rainwater collection amount of the rainwater collection root zone irrigation device on the tth day is calculated and obtained using Formula I; the formula I is as follows: Where: R t is the amount of rainwater collected by the rainwater collecting root zone irrigation device on day t, in m 3 ; P t is the precipitation on the tth day, in mm; F t is the precipitation loss on the tth day, in mm; A is the rainwater collection area, in m 2 ; E is the precipitation collection efficiency, in %; Step 2: Calculate the overflow volume on day t: If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collection root zone irrigation device on day t is less than or equal to the volume of the water storage tank, then the overflow rate on day t is 0 according to formula II-1; If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone recharge irrigation device on day t is greater than the volume of the water storage tank, then according to the actual water storage capacity of the water storage tank on day t-1, the rainwater collected by the rainwater collecting root zone recharge irrigation device on day t and the volume of the water storage tank, the overflow volume on day t is calculated and obtained using formula II-2; The formula II-1 and formula II-2 are shown below: Where: O t is the overflow volume on day t, in m 3 ; S is the volume of the water tank, in m 3 ; S t-1 is the actual water storage capacity of the water tank on day t-1, in m 3 ; Step 3: Calculate the actual water supply on day t: If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is equal to 0, then the actual water supply on day t is 0 according to formula IV-1; If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than 0 and less than or equal to the preset water supply on day t, then the actual water supply on day t is calculated using formula IV-2; If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than the preset water supply on day t, the actual water supply on day t is obtained according to formula IV-3; The formula IV-1, formula IV-2 and formula IV-3 are shown below: Where: D t The preset water supply volume for day t, in m 3 ; D t ' is the actual water supply on day t, in m 3 ; Step 4: Calculate the actual water storage capacity of the water tank on day t: If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is less than or equal to the volume of the water storage tank, then the actual water storage capacity of the water storage tank on day t is calculated using formula III-1; If the sum of the actual water storage capacity of the water storage tank on day t-1 and the rainwater collected by the rainwater collecting root zone irrigation device on day t is greater than the volume of the water storage tank, then the actual water storage capacity of the water storage tank on day t is calculated using formula III-2; The formula III-1 and formula III-2 are shown below: Where: S t is the water storage capacity of the device on day t, in m 3 ; The preset water supply volume on the tth day is calculated and obtained using formula VII; the formula VII is as follows: D t =nQ t Formula VII; Where: n is the number of ceramic emitters connected to the water tank; Q t is the rated flow rate of the ceramic sprinkler, that is, the outflow rate of the ceramic sprinkler on the tth day, in m 3 day -1 ; The outflow rate of the ceramic emitter on the tth day is calculated and obtained by using formula VIII; the formula VIII is as follows: Where: k is the water conductivity of ceramic material, unit is m day -1 ; a is the seepage area of ​​ceramic material, unit is m 2 ; lThe length of the seepage path of the ceramic material, in meters; H t-1 is the working water head on the t-1th day, in m.

2. The design method of structural parameters of the rainwater collecting root zone irrigation device according to claim 1 is characterized in that: The method further includes: Step 5: Calculate the actual total number of days during the total operation period of the rainwater collection root zone irrigation device that cannot meet the use requirements: The preset total number of days during the total operation cycle of the rainwater collection root area irrigation device that cannot meet the use requirements is assigned a value of 0; If the actual water supply on the tth day is greater than the reference afforestation seedling water requirement, then the actual total number of days that the rainwater collection root zone irrigation device cannot meet the use requirements within the total operation cycle is 0 according to Formula V-1; If the actual water supply on the tth day is less than or equal to the reference afforestation seedling water requirement, then the actual total number of days during the total operation cycle of the rainwater collection root zone irrigation device that cannot meet the use requirements is calculated using formula V-2; The formula V-1 and formula V-2 are as follows: Where: U' is the actual total number of days during the total operation cycle of the rainwater collection root zone irrigation device that cannot meet the use requirements; U is the preset total number of days during the total operation cycle of the rainwater harvesting root zone irrigation device that cannot meet the use requirements; ET c It is the water requirement of afforestation seedlings, in mm.

3. The design method of structural parameters of the rainwater collecting root zone irrigation device according to claim 1 is characterized in that: The method further includes: Step 6: Calculate the safe operation guarantee rate of the rainwater collection root area irrigation device: According to the total number of days in the total operation cycle of the rain-collecting root zone supplementary irrigation device and the actual total number of days in which the rain-collecting root zone supplementary irrigation device cannot meet the use requirements within the total operation cycle, the safe operation guarantee rate of the rain-collecting root zone supplementary irrigation device is calculated and obtained using formula VI; the formula VI is as follows: Where: DOR is the device safe operation guarantee rate, in %; N is the total number of days of the total operation cycle of the rainwater harvesting root zone irrigation device; When the actual water supply on the t day is greater than the water demand of the afforestation seedlings on that day, the rain-collecting root zone irrigation device is in a safe operating state; when the actual water supply on the t day is less than or equal to the water demand of the afforestation seedlings on that day, the rain-collecting root zone irrigation device is not in a safe operating state.

4. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 1, characterized in that: The working water head on the t-1 day is calculated and obtained using Formula IX; the Formula IX is as follows: Where: A t is the bottom area of ​​the water tank, in m 2 ; d is the burial depth of the ceramic emitter, in meters.

5. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 1, characterized in that: The water requirement of the afforestation seedlings is calculated and obtained using Formula X; the Formula X is as follows: ET c = K c × ET0 formula Ⅹ; Where: K c is the crop coefficient; K c The value of is 0.6; ET0 is the reference crop evapotranspiration, in mm.

6. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 1, characterized in that: The rain-collecting root zone irrigation device comprises a water storage tank (1), a rain-collecting tray (2) is installed in the water storage tank (1), a ceramic water injector (3) is arranged below the water storage tank (1), and the ceramic water injector (3) and the water storage tank (1) are connected through a hose (4); the bottom of the water storage tank (1), the ceramic water injector (3) and the hose (4) are all buried under the ground (5); the top surface of the rain-collecting tray (2) is a rain-collecting surface, and the rain-collecting surface is exposed on the ground (5) where the device is used; plants (6) are planted on the ground where the device is used, and the water storage tank (1) and the rain-collecting tray (2) are sleeved outside the bottom of the plants (6).

7. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 6, characterized in that: The water tank (1) comprises a water tank main shell (101), the bottom end of which is integrally provided with a water tank bottom plate (102); a pair of water tank shell extension plates (103) are integrally provided in the water tank main shell (101), the water tank shell extension plates (103) are arranged along the radial direction of the water tank bottom plate (102), and the pair of water tank shell extension plates (103) are arranged parallel to each other; a water tank bottom plate (102) is integrally provided at the center of the water tank bottom plate (102). The water tank central tube (104) is provided with a notch of the water tank main shell (101), and the space enclosed by the water tank central tube (104) is coaxial with the central hole of the water tank bottom plate (102); the water tank central tube (104) and the water tank shell extension plate (103) are integrated, and the gap between the pair of water tank shell extension plates (103) and the space enclosed by the water tank central tube (104) are connected and together form a water tank opening (105).

8. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 6, characterized in that: The notch of the rain collecting tray (2) is aligned with the notch of the main shell (101) of the water tank, the central opening of the rain collecting tray (2) is a rain collecting plate mounting opening (201), and the rain collecting tray (2) is sleeved on the central tube (104) of the water tank through the rain collecting plate mounting opening (201); the rain collecting tray (2) comprises a plurality of rain collecting prisms (202) protruding upwards, the plurality of rain collecting prisms (202) are evenly arranged along the circumferential direction, the rain collecting prisms (202) are inclined along the radial direction and the radial outer ends thereof are higher than the radial inner ends; the connection between two adjacent rain collecting prisms (202) is recessed downwards to form a rain collecting groove (203); a long through hole is provided on the rain collecting tray (2) around the rain collecting plate mounting opening (201), and the long through hole is a converging water inlet (204).

9. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 6, characterized in that: A pair of soil retaining plates (205) are integrally arranged at the edge of the rain collecting tray (2), and the gap between the pair of soil retaining plates (205) is the notch of the rain collecting tray (2).

10. The method for designing structural parameters of the rainwater collecting root zone irrigation device according to claim 6, characterized in that: The ceramic emitter (3) comprises an emitter lower shell (301), which is a hollow flat cylindrical structure. An emitter upper shell (302) is installed in the emitter lower shell (301), and an emitter water inlet (303) is arranged on the top of the emitter upper shell (302). The emitter water inlet (303) is connected to the water storage tank (1) through a hose (4), and the open bottom end of the emitter lower shell (301) is an emitter water outlet (304); a water seepage sheet (305) is installed in the emitter lower shell (301), and the water seepage sheet (305) is located between the emitter upper shell (302) and the emitter water outlet (304).

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