Ecological multi-strand narrow and deep river channel remodeling method for reducing water evaporation of river in desert region

Abstract

The invention discloses an ecological multi-strand narrow and deep river channel remodeling method for reducing water evaporation of a river in a desert region, which comprises the following four steps of: remodeling the shape of a river channel section: reconstructing an original wide and shallow river channel into 2-5 deep and narrow main streams under the condition of keeping the total water passing section area unchanged, and adopting a specific combined structure; arranging ecological vegetation among the branches, reserving an ecological isolation belt, planting three layers of local vegetation, and arranging a step type green plant belt; flood regulation and storage and flood control facilities are constructed, and overflow ports and buffer water retention grooves are formed in the isolation belts to meet flood control standards; vegetation water utilization and hydrological cycle optimization are carried out, water vapor microcirculation is promoted through the elevation difference, a straw covering layer is laid, and vegetation is monitored and supplemented. Water evaporation is remarkably reduced while flood prevention capacity is guaranteed, the problems of large evaporation loss, low vegetation survival rate, contradiction between flood prevention and ecological functions and the like in traditional riverway treatment are solved, and an effective scheme is provided for ecological restoration of the riverway in the desert region.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to an ecological multi-stream narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas. Background Art

[0002] Traditional river management techniques primarily focus on flood control, drainage, and smooth drainage. These techniques, such as dredging single sections and hardening banks, can improve flood control capacity in the short term, but they also further expose water areas and exacerbate evaporation losses. For example, some irrigation canals are lined with concrete. While this reduces leakage, the smooth surface allows for ample contact between water and air, increasing evaporation by 15%-20% compared to natural river channels. Furthermore, some ecological restoration projects have introduced southern aquatic vegetation, which has died due to incompatibility with the local drought and salinization environment. This not only fails to provide shade, but also wastes ecological resources.

[0003] In existing technologies, measures for controlling water evaporation have the following limitations: The river channel design did not consider the quantitative relationship between water depth and evaporation area. Simply deepening the river channel can easily lead to siltation, while shallowing it will not reduce evaporation. Vegetation selection ignores the ecological adaptability of arid areas, the introduction of alien species results in low survival rates, and an effective shading-cooling-humidification ecological chain is not formed; There is a conflict between flood control and evaporation control. Most narrow and deep designs sacrifice water flow capacity during floods, making it difficult to meet regulatory requirements. The coordinated mechanism of river morphology, vegetation and hydrological cycle has not been established, and it is impossible to utilize the interactive relationship between vegetation transpiration and water evaporation to achieve evaporation control.

[0004] Based on this, the present invention proposes a collaborative technical route of river shaping + water depth increase + area compression + vegetation shading. By reshaping multiple narrow and deep river channels and configuring local vegetation, water evaporation can be significantly reduced while ensuring flood control capabilities, providing a new solution for river ecological restoration in desert areas.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is: An ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas comprises the following steps: Step S1: Reshaping the river channel cross-section: Under the premise of keeping the total cross-sectional area unchanged, the original wide and shallow river channel is reconstructed into 2-5 deep and narrow main streams, with a single stream width of 2-4 meters and an average water depth of 1.5-2 times the original river channel, using a V-shaped stepped or curved trough structure; Step S2: Layout of ecological vegetation between sub-branches: Leave an ecological isolation zone of 1-3 meters wide between the main streams, plant three layers of native vegetation in sequence: herbs, shrubs, and trees, and set up stepped green belts on the slope side; Step S3: Construction of flood storage and flood control facilities: Set up overflow outlets with warning water levels on the isolation belt and buffer water retention tanks below to ensure that the total water flow capacity meets flood control standards; Step S4: Optimization of vegetation water utilization and hydrological cycle: Utilize the elevation difference of the mainstream to promote water vapor microcirculation, lay straw mulch in the isolation belt, and regularly monitor and replenish vegetation.

[0007] As a priority of the present invention, in step S1, the slope ratio of the V-shaped section is 1:2.5-1:3, the height of each step of the stepped section is 0.3-0.5 meters, the riverbed elevation is 0.5-1 meters lower than the original riverbed, and the siltation warning value is a 0.3-meter increase in the riverbed elevation.

[0008] As a preference of the present invention, in step S2, the herb layer selects Leymus chinensis, Puccinellia tenuifolia, Stipa grassi or Phragmites australis, with a planting density of 20-30 plants / ㎡; the shrub layer selects Calligonum mongolica, Elaeagnus scoparia, Caragana korshinskii, Salix psammophila or Haloxylon ammodendron, with a plant spacing of 1-1.5 meters and a row spacing of 2 meters; the tree layer selects Populus euphratica, Ulmus pumila, Elaeagnus angustifolia or Pinus sylvestris var. mongolica, with a plant spacing of 3-4 meters and a row spacing of 4 meters.

[0009] As a preference of the present invention, in step S2, the elevation of the ecological isolation zone is 0.2-0.5 meters higher than the normal water level of the mainstream stock, the stepped green belt is 0.3 meters high and 0.5 meters wide, and is planted with reeds or alkali reeds.

[0010] As a preference of the present invention, in step S3, the overflow outlet is 0.5-1 meter wide, 1-2 overflow outlets are provided every 100-150 meters, the buffer water tank is 0.3-0.5 meter deep and 1 meter wide, and is filled with pebbles with a particle size of 10-20 cm.

[0011] As a preference of the present invention, in step S4, the elevation difference between the main strands is 0.2-0.3 meters, the straw covering layer is 5-10 cm thick, and corn straw or wheat straw is selected.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The invention is based on the synergistic mechanism of "river shaping + water depth increase + area compression + vegetation shading", and adopts the technology of reshaping multiple narrow and deep water channels, namely: reconstructing the cross-section of the river channel from the original "wide and shallow plane" into several deep and narrow mainstream streams, so that the evaporation area per unit volume of water is reduced, the flow rate is enhanced, and the heat exchange is weakened, and shade vegetation belts are arranged between the streams to further weaken the heat flux and wind field disturbances through ecological cover.

[0013] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the attached figure: Figure 1 This is a flow chart of an ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention. Example

[0016] like Figure 1 As shown, an ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas includes the following steps: Step S1: Reshaping the river channel cross-section: Under the premise of keeping the total cross-sectional area unchanged, the original wide and shallow river channel is reconstructed into 2-5 deep and narrow main streams, with a single stream width of 2-4 meters and an average water depth of 1.5-2 times the original river channel, using a V-shaped stepped or curved trough structure; Step S2: Layout of ecological vegetation between sub-branches: Leave an ecological isolation zone of 1-3 meters wide between the main streams, plant three layers of native vegetation in sequence: herbs, shrubs, and trees, and set up stepped green belts on the slope side; Step S3: Construction of flood storage and flood control facilities: Set up overflow outlets with warning water levels on the isolation belt and buffer water retention tanks below to ensure that the total water flow capacity meets flood control standards; Step S4: Optimization of vegetation water utilization and hydrological cycle: Utilize the elevation difference of the mainstream to promote water vapor microcirculation, lay straw mulch in the isolation belt, and regularly monitor and replenish vegetation.

[0017] In a specific embodiment, in step S1, the slope ratio of the V-shaped section is 1:2.5-1:3, the height of each step of the stepped section is 0.3-0.5 meters, the riverbed elevation is 0.5-1 meters lower than the original riverbed, and the siltation warning value is a 0.3-meter increase in the riverbed elevation.

[0018] Furthermore, in step S2, the herb layer is selected from Leymus chinensis, Puccinellia tenuifolia, Stipa grassi or Phragmites australis, with a planting density of 20-30 plants / ㎡; the shrub layer is selected from Calligonum mongolica, Caragana korshinskii, Salix psammophila or Haloxylon ammodendron, with a plant spacing of 1-1.5 meters and a row spacing of 2 meters; the tree layer is selected from Populus euphratica, Ulmus pumila, Elaeagnus angustifolia or Pinus sylvestris var. mongolica, with a plant spacing of 3-4 meters and a row spacing of 4 meters. In step S2, the elevation of the ecological isolation zone is 0.2-0.5 meters higher than the normal water level of the mainstream stock, and the stepped green belt The height is 0.3 meters, the width is 0.5 meters, and reeds or alkali grass are planted. In the step S3, the overflow outlet is 0.5-1 meters wide, and 1-2 overflow outlets are set every 100-150 meters. The buffer water tank is 0.3-0.5 meters deep and 1 meter wide, and is filled with pebbles with a particle size of 10-20 cm. In the step S4, the elevation difference between the main streams is 0.2-0.3 meters, the thickness of the straw covering layer is 5-10 cm, and corn straw or wheat straw is selected.

[0019] Experimental Example 1: Reconstruction of the middle and lower reaches of Laigou River in a certain area Original river channel conditions: 20-30 meters wide, average water depth 0.5 meters, sandy soil, annual evaporation 2200mm, seasonal dry period of 6 months, and shore vegetation coverage rate of less than 15%.

[0020] Remodeling plan: Cross-sectional morphology: Reconstructed into three main streams, each 3 meters wide, with an average water depth of 1.2 meters (2.4 times the original water depth), using a "V-shaped" cross-section (slope ratio 1:3); Ecological isolation zone: 2 meters wide, planted with Stipa (herb layer), Coleus (shrub layer), and Elaeagnus angustifolia (tree layer) in sequence, and reeds are planted in the stepped green belt on the slope; Flood control facilities: an overflow outlet (0.8m wide) is set up every 100m, and the buffer water tank is filled with pebbles; Hydrological optimization: the elevation difference of the mainstream stock is 0.2 meters, and the isolation belt is covered with a layer of corn straw.

[0021] Implementation effect: The evaporation area of ​​water bodies was reduced by 40%, the duration of ecological base flow was extended by 2 months, the vegetation coverage rate was increased to 65%, and the flood control capacity met the standard of once in 20 years.

[0022] Experimental Example 2: Reshaping of river channels in a certain region Original river channel conditions: 15-25 meters wide, average water depth 0.4 meters, slightly saline soil, annual evaporation 2400mm, and the shoreline is mostly bare sand.

[0023] Remodeling plan: Cross-sectional morphology: Reconstructed into two main streams, each 4 meters wide, with an average water depth of 1.0 meter (2.5 times the original water depth), and a "stepped" cross-section (each step is 0.3 meters high); Ecological isolation zone: 3 meters wide, planting alkali grass (herb layer), saxifrage (shrub layer), poplar (tree layer), and alkali grass on the slope bank; Flood control facilities: 2 overflow outlets (0.5 meters wide) every 150 meters, and buffer water detention tanks filled with a mixture of pebbles and sand; Hydrological optimization: 0.3 meters of elevation difference between the main stream and the isolation zone, and straw mulch on the isolation zone.

[0024] Implementation effect: Water evaporation is reduced by 35%, soil salinization is reduced (pH value decreases by 0.5-0.8), and vegetation survival rate reaches 85%, meeting the ecological needs of connecting irrigation channels with rivers.

[0025] The implementation principle of the ecological multi-stream narrow and deep riverway reshaping method for reducing water evaporation in desert areas in this embodiment is as follows: 1. Riverway cross-section reshaping Step 1.1: Conduct hydrological survey on the target riverway to determine the average annual flow, maximum flood flow during flood season, river bottom elevation, and soil type (sandy, saline-alkali, or calcified); Step 1.2: Under the premise of keeping the total overwater cross-sectional area unchanged, reshape the original wide and shallow riverway cross-section into 2-5 deep and narrow main streams, with a single stream width of 2-4 meters and an average water depth of 1.5-2 times that of the original riverway; Step 1.3: The main stream adopts a "V-shaped", "stepped", or "bend slot" combined structure: in sandy soil areas, preferentially choose a "V-shaped" cross-section (slope ratio 1:2.5-1:3) to enhance erosion resistance; in saline-alkali soil areas, adopt a "stepped" cross-section (each step height 0.3-0.5 meters) to reduce slope collapse; at river bends, adopt a "bend slot" (concave bank deep, convex bank shallow) to utilize centrifugal force to promote water flow; Step 1.4: Control the river bottom elevation to ensure that the deep slot bottom is 0.5-1 meters lower than the original river bottom to avoid excessive depth leading to sediment accumulation (set the sediment accumulation warning value at 0.3 meters of river bottom elevation rise to initiate dredging).

[0026] 2. Ecological vegetation arrangement between streams Step 2.1: Leave 1-3 meters wide ecological isolation zones between the main streams, with an elevation 0.2-0.5 meters higher than the main stream's normal water level to prevent long-term flooding; Step 2.2: According to the isolation zone's terrain height (from the water edge to the bank slope), plant grass, shrubs, and trees in three layers: Grass layer: choose sheep grass, alkali grass, and needle grass (for sandy soil) or reed (for slightly saline-alkali soil), with a planting density of 20-30 plants per square meter; Shrub layer: use sand carob, flower stick, and sand willow (for sandy soil) or shrub willow and saxifrage (for saline-alkali soil), with a plant spacing of 1-1.5 meters and a row spacing of 2 meters; Arbor layer: Select Populus euphratica, Elaeagnus angustifolia (for saline-alkali soil) or Ulmus pumila, Pinus sylvestris (for sandy soil), with a plant spacing of 3-4 meters and a row spacing of 4 meters; Step 2.3: Set up a stepped green belt on the slope side, with a step height of 0.3 meters and a width of 0.5 meters. Plant moisture-resistant herbs such as reeds and alkali grass to form a "water surface-steps-beach" composite ecological structure.

[0027] 3. Construction of flood storage and flood control facilities Step 3.1: Install controllable overflow channels (overflow outlets) in the isolation zone between the main streams. The bottom elevation of the overflow channel should be the same as the 20-year flood level of the river channel. The width of the overflow channel should be 0.5-1 meter. The number of overflow channels should be 1-2 per 100 meters of river channel. Step 3.2: Set up a buffer water retention trough (0.3-0.5m deep, 1m wide) below the ecological isolation zone and fill it with pebbles (10-20cm in size) to enhance water retention and energy dissipation during floods. Step 3.3: Ensure that the total cross-sectional area of ​​the reshaped river channel is consistent with the original river channel and meets the flood control standards in the "Urban Flood Control Code" (GB50201) and the "River Channel Design Code" (GB50707).

[0028] 4. Vegetation water use and hydrological cycle optimization Step 4.1: Design the elevation difference between the main streams (0.2-0.3 meters) to promote water microcirculation and enhance water vapor exchange between the deep water area and the shallow interzone by using the water level difference; Step 4.2: Lay a 5-10cm thick layer of straw mulch (corn straw or wheat straw) on the surface of the ecological isolation zone to reduce soil surface evaporation and promote the rise of underground capillary water to the plant root zone; Step 4.3: Regularly monitor vegetation growth and soil moisture. When the herbaceous layer coverage is less than 60%, reseed should be carried out. When the shrub or tree mortality rate exceeds 10%, seedlings of the same species should be replanted in a timely manner.

Claims

1. An ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas, characterized in that: The steps include: Step S1: Reshaping the river channel cross-section: Under the premise of keeping the total cross-sectional area unchanged, the original wide and shallow river channel is reconstructed into 2-5 deep and narrow main streams, with a single stream width of 2-4 meters and an average water depth of 1.5-2 times the original river channel, using a V-shaped stepped or curved trough structure; Step S2: Layout of ecological vegetation between sub-branches: Leave an ecological isolation zone of 1-3 meters wide between the main streams, plant three layers of native vegetation in sequence: herbs, shrubs, and trees, and set up stepped green belts on the slope side; Step S3: Construction of flood storage and flood control facilities: Set up overflow outlets with warning water levels on the isolation belt and buffer water retention tanks below to ensure that the total water flow capacity meets flood control standards; Step S4: Optimization of vegetation water utilization and hydrological cycle: Utilize the elevation difference of the mainstream to promote water vapor microcirculation, lay straw mulch in the isolation belt, and regularly monitor and replenish vegetation.

2. The ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas according to claim 1 is characterized in that: In step S1, the slope ratio of the V-shaped section is 1:2.5-1:3, the height of each step of the stepped section is 0.3-0.5 meters, the riverbed elevation is 0.5-1 meters lower than the original riverbed, and the siltation warning value is a 0.3-meter increase in the riverbed elevation.

3. The ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas according to claim 1 is characterized in that: In step S2, the herbaceous layer is selected from Leymus chinensis, Puccinellia tenuifolia, Stipa grassi or Phragmites australis, with a planting density of 20-30 plants / ㎡; the shrub layer is selected from Calligonum mongolica, Elaeagnus truncatula, Caragana korshinskii, Salix psammophila or Haloxylon ammodendron, with a plant spacing of 1-1.5 meters and a row spacing of 2 meters; the tree layer is selected from Populus euphratica, Ulmus pumila, Elaeagnus angustifolia or Pinus sylvestris var. mongolica, with a plant spacing of 3-4 meters and a row spacing of 4 meters.

4. The ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas according to claim 1 is characterized in that: In step S2, the elevation of the ecological isolation zone is 0.2-0.5 meters higher than the normal water level of the mainstream stock, the stepped green belt is 0.3 meters high and 0.5 meters wide, and is planted with reeds or alkali reeds.

5. The ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas according to claim 1 is characterized in that: In step S3, the overflow outlet is 0.5-1 meter wide, with 1-2 overflow outlets provided every 100-150 meters. The buffer water retention tank is 0.3-0.5 meter deep and 1 meter wide, and is filled with pebbles with a particle size of 10-20 cm.

6. The ecological multi-branch narrow and deep river channel reconstruction method for reducing evaporation of river water in desert areas according to claim 1 is characterized in that: In step S4, the elevation difference between the main strands is 0.2-0.3 meters, the thickness of the straw covering layer is 5-10 cm, and corn straw or wheat straw is selected.

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