Method for acquiring agricultural water taking amount and water-saving space based on production-ecology collaborative model

Abstract

The invention discloses an agricultural water taking amount and water saving space obtaining method based on a production-ecology collaborative model, and is applied to the technical field of agricultural water saving. Comprising the following steps: analyzing water consumption and salt tolerance of crops in the arid and semi-arid regions; analyzing the water circulation process of the irrigated area, disassembling water circulation constituent elements and the mutual influence relation thereof, and constructing a field net irrigation water demand equation; analyzing the effect of irrigation on agricultural ecology and the influence of irrigation on agricultural production; analyzing ecological and production water threshold values; constructing an agricultural production-ecological cooperation water taking amount calculation model, and setting constraint conditions; and calculating the water-saving space of production-ecology collaboration by taking the minimum water taking amount as a target. According to the method, the crop water consumption and the salt tolerance threshold value are determined, the effect of irrigation on farmland ecology, the influence of irrigation on agricultural production and the production and ecological water threshold value of arid and semi-arid areas are analyzed, and the agricultural water taking amount boundary and the water saving space are given.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural water conservation, and more specifically, to a method for obtaining agricultural water withdrawal amount and water-saving space based on a production-ecology synergy model. Background Technique

[0002] Agricultural irrigation involves multiple systems such as water resources, food production, and agricultural ecology. It mainly connects the tripartite relationship of water-food-ecology with water resources as the link, including real contradictions in space, contradictions between production and ecological water use, and synergistic gain effects. When there is a change in the action process of one system, it generally has an impact on other systems. Especially in arid and semi-arid regions, the contradiction between water supply and demand is prominent, the ecological background is fragile, and climate change and human activities have a significant impact on the water cycle process. While affecting the structure and function of natural ecosystems, it also has an impact on crop production and food security. Agriculture is a key area for water conservation with great water-saving potential, and it is very necessary to strengthen the research on agricultural water conservation. The agricultural development in arid and semi-arid regions not only shoulders the heavy responsibility of agricultural production and ensuring food security but also plays an indispensable role in the local ecological environment construction. Artificial irrigation is an inevitable means to maintain the growth of crops and vegetation in the irrigation areas of arid and semi-arid regions. Unreasonable irrigation will not only make the farmland face the risk of salinization, which will further affect the ecosystem and agricultural production, making it difficult to achieve the goal of water conservation and unable to alleviate the local water use contradiction. Determining a reasonable agricultural water withdrawal amount and water-saving space can not only meet the actual needs of coordinated guarantee of ecological security and food security in arid and semi-arid regions but also provide a scientific basis and decision-making support for the comprehensive regulation and water-saving management of regional and basin-related departments. Therefore, how to provide a method for obtaining agricultural water withdrawal amount and water-saving space based on a production-ecology synergy model is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0003] In view of this, the present invention provides a method for obtaining agricultural water withdrawal amount and water-saving space based on a production-ecology synergy model to solve the problems in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for obtaining agricultural water withdrawal amount and water-saving space based on a production-ecology synergy model, comprising the following steps:

[0006] Analyze the crop water consumption and salt tolerance in arid and semi-arid regions;

[0007] Analyze the water cycle process in the irrigation area, disassemble the components of the water cycle and their mutual influence relationships, and construct an equation for the net irrigation water demand in the field;

[0008] Analyze the role of irrigation in agricultural ecology and its impact on agricultural production;

[0009] Analyze the thresholds of ecological and production water use;

[0010] Construct a water intake calculation model for the coordination of agricultural production and ecology, and set constraints;

[0011] Calculate the water-saving space for the coordination of production and ecology with the goal of minimizing water intake.

[0012] Optionally, the water consumption of crops refers to the total amount of water required for plant transpiration, soil evaporation between plants, and the growth and development of plants under various different soil moisture conditions; the salt tolerance of crops refers to the ability of crops to reduce and offset the damage of salts through physiological pathways and maintain basic growth in a salt stress environment.

[0013] Optionally, the effects of irrigation on agricultural ecology include the impact of groundwater on soil salinity, the impact of groundwater on natural vegetation, the impact of irrigation on the groundwater depth, and the impact of irrigation on soil water and salt.

[0014] Optionally, the analysis of the impact of groundwater on soil salinity is specifically to fit the relationship between soil salt content and groundwater depth to obtain the functional relationship between soil salt content and groundwater depth; the analysis of the impact of groundwater on natural vegetation is specifically to analyze the maximum height of capillary water rise, local vegetation types and their root depths in the local area to determine the maximum value of groundwater depth; the analysis of the impact of irrigation on groundwater depth is specifically to determine the functional relationship between agricultural water intake and groundwater depth; the analysis of the impact of irrigation on soil water and salt is specifically to determine the relationship between soil salt content and agricultural water intake by combining the impact of groundwater on soil salinity, the impact of groundwater on natural vegetation, and the impact of irrigation on groundwater depth.

[0015] Optionally, the effects of irrigation on agricultural production include the water production function, water use efficiency, phreatic evaporation, and the relationship between irrigation and crop yield.

[0016] Optionally, the water production function is the relationship curve between crop yield and water input. Water use efficiency represents the ability to produce crop yield per unit of water resource, reflecting the relationship between crop water consumption and dry matter accumulation. Phreatic evaporation is calculated through the relationship between groundwater depth and phreatic evaporation. The relationship between irrigation and crop yield refers to the relationship between the net irrigation water requirement in the crop field and the corresponding yield.

[0017] Optionally, analyzing the thresholds of ecological and production water use specifically means: determining the groundwater depth position according to the law of soil salinization, the salt tolerance of crops, and the water requirements of natural vegetation, and then determining the range of agricultural water intake; determining the lower limit of agricultural water intake according to the water consumption law of crops, geographical climate and soil conditions on the premise of ensuring the highest crop yield.

[0018] Optionally, the water intake calculation model for the coordination of agricultural production and ecology includes:

[0019] Net irrigation water requirement in the field:

[0020] W IR = W C + W D + W I + ΔW S - W P - W E

[0021] W J = W IR - W D - W I

[0022] Relationship between groundwater depth and soil salt content:

[0023] α = f(h)

[0024] Relationship between agricultural water withdrawal and groundwater depth:

[0025] h = f(Q q )

[0026] Relationship between crop water consumption and yield:

[0027] y i = f(W ci )

[0028] Relationship between phreatic evaporation and groundwater depth:

[0029]

[0030] Function for determining the minimum agricultural water withdrawal under the highest crop yield:

[0031]

[0032] Effective utilization coefficient of irrigation water:

[0033] η = f(w m )

[0034] Where, W IR is the field irrigation water volume, W P is the precipitation, W E is the phreatic evaporation, W C is the crop transpiration evaporation, W D is the farmland drainage volume, W I is the field infiltration recharge volume, ΔW S is the field soil water storage variable, W J is the net irrigation water requirement in the field, y i is the yield of crop i, W ci is the water consumption of crop i, Qqmin The minimum agricultural water withdrawal to ensure crop yield, h is the groundwater depth, α is the soil salt content, Q q is the agricultural water withdrawal, M i is the irrigation area of crop i, i is the crop variety, W Ji is the net irrigation water requirement in the field when the yield of crop i is the highest, η is the effective utilization coefficient of irrigation water, w m is the water consumption per mu, k is the proportion of water consumption for forestry, animal husbandry and fishery in the total water consumption, E0 is the water surface evaporation intensity, h max is the limit evaporation depth of groundwater, l is the empirical coefficient.

[0035] Optionally, the set constraints include:

[0036] The agricultural water withdrawal should not be less than the minimum agricultural water withdrawal to ensure crop yield:

[0037] Q q > Q qmin

[0038] The groundwater depth should neither affect the growth of crop roots nor support the water use of natural vegetation:

[0039] h ∈ (1.73, 3.5)

[0040] The soil salt content meets the requirements for crop growth:

[0041] α ∈ (0, 2.02)

[0042] All variables of the model are greater than 0;

[0043] In the formula, Q qmin is the minimum agricultural water withdrawal to ensure crop yield, h is the groundwater depth, α is the soil salt content, Q q is the agricultural water withdrawal.

[0044] Optionally, taking the minimum water withdrawal as the goal, the specific water-saving space for the coordinated production-ecology is calculated as:

[0045]

[0046] In the formula, W is the water-saving space, Q0 is the agricultural water withdrawal under the current water use level, is the boundary value of the agricultural water withdrawal for the coordinated production-ecology, is the minimum value of the agricultural water withdrawal.

[0047] As can be seen from the above technical solutions, compared with the prior art, the present invention provides a method for obtaining agricultural water withdrawal and water-saving space based on a production-ecology collaborative model, which has the following beneficial effects: The present invention establishes the "natural-artificial" dual water cycle and water balance relationship in the irrigation area, clarifies the crop water consumption and salt tolerance threshold, analyzes the role of irrigation on farmland ecology and the impact of irrigation on agricultural production, and on the basis of distinguishing the physical quantitative relationship among irrigation-production-ecology, analyzes the production and ecological water use thresholds in arid and semi-arid regions, constructs a calculation model for the collaborative water withdrawal of agricultural production-ecology, gives the boundary of agricultural water withdrawal and water-saving space, and provides data reference for agricultural water-saving optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0049] Figure 1 It is a flow chart of the method for obtaining agricultural water withdrawal and water-saving space of the present invention;

[0050] Figure 2 It is a schematic diagram of the annual water consumption of the main crops in the embodiments of the present invention;

[0051] Figure 3 It is a schematic diagram of the water cycle in the irrigation area in the embodiments of the present invention;

[0052] Figure 4 It is a schematic diagram of the water movement process of the groundwater-soil-vegetation-atmosphere system in the embodiments of the present invention;

[0053] Figure 5 It is a schematic diagram of the influence of the groundwater depth on the soil water and salt in the embodiments of the present invention;

[0054] Figure 6 It is a schematic diagram of the interaction relationship between agricultural irrigation water volume and groundwater in arid and semi-arid regions in the embodiments of the present invention;

[0055] Figure 7 It is a schematic diagram of the relationship between agricultural water withdrawal and the groundwater depth in the monitoring area in the embodiments of the present invention;

[0056] Figure 8 It is a schematic diagram of the water production function of the main crops in arid and semi-arid regions in the embodiments of the present invention;

[0057] Figure 9 It is a schematic diagram of the relationship between groundwater depth and phreatic evaporation in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0059] The embodiment of the present invention discloses a method for obtaining agricultural water intake and water-saving space based on a production-ecology synergy model, as Figure 1 shown, which includes the following steps:

[0060] Analyze the crop water consumption and salt tolerance in arid and semi-arid regions;

[0061] Analyze the irrigation water cycle process, disassemble the components of the water cycle and their mutual influence relationships, and construct an equation for the net irrigation water demand in the field;

[0062] Analyze the role of irrigation on agricultural ecology and its impact on agricultural production;

[0063] Analyze the ecological and production water use thresholds;

[0064] Construct a water intake calculation model for agricultural production-ecology synergy and set constraint conditions;

[0065] Calculate the water-saving space for production-ecology synergy with the goal of minimizing water intake.

[0066] Furthermore, the water consumption of crops refers to the total amount of water required for plant transpiration, soil evaporation between plants, and the growth and development of plants under various different soil moisture conditions; the salt tolerance of crops refers to the ability of crops to reduce and offset the damage of salts through physiological pathways and maintain basic growth in a salt stress environment.

[0067] In the embodiment of the present invention, the main cultivated crops in arid and semi-arid regions include: wheat, corn, rice, and potatoes. The annual water consumption of crops during the entire growth period under normal years (50% rainfall frequency) is as Figure 2 shown. From the perspective of crop water consumption, the water consumption of rice is the largest, which is 581 m 3 / mu*year, followed by corn, which is 334 m 3 / mu*year. The water consumption of wheat and potatoes is 284 m 3 / mu*year and 300 m 3 / mu*year respectively. Taking other crops such as soybeans as an example, the water consumption is 295 m 3 / mu*year.

[0068] According to the national agricultural product cost and income situation, in the embodiment of the present invention, taking Ningxia Hui Autonomous Region as an example, the crop with the highest per-acre output value is potatoes, reaching 2,616 yuan per mu, and the per-acre output efficiency is 8.72 yuan / m 3 ; followed by rice, with a per-acre output value of 1,716 yuan per mu and an output efficiency of 2.95 yuan / m 3 ; the per-acre output value of corn is 1,398 yuan per mu, and the output efficiency is 4.19 yuan / m 3 , second only to potato crops; the crop with the lowest per-acre output value among wheat crops is wheat, which is 997 yuan per mu, and the output efficiency is 2.99 yuan / m 3 .

[0069] In an environment with a certain limit of salt concentration, the crop yield remains stable as the salt concentration increases. If the salt concentration continues to increase, the crop yield will decrease sharply with the increase of soil salt content. In the embodiment of the present invention, taking the crop yield as the evaluation criterion, the salt tolerance standards of wheat, corn, rice, and potato crops with similar soil properties are determined. When the soil salt content in the 0-20 cm soil layer reaches 2.926 g / kg, the wheat yield begins to decline. When the soil layer salt content reaches 3.862 g / kg, the wheat yield decreases by 50%. When the soil layer salt content reaches 5.404 g / kg, the wheat dies; when the salt content in the 0-20 cm soil layer is lower than 2.03 g / kg, it is very suitable for corn growth and basically does not affect its yield. When the soil salt content is higher than 3.465 g / kg, it is not suitable for corn growth; rice is a crop that is more sensitive to salt stress, and the salt tolerance threshold is 0-2.60 g / kg; the salt tolerance of potatoes is better than that of other crops. When the salt content is greater than 6 g / kg, the yield decreases significantly, and when the salt stress damage rate is greater than 10 g / kg, it reaches 100%.

[0070] In the embodiment of the present invention, as Figure 3As shown in the figure, the specific analysis of the water cycle process in the irrigation area is as follows: The natural part includes atmospheric water resources, surface water resources, groundwater resources, soil water resources, etc. The relevant water cycle processes include natural processes such as rainfall, evaporation, surface runoff, infiltration recharge, phreatic evaporation, and lateral recharge between rivers and groundwater; while behaviors such as water intake, water conveyance, water use, water consumption, and drainage belong to social human activities. The water use processes such as water diversion irrigation, ecological water replenishment, water conveyance leakage, water evaporation, and irrigation area drainage in the irrigation and drainage canal systems of the irrigation area make human factors intervene in the water cycle process of the irrigation area, thus jointly creating a complete water cycle in the irrigation area under the intervention of human activities. In the entire water cycle process of the irrigation area, the factors affecting groundwater include rainfall, evaporation, irrigation water volume, and river water level, etc. Among them, the main recharge sources are field irrigation and canal system leakage, both of which recharge water to the groundwater through infiltration in the vadose zone. When the influencing factors change, the groundwater depth will also be affected accordingly; at the same time, groundwater can also be transferred and supplemented to surface water. When a large amount of lake water resources are exploited, the nearby groundwater will flow to the lake to supplement its water volume. Groundwater is transformed into surface water in mountain depressions and then flows to the flat areas of the irrigation area. Inside the irrigation area, there are local differences in the elevation difference, which will also lead to different exchange mechanisms between groundwater and surface water. Areas with lower terrain are more likely to receive groundwater recharge. The water cycle not only drives the change of water, but also drives the change of soil salinity and conducts the exchange of matter and energy. During the irrigation process in the irrigation area, a large amount of salt is introduced into the soil. Due to strong evaporation, some salts will remain in the soil, and then along with the water cycle, the salts will migrate between the surface and groundwater with the water. In order to maintain the safety of the soil, surface water transports the salts to the groundwater through the water cycle, making the groundwater also become the storage space for substances.

[0071] Furthermore, the effects of irrigation on agricultural ecology include the influence of groundwater on soil salinity, the influence of groundwater on natural vegetation, the influence of irrigation on groundwater depth, and the influence of irrigation on soil water and salt.

[0072] Furthermore, the specific analysis of the influence of groundwater on soil salinity is to fit the relationship between soil salt content and groundwater depth to obtain the functional relationship between soil salt content and groundwater depth; the analysis of the influence of groundwater on natural vegetation is to analyze the maximum height of capillary water rise, local vegetation types and their root depths in the local area to determine the maximum value of groundwater depth; the analysis of the influence of irrigation on groundwater depth is to determine the functional relationship between agricultural water intake and groundwater depth; the analysis of the influence of irrigation on soil water and salt is to determine the relationship between soil salt content and agricultural water intake by combining the influence of groundwater on soil salinity, the influence of groundwater on natural vegetation, and the influence of irrigation on groundwater depth.

[0073] In arid regions, the change in soil salinity is caused by the capillary transportation of shallow groundwater to the soil surface for evaporation. During the capillary water transportation to the surface, the salts in the water are also carried to the soil surface. When the water evaporates, the salts in the soil remain on the surface and in the shallow soil layer. The salts move with the water, and the movement of water drives the movement of salts. Groundwater enters the vadose zone soil layer through capillary action in soil pores, bringing in water and salts, and directly participating in the mutual transformation process of substances and energy within the soil. This leads to complex physical, chemical, or biological processes among various chemical ions, microorganisms, etc. in the vadose zone, which are coupled with the groundwater dynamics, forming a complex dynamic system. The water movement process in the groundwater-soil-vegetation-atmosphere system is as Figure 4 shown.

[0074] In the embodiment of the present invention, the following formula is set to quantify the relationship between the groundwater depth and the soil salt content:

[0075] α = f(h)

[0076] As Figure 5 shown, based on investigations and literature data, the relationship between the salt content in the 0-20 cm surface layer of the soil and the groundwater depth is obtained. An increase in the groundwater depth will cause a decrease in the salt content in the surface soil. The 0-20 cm soil layer is the tillage layer of the crop, which has a direct relationship with crop growth. It can be seen that as the groundwater depth increases, the salt content on the soil surface decreases exponentially. Fitting the relationship between the soil salt content and the groundwater depth, the functional relationship is:

[0077] α = f(h) = 45.688e -0.922h

[0078] The correlation coefficient is 0.83, and the fitting result is good.

[0079] From Figure 4 the water movement process shown, the water content in the soil surface layer will gradually decrease with the increase of the groundwater depth. When the plant roots reach the water table or the capillary zone, the plants can absorb groundwater. On the contrary, when the groundwater depth is greater than the sum of the plant root depth and the capillary water rise height of the water table, the vegetation cannot absorb water, which will lead to a decline in the vegetation structure and function of the natural system. Therefore, the groundwater depth plus the capillary rise height should not exceed the soil root depth. This requires an analysis of the maximum capillary water rise height in the local area, the local vegetation type, and its root depth;

[0080] In the embodiment of the present invention, the calculation formula for the capillary water rise height is:

[0081]

[0082] Wherein, h is the capillary water rise height, a is a parameter, a = (γ / (ρg))^0.5, γ is the surface tension coefficient, ρ is the liquid density, g is the acceleration of gravity, r is the pipe diameter, θ is the contact angle between the liquid and the pipe wall. When the capillary water rises to the highest level, due to the surface tension, the surface of the capillary water in contact with the air is spherical, so the water-air contact angle is zero degree. The soil capillary pore diameter should be the soil equivalent pore diameter R. At this time, the calculation formula for the maximum capillary water rise height H can be expressed as follows:

[0083]

[0084] In the embodiment of the present invention, the maximum capillary water rise height H of the vadose zone soil in the grassland desert is selected to be 1.6 m;

[0085] The main natural vegetation types in arid and semi-arid regions include forest vegetation, grassland vegetation, desert steppe, etc. Grassland vegetation mainly consists of herbaceous plants and also includes some low shrubs, such as Caragana korshinskii, Tamarix chinensis, etc. The root length of shrubs is generally between 1 - 4 m. Desert steppe vegetation mainly consists of herbaceous plants, such as Artemisia scoparia, Agropyron mongolicum, Thymus mongolicus, Stipa bungeana, etc. The root length of herbaceous plants is significantly shorter than that of shrubs and trees, mostly between 0.13 - 1.9 m. Considering the capillary water rise height, the suitable critical groundwater depth is between 1.73 - 3.5 m, and the groundwater depth suitable for the growth of all vegetation is between 2 - 5 m. When the groundwater depth exceeds 5 m, the groundwater cannot provide water for the soil surface and plant roots, and almost no vegetation grows. When the groundwater is at 2.5 - 3.5 m, the vegetation coverage is the largest. In the embodiment of the present invention, the maximum value of the groundwater depth to ensure ecological safety should not exceed 3.5 m.

[0086] The interaction relationship between agricultural irrigation water volume and groundwater in arid and semi-arid regions is as Figure 6 shown. The groundwater depth is affected by human activities and climatic conditions. Among them, the irrigation water volume, rainfall, evaporation, and artificial extraction volume are the main factors affecting the groundwater depth, and the influence degree is in the order of agricultural irrigation water intake > rainfall > evaporation > artificial extraction. And for arid and semi-arid regions, the influence degree of the irrigation water volume on groundwater is much higher than that of rainfall. Therefore, when quantifying the relationship between irrigation and groundwater depth in arid and semi-arid regions, two indicators of agricultural water intake and groundwater depth can be selected to analyze and determine the relevant relationship:

[0087] h = f(Q q )

[0088] In the embodiment of the present invention, taking the Ningxia Hui Autonomous Region as an example to analyze the relationship between agricultural water intake and groundwater depth. The groundwater resources in the Ningxia Hui Autonomous Region are concentrated in the Yellow River irrigation area. In 2021, the total groundwater resources in the Ningxia Hui Autonomous Region were 1.6 billion m 3, mainly receiving the replenishment of the water volume of the Yellow River. In 2021, the groundwater resources volume in the Yellow River diversion irrigation area was 1.2652 billion m 3 , and the canal system and field leakage replenishment in the irrigation area was 1.2141 billion m 3 , and the precipitation replenishment was only 0.0511 billion m 3 . The relationship between the agricultural water withdrawal volume and the groundwater level depth in the monitoring area is as shown in Figure 7 . It can be seen that as the agricultural water withdrawal volume decreases, the groundwater depth gradually increases. By performing a linear fit on it, the relationship formula between the agricultural water consumption volume and the groundwater depth can be obtained:

[0089] h = f(Q q ) = -22.163h + 114.98

[0090] The correlation coefficient is 0.7238, and the fitting result is good.

[0091] According to the above analysis, the relationship between the soil salt content and the agricultural water withdrawal volume can be obtained as:

[0092] α = f(h) = 45.688e -0.922h

[0093] h = f(Q q ) = -22.163h + 114.98

[0094] Furthermore, the impacts of irrigation on agricultural production include the crop water production function, water use efficiency, phreatic evaporation, and the relationship between irrigation and crop yield.

[0095] Furthermore, the crop water production function is the relationship curve between crop yield and the input water volume. The water use efficiency represents the ability to produce crop yield per unit of water resources volume, reflecting the relationship between crop water consumption and dry matter accumulation. The phreatic evaporation is calculated through the relationship between the groundwater depth and the phreatic evaporation. The relationship between irrigation and crop yield refers to the relationship between the net irrigation water requirement in the crop field and the corresponding yield.

[0096] The crop water production function is a mathematical relationship formula that quantifies the association between crop yield and water factors. Assuming the same irrigation method and other growth factors are fixed, the relationship curve between the water volume W and the yield Y is: y i = f(W ci ). According to the existing research data, a fit is performed on the relationship curve between the water volume W and the yield Y, and the fitting results are as shown in Figure 8 and Table 1:

[0097] Table 1 Fitting results of the crop water production function for different crops

[0098]

[0099] Among them, w c is the crop water consumption. It can be seen that the yields of several major crops have similar patterns with the change of water consumption, which all increase first and then gradually slow down or decline. The correlation coefficients of each crop are as follows: wheat 0.979, corn 0.9968, rice 0.8672, and potatoes 0.9893, with good fitting effects. Looking at the crop water characteristic curves, there are significant differences in the crop water consumption characteristics. The water consumption of corn is in the range of 182 - 374 mm, and the highest yield is 8611 kg / hm 2 , and the corresponding water consumption is 374; the water consumption of wheat is in the range of 422 - 661 mm, and the highest yield is 8070 kg / hm 2 , and the corresponding water consumption is 598 mm; the water consumption of dryland rice is in the range of 415 - 660 mm, and the highest yield is 7918 kg / hm 2 , and the corresponding water consumption is 660 mm; the water consumption of potatoes is in the range of 194 - 498 mm, and the highest yield is 39894 kg / hm 2 , and the corresponding water consumption is 398.2 mm.

[0100] In the embodiment of the present invention, the crop water use efficiency range of wheat is 1.1 - 1.5 kg / m 3 , and when the water consumption is 456 mm, the highest water use efficiency is 1.5 kg / m 3 ; the crop water use efficiency range of rice is 1.0 - 1.3 kg / m 3 , and when the water consumption is 509 mm, the highest water use efficiency is 1.3 kg / m 3 ; the crop water use efficiency range of corn is 2.0 - 2.5 kg / m 3 , and when the water consumption is 317 mm, the highest water use efficiency is 2.5 kg / m 3 ; the crop water use efficiency range of potatoes is 7.9 - 12.0 kg / m 3 , and when the water consumption is 194.6 mm, the highest water use efficiency is 12.0 kg / m 3 . The water consumption at the highest point of the crop water use efficiency is not consistent with the water consumption under the highest yield. At the highest point of the water use efficiency, the amount of product reached by investing one unit of water on average is the largest, and this point is in the optimal period of resource utilization. If starting from the perspective of maximizing resource utilization, the crop irrigation amount can be based on this, but the resource potential is not fully utilized; if starting from the perspective of economic benefits, the crop irrigation amount can be calculated based on the water consumption corresponding to the highest yield.

[0101] In arid and semi-arid regions, for the evaporation of bare land and the water consumption of natural vegetation, in the absence of rainfall and artificial irrigation, it mainly comes from the recharge of phreatic water. For a relatively long period of time, if the soil water storage variable and lateral seepage are not considered, the water consumption of vegetation is equal to the phreatic evaporation, and its calculation formula is:

[0102]

[0103] In the embodiment of the present invention, taking the research data of the Weining Plain in Ningxia Hui Autonomous Region as an example, the relationship between the groundwater depth and the phreatic evaporation is as Figure 9 shown. The phreatic evaporation decreases sharply with the increase of the groundwater depth. When the groundwater depth exceeds the limit water depth of 5m, the groundwater evaporation is almost 0. At this water level, if the influence of rainfall and irrigation is not considered, crops and vegetation can hardly survive, which belongs to the limit groundwater depth. According to the above data results, l is taken as 1.3, h max is 5m, and E0 is 600mm. The phreatic evaporation formula for the Ningxia Hui Autonomous Region is obtained as:

[0104]

[0105] According to the above research, the relationship between irrigation and crop yield in this embodiment can be obtained as:

[0106] W IR = W C + W D + W I + ΔW S - W P - W E

[0107] W J = W IR - W D - W I

[0108]

[0109] y i = f(W ci )

[0110] Furthermore, the specific analysis of the ecological and production water use thresholds is as follows: Determine the groundwater depth position according to the soil salinization law, the salt tolerance of crops, and the water demand requirements of natural vegetation, and then determine the range of agricultural water intake; Determine the lower limit of agricultural water intake according to the water consumption law of crops, geographical climate, and soil conditions on the premise of ensuring the highest crop yield.

[0111] In the embodiment of the present invention, the groundwater risk water levels for crops under salt stress are shown in Table 2:

[0112] Table 2 Crop Risk Water Levels

[0113] Crop Salt tolerance threshold Salt content Safe deep burial water level Wheat 0 - 5.404 g / kg < 2.926 g / kg ＞2.98m Maize 0 - 3.465 g / kg < 2.02 g / kg ＞3.38m Rice 0 - 2.60 g / kg < 2.03 g / kg ＞3.38m Potatoes 0 - 10 g / kg < 6 g / kg ＞2.2m

[0114] It can be seen that when the groundwater depth exceeds 2.98 m, it will not have a salinization effect on wheat. For corn crops, the safe groundwater depth should be controlled at 3.38 m or more. The safe groundwater depth for rice should be controlled at 3.38 m or more, and for potatoes, it should be controlled at more than 2.2 m. Combining the above analysis, the appropriate groundwater level in this embodiment should be controlled at 3.38 m or more, which will not have a salt effect on crop yields. Considering the comprehensive requirements of crop growth and the ecosystem, the ecological threshold in arid and semi-arid regions is 1.73 m < h < 3.5 m, and the optimal depth is set at 3.38 m.

[0115] To ensure the safety of agricultural food production, it is necessary to determine the minimum agricultural water intake that guarantees crop yields. The determination method is as follows: First, based on the crop water production function, determine the water consumption under the maximum crop yield, and then calculate the corresponding net irrigation water requirement. After that, calculate the minimum agricultural water intake:

[0116]

[0117] Furthermore, the water intake calculation model for agricultural production-ecosystem coordination includes:

[0118] Field net irrigation water requirement:

[0119] W IR = W C + W D + W I + ΔW S - W P - W E

[0120] W J = W IR - W D - W I

[0121] Relationship between groundwater depth and soil salt content:

[0122] α = f(h)

[0123] Relationship between agricultural water intake and groundwater depth:

[0124] h = f(Q q )

[0125] Relationship between crop water consumption and yield:

[0126] y i = f(W ci )

[0127] Relationship between phreatic evaporation and groundwater depth:

[0128]

[0129] The function for determining the minimum agricultural water withdrawal for maximum crop yield is:

[0130]

[0131] Irrigation water effective utilization coefficient:

[0132] η=f(w m )

[0133] Where W IR is the amount of irrigation water in the field, W P is the precipitation, W E is the evaporation of water, W C is crop transpiration, W D is the farmland drainage volume, W I is the field infiltration recharge, ΔW S is the field soil water storage variable, W J is the net irrigation water requirement of the field, y i is the yield of crop i, W ci is the water consumption of crop i, Q qmin To ensure the minimum agricultural water withdrawal for crop yield, h is the groundwater depth, α is the soil salinity, Q q is the amount of water used for agriculture, M i is the irrigated area of crop i, i is the crop variety, W Ji is the net irrigation water requirement of the field when the yield of crop i is the highest, η is the effective utilization coefficient of irrigation water, w m is the average water consumption per mu, k is the proportion of forestry, animal husbandry and fishery water consumption in the total water consumption, E0 is the evaporation intensity of the water surface, h max is the maximum evaporation depth of groundwater, and l is the empirical coefficient.

[0134] Furthermore, setting constraints includes:

[0135] Agricultural water withdrawal should not be less than the minimum agricultural water withdrawal required to ensure crop yields:

[0136] Q q >Q qmin

[0137] The depth of groundwater should not affect the growth of crop roots, but should be sufficient to support the water use of natural vegetation:

[0138] h∈(1.73,3.5)

[0139] Soil salinity meets crop growth requirements:

[0140] α ∈ (0, 2.02)

[0141] All variables of the model are greater than 0;

[0142] In the formula, Q qmin is the minimum agricultural water withdrawal to ensure crop yield, h is the groundwater depth, α is the soil salt content, and Q q is the agricultural water withdrawal.

[0143] Furthermore, taking the minimum water withdrawal as the goal, the specific water-saving space for the production-ecology synergy is calculated as follows:

[0144]

[0145] In the formula, W is the water-saving space, Q0 is the agricultural water withdrawal under the current water use level, is the boundary value of the agricultural water withdrawal for the production-ecology synergy, is the minimum value of the agricultural water withdrawal.

[0146] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0147] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for obtaining agricultural water withdrawal volume and water-saving space based on a production-ecology synergy model, characterized in that, It includes the following steps: Analyze the crop water consumption and salt tolerance in arid and semi-arid regions; Analyze the water cycle process in the irrigation area, disassemble the components of the water cycle and their mutual influence relationships, and construct the equation for the net irrigation water demand in the field; Analyze the role of irrigation in agricultural ecology and its impact on agricultural production; Analyze the thresholds of ecological and production water use; Construct a water intake calculation model for the coordination of agricultural production and ecology, and set constraints; Calculate the water-saving space for the coordination of production and ecology with the goal of minimizing water intake.

2. The method for obtaining agricultural water withdrawal volume and water-saving space based on the production-ecology collaborative model according to claim 1, wherein The water consumption of crops refers to the total amount of water required for plant transpiration, soil evaporation between plants, and the growth and development of plants under various different soil moisture conditions; the salt tolerance of crops refers to the ability of crops to reduce and offset the damage of salts through physiological pathways and maintain basic growth in a salt stress environment.

3. The method for obtaining agricultural water withdrawal amount and water-saving space based on the production-ecology collaborative model according to claim 1, characterized in that The role of irrigation in agricultural ecology includes the impact of groundwater on soil salinity, the impact of groundwater on natural vegetation, the impact of irrigation on the groundwater depth, and the impact of irrigation on soil water and salt.

4. The method for obtaining agricultural water withdrawal volume and water-saving space based on the production-ecology collaborative model according to claim 3, wherein The analysis of the impact of groundwater on soil salinity specifically involves fitting the relationship between soil salt content and groundwater depth to obtain the functional relationship between soil salt content and groundwater depth; the analysis of the impact of groundwater on natural vegetation specifically involves analyzing the maximum height of capillary water rise, local vegetation types and their root depths to determine the maximum value of groundwater depth; the analysis of the impact of irrigation on groundwater depth specifically involves determining the functional relationship between agricultural water intake and groundwater depth; the analysis of the impact of irrigation on soil water and salt specifically involves determining the relationship between soil salt content and agricultural water intake by combining the impact of groundwater on soil salinity, the impact of groundwater on natural vegetation, and the impact of irrigation on groundwater depth.

5. A method for obtaining agricultural water withdrawal and water-saving space based on a production-ecology collaborative model according to claim 1, characterized in that, The impact of irrigation on agricultural production includes the water production function, water use efficiency, phreatic evaporation, and the relationship between irrigation and crop yield.

6. The method for obtaining agricultural water withdrawal volume and water-saving space based on the production-ecology collaborative model according to claim 5, characterized in that, The water production function is the relationship curve between crop yield and water input. The water use efficiency represents the ability to produce crop yield per unit of water resource, reflecting the relationship between crop water consumption and dry matter accumulation. The phreatic evaporation is calculated through the relationship between groundwater depth and phreatic evaporation. The relationship between irrigation and crop yield refers to the relationship between the net irrigation water demand in the crop field and the corresponding yield.

7. The method for obtaining agricultural water withdrawal amount and water saving space based on the production-ecology collaborative model according to claim 1, characterized in that Analyzing the thresholds of ecological and production water use specifically means: determining the position of groundwater depth according to the law of soil salinization, the salt tolerance of crops, and the water demand requirements of natural vegetation, and then determining the range of agricultural water intake; determining the lower limit of agricultural water intake according to the water consumption law of crops, geographical climate and soil conditions on the premise of ensuring the highest crop yield.

8. A method for obtaining agricultural water withdrawal and water-saving space based on a production-ecology synergy model according to claim 1, characterized in that The water intake calculation model for the coordination of agricultural production and ecology includes: Net irrigation water demand in the field: W IR = W C + W D + W I + ΔW S - W P - W E W J = W IR -W D -W I Relationship between groundwater depth and soil salt content: α = f(h) Relationship between agricultural water intake and groundwater depth: h = f(Q q ) Relationship between crop water consumption and yield: y i = f(W ci ) Relationship between phreatic evaporation and groundwater depth: Function for determining the minimum agricultural water intake under the condition of the highest crop yield: Effective utilization coefficient of irrigation water: η = f(w m ) Where, W IR is the field irrigation water volume, W P is the precipitation, W E is the phreatic evaporation, W C is the evapotranspiration of crops, W D is the farmland drainage volume, W I is the field infiltration recharge, ΔW S is the field soil water storage variable, W J is the net irrigation water demand of the field, y i is the yield of crop i, W ci is the water consumption of crop i, Q qmin is the minimum agricultural water withdrawal to ensure the crop yield, h is the groundwater depth, α is the soil salt content, Q q is the agricultural water withdrawal, M i is the irrigation area of crop i, i is the crop variety, W Ji is the net irrigation water demand of the field when the yield of crop i is the highest, η is the effective utilization coefficient of irrigation water, w m is the water consumption per mu, k is the proportion of water consumption for forestry, animal husbandry and fishery in the total water consumption, E0 is the water surface evaporation intensity, h max is the limit evaporation depth of groundwater, l is the empirical coefficient.

9. The method for obtaining agricultural water withdrawal volume and water-saving space based on the production-ecology synergy model according to claim 1, wherein The set constraints include: The agricultural water intake should not be less than the minimum value of agricultural water intake to ensure crop yield: Q q > Q qmin The groundwater depth should neither affect the growth of crop roots nor support the water use of natural vegetation: h∈(1.73,3.5) The soil salt content meets the growth requirements of crops: α∈(0,2.02) All variables of the model are greater than 0; Where Q qmin is the minimum agricultural water withdrawal to ensure crop yield, h is the groundwater depth, α is the soil salt content, and Q q is the agricultural water withdrawal.

10. The method for obtaining agricultural water withdrawal volume and water saving space based on the production-ecology collaborative model according to claim 1, wherein Calculating the water-saving space for the coordination between production and ecology with the goal of minimizing water intake is specifically as follows: Where W is the water-saving space, Q0 is the agricultural water withdrawal under the current water use level, is the boundary value of agricultural water withdrawal for production-ecology coordination, is the minimum value of agricultural water withdrawal.

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