A calculation method for agricultural water-saving potential based on system dynamics

Abstract

The present invention discloses a calculation method for agricultural water-saving potential based on system dynamics, which includes dividing agricultural water-saving into five subsystems and selecting water-saving indicators for each subsystem; determining constant variables and intermediate variables, and constructing functional relationships between all water-saving indicators and constant variables and intermediate variables in each subsystem; according to the functional relationships, using Vensim PLE software to construct dynamic models of the five subsystems respectively; setting initial values of water-saving indicators, constant variables and intermediate variables, obtaining multiple verification objects and their annual water-saving indicators in the time boundary, and conducting authenticity tests on the system dynamic model composed of the five dynamic models. When the verification fails, adjust the constant variables and / or the water-saving potential relational expressions of the system dynamic model, and then return to the authenticity test step; after passing the verification, use the functional relationships and water-saving potential relational expressions of the system dynamic model to calculate the agricultural water-saving potential of the research area in the current year or the predicted year.

Description

Technical Field

[0001] The present invention relates to agricultural water-saving technologies, and particularly to a method for calculating agricultural water-saving potential based on system dynamics. Background Art

[0002] The estimation and evaluation of water-saving potential are the premise and foundation for the development of agricultural water-saving. To understand the water-saving capabilities of different regions across the country and resolve the contradiction in agricultural water use in irrigation areas, there is an urgent need to explore an efficient method for calculating water-saving potential.

[0003] In recent years, many scholars have calculated agricultural water-saving potential at the scale of irrigation areas or provinces. Feng Shaoyuan et al. considered factors such as effective precipitation recharge, water conveyance, and field losses, and established a calculation formula for the water-saving potential of agricultural resources in the Inner Mongolia Hetao Irrigation Area. Although this method incorporates precipitation recharge and water conveyance losses, it only considers water-saving in the field of agricultural irrigation, lacking a comprehensive and integrated consideration of agriculture and related industries, and the internal structural relationships are not clear, resulting in inaccurate calculation and prediction of water-saving potential. Summary of the Invention

[0004] Aiming at the above deficiencies in the prior art, the method for calculating agricultural water-saving potential based on system dynamics provided by the present invention solves the problem of inaccurate prediction due to incomplete consideration in the existing calculation of agricultural water-saving potential.

[0005] To achieve the above-mentioned invention objective, the technical solution adopted by the present invention is as follows:

[0006] Provide a method for calculating agricultural water-saving potential based on system dynamics, which includes the steps of:

[0007] S1. Divide agricultural water-saving into five subsystems: engineering water-saving, management water-saving, technical water-saving, rainfall replenishment, and water-saving losses, and select water-saving indicators for each subsystem according to official and local statistical data;

[0008] S2. Determine the constant variables related to crop irrigation and the intermediate variables related to crop water-saving, and construct the functional relationships between all water-saving indicators and the constant variables and intermediate variables in each subsystem;

[0009] S3. According to the functional relationships of each subsystem, use Vensim PLE software to construct dynamic models for calculating agricultural water-saving potential in the five subsystems respectively;

[0010] S4. Set the time boundary and time step of the dynamic model, assign initial values to the water-saving indicators, constant variables, and intermediate variables, and obtain multiple verification objects and their annual water-saving indicators within the time boundary;

[0011] S5. According to the water-saving indicators of the verification objects, conduct authenticity tests on the system dynamics model composed of five dynamic models. When the verification fails, enter step S6; when the verification passes, enter step S7;

[0012] S6. Adjust the constant variables and / or the water-saving potential relationship formula of the system dynamics model, and then return to step S5;

[0013] S7. Obtain the known water-saving indicators of the current year or the predicted year in the research area, and use the functional relationship and the water-saving potential relationship formula of the system dynamics model to calculate the agricultural water-saving potential in the current year or the predicted year in the research area.

[0014] Furthermore, the methods for conducting authenticity tests include:

[0015] S51. Calculate the maximum water-saving amount of each verification object in the current year using the quota method:

[0016] ΔW 大 = A1×(Q0 - Q t )

[0017] where, ΔW 大 is the maximum water-saving amount, m 3 ; A1 is the actual agricultural irrigation area of the verification object in the current year, hm 2 ; Q0 and Q t are the comprehensive agricultural irrigation quotas in the current year and the planned year respectively, m 3 / hm 2 ;

[0018] S52. According to the water-saving indicators of the verification objects, use the functional relationship of each subsystem to calculate the agricultural water-saving potential of multiple verification objects in the current year respectively;

[0019] S53. According to the total agricultural water-saving potential of all subsystems of the same verification object, use the water-saving potential relationship formula to obtain the agricultural water-saving potential of each verification object;

[0020] S54. According to the maximum water-saving amount and the total agricultural water-saving potential of each verification object, calculate the ratio of the difference between the two to the maximum water-saving amount as the error value;

[0021] S55. Determine whether the average error of multiple verification objects is greater than the preset error. If so, the system dynamics model fails the authenticity test; otherwise, the system dynamics model passes the authenticity test.

[0022] The beneficial effects of the above technical solution are as follows: Compared with other inspection methods, the true inspection of this solution can independently evaluate the uncertainties of various subsystems by using reference data of relative true values within the research scope (such as a series of indicators such as water-saving coverage area and agricultural water use quota), and give the process of exact accuracy indicators. This is an important basis for improving the model fitting accuracy and improving the water-saving prediction quality, and is an important guarantee for promoting the application scope and quantitative application level of the water-saving process system dynamics.

[0023] Furthermore, the methods for adjusting the constant variables and / or the water-saving potential relational expressions of the system dynamics model include:

[0024] S61. Adjust all the constant variables according to the first preset ratio. When the number of adjustment times is greater than the first preset number and the system dynamics model still fails the inspection, then go to step S62;

[0025] S62. Adjust all the constant variables according to the second preset ratio. When the number of adjustment times is greater than the second preset number and the system dynamics model still fails the inspection, then go to step S63;

[0026] S63. Select a verification object, calculate the maximum water-saving amount of each subsystem by using the quota method, and calculate the ratio of the difference between the maximum water-saving amount of the subsystem and its agricultural water-saving potential to the maximum water-saving amount;

[0027] S64. When the ratio of the subsystem is greater than the preset ratio, update the agricultural water-saving potential of the corresponding subsystem = preset adjustment parameter × agricultural water-saving potential, and update the water-saving potential relational expression.

[0028] The beneficial effects of the above technical solution are as follows: The initial constant variables in this method are consistent and stable on the time scale, generally not affected by time fluctuations and index changes, but can affect the overall evaluation result, avoiding the problem of uneven distribution caused by adjusting the initial index variables, achieving the purpose of optimizing the structure and parameters of the model, and thus improving the prediction accuracy of the model.

[0029] Furthermore, the method for calculating the agricultural water-saving potential based on system dynamics also includes a rationality test of the system dynamics model, which respectively includes:

[0030] Use the "Unites Check" function in the Vensim PLE software to detect whether the units of all parameters in all functional relationships are consistent;

[0031] Use the "Check Model" function in the Vensim PLE software to verify whether the logic between all parameters in all functional relationships is correct;

[0032] Set multiple step lengths, collect the statistical data of a verification object within the time boundary, and calculate the agricultural water-saving potential of the verification object using functional relationships and water-saving potential relationships; when the agricultural water-saving potentials calculated under multiple time step lengths are basically the same, the step length test is satisfied.

[0033] The beneficial effects of the above technical solutions are as follows: The rationality tests adopted in this solution are all the built-in test functions of the system. Among them, "Unites Check" and "Check Model" are more convenient, fast, and efficient. The system automatically identifies the parameter logic and prompts the error source, greatly shortening the test time; while the step length test verifies the stability of the results under different step length changes, and determines the optimal step length setting in combination with specific task requirements and data characteristics to balance the model performance and calculation efficiency.

[0034] Furthermore, the water-saving indicators of the project water-saving subsystem include canal system water utilization coefficient, water diversion volume at the canal head, high-efficiency water-saving area, crop sown area, agricultural water consumption, effective irrigation water utilization coefficient, original value of fixed assets, newly built investment funds, and maintenance costs;

[0035] The water-saving indicators of the management water-saving subsystem include optimized irrigation system area, optimized irrigation system quota, deficit irrigation area, deficit irrigation quota, grain-to-economic ratio, comprehensive irrigation quota for food crops, comprehensive irrigation quota for cash crops, plastic film mulching area, film mulching and moisture conservation irrigation quota, high-standard farmland area, water-saving capacity per unit area, water-saving reward expenses, and precise subsidy expenses;

[0036] The water-saving indicators of the technical water-saving subsystem include drought-resistant variety sown area, drought-resistant variety irrigation quota, reasonable planting density area, reasonable planting density irrigation quota, irrigation water quality compliance rate, irrigation water consumption, unconventional water volume, proportion of unconventional water in agriculture, fishpond water consumption, and aquaculture area;

[0037] The water-saving indicators of the precipitation supplement subsystem include actual precipitation and effective irrigation area;

[0038] The water-saving indicators of the water-saving loss subsystem include pesticide application amount, pure amount of nitrogen and phosphorus fertilizers, number of livestock and poultry raised, cultivated land area, land salinization rate, desertification area, afforestation area, land surface evaporation, precipitation erosion factor, soil erodibility factor, slope length and slope factor, vegetation cover factor, soil and water conservation factor, and soil volume moisture content;

[0039] The constant variables include crop irrigation quota, irrigation adjustment coefficient, irrigation proportion, depreciation rate, added value of water saving per 10,000 yuan, subsidy standard, fishery water use quota, border irrigation quota, flood irrigation quota, pesticide pollution emission coefficient, pesticide loss coefficient, nitrogen and phosphorus pollution emission coefficient, nitrogen and phosphorus fertilizer loss coefficient, annual excretion coefficient of livestock and poultry manure and pollutants, loss rate of livestock and poultry manure and pollutants, and pollutant emission coefficient;

[0040] The intermediate variables include the water savings in efficient irrigation, land leveling, canal seepage control, hub projects, field water use coefficient, water savings in deficit irrigation, comprehensive reform of agricultural water prices, optimized irrigation regime, adjusted planting structure, covering and moisturizing, high-standard farmland construction, reasonable aquaculture in fisheries, reasonable crop density, utilization of unconventional agricultural water, water savings in water quality improvement, drought-resistant breeding, soil loss, soil erosion loss, desertification loss, salinization loss, pesticide pollution emissions, farmland chemical fertilizer pollution emissions, livestock and poultry breeding pollution emissions, and non-point source pollution.

[0041] The beneficial effects of the above technical solution are as follows: The existing technical solutions focus on qualitatively evaluating the magnitude of agricultural water-saving potential. However, the index elements selected in this solution can all be quantitatively calculated. The considered indicators are numerous, with a wide range, objective and reasonable, and each indicator can be obtained from statistical data and local departments to meet the needs of different decision-making scenarios, avoiding subjective arbitrariness and estimating the agricultural water-saving potential value more accurately and flexibly.

[0042] Furthermore, the water-saving potential relational formula:

[0043] ΔW = ΔW E + ΔW M + ΔW T + W R - W L

[0044] Where, ΔW is the agricultural water-saving potential, m 3 ; ΔW E , ΔW M , ΔW T are the water savings in engineering, management, and technology respectively, m 3 ; W R is the precipitation supplement, m 3 ; W L is the water-saving loss, m 3 .

[0045] Furthermore, the functional relationships of the engineering water-saving subsystem include:

[0046] ΔW E = W 枢纽 + W 高效 + W 田块 + W 衬砌

[0047] W 枢纽 = ρ×[(1 - τ)f 原 + f 新 + f 护 ​

[0048]

[0049]

[0050]

[0051] Among them, W 高效 、W 衬砌 、W 田块 、W 枢纽 are the water savings of efficient water-saving irrigation, canal lining, field land leveling, and water conservancy project construction respectively, m 3 ; ρ is the added value of water savings per 10,000 yuan, taking 150 m 3 / 10,000 yuan; f 原 、f 新 、f 护 are the original value of fixed assets of the irrigation area hub project, new construction investment cost, and maintenance cost respectively, 10,000 yuan; τ is the depreciation rate; A i is the area of the i-th efficient water-saving irrigation measure, hm 2 ; E j is the irrigation quota of the j-th crop, m 3 / hm 2 ; β j is the proportion of the sown area of the j-th crop; K i is the irrigation water quota adjustment coefficient of the i-th efficient water-saving method; m is the number of types of efficient water-saving irrigation; n is the number of types of crops; Q 农 is the agricultural water consumption, m 3 ; λ is the proportion of irrigation water consumption in agricultural water consumption, %; μ a 、μ b are the field water use coefficients in the base year and the current year respectively; Q 首 is the water diversion volume at the canal head in the current year, m 3 ; η a 、η b are the canal system water use coefficients in the base year and the current year respectively;

[0052] The functional relationships of the management water-saving subsystem include:

[0053] ΔW M =W 结构 +W 制度 +W 亏缺 +W 覆膜 +W 高标 +W 水价

[0054]

[0055] W覆膜 = A 膜 × (w m - w n )

[0056] W 高标 = A 标 × η 标 ,

[0057] wherein, W 结构 , W 制度 , W 亏缺 , W 覆膜 , W 高标 , W 水价 are respectively the water savings generated by the adjustment of planting structure, the optimization of irrigation system, the moisture preservation by film mulching, the construction of high-standard farmland, the comprehensive reform of agricultural water price, and deficit irrigation method, m 3 ; α a , α b are respectively the grain-to-cash crop ratio in the base year and the current year; E a , E b are respectively the comprehensive irrigation quotas for cash crops and food crops, m 3 / hm 2 ; A0 is the effective irrigation area, hm 2 ; A i制 is the optimized irrigation area of the i-th crop, hm 2 ; E im , E in are respectively the irrigation quotas of the i-th crop before and after the system optimization, m 3 / hm 2 ; A i缺 is the deficit irrigation area of the i-th crop, hm 2 ; E ip , E iq are respectively the irrigation quotas of the i-th crop before and after deficit irrigation, m 3 / hm 2 ; A 膜 is the film mulching area, hm 2 ; w m , w n are respectively the irrigation quotas before and after moisture preservation by film mulching, m 3 / hm 2 ; A 标 is the high-standard farmland area, hm 2 ; η 标 is the water-saving capacity per unit area of high-standard farmland, m 3 / hm 2 ; k1 and k2 are respectively the water-saving reward and the precise subsidy cost, yuan; is the subsidy standard, with a value range of 0.15 - 0.2 yuan / m3 ;

[0058] The functional relationships of the technical water-saving subsystem include:

[0059] ΔW T =W 密植 +W 育种 +W 水质 +W 渔业 +W 非常

[0060]

[0061] W 渔业 =A f ×E f -w f

[0062] W 非常 =w c ×β c

[0063] Among them, W 密植 , W 育种 , W 水质 , W 渔业 , W 非常 are the water-saving amounts generated by the utilization of unconventional water, reasonable stocking in fishery, reasonable close planting of crops, breeding of drought-resistant crops, and improvement of agricultural water quality, respectively, m 3 ; A i密 is the reasonable close-planting area of the i-th crop, hm 2 ; E iu , E iv are the irrigation quotas of the i-th crop before and after reasonable close planting, m 3 / hm 2 ; A ij is the sowing area of the j-th drought-resistant variety of the i-th crop, hm 2 ; E ij is the irrigation quota of the j-th drought-resistant variety of the i-th crop, m 3 / hm 2 ; E i0 is the conventional irrigation quota of the i-th crop, m 3 / hm 2 ; n is the number of crop types; M is the number of drought-resistant varieties of each crop; δ0 and δ1 are the irrigation water quality compliance rates in the base year and the current year, respectively, %; A f is the aquaculture area, hm 2 ; E f is the water use quota for fishery, m 3 / hm 2 ; w fis the water consumption of fish ponds in the base year, m 3 ; w c is the non-conventional water consumption, m 3 ; β c is the proportion of non-conventional water in agriculture;

[0064] The functional relationships of the water-saving loss subsystem include:

[0065] W L = W 盐渍 + W 荒漠 + W 水土 + W 面源

[0066] W 面源 = PE × η 肥 × x 肥 + CH × η 药 × x 药 + EU × q 畜 × η 畜 × x 畜

[0067] W 水土 = θ0 × W 土 = θ0 × r × k × ls × c × p

[0068] W 盐渍 = ξ0 × A 耕 × (E 漫 - E 畦 )

[0069] W 荒漠 = ET0 × (A 荒 - A 林 )

[0070] In the formula: W 盐渍 , W 荒漠 , W 水土 , W 面源 are the loss amounts caused by soil salinization, land desertification, agricultural soil and water loss, and agricultural non-point source pollution respectively, m 3 ; PE is the pure amount of nitrogen and phosphorus fertilizers, 10,000 tons; η 肥 is the nitrogen and phosphorus fertilizer loss coefficient; x 肥 is the nitrogen and phosphorus pollution emission coefficient; CH is the amount of pesticides applied, 10,000 tons; η 药 is the pesticide loss coefficient; x 药 is the pesticide pollution emission coefficient; EU is the number of livestock and poultry farms; q 畜 is the annual excretion coefficient of livestock and poultry manure and pollutants; η 畜 is the loss rate of livestock and poultry manure and pollutants; x 畜 is the pollutant emission coefficient; θ0 is the soil volume moisture content, %; w 土 is the soil loss amount, m3 ; r is the precipitation erosion factor; k is the soil erodibility factor; ls is the slope length and slope factor; c is the vegetation cover factor; p is the soil and water conservation factor; ξ0 is the land salinization rate, %; A 耕 is the cultivated land area, hm 2 ; E 漫 and E 畦 are the water use quotas for flood irrigation and conventional border irrigation respectively, m 3 / hm 2 ; ET0 is the land surface evaporation, mm; A 荒 and A 林 are the areas of land desertification and afforestation respectively, hm 2 .

[0071] The beneficial effects of the above technical solution are as follows: Compared with the traditional index weight estimation, each step of the structure of this technical solution is connected by corresponding formulas, forming a calculation process from the initial index to the process variable and then to the state variable, with a more rigorous and clear structure; moreover, the behavior pattern and characteristics are mainly determined by the internal dynamic structure and feedback mechanism of the system, without being interfered by external factors. Therefore, it can be used to simulate the long-term and periodic water-saving potential estimation problems.

[0072] Furthermore, the functional relationship of the rainfall replenishment subsystem includes:

[0073] W R = P e × A0 × 10

[0074]

[0075] where P e is the effective precipitation in a certain period, mm; A0 is the effective irrigation area, hm 2 ; P is the actual precipitation in the corresponding period, mm; and 10 is the unit conversion coefficient.

[0076] Furthermore, when calculating the agricultural water-saving potential of the verification object and the research area, the unknown water-saving indicators, constant variables, and intermediate variables all adopt initial values.

[0077] Furthermore, the time boundary is at least greater than 10 years, and the time step is 1 year.

[0078] The beneficial effects of the present invention are as follows: The system dynamics model constructed in this solution considers five subsystems, can organically connect the parts of the interactions between the five subsystems, can be quickly and efficiently applied to the simulation and prediction of agricultural water-saving potential, and is convenient for relevant departments to clearly know which subsystem has the adjustment potential through the agricultural water-saving potential of each subsystem in adjacent years, so as to make targeted adjustments in future agricultural water conservation to increase the agricultural water-saving potential.

[0079] The system dynamics model constructed by this solution can calculate and predict the agricultural water-saving potential in a certain year in combination with the water-saving plans of relevant departments, so as to assist relevant departments in determining whether the water-saving plan is reasonable, making targeted adjustments, ensuring high crop yields while improving the agricultural water-saving potential; through the cooperation of multiple subsystems, this solution can improve the accuracy of agricultural water-saving potential prediction.

[0080] Since this solution includes multiple subsystems, it can transform the agricultural water-saving system into a causal feedback mechanism of multiple information, conduct an overall assessment of multi-department, multi-level, and non-linear complex systems in the field of agricultural water-saving, and can set different scenarios according to the water-saving indicators in the regional development plan to predict the size of the agricultural water-saving potential in future years.

[0081] The water-saving indicators selected in this solution all come from official and local statistical data, making the parameters selected in this solution relatively comprehensive. On a large scale, it can be applied to the whole country, different water resource regions, different basins, different provinces and prefecture-level cities, and on a small scale, it can be applied to units such as counties, districts, and irrigation areas with complete data. Description of the Drawings

[0082] Figure 1 It is a flow chart of the agricultural water-saving potential calculation method based on system dynamics.

[0083] Figure 2 It is a schematic diagram of the dynamic model of the project water-saving subsystem.

[0084] Figure 3 It is a schematic diagram of the dynamic model of the management water-saving subsystem.

[0085] Figure 4 It is a schematic diagram of the dynamic model of the technical water-saving subsystem.

[0086] Figure 5 It is a schematic diagram of the dynamic model of the rainfall supplement subsystem.

[0087] Figure 6 It is a schematic diagram of the dynamic model of the water-saving loss subsystem.

[0088] Figure 7 It is a schematic diagram of the step size test result of the system dynamics model.

[0089] Figure 8 It is a schematic diagram of the authenticity test results of multiple verification objects based on the system dynamics model; (a) is the schematic diagram of the authenticity test results of Ordos City, (b) is the schematic diagram of the authenticity test results of Bayannur City, and (c) is the schematic diagram of the authenticity test results of Alxa League. Detailed Implementation Modes

[0090] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0091] Reference Figure 1 , Figure 1 shows a flowchart of a method for calculating the agricultural water-saving potential based on system dynamics. As Figure 1 shown, the method S includes steps S1 to S7.

[0092] In step S1, agricultural water conservation is divided into five subsystems: engineering water conservation, management water conservation, technical water conservation, rainfall supplement, and water-saving loss. According to official and local statistical data, water-saving indicators for each subsystem are selected.

[0093] In implementation, the water-saving indicators of the engineering water conservation subsystem preferably include the canal system water utilization coefficient, canal head water diversion volume, high-efficiency water-saving area, crop sown area, agricultural water consumption, effective irrigation water utilization coefficient, original value of fixed assets, newly built investment funds, and maintenance and repair costs;

[0094] The water-saving indicators of the management water conservation subsystem include the optimized irrigation system area, optimized irrigation system quota, deficit irrigation area, deficit irrigation quota, grain-to-economic crop ratio, comprehensive irrigation quota for food crops, comprehensive irrigation quota for economic crops, plastic film mulching area, film mulching and soil moisture conservation irrigation quota, high-standard farmland area, water-saving capacity per unit area, water-saving incentive costs, and precise subsidy costs;

[0095] The water-saving indicators of the technical water conservation subsystem include the sown area of drought-resistant varieties, irrigation quota of drought-resistant varieties, reasonably dense planting area, reasonably dense planting irrigation quota, irrigation water quality compliance rate, irrigation water consumption, unconventional water volume, proportion of unconventional water in agriculture, fish pond water consumption, and aquaculture area;

[0096] The water-saving indicators of the precipitation supplement subsystem include the actual precipitation and the effective irrigation area;

[0097] The water-saving indicators of the water-saving loss subsystem include the amount of pesticide application, pure nitrogen and phosphorus fertilizer amount, number of livestock and poultry breeding, cultivated land area, land salinization rate, desertification area, afforestation area, land surface evaporation, precipitation erosion factor, soil erodibility factor, slope length and slope factor, vegetation cover factor, soil and water conservation factor, and soil volume moisture content;

[0098] In step S2, determine the constant variables associated with crop irrigation and the intermediate variables associated with crop water conservation, and construct the functional relationships between all water conservation indicators and the constant variables and intermediate variables in each subsystem;

[0099] In implementation, the preferred constant variables in this solution include crop irrigation quota, irrigation adjustment coefficient, irrigation proportion, depreciation rate, added value of water conservation per 10,000 yuan, subsidy standard, fishery water use quota, border irrigation quota, flood irrigation quota, pesticide pollution emission coefficient, pesticide loss coefficient, nitrogen and phosphorus pollution emission coefficient, nitrogen and phosphorus fertilizer loss coefficient, annual excretion coefficient of livestock and poultry manure and pollutants, loss rate of livestock and poultry manure and pollutants, and pollutant emission coefficient;

[0100] The intermediate variables include water savings from efficient irrigation, water savings from land leveling, water savings from canal seepage prevention, water savings from key projects, field water use coefficient, water savings from deficit irrigation, water savings from comprehensive reform of agricultural water price, water savings from optimized irrigation system, water savings from adjusted planting structure, water savings from covering and moisturizing, water savings from construction of high-standard farmland, reasonable water savings from fishery farming, reasonable water savings from rational crop planting density, utilization amount of agricultural non-conventional water, water savings from water quality improvement, water savings from drought-resistant breeding, soil loss amount, soil erosion loss amount, desertification loss amount, salinization loss amount, pesticide pollution emission amount, farmland chemical fertilizer pollution emission amount, livestock and poultry breeding pollution emission amount, and non-point source pollution amount.

[0101] In step S3, according to the functional relationships of each subsystem, use Vensim PLE software to construct dynamic models for calculating agricultural water conservation potential in five subsystems respectively;

[0102] In an embodiment of the present invention, the functional relationship of the project water conservation subsystem includes:

[0103] ΔW E =W 枢纽 +W 高效 +W 田块 +W 衬砌

[0104] W 枢纽 =ρ×[(1 - τ)f 原 +f 新 +f 护

[0105]

[0106]

[0107]

[0108] Among them, W 高效 、W 衬砌 、W 田块 、W​枢纽 The water savings for efficient water-saving irrigation, canal lining, field land leveling, and water conservancy project construction are \(m\), respectively 3 ; \(\rho\) is the added value of water savings per 10,000 yuan, taking \(150m\) 3 / 10,000 yuan; \(f\) 原 , \(f\) 新 , \(f\) 护 are the original value of fixed assets, newly built investment cost, and maintenance cost of the irrigation area hub project, in 10,000 yuan; \(\tau\) is the depreciation rate; \(A\) i is the area of the \(i\)-th efficient water-saving irrigation measure, in \(hm\) 2 ; \(E\) j is the irrigation quota of the \(j\)-th crop, in \(m\) 3 / \(hm\) 2 ; \(\beta\) j is the proportion of the sown area of the \(j\)-th crop; \(K\) i is the regulation coefficient of the irrigation water quota for the \(i\)-th efficient water-saving method; \(m\) is the number of types of efficient water-saving irrigation; \(n\) is the number of types of crops; \(Q\) 农 is the agricultural water consumption, in \(m\) 3 ; \(\lambda\) is the proportion of irrigation water consumption in agricultural water consumption, in %; \(\mu\) a , \(\mu\) b are the field water use coefficients in the base year and the current year, respectively; \(Q\) 首 is the water diversion volume at the canal head in the current year, in \(m\) 3 ; \(\eta\) a , \(\eta\) b are the canal system water use coefficients in the base year and the current year, respectively.

[0109] For the engineering water-saving subsystem, in China, efficient irrigation methods such as spraying and micro-irrigation can irrigate according to the needs of crop growth, canceling the field canals and drainage ditches, saving water and increasing the sown area, which is the main way of agricultural water saving. At the same time, canal seepage prevention is achieved through canal lining and maintenance, and its water savings can be calculated from the water diversion volume at the canal head and the canal system water use coefficient. In addition, field land leveling and irrigation area water conservancy projects can both improve the utilization efficiency of agricultural water resources and achieve the goal of water saving and efficiency increase.

[0110] The functional relationship of the management water-saving subsystem includes:

[0111] \(\Delta W\) M = \(W\) 结构 +\(W\) 制度 +\(W\) 亏缺 +\(W\) 覆膜 +\(W\) 高标 +\(W\) 水价

[0112]

[0113] \(W\) 覆膜= A 膜 × (w m - w n )

[0114] W 高标 = A 标 × η 标 ,

[0115] where W 结构 , W 制度 , W 亏缺 , W 覆膜 , W 高标 , W 水价 are the water savings generated by the adjustment of planting structure, optimization of irrigation system, film mulching for moisture conservation, construction of high-standard farmland, comprehensive reform of agricultural water price, and deficit irrigation method, respectively, in m 3 ; α a , α b are the ratios of grain to cash crops in the base year and the current year, respectively; E a , E b are the comprehensive irrigation quotas for cash crops and food crops, respectively, in m 3 / hm 2 ; A0 is the effective irrigation area, in hm 2 ; A i制 is the optimized irrigation area of the i-th crop, in hm 2 ; E im , E in are the irrigation quotas of the i-th crop before and after the system optimization, respectively, in m 3 / hm 2 ; A i缺 is the deficit irrigation area of the i-th crop, in hm 2 ; E ip , E iq are the irrigation quotas of the i-th crop before and after the deficit irrigation, respectively, in m 3 / hm 2 ; A 膜 is the film mulching area, in hm 2 ; w m , w n are the irrigation quotas before and after film mulching for moisture conservation, respectively, in m 3 / hm 2 ; A 标 is the high-standard farmland area, in hm 2 ; η 标 is the water-saving capacity per unit area of high-standard farmland, in m 3 / hm 2 ; k1 and k2 are the water-saving rewards and precise subsidy costs, in yuan; is the subsidy standard, with a value range of 0.15 - 0.2 yuan / m 3 .

[0116] For the parameters involved in the functional relationship of the water-saving management subsystem, the water saved by the adjustment of the planting structure is calculated by the ratio of grain to economic crops in agriculture and the irrigation water quota of crops, while the optimized irrigation area, plastic film mulching area, high-standard farmland area, deficit irrigation area, water-saving rewards and precise subsidy amounts can all be obtained from the local agricultural and water conservancy departments.

[0117] The functional relationship of the technical water-saving subsystem includes:

[0118] ΔW T = W 密植 + W 育种 + W 水质 + W 渔业 + W 非常

[0119]

[0120] W 渔业 = A f × E f - w f

[0121] W 非常 = w c × β c

[0122] Among them, W 密植 、W 育种 、W 水质 、W 渔业 、W 非常 are the water savings generated by the utilization of unconventional water, reasonable stocking of fisheries, reasonable close planting of crops, breeding of drought-resistant crops, and improvement of agricultural water quality, respectively, m 3 ; A i密 is the reasonable close-planting area of the i-th crop, hm 2 ; E iu 、E iv are the irrigation quotas of the i-th crop before and after reasonable close planting, respectively, m 3 / hm 2 ; A ij is the sowing area of the j-th drought-resistant variety of the i-th crop, hm 2 ; E ij is the irrigation quota of the j-th drought-resistant variety of the i-th crop, m 3 / hm 2 ; E i0 is the conventional irrigation quota of the i-th crop, m 3 / hm 2; n is the number of crop types; M is the number of drought-resistant varieties for each crop; δ0 and δ1 are the irrigation water quality compliance rates in the base year and the current year, respectively, %; A f is the aquaculture area, hm 2 ; E f is the fishing water quota, m 3 / hm 2 ; w f is the water consumption of fish ponds in the current year, m 3 ; w c is the non-conventional water consumption, m 3 ; β c is the proportion of non-conventional water used in agriculture.

[0123] For the technical water-saving subsystem, since reclaimed water, brackish water, and rainwater in non-conventional water can be used for agricultural irrigation, the improvement of fishery breeding technology will also reduce water consumption, and appropriately adjusting the planting density can increase yields and water productivity.

[0124] The functional relationships of the water-saving loss subsystem include:

[0125] W L = W 盐渍 + W 荒漠 + W 水土 + W 面源

[0126] W 面源 = PE × η 肥 × x 肥 + CH × η 药 × x 药 + EU × q 畜 × η 畜 × x 畜

[0127] W 水土 = θ0 × w 土 = θ0 × r × k × ls × c × p

[0128] W 盐渍 = ξ0 × A 耕 × (E 漫 - E 畦 )

[0129] W 荒漠 = ET0 × (A 荒 - A 林 )

[0130] In the formula: W 盐渍 , W 荒漠 , W 水土 , W 面源 are the loss amounts caused by soil salinization, land desertification, agricultural soil and water loss, and agricultural non-point source pollution, respectively, m3 ; PE is the pure amount of nitrogen and phosphorus fertilizers, in 10,000 tons; η 肥 is the loss coefficient of nitrogen and phosphorus fertilizers; x 肥 is the pollution emission coefficient of nitrogen and phosphorus; CH is the application amount of pesticides, in 10,000 tons; η 药 is the loss coefficient of pesticides; x 药 is the pollution emission coefficient of pesticides; EU is the number of livestock and poultry breeding; q 畜 is the annual excretion coefficient of livestock and poultry manure and pollutants; η 畜 is the loss rate of livestock and poultry manure and pollutants; x 畜 is the pollution emission coefficient; θ0 is the soil volume water content, %; w 土 is the soil loss amount, m 3 ; r is the rainfall erosion factor; k is the soil erodibility factor; ls is the slope length and slope factor; c is the vegetation cover factor; p is the soil and water conservation factor; ξ0 is the land salinization rate, %; A 耕 is the cultivated land area, hm 2 ; E 漫 、E 畦 are the water use quotas for flood irrigation and conventional border irrigation respectively, m 3 / hm 2 ; ET0 is the land surface evaporation, mm; A 荒 、A 林 are the desertification area and afforestation area respectively, hm 2 .

[0131] The functional relationship of the rainfall supplement subsystem includes:

[0132] W R =P e ×A0×10

[0133]

[0134] Among them, P e is the effective precipitation in a certain period, mm; A0 is the effective irrigation area, hm 2 ; P is the actual precipitation in the corresponding period, mm; among which 10 is the unit conversion coefficient.

[0135] In step S4, set the time boundary and time step of the kinetic model, assign initial values to the water-saving indicators, constant variables and intermediate variables, and obtain multiple verification objects and their annual water-saving indicators within the time boundary; the time boundary is at least greater than 10 years, and the time step is 1 year.

[0136] In step S5, according to the water-saving indicators of the verification objects, conduct a authenticity test on the system dynamics model composed of five kinetic models, and enter step S6 when the verification fails, and enter step S7 when the verification passes;

[0137] In one embodiment of the present invention, the method for conducting a real test includes:

[0138] S51. Calculate the maximum water saving amount of each verification object in the current year using the quota method:

[0139] ΔW 大 = A1×(Q0 - Q t )

[0140] where ΔW 大 is the maximum water saving amount, m 3 ; A1 is the actual agricultural irrigation area of the verification object in the current year, hm 2 ; Q0 and Q t are the comprehensive agricultural irrigation quotas in the current year and the planned year respectively, m 3 / hm 2 ;

[0141] S52. According to the water saving index of the verification object, use the functional relationship of each subsystem to calculate the agricultural water saving potential of multiple verification objects in the current year respectively;

[0142] S53. According to the agricultural water saving potential of all subsystems of the same verification object, use the water saving potential relationship formula to obtain the total agricultural water saving potential of each verification object;

[0143] S54. According to the maximum water saving amount and the total agricultural water saving potential of each verification object, calculate the ratio of the difference between the two to the maximum water saving amount as the error value;

[0144] S55. Determine whether the average error of multiple verification objects is greater than the preset error. If so, the system dynamics model fails the real test; otherwise, the system dynamics model passes the real test.

[0145] In step S6, adjust the constant variables and / or the water saving potential relationship formula of the system dynamics model, and then return to step S5;

[0146] During implementation, this solution preferably uses the water saving potential relationship formula:

[0147] ΔW = ΔW E + ΔW M + ΔW T + W R - W L

[0148] where ΔW is the agricultural water saving potential, m 3 ; ΔW E , ΔW M , ΔW T are the engineering water saving amount, management water saving amount, and technical water saving amount respectively, m 3 ; WR Precipitation supplement amount, m 3 ; W L Water saving loss amount, m 3 .

[0149] In an embodiment of the present invention, the method for adjusting the constant variables and / or the water saving potential relational expression of the system dynamics model includes:

[0150] S61. Adjust all the constant variables according to the first preset ratio. When the number of adjustment times is greater than the first preset number and the system dynamics model still fails the test, go to step S62;

[0151] S62. Adjust all the constant variables according to the second preset ratio. When the number of adjustment times is greater than the second preset number and the system dynamics model still fails the test, go to step S63;

[0152] S63. Select a verification object, calculate the maximum water saving amount of each subsystem by using the quota method, and calculate the ratio of the difference between the maximum water saving amount of the subsystem and its agricultural water saving potential to the maximum water saving amount;

[0153] Taking the project water saving subsystem as an example, the following describes the acquisition of the maximum water saving amount in step S63. The maximum water saving amount is equal to the difference between the agricultural water use quota E i1 before project water saving and the agricultural water use quota E i2 after project water saving multiplied by the area of the project water saving measures, that is, W i =(E i1 -E i2 )×A i ; The other subsystems are obtained in a similar way and will not be elaborated here.

[0154] S64. When the ratio of the subsystem is greater than the preset ratio, update the agricultural water saving potential of the corresponding subsystem = preset adjustment parameter × agricultural water saving potential, and update the water saving potential relational expression.

[0155] In step S7, obtain the known water saving indicators of the current year or the predicted year in the study area, and calculate the agricultural water saving potential of the study area in the current year or the predicted year by using the functional relationship and the water saving potential relational expression of the system dynamics model.

[0156] The calculation method of agricultural water saving potential based on system dynamics also includes a rationality test of the system dynamics model, which respectively includes:

[0157] Use the "Unites Check" function in Vensim PLE software to detect whether the units of all parameters in all functional relationships are consistent;

[0158] Use the "Check Model" function in Vensim PLE software to verify the logical correctness among all parameters in all functional relationships;

[0159] Set multiple step sizes, collect the statistical data of a verification object within the time boundary, and calculate the agricultural water-saving potential of the verification object using the functional relationship and the water-saving potential relational formula; when the agricultural water-saving potential calculated under multiple time step sizes is basically the same, the step size test is satisfied.

[0160] In steps S5 and S7, when calculating the agricultural water-saving potential of the verification object and the research area, the unknown water-saving indicators, constant variables, and intermediate variables all adopt the initial values.

[0161] To evaluate the simulation effect of the system dynamics model constructed by this solution, the following will be illustrated with specific examples:

[0162] This example selects Ordos City, Bayannur City, and Alxa League in Inner Mongolia as verification objects, sets the time boundary (historical statistical years) from 2014 to 2023, and determines the time step size to be 1 year.

[0163] The system dynamics model test is mainly carried out in two aspects: structural rationality test and authenticity test. The structural rationality test of the model is carried out through the two functions of "Unites Check" and "Check Model" built in Vensim PLE software. The Unites Check function can check the consistency of the units of variables and parameters in all equations and formulas in the model, and the Check Model function is used to verify the logical correctness among the equations, parameters, and variables in the model.

[0164] The integral error test, also known as the step size test, mainly verifies whether the time interval is reasonable. Taking Bayannur City as an example, the step size (Step) is set to 1, 0.5, 0.25, and 0.125 respectively, and the results of simulating four step size conditions are collected from the statistical data from 2014 to 2023. The simulation results are referred to Figure 7 .

[0165] Through Figure 7 the results, it can be seen that the water-saving potential of the system dynamics model of this solution is consistent in the four simulations, and the step size test passes. At the same time, the model meets the dimensional consistency, the extreme conditions of the equations, and the suitability of the model boundaries, so the rationality test passes.

[0166] Authenticity test is a commonly used method to guide model improvement and optimization, and the accuracy and adaptability of the model can be evaluated by comparing the calculation results with those of other methods. In this embodiment, the widely used quota method is adopted for calculation, and the maximum water saving amount is calculated through the comprehensive irrigation quotas of the current year and the future year. This method covers the comprehensive water saving effects of engineering and non-engineering measures and can more realistically reflect the actual water use situation in agriculture.

[0167] ΔW 大 = A1×(Q0 - Q t )

[0168] Where, ΔW 大 is the maximum water saving amount, m 3 ; A1 is the actual agricultural irrigation area in the current year, hm 2 ; Q0 and Q t are the comprehensive agricultural irrigation quotas in the current year and the planned year respectively, m 3 / hm 2 .

[0169] Using the above method for result comparison and verification, the calculation results of Ordos City, Bayannur City, and Alxa League are as shown in (a), (b), and (c) in Figure 8 . The results show that the errors between the calculated values and the simulated values in the three cities (leagues) are all within ±20%, and the average error is within ±10%, indicating that the authenticity test passes.

[0170] The above comparative test shows that the system dynamics model and the setting of parameter initial values constructed by this scheme can ensure the accuracy of subsequent prediction of agricultural water saving potential.

Claims

1. A calculation method for agricultural water-saving potential based on system dynamics, characterized in that, Including the steps: S1. Divide agricultural water conservation into five subsystems: engineering water conservation, management water conservation, technical water conservation, rainfall supplement, and water conservation loss. According to official and local statistical data, select water conservation indicators for each subsystem; S2. Determine the constant variables related to crop irrigation and the intermediate variables related to crop water conservation, and construct the functional relationships between all water conservation indicators and the constant variables and intermediate variables in each subsystem: The functional relationships of the engineering water conservation subsystem include: Among them, W 高效 , W 衬砌 , W 田块 , W 枢纽 are the water savings of efficient water-saving irrigation, canal lining, field land leveling, and water conservancy project construction, respectively, m 3 ; ρ is the added value of water savings per 10,000 yuan, taking 150 m 3 / 10,000 yuan; f 原 , f 新 , f 护 are the original value of fixed assets of the irrigation area hub project, new construction investment cost, and maintenance cost, respectively, 10,000 yuan; τ is the depreciation rate; A i is the area of the i-th efficient water-saving irrigation measure, hm 2 ; E j is the irrigation quota of the j-th crop, m 3 / hm 2 ; β j is the proportion of the sown area of the j-th crop; K i is the irrigation water quota adjustment coefficient of the i-th efficient water-saving method; m is the number of types of efficient water-saving irrigation; n is the number of types of crops; Q 农 is the agricultural water consumption, m 3 ; λ is the proportion of irrigation water consumption in agricultural water consumption, %; μ a , μ b are the field water utilization coefficients in the base year and the current year, respectively; Q 首 is the water diversion volume at the canal head in the current year, m 3 ; η a , η b are the canal system water utilization coefficients in the base year and the current year, respectively; The functional relationships of the management water conservation subsystem include: ， ， ， Among them, W 结构 、W 制度 、W 亏缺 、W 覆膜 、W 高标 、W 水价 are respectively the water savings generated by the adjustment of planting structure, the optimization of irrigation system, deficit irrigation methods, film mulching for moisture preservation, construction of high-standard farmland, and comprehensive reform of agricultural water prices, m 3 ; are respectively the grain-to-cash crop ratios in the base year and the current year; E a 、E b are respectively the comprehensive irrigation quotas for cash crops and food crops, m 3 / hm 2 ; A0 is the effective irrigation area, hm 2 ; A i制 is the optimized irrigation area of the i-th crop, hm 2 ; E im 、E in are respectively the irrigation quotas of the i-th crop before and after system optimization, m 3 / hm 2 ; A i缺 is the deficit irrigation area of the i-th crop, hm 2； 、 are respectively the irrigation quotas of the i-th crop before and after deficit irrigation, m 3 / hm 2 ; A 膜 is the film mulching area, hm 2 ; w m 、w n are respectively the irrigation quotas before and after film mulching for moisture preservation, m 3 / hm 2 ; A 标 is the high-standard farmland area, hm 2 ; η 标 is the water-saving capacity per unit area of high-standard farmland, m 3 / hm 2 ; k1 and k2 are respectively the water-saving rewards and precise subsidy costs, yuan; φ is the subsidy standard, with a value range of 0.15 - 0.2 yuan / m 3 ; The functional relationships of the technical water conservation subsystem include: ， ， Among them, W 密植 、W 育种 、W 水质 、W 渔业 、W 非常 are respectively the water savings generated by reasonable crop planting density, breeding of drought-resistant crops, improvement of agricultural water quality, reasonable stocking in fishery, and utilization of unconventional water, m 3 ; A i密 is the reasonable planting area of the i-th crop, hm 2 ; E iu 、E iv are respectively the irrigation quotas of the i-th crop before and after reasonable planting density, m 3 / hm 2 ; A ij is the sowing area of the j-th drought-resistant variety of the i-th crop, hm 2 ; E ij is the irrigation quota of the j-th drought-resistant variety of the i-th crop, m 3 / hm 2 ; is the conventional irrigation quota of the i-th crop, m 3 / hm 2 ; n is the number of crop types; M is the number of drought-resistant varieties of each crop; δ0 and δ1 are respectively the irrigation water quality compliance rates in the base year and the current year, %; A f is the aquaculture area, hm 2 ; E f is the water use quota for fishery, m 3 / hm 2 ; w f is the water consumption of fish ponds in the current year, m 3 ; w c is the unconventional water consumption, m 3 ; β c is the proportion of agricultural use of unconventional water; The functional relationships of the water conservation loss subsystem include: Where: W L is the water-saving loss; W 盐渍 , W 荒漠 , W 水土 , W 面源 are the losses caused by soil salinization, land desertification, agricultural soil and water loss, and agricultural non-point source pollution respectively; PE is the pure amount of nitrogen and phosphorus fertilizers; η 肥 is the loss coefficient of nitrogen and phosphorus fertilizers; x 肥 is the pollution discharge coefficient of nitrogen and phosphorus; CH is the application amount of pesticides; η 药 is the loss coefficient of pesticides; x 药 is the pollution discharge coefficient of pesticides; EU is the number of livestock and poultry breeding; q 畜 is the annual excretion coefficient of livestock and poultry manure and pollutants; η 畜 is the loss rate of livestock and poultry manure and pollutants; x 畜 is the pollution discharge coefficient; θ0 is the soil volume water content; w 土 is the soil loss; r is the rainfall erosion factor; k is the soil erodibility factor; ls is the slope length and slope factor; c is the vegetation cover factor; p is the soil and water conservation factor; ξ0 is the land salinization rate; A 耕 is the cultivated land area; E 漫 , E 畦 are the water use quotas for flood irrigation and conventional border irrigation respectively; ET0 is the land surface evaporation; A 荒 , A 林 are the land desertification area and the afforestation area respectively; S3. According to the functional relationships of each subsystem, use Vensim PLE software to construct dynamic models for calculating the agricultural water conservation potential of the five subsystems respectively; S4. Set the time boundary and time step of the dynamic model, assign initial values to the water conservation indicators, constant variables, and intermediate variables, and obtain multiple verification objects and their annual water conservation indicators within the time boundary; S5. According to the water conservation indicators of the verification objects, conduct authenticity tests on the system dynamic model composed of the five dynamic models. When the verification fails, go to step S6; when the verification passes, go to step S7; S6. Adjust the constant variables and / or the water conservation potential relationship formula of the system dynamic model, and then return to step S5; the water conservation potential relationship formula is: Among them, ΔW is the agricultural water-saving potential, m 3 ; ΔW E , ΔW M , ΔW T are the water savings from engineering, water savings from management, and water savings from technology respectively, m 3 ; W R is the precipitation supplement, m 3 ; W L is the water-saving loss, m 3 ; S7. Obtain the known water conservation indicators of the current year or the predicted year in the research area, and use the functional relationships and water conservation potential relationship formula of the system dynamic model to calculate the agricultural water conservation potential of the research area in the current year or the predicted year; The constant variables include the pesticide pollution emission coefficient, pesticide loss coefficient, nitrogen and phosphorus pollution emission coefficient, nitrogen and phosphorus fertilizer loss coefficient, annual excretion coefficient of livestock and poultry manure and pollutants, loss rate of livestock and poultry manure and pollutants, and pollutant emission coefficient; The methods for conducting authenticity tests include: S51. Calculate the maximum water conservation amount of each verification object in the current year using the quota method: Among them, is the maximum water saving amount, m 3 ; A1 is the actual agricultural irrigation area of the verification object in the current year, hm 2 ; Q0 and Q t are the comprehensive agricultural irrigation quotas in the current year and the planned year respectively, m 3 / hm 2 ; S52. According to the water conservation indicators of the verification objects, use the functional relationships of each subsystem to calculate the agricultural water conservation potential of multiple verification objects in the current year respectively; S53. According to the agricultural water conservation potential of all subsystems of the same verification object, use the water conservation potential relationship formula to obtain the total agricultural water conservation potential of each verification object; S54. According to the maximum water conservation amount and the total agricultural water conservation potential of each verification object, calculate the ratio of the difference between the two to the maximum water conservation amount as the error value; S55. Judge whether the average error of multiple verification objects is greater than the preset error. If so, the system dynamic model fails the authenticity test; otherwise, the system dynamic model passes the authenticity test; The methods for adjusting the constant variables and / or the water conservation potential relationship formula of the system dynamic model include: S61. Adjust all the constant variables according to the first preset ratio. When the number of adjustments is greater than the first preset number and the system dynamic model still fails the test, go to step S62; S62. Adjust all the constant variables according to the second preset ratio. When the number of adjustments is greater than the second preset number and the system dynamic model still fails the test, go to step S63; S63. Select a verification object, calculate the maximum water saving amount of each subsystem using the quota method, and calculate the ratio of the difference between the maximum water saving amount of the subsystem and its agricultural water saving potential to the maximum water saving amount. S64. When the ratio of the subsystem is greater than the preset ratio, update the agricultural water saving potential of the corresponding subsystem = preset adjustment parameter × agricultural water saving potential, and update the water saving potential relationship formula.

2. The agricultural water-saving potential calculation method based on system dynamics according to claim 1, wherein It also includes a rationality test for the system dynamics model, which respectively includes: Use the "Unites Check" function in Vensim PLE software to detect whether the units of all parameters in all functional relationships are consistent; Use the "Check Model" function in Vensim PLE software to verify whether the logic between all parameters in all functional relationships is correct; Set multiple step sizes, collect the statistical data of a verification object within the time boundary, and calculate the total agricultural water saving potential of the verification object using the functional relationship and the water saving potential relationship formula; when the agricultural water saving potential calculated under multiple time step sizes is basically the same, the step size test is satisfied.

3. The agricultural water-saving potential calculation method based on system dynamics according to claim 1, wherein The water saving indicators of the project water saving subsystem include canal system water utilization coefficient, canal head water diversion volume, high-efficiency water saving area, crop sown area, agricultural water consumption, effective irrigation water utilization coefficient, original value of fixed assets, newly built investment funds, and maintenance costs; The water saving indicators of the management water saving subsystem include optimized irrigation system area, optimized irrigation system quota, deficit irrigation area, deficit irrigation quota, grain-to-economic crop ratio, comprehensive irrigation quota for food crops, comprehensive irrigation quota for cash crops, plastic film mulching area, film mulching and moisture conservation irrigation quota, high-standard farmland area, water saving capacity per unit area, water saving reward expenses, and precise subsidy expenses; The water saving indicators of the technical water saving subsystem include drought-resistant variety sown area, drought-resistant variety irrigation quota, reasonable close planting area, reasonable close planting irrigation quota, irrigation water quality compliance rate, irrigation water consumption, unconventional water volume, proportion of unconventional water in agriculture, fish pond water consumption, and aquaculture area; The water saving indicators of the precipitation supplement subsystem include actual precipitation and effective irrigation area; The water saving indicators of the water saving loss subsystem include pesticide application amount, pure amount of nitrogen and phosphorus fertilizers, number of livestock and poultry raised, cultivated land area, land salinization rate, desertification area, afforestation area, land surface evaporation, precipitation erosion factor, soil erodibility factor, slope length and slope factor, vegetation cover factor, soil and water conservation factor, and soil volume water content; The constant variables include crop irrigation quota, irrigation adjustment coefficient, irrigation proportion, depreciation rate, added value of water saving per ten thousand yuan, subsidy standard, fishery water use quota, border irrigation quota, and flood irrigation quota; The intermediate variables include the water savings in efficient irrigation, the water savings in land leveling, the water savings in canal seepage prevention, the water savings in pivotal projects, the coefficient of field water utilization, the water savings in deficit irrigation, the water savings in the comprehensive reform of agricultural water prices, the water savings in optimized irrigation systems, the water savings in adjusted planting structures, the water savings in covering and moisturizing, the water savings in the construction of high-standard farmland, the water savings in reasonable aquaculture in fisheries, the water savings in reasonable crop planting density, the utilization amount of unconventional water in agriculture, the water savings in water quality improvement, the water savings in drought-resistant breeding, the soil loss amount, the loss amount of soil and water loss, the loss amount of desertification, the loss amount of salinization, the emission amount of pesticide pollution, the emission amount of farmland chemical fertilizer pollution, the emission amount of livestock and poultry breeding pollution, and the non-point source pollution amount.

4. The agricultural water-saving potential calculation method based on system dynamics according to claim 1, characterized in that The functional relationships of the rainfall supplement subsystem include: Among them, P e is the effective precipitation during a certain period, in mm; A0 is the effective irrigation area, in hm 2 ; P is the actual precipitation during the corresponding period, in mm; where 10 is the unit conversion coefficient.

5. The agricultural water-saving potential calculation method based on system dynamics according to claim 1, wherein When calculating and verifying the agricultural water-saving potential of the object and the research area, the unknown water-saving indicators, constant variables, and intermediate variables all adopt the initial values.

6. The agricultural water-saving potential calculation method based on system dynamics according to claim 1, wherein The time boundary is at least greater than 10 years, and the time step is 1 year.

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