Agricultural water-saving potential calculation method based on system dynamics

Abstract

The invention discloses an agricultural water saving potential calculation method based on system dynamics, and the method comprises the steps: dividing agricultural water saving into five subsystems, and selecting a water saving index of each subsystem; determining a constant variable and an intermediate variable, and constructing a function relationship between all water-saving indexes in each subsystem and the constant variable and the intermediate variable; according to the function relationship, adopting Vensim PLE software to respectively construct dynamic models of the five subsystems; setting initial values of a water-saving index, a constant variable and an intermediate variable, obtaining a plurality of verification objects and water-saving indexes of the verification objects in each year in a time boundary to perform authenticity verification on a system dynamic model formed by five dynamic models, and adjusting a water-saving potential relational expression of the constant variable and / or the system dynamic model when verification is not passed; returning to the authenticity checking step; and after verification, calculating the agricultural water-saving potential of the research area in the current year or the prediction year by adopting the function relationship of the system dynamics model and the water-saving potential relational expression.

Description

Technical Field

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

[0002] The estimation and evaluation of water-saving potential is the premise and basis for the development of agricultural water conservation. In order to understand the water-saving capabilities of different regions across the country and solve the contradiction of agricultural water use in irrigation areas, it is urgent to explore efficient methods for calculating water-saving potential.

[0003] In recent years, many scholars have calculated the agricultural water-saving potential from the irrigation area or provincial scale. Feng Shaoyuan and others considered factors such as effective precipitation replenishment, water transfer and field losses, and established a calculation formula for the agricultural resource-based water-saving potential in the Hetao Irrigation District of Inner Mongolia. Although this method incorporates precipitation replenishment and water transfer losses, the influencing factors only consider water-saving in the field of agricultural irrigation. It lacks the improvement and comprehensive thinking of agriculture and related industries, is not comprehensive and in-depth, and the internal structural relationship is unclear, resulting in inaccurate calculation and prediction of water-saving potential. Summary of the invention

[0004] In view of the above-mentioned 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 that the existing agricultural water-saving potential calculation is not comprehensive, resulting in low prediction accuracy.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A method for calculating agricultural water-saving potential based on system dynamics is provided, which comprises the following steps:

[0007] S1. Divide agricultural water conservation into five subsystems: engineering water conservation, management water conservation, technical water conservation, rainfall supplementation and water conservation loss, and select water conservation indicators for each subsystem based on official and local statistical data;

[0008] S2. Determine the constant variables associated with crop irrigation and the intermediate variables associated with crop water saving, and construct the functional relationship between all water saving indicators and the constant variables and intermediate variables in each subsystem;

[0009] S3. Based on the functional relationship of each subsystem, the Vensim PLE software was used to construct dynamic models for calculating the agricultural water-saving potential of the five subsystems;

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

[0011] S5. According to the water-saving index of the verification object, the authenticity of the system dynamics model composed of the five dynamic models is verified, and if the verification fails, the process proceeds to step S6, and if the verification passes, the process proceeds to step S7;

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

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

[0014] Furthermore, the method of conducting the truth test includes:

[0015] S51. Use the quota method to calculate the maximum water saving of each verification object in the current year:

[0016] ΔW 大 =A1×(Q0-Q t )

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

[0018] S52, according to the water-saving index of the verification object, using the functional relationship of each subsystem to calculate the agricultural water-saving potential of multiple verification objects in the current year;

[0019] S53, according to the total agricultural water-saving potential of all subsystems of the same verification object, using the water-saving potential relationship 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, calculating the ratio between the difference between the two and the maximum water saving amount as the error value;

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

[0022] The beneficial effects of the above technical scheme are: compared with other verification methods, the real verification of this scheme can use the reference data of relative true values ​​within the research scope (such as water-saving coverage area, agricultural water quota and other series of indicators) to independently evaluate the uncertainty of various subsystems and give the process of accurate accuracy indicators. This is an important basis for improving the accuracy of model fitting and improving the quality of water-saving prediction, and is an important guarantee for promoting the application scope and quantitative application level of system dynamics of water-saving processes.

[0023] Further, the method of adjusting the constant variables and / or the water saving potential relationship of the system dynamics model includes:

[0024] S61, adjusting all constant variables according to a first preset ratio. When the number of adjustments is greater than the first preset number, and the system dynamics model still fails to pass the test, proceeding to step S62;

[0025] S62, adjusting all constant variables according to a second preset ratio. When the number of adjustments is greater than the second preset number, and the system dynamics model still fails the test, proceeding to step S63;

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

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

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

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

[0030] Use the "Units Check" function in Vensim PLE software to check whether all parameter units in all function relationships are consistent;

[0031] Use the "Check Model" function in Vensim PLE software to verify the logic correctness of all parameters in all functional relationships;

[0032] Set multiple step sizes, collect statistical data of a verification object within the time boundary, and use the functional relationship and water-saving potential relationship to calculate the agricultural water-saving potential of the verification object; when the agricultural water-saving potential calculated under multiple time steps is basically the same, the step size test is satisfied.

[0033] The beneficial effects of the above technical solution are as follows: the rationality checks adopted in this solution are all built-in test functions of the system, among which "Unites Check" and "Check Model" are more convenient, fast and efficient. The system automatically identifies the logic of parameters and prompts the source of errors, which greatly shortens the test time; and the step size test verifies the stability of the results due to different step size changes, and determines the optimal step size setting based on specific task requirements and data characteristics to balance model performance and computational efficiency.

[0034] Furthermore, the water-saving indicators of the engineering water-saving subsystem include the canal water utilization coefficient, canal head water diversion volume, high-efficiency water-saving area, crop planting area, agricultural water consumption, irrigation water effective utilization coefficient, original value of fixed assets, new construction investment funds and maintenance costs;

[0035] The water-saving indicators of the water-saving management subsystem include irrigation system optimization area, irrigation system optimization quota, deficit irrigation area, deficit irrigation quota, grain-to-economic ratio, comprehensive irrigation quota for grain crops, comprehensive irrigation quota for economic crops, mulch coverage area, mulch moisture conservation irrigation quota, high-standard farmland area, water-saving capacity per unit area, water-saving reward fee and precision subsidy fee;

[0036] The water-saving indicators of the technical water-saving subsystem include the sowing area of ​​drought-resistant varieties, the irrigation quota of drought-resistant varieties, the reasonable dense planting area, the reasonable dense planting irrigation quota, the irrigation water quality compliance rate, the irrigation water consumption, the unconventional water consumption, the proportion of unconventional water agriculture, the water consumption of fish ponds and the 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, nitrogen and phosphorus fertilizer conversion, livestock and poultry breeding quantity, 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 coverage 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, ten thousand yuan water-saving added value, subsidy standard, fishery water 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, livestock and poultry manure and pollutant annual excretion coefficient, livestock and poultry manure and pollutant loss rate and pollutant emission coefficient;

[0040] The intermediate variables include water saving due to efficient irrigation, water saving due to land leveling, water saving due to channel anti-seepage, water saving due to key projects, field water utilization coefficient, water saving due to insufficient irrigation, water saving due to comprehensive reform of agricultural water prices, water saving due to optimization of irrigation system, water saving due to adjustment of planting structure, water saving due to covering and moisture retention, water saving due to high-standard farmland construction, water saving due to reasonable fishery breeding, water saving due to reasonable crop density, water saving due to unconventional water utilization in agriculture, water saving due to improved water quality, water saving due to drought-resistant breeding, soil loss, loss due to soil and water erosion, loss due to desertification, loss due to salinization, pesticide pollution emissions, farmland fertilizer pollution emissions, livestock and poultry breeding pollution emissions and non-point source pollution.

[0041] The beneficial effects of the above technical scheme are as follows: the existing technical scheme focuses on evaluating the size of agricultural water-saving potential from a qualitative perspective, while the indicator elements selected in this scheme can be quantified and calculated, and more indicators are considered with a wider range and are objective and reasonable. Moreover, 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 relationship is:

[0043] ΔW=ΔW E +ΔW M +ΔW T +W R -W L

[0044] Among them, ΔW is the agricultural water saving potential, m 3 ; ΔW E , ΔW M , ΔW T They are engineering water saving, management water saving and technical water saving, m 3 ; W R is the precipitation replenishment, m 3 ; W L is the water saving loss, m 3 .

[0045] Furthermore, the functional relationship of the engineering water-saving subsystem includes:

[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 The water saving amounts of efficient water-saving irrigation, channel lining, field land leveling and water conservancy hub construction are respectively, m 3 ρ is the added value of water saving of 10,000 yuan, taking 150m 3 / 10,000 yuan; f 原 、f 新 、f 护 are the original value of fixed assets, new construction investment costs, and repair and maintenance costs of the irrigation hub project, in ten thousand 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 for the jth crop, m 3 / hm 2 β j is the proportion of sown area of ​​the jth crop; K i is the irrigation water quota adjustment coefficient of the i-th efficient water-saving method; m is the number of efficient water-saving irrigation types; n is the number of crop types; Q 农 is agricultural water consumption, m 3 ; λ is the proportion of irrigation water consumption to 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 current annual headwater diversion volume, m 3 ; η a , η b are the canal water utilization coefficients for the base year and the current year, respectively;

[0052] The functional relationship of the water-saving management subsystem includes:

[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] Among them, W 结构 , W 制度 , W 亏缺 , W 覆膜 , W 高标 , W 水价 They are the water saving amount caused by planting structure adjustment, irrigation system optimization, film covering and moisture retention, high-standard farmland construction, comprehensive reform of agricultural water prices, and deficit irrigation methods, m 3 ; α a , α b are the grain-to-economy ratios of the base year and the current year, respectively; E a 、E b are 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 Optimal area for irrigation schedule of crop i, hm 2 ; E im 、E in are 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 ; E ip 、E iq are the irrigation quotas of the i-th crop before and after deficit irrigation, m 3 / hm 2 ; A 膜 is the film covering area, hm 2 ;w m 、w n are the irrigation quotas before and after mulching to conserve soil moisture, m 3 / hm 2 ; A 标 is the area of ​​high-standard farmland, hm 2 ; η 标 is the water-saving capacity of high-standard farmland per unit area, m 3 / hm 2 ; k1 and k2 are water-saving reward and precision subsidy costs, yuan; Subsidy standard, ranging from 0.15 to 0.2 yuan / m3 ;

[0058] The functional relationship of the technical water-saving subsystem includes:

[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 The water saving amount generated by unconventional water utilization, reasonable stocking of fisheries, reasonable crop density, drought-resistant crop breeding, and agricultural water quality improvement, m 3 ; A i密 is the reasonable dense 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 density planting, m 3 / hm 2 ; A ij is the sowing area of ​​the jth drought-resistant variety of the i-th crop, hm 2 ; E ij is the irrigation quota for the jth drought-resistant variety of the i-th crop, m 3 / hm 2 ; E i0 is the conventional irrigation quota for 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 The water quota for fisheries, m 3 / hm 2 ;w fis the current annual water consumption of fish ponds, m 3 ;w c is the unconventional water consumption, m 3 β c The proportion of unconventional water agriculture;

[0064] The functional relationship of the water saving loss subsystem includes:

[0065] W L =W 盐渍 +W 荒漠 +W 水土 +W 面源

[0066] W 面源 =PE×η 肥 × 肥 +CH×η 药 × 药 +EU×q 畜 ×η 畜 × 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] Where: W 盐渍 , W 荒漠 , W 水土 , W 面源 are the losses caused by soil salinization, land desertification, agricultural soil erosion, and agricultural non-point source pollution, m 3 ; PE is the pure amount of nitrogen and phosphorus fertilizer, 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 pesticide 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 breeding; q 畜 is the annual excretion coefficient of livestock and poultry feces and pollutants; η 畜 is the loss rate of livestock and poultry feces and pollutants; x 畜 is the pollutant emission coefficient; θ0 is the soil volume moisture content, %; w 土 is the amount of soil loss, 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 coverage factor; p is the soil and water conservation factor; ξ0 is the land salinity rate, %; A 耕 is the cultivated land area, hm 2 ; E 漫 、E 畦 The water quotas for flood irrigation and conventional border irrigation, m 3 / hm 2 ; ET0 is the land surface evaporation, mm; A 荒 , A 林 are the land desertification area and afforestation area, hm 2 .

[0071] The beneficial effects of the above technical scheme are as follows: compared with the traditional indicator weight estimation, each step structure of this technical scheme is connected by a corresponding formula, forming a calculation process from the initial indicator to the process variable and then to the state variable, and the structure is more rigorous and clear; and the behavior patterns and characteristics are mainly determined by the dynamic structure and feedback mechanism within the system, and are not affected by external factors. Therefore, it can be used to simulate long-term and periodic water-saving potential estimation problems.

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

[0073] W R =P e ×A0×10

[0074]

[0075] 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; 10 is the unit conversion coefficient.

[0076] Furthermore, when calculating the agricultural water-saving potential of the verification object and the study area, the unknown water-saving indicators, constant variables and intermediate variables all use 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 by this scheme takes into account five subsystems, can organically connect the various parts of the interactions between the five subsystems, and can be quickly and efficiently applied to the simulation and prediction of agricultural water-saving potential, so that relevant departments can clearly know which subsystem has the regulation potential through the agricultural water-saving potential of each subsystem in adjacent years, so as to make targeted adjustments in the future agricultural water-saving to increase the agricultural water-saving potential.

[0079] The system dynamics model constructed by this scheme can be combined with the water-saving plans of relevant departments to calculate the agricultural water-saving potential in the forecast year, so as to assist relevant departments in determining whether the water-saving plans are reasonable and make targeted adjustments to ensure high crop yields while improving the agricultural water-saving potential. This scheme can improve the accuracy of agricultural water-saving potential prediction through the coordination of multiple subsystems.

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

[0081] The water-saving indicators selected in this plan are all derived from official and local statistical data, which makes the parameters selected in this plan relatively comprehensive. On a large scale, it can be applied to the entire country, different water resource zones, different river basins, different provinces and prefecture-level cities; on a small scale, it can be applied to counties, irrigation areas and other units with complete data. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 Flowchart of the method for calculating agricultural water saving potential based on system dynamics.

[0083] Figure 2 Schematic diagram of the dynamic model of the engineering water-saving subsystem.

[0084] Figure 3 Schematic diagram of the kinetic model for managing the water conservation subsystem.

[0085] Figure 4 Schematic diagram of the dynamic model of the technical water-saving subsystem.

[0086] Figure 5 Schematic diagram of the dynamic model for the rainfall replenishment subsystem.

[0087] Figure 6 Schematic diagram of the dynamic model of the water saving loss subsystem.

[0088] Figure 7 Schematic diagram of the step length test results of the system dynamics model.

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

[0090] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0091] refer to Figure 1 , Figure 1 A flow chart showing the method for calculating agricultural water saving potential based on system dynamics is shown in Figure 1 As 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 replenishment, and water conservation loss. Water conservation indicators for each subsystem are selected based on official and local statistical data.

[0093] During implementation, the water-saving indicators of the water-saving subsystem of the project selected in this plan include the canal water utilization coefficient, canal head water diversion volume, high-efficiency water-saving area, crop planting area, agricultural water consumption, irrigation water effective utilization coefficient, original value of fixed assets, new construction investment funds and maintenance costs;

[0094] The water-saving indicators of the water-saving management subsystem include irrigation system optimization area, irrigation system optimization quota, deficit irrigation area, deficit irrigation quota, grain-to-economic ratio, comprehensive irrigation quota for grain crops, comprehensive irrigation quota for economic crops, mulch coverage area, mulch moisture conservation irrigation quota, high-standard farmland area, water-saving capacity per unit area, water-saving reward fee and precision subsidy fee;

[0095] The water-saving indicators of the technical water-saving subsystem include the sowing area of ​​drought-resistant varieties, the irrigation quota of drought-resistant varieties, the reasonable dense planting area, the reasonable dense planting irrigation quota, the irrigation water quality compliance rate, the irrigation water consumption, the unconventional water consumption, the proportion of unconventional water agriculture, the water consumption of fish ponds and the aquaculture area;

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

[0097] The water-saving indicators of the water-saving loss subsystem include pesticide application amount, nitrogen and phosphorus fertilizer conversion, livestock and poultry breeding quantity, 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 coverage factor, soil and water conservation factor and soil volume moisture content;

[0098] In step S2, a constant variable associated with crop irrigation and an intermediate variable associated with crop water saving are determined, and a functional relationship between all water saving indicators and the constant variables and the intermediate variables in each subsystem is constructed;

[0099] During implementation, the preferred constant variables of this plan include crop irrigation quota, irrigation adjustment coefficient, irrigation proportion, depreciation rate, ten thousand yuan water-saving added value, subsidy standard, fishery water 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, livestock and poultry manure and pollutant annual excretion coefficient, livestock and poultry manure and pollutant loss rate and pollutant emission coefficient;

[0100] The intermediate variables include water saving due to efficient irrigation, water saving due to land leveling, water saving due to channel anti-seepage, water saving due to key projects, field water utilization coefficient, water saving due to insufficient irrigation, water saving due to comprehensive reform of agricultural water prices, water saving due to optimization of irrigation system, water saving due to adjustment of planting structure, water saving due to covering and moisture retention, water saving due to high-standard farmland construction, water saving due to reasonable fishery breeding, water saving due to reasonable crop density, water saving due to unconventional water utilization in agriculture, water saving due to improved water quality, water saving due to drought-resistant breeding, soil loss, loss due to soil and water erosion, loss due to desertification, loss due to salinization, pesticide pollution emissions, farmland fertilizer pollution emissions, livestock and poultry breeding pollution emissions and non-point source pollution.

[0101] In step S3, according to the functional relationship of each subsystem, the Vensim PLE software is used to construct the dynamic models of the five subsystems to calculate the agricultural water saving potential;

[0102] In one embodiment of the present invention, the functional relationship of the engineering water-saving 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 saving amounts of efficient water-saving irrigation, channel lining, field land leveling and water conservancy hub construction are respectively, m 3 ρ is the added value of water saving of 10,000 yuan, taking 150m 3 / 10,000 yuan; f 原 、f 新 、f 护 are the original value of fixed assets, new construction investment costs, and repair and maintenance costs of the irrigation hub project, in ten thousand 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 for the jth crop, m 3 / hm 2 β j is the proportion of sown area of ​​the jth crop; K i is the irrigation water quota adjustment coefficient of the i-th efficient water-saving method; m is the number of efficient water-saving irrigation types; n is the number of crop types; Q 农 is the agricultural water consumption, m 3 ; λ is the proportion of irrigation water consumption to 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 current annual headwater diversion volume, m 3 ; η a , η b are the canal water utilization coefficients for the base year and the current year, respectively.

[0109] As for the engineering water-saving subsystem, in my country, high-efficiency irrigation methods such as spraying and micro-irrigation can irrigate according to the needs of crop growth, eliminating field channels and drainage ditches, saving water and increasing the sown area, which is the main way to save water in agriculture. At the same time, channel anti-seepage is achieved through channel lining and maintenance, and its water saving can be calculated by the water diversion volume at the head of the channel and the water utilization coefficient of the channel system. In addition, field land leveling and irrigation area water conservancy hub projects can improve the efficiency of agricultural water resource utilization and achieve the purpose of saving water and increasing efficiency.

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

[0111] ΔW 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] Among them, W 结构 , W 制度 , W 亏缺 , W 覆膜 , W 高标 , W 水价 They are the water saving amount caused by planting structure adjustment, irrigation system optimization, film covering and moisture retention, high-standard farmland construction, comprehensive reform of agricultural water prices, and deficit irrigation methods, m 3 ; α a , α b are the grain-to-economy ratios of the base year and the current year, respectively; E a 、E b are 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 Optimal area for irrigation schedule of crop i, hm 2 ; E im 、E in are 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 ; E ip 、E iq are the irrigation quotas of the i-th crop before and after deficit irrigation, m 3 / hm 2 ; A 膜 is the film covering area, hm 2 ;w m 、w n are the irrigation quotas before and after mulching to conserve soil moisture, m 3 / hm 2 ; A 标 is the area of ​​high-standard farmland, hm 2 ; η 标 is the water-saving capacity of high-standard farmland per unit area, m 3 / hm 2 ; k1 and k2 are water-saving reward and precision subsidy costs, yuan; Subsidy standard, ranging from 0.15 to 0.2 yuan / m 3 .

[0116] For the parameters involved in the functional relationship of the management water-saving subsystem, the amount of water saved by adjusting the planting structure is calculated by the agricultural grain-to-economic ratio and the crop irrigation water quota, while the irrigation system optimization area, film covering area, high-standard farmland area, deficit irrigation area, water-saving rewards and precise subsidy amounts can all be obtained through local agricultural departments 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 The water saving amount generated by unconventional water utilization, reasonable stocking of fisheries, reasonable crop density, drought-resistant crop breeding, and agricultural water quality improvement, m 3 ; A i密 is the reasonable dense 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 density planting, m 3 / hm 2 ; A ij is the sowing area of ​​the jth drought-resistant variety of the i-th crop, hm 2 ; E ij is the irrigation quota for the jth drought-resistant variety of the i-th crop, m 3 / hm 2 ; E i0 is the conventional irrigation quota for 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 The water quota for fisheries, m 3 / hm 2 ;w f is the current annual water consumption of fish ponds, m 3 ;w c is the unconventional water consumption, m 3 β c The proportion of unconventional water agriculture.

[0123] For the technical water-saving subsystem, since recycled water, brackish water and rainwater in unconventional water can be used for agricultural irrigation, improvements in fishery farming technology will also reduce water consumption, and appropriate adjustment of planting density can increase yield and water productivity.

[0124] The functional relationship of the water saving loss subsystem includes:

[0125] W L =W 盐渍 +W 荒漠 +W 水土 +W 面源

[0126] W 面源 =PE×η 肥 × 肥 +CH×η 药 × 药 +EU×q 畜 ×η 畜 × 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] Where: W 盐渍 , W 荒漠 , W 水土 , W 面源 are the losses caused by soil salinization, land desertification, agricultural soil erosion, and agricultural non-point source pollution, m3 ; PE is the pure amount of nitrogen and phosphorus fertilizer, 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 pesticide 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 breeding; q 畜 is the annual excretion coefficient of livestock and poultry feces and pollutants; η 畜 is the loss rate of livestock and poultry feces and pollutants; x 畜 is the pollutant emission coefficient; θ0 is the soil volume moisture content, %; w 土 is the amount of soil loss, m 3 ; r is the precipitation erosion factor; k is the soil erodibility factor; ls is the slope length and slope factor; c is the vegetation coverage factor; p is the soil and water conservation factor; ξ0 is the land salinity rate, %; A 耕 is the cultivated land area, hm 2 ; E 漫 、E 畦 The water quotas for flood irrigation and conventional border irrigation, m 3 / hm 2 ; ET0 is the land surface evaporation, mm; A 荒 , A 林 are the land desertification area and afforestation area, 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; 10 is the unit conversion coefficient.

[0135] In step S4, the time boundary and time step of the dynamic model are set, initial values ​​are assigned to water-saving indicators, constant variables and intermediate variables, and multiple verification objects and their annual water-saving indicators in the time boundary are obtained; 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 index of the verification object, the authenticity of the system dynamics model composed of the five dynamic models is verified, and if the verification fails, the process proceeds to step S6, and if the verification passes, the process proceeds to step S7;

[0137] In one embodiment of the present invention, the method for performing authenticity verification includes:

[0138] S51. Use the quota method to calculate the maximum water saving of each verification object in the current year:

[0139] ΔW 大 =A1×(Q0-Q t )

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

[0141] S52, according to the water-saving index of the verification object, using the functional relationship of each subsystem to calculate the agricultural water-saving potential of multiple verification objects in the current year;

[0142] S53, according to the agricultural water-saving potential of all subsystems of the same verification object, the total agricultural water-saving potential of each verification object is obtained by using a water-saving potential relationship;

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

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

[0145] In step S6, the constant variables and / or the water-saving potential relationship of the system dynamics model are adjusted, and then the process returns to step S5;

[0146] During implementation, this scheme preferably adopts the water-saving potential relationship:

[0147] ΔW=ΔW E +ΔW M +ΔW T +W R -W L

[0148] Among them, ΔW is the agricultural water saving potential, m 3 ; ΔW E , ΔW M , ΔW T They are engineering water saving, management water saving and technical water saving, m 3 ; WR is the precipitation replenishment, m 3 ; W L is the water saving loss, m 3 .

[0149] In one embodiment of the present invention, the method of adjusting the constant variable and / or the water saving potential relationship of the system dynamics model includes:

[0150] S61, adjusting all constant variables according to a first preset ratio. When the number of adjustments is greater than the first preset number, and the system dynamics model still fails to pass the test, proceeding to step S62;

[0151] S62, adjusting all constant variables according to a second preset ratio. When the number of adjustments is greater than the second preset number, and the system dynamics model still fails the test, proceeding to step S63;

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

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

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

[0155] In step S7, the known water-saving indicators of the study area in the current year or the forecast year are obtained, and the agricultural water-saving potential of the study area in the current year or the forecast year is calculated using the functional relationship of the system dynamics model and the water-saving potential relationship.

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

[0157] Use the "Units Check" function in Vensim PLE software to check whether all parameter units in all function relationships are consistent;

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

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

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

[0161] In order to evaluate the effect of the system dynamics model simulation constructed by this scheme, the following is an explanation 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 year) to 2014-2023, and determines the time step to be 1 year.

[0163] The system dynamics model test is mainly carried out in two aspects: structural rationality test and authenticity test. The model structure rationality test is carried out through the two functions of "Unites Check" and "Check Model" in the 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 between equations, parameters and variables in the model.

[0164] The integral error test is also called the step test, which 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 statistical data from 2014 to 2023 are collected to simulate the results under four step size conditions. The simulation results are referenced Figure 7 .

[0165] pass Figure 7 The results show that the water-saving potential of the system dynamics model of this scheme 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 model boundaries meet the suitability, so the rationality test passes.

[0166] Authenticity testing is a common method to guide model improvement and optimization. The accuracy and adaptability of the model can be evaluated by comparing the results of the calculations with other methods. This embodiment adopts the currently widely used quota method to calculate the maximum water saving amount through the comprehensive irrigation quota 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, m 3 ; A1 is the actual agricultural irrigation area in the current year, hm 2 ; Q0, Q t They are the current year and the planned year agricultural comprehensive irrigation quota, m 3 / hm 2 .

[0169] The above method is used to compare and verify the results. The calculation results of Ordos City, Bayannur City, and Alxa League are as follows: Figure 8 The results show that the errors between the calculated values ​​and the simulated values ​​of the three cities (leagues) are within ±20%, and the average error is within ±10%, and the error shows that the authenticity test has passed.

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

Claims

1. A method for calculating agricultural water-saving potential based on system dynamics, characterized in that: Includes steps: S1. Divide agricultural water conservation into five subsystems: engineering water conservation, management water conservation, technical water conservation, rainfall supplementation and water conservation loss, and select water conservation indicators for each subsystem based on official and local statistical data; S2. Determine the constant variables associated with crop irrigation and the intermediate variables associated with crop water saving, and construct the functional relationship between all water saving indicators and the constant variables and intermediate variables in each subsystem; S3. Based on the functional relationship of each subsystem, the Vensim PLE software was used to construct dynamic models for calculating the agricultural water-saving potential of the five subsystems; S4. Set the time boundary and time step of the dynamic model, assign initial values ​​to water-saving indicators, constant variables and intermediate variables, and obtain multiple verification objects and their annual water-saving indicators in the time boundary; S5. According to the water-saving index of the verification object, the authenticity of the system dynamics model composed of the five dynamic models is verified, and if the verification fails, the process proceeds to step S6, and if the verification passes, the process proceeds to step S7; S6, adjusting the constant variables and / or the water-saving potential relationship of the system dynamics model, and then returning to step S5; S7. Obtain known water-saving indicators for the current or predicted year in the study area, and use the functional relationship of the system dynamics model and the water-saving potential relationship to calculate the agricultural water-saving potential of the study area in the current or predicted year.

2. The method for calculating agricultural water-saving potential based on system dynamics according to claim 1, characterized in that: Methods for conducting reality checks include: S51. Use the quota method to calculate the maximum water saving of each verification object in the current year: ΔW 大 =A1×(Q0-Q t ) Where, ΔW 大 is the maximum water saving, m 3 ; A1 is the actual agricultural irrigation area of ​​the verification object in the current year, hm 2 ; Q0, Q t The agricultural comprehensive irrigation quotas for the current year and the planned year, respectively, m 3 / hm 2 ; S52, according to the water-saving index of the verification object, using the functional relationship of each subsystem to calculate the agricultural water-saving potential of multiple verification objects in the current year; S53, according to the agricultural water-saving potential of all subsystems of the same verification object, the total agricultural water-saving potential of each verification object is obtained by using a water-saving potential relationship; S54, according to the maximum water saving amount and the total agricultural water saving potential of each verification object, calculating the ratio between the difference between the two and the maximum water saving amount as the error value; S55. Determine whether the average error of multiple verification objects is greater than a preset error. If so, the system dynamics model fails the true test; otherwise, the system dynamics model passes the true test.

3. The method for calculating agricultural water-saving potential based on system dynamics according to claim 1 or 2, characterized in that: Methods for adjusting the water conservation potential relationships for constant variables and / or system dynamics models include: S61, adjusting all constant variables according to a first preset ratio. When the number of adjustments is greater than the first preset number, and the system dynamics model still fails to pass the test, proceeding to step S62; S62, adjusting all constant variables according to a second preset ratio. When the number of adjustments is greater than the second preset number, and the system dynamics model still fails the test, proceeding to step S63; S63. Select a verification object, use the quota method to calculate the maximum water saving of each subsystem, and calculate the ratio of the difference between the maximum water saving of the subsystem and its agricultural water saving potential to the maximum water saving; S64. When the ratio of the subsystem is greater than the preset ratio, the agricultural water-saving potential of the corresponding subsystem is updated = preset adjustment parameter × agricultural water-saving potential, and the water-saving potential relationship is updated.

4. The method for calculating agricultural water-saving potential based on system dynamics according to claim 1, characterized in that: It also includes a rationality check of the system dynamics model, which includes: Use the "Units Check" function in the Vensim PLE software to check whether all parameter units in all function relationships are consistent; Use the "Check Model" function in Vensim PLE software to verify the logic correctness of all parameters in all functional relationships; Set multiple step sizes, collect statistical data of a verification object within the time boundary, and use the functional relationship and water-saving potential relationship to calculate the total agricultural water-saving potential of the verification object; when the agricultural water-saving potential calculated under multiple time steps is basically the same, the step test is satisfied.

5. The method for calculating agricultural water-saving potential based on system dynamics according to claim 1, characterized in that: The water-saving indicators of the engineering water-saving subsystem include the canal water utilization coefficient, canal head water diversion volume, high-efficiency water-saving area, crop planting area, agricultural water consumption, irrigation water effective utilization coefficient, original value of fixed assets, new construction investment and maintenance costs; The water-saving indicators of the water-saving management subsystem include irrigation system optimization area, irrigation system optimization quota, deficit irrigation area, deficit irrigation quota, grain-to-economic ratio, comprehensive irrigation quota for grain crops, comprehensive irrigation quota for economic crops, mulch coverage area, mulch moisture conservation irrigation quota, high-standard farmland area, water-saving capacity per unit area, water-saving reward fee and precision subsidy fee; The water-saving indicators of the technical water-saving subsystem include the sowing area of ​​drought-resistant varieties, the irrigation quota of drought-resistant varieties, the reasonable dense planting area, the reasonable dense planting irrigation quota, the irrigation water quality compliance rate, the irrigation water consumption, the unconventional water consumption, the proportion of unconventional water agriculture, the water consumption of fish ponds and the 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, nitrogen and phosphorus fertilizer conversion, livestock and poultry breeding quantity, 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 coverage factor, soil and water conservation factor and soil volume moisture content; The constant variables include crop irrigation quota, irrigation adjustment coefficient, irrigation proportion, depreciation rate, ten thousand yuan water-saving added value, subsidy standard, fishery water 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, livestock and poultry manure and pollutant annual excretion coefficient, livestock and poultry manure and pollutant loss rate and pollutant emission coefficient; The intermediate variables include water saving due to efficient irrigation, water saving due to land leveling, water saving due to channel anti-seepage, water saving due to key projects, field water utilization coefficient, water saving due to insufficient irrigation, water saving due to comprehensive reform of agricultural water prices, water saving due to optimization of irrigation system, water saving due to adjustment of planting structure, water saving due to covering and moisture retention, water saving due to high-standard farmland construction, water saving due to reasonable fishery breeding, water saving due to reasonable crop density, water saving due to unconventional water utilization in agriculture, water saving due to improved water quality, water saving due to drought-resistant breeding, soil loss, loss due to soil and water erosion, loss due to desertification, loss due to salinization, pesticide pollution emissions, farmland fertilizer pollution emissions, livestock and poultry breeding pollution emissions and non-point source pollution.

6. The method for calculating agricultural water-saving potential based on system dynamics according to claim 5, characterized in that: The water saving potential relationship is: ΔW=ΔW E +ΔW M +ΔW T +WR-WL Among them, ΔW is the agricultural water saving potential, m 3 ; ΔW E , ΔW M , ΔW T They are engineering water saving, management water saving and technical water saving, m 3 ; W R is the precipitation replenishment, m 3 ; W L is the water saving loss, m 3 .

7. The method for calculating agricultural water-saving potential based on system dynamics according to claim 6, characterized in that: The functional relationship of the engineering water-saving subsystem includes: ΔW E =In 枢纽 +W 高效 +W 田块 +W 衬砌 W 枢纽 =ρ×[(1-τ)f 原 +f 新 +f 护 ] Among them, W 高效 , W 衬砌 , W 田块 , W 枢纽 The water saving amounts of efficient water-saving irrigation, channel lining, field land leveling and water conservancy hub construction are respectively, m 3 ρ is the added value of water saving of 10,000 yuan, taking 150m 3 / 10,000 yuan; f 原 、f 新 、f 护 are the original value of fixed assets, new construction investment costs, and repair and maintenance costs of the irrigation hub project, in ten thousand 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 for the jth crop, m 3 / hm 2 β j is the proportion of sown area of ​​the jth crop; K i is the irrigation water quota adjustment coefficient of the i-th efficient water-saving method; m is the number of efficient water-saving irrigation types; n is the number of crop types; Q 农 is agricultural water consumption, m 3 ; λ is the proportion of irrigation water consumption to 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 current annual headwater diversion volume, m 3 ; η a , η b are the canal water utilization coefficients for the base year and the current year, respectively; The functional relationship of the water-saving management subsystem includes: ΔW M =In 结构 +W 制度 +W 亏缺 +W 覆膜 +W 高标 +W 水价 Among them, W 结构 , W 制度 , W 亏缺 , W 覆膜 , W 高标 , W 水价 They are the water saving amount caused by planting structure adjustment, irrigation system optimization, film covering and moisture retention, high-standard farmland construction, comprehensive reform of agricultural water prices, and deficit irrigation methods, m 3 ; α a , α b are the grain-to-economy ratios in the base year and the current year, respectively; E a 、E b are 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 Optimal area for irrigation schedule of crop i, hm 2 ; E im 、E in are 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 ; E ip 、E iq are the irrigation quotas of the i-th crop before and after deficit irrigation, m 3 / hm 2 ; A 膜 is the film covering area, hm 2 ;w m 、w n are the irrigation quotas before and after mulching to conserve soil moisture, m 3 / hm 2 ; A 标 is the area of ​​high-standard farmland, hm 2 ; η 标 is the water-saving capacity of high-standard farmland per unit area, m 3 / hm 2 ; k1 and k2 are water-saving reward and precision subsidy costs, yuan; Subsidy standard, ranging from 0.15 to 0.2 yuan / m 3 ; The functional relationship of the technical water-saving subsystem includes: ΔW T =In 密植 +W 育种 +W 水质 +W 渔业 +W 非常 IN 非常 =wc×βc Among them, W 密植 , W 育种 , W 水质 , W 渔业 , W 非常 The water saving amount generated by unconventional water utilization, reasonable stocking of fisheries, reasonable crop density, drought-resistant crop breeding, and agricultural water quality improvement, m 3 ; A i密 is the reasonable dense 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 density planting, m 3 / hm 2 ; A ij is the sowing area of ​​the jth drought-resistant variety of the i-th crop, hm 2 ; E ij is the irrigation quota for the jth drought-resistant variety of the i-th crop, m 3 / hm 2 ; E i0 is the conventional irrigation quota for 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 The water quota for fisheries, m 3 / hm 2 ;w f is the current annual water consumption of fish ponds, m 3 ;w c is the unconventional water consumption, m 3 β c The proportion of unconventional water agriculture; The functional relationship of the water saving loss subsystem includes: WL=W 盐渍 +W 荒漠 +W 水土 +W 面源 IN 面源 =PE×η 肥 ×x 肥 +CH×η 药 ×x 药 +EU×q 畜 ×η 畜 ×x 畜 IN 水土 =θ0×w 土 =θ0×r×k×ls×c×p W 盐渍 =ξ0×A 耕 ×(E 漫 -HAVE BEEN 畦 ) W 荒漠 =ET0×(A 荒 -A 林 ) Where: W 盐渍 , W 荒漠 , W 水土 , W 面源 are the losses caused by soil salinization, land desertification, agricultural soil erosion, and agricultural non-point source pollution, m 3 ; PE is the pure amount of nitrogen and phosphorus fertilizer, 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 pesticide 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 breeding; q 畜 is the annual excretion coefficient of livestock and poultry feces and pollutants; η 畜 is the loss rate of livestock and poultry feces and pollutants; x 畜 is the pollutant emission coefficient; θ0 is the soil volume moisture content, %; w 土 is the amount of soil loss, m 3 ; r is the precipitation erosion factor; k is the soil erodibility factor; ls is the slope length and slope factor; c is the vegetation coverage factor; p is the soil and water conservation factor; ξ0 is the land salinity rate, %; A 耕 is the cultivated land area, hm 2 ; E 漫 、E 畦 The water quotas for flood irrigation and conventional border irrigation, m 3 / hm 2 ; ET0 is the land surface evaporation, mm; A 荒 , A 林 are the land desertification area and afforestation area, hm 2 .

8. The method for calculating agricultural water-saving potential based on system dynamics according to claim 6, characterized in that: The functional relationship of the rainfall supplement subsystem includes: WR=Pe×A0×10 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; 10 is the unit conversion coefficient.

9. The method for calculating agricultural water-saving potential based on system dynamics according to claim 1, characterized in that: When calculating the agricultural water-saving potential of the verification object and the study area, the unknown water-saving indicators, constant variables and intermediate variables all use initial values.

10. The method for calculating agricultural water-saving potential based on system dynamics according to claim 1, characterized in that: The time boundary is at least greater than 10 years, and the time step is 1 year.

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