Quantitative calculation method for ecological water demand of natural vegetation in arid region based on remote sensing evapotranspiration model

Abstract

The invention provides an arid region natural vegetation ecological water demand quantitative calculation method based on a remote sensing evapotranspiration model, and the calculation method comprises the steps: collection of basic data of a research region, collection and processing of long time sequence satellite remote sensing data, regional actual evapotranspiration calculation based on a model set, and actual evapotranspiration evaluation and verification. The method comprises the steps of calculation of a regional reference evapotranspiration ratio, calculation of a natural vegetation blue water evapotranspiration amount, water balance-based natural vegetation blue water evapotranspiration correction, calculation of a natural vegetation blue water evapotranspiration coefficient and calculation of a natural vegetation ecological water demand amount. By adopting the method, accurate calculation of the ecological water demand of the natural vegetation in the arid region can be realized, and the method has practicability and operability of regional application; the method can serve the business application fields of arid region water resource management, ecological protection and restoration, basin water resource planning, water resource optimal configuration and the like.

Description

Technical Field

[0001] The invention belongs to the field of water conservancy in arid areas, and particularly relates to a quantitative calculation method for ecological water demand of natural vegetation in arid areas based on a remote sensing evapotranspiration model. Background Art

[0002] The ecological water demand of natural vegetation refers to the water demand of the ecosystem to which the natural vegetation belongs in a specific area. In a broad sense, ecological water demand refers to the water needed to maintain the water balance of the global biogeographical ecosystem, including water-heat balance, water-sediment balance, water-salt balance, etc.; in a narrow sense, ecological environmental water use refers to the total amount of water resources needed to maintain the ecological environment from deteriorating and gradually improving. At present, my country's water resources allocation mainly focuses on the optimal allocation of runoff blue water resources. In order to protect the stability and non-degradation of the ecosystem in arid areas, it is urgent to accurately characterize the runoff blue water resources required by natural vegetation, thereby providing key support for ecological restoration and optimal allocation of water resources in arid areas.

[0003] At present, the ecological water demand of natural vegetation is usually calculated using the following methods: (1) Ecological water demand quota method; this method usually divides the vegetation types in the study area into high, medium and low coverage forest and grassland types, and then combines the ecological water demand quota obtained from literature research to calculate the ecological water demand of the region. This method is simple and easy to use, but the ecological water demand quota is often difficult to obtain accurately, resulting in a wide range of estimation results and cannot guide actual production practice. (2) Phreatic evaporation method; that is, the area of ​​a certain vegetation type at a certain phreatic level multiplied by the phreatic evaporation at the phreatic level. The physical basis of this method is improved compared to the ecological water demand quota method, but the depth of regional groundwater and phreatic evaporation at different depths are difficult to obtain accurately, resulting in large errors in the estimation results. In addition, the above two methods do not have water balance constraints. Under unreasonable quota values, they will also lead to a serious overestimation of the ecological water demand of natural vegetation.

[0004] Especially for the calculation of ecological water demand of natural vegetation in arid areas, different scholars use different methods and the calculation results of quotas are quite different, which cannot provide scientific support for water resources management and scheduling. Therefore, how to accurately and reliably realize the quantitative calculation of ecological water demand of natural vegetation in arid areas and describe the ecological water demand of ecological vegetation in arid areas is an urgent problem to be solved. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a quantitative calculation method for the ecological water demand of natural vegetation in arid areas based on a remote sensing evapotranspiration model. The method realizes the segmentation calculation of the water consumption source of natural ecological vegetation on the basis of accurately describing the water consumption status of natural ecological vegetation, thereby accurately and reliably realizing the quantitative calculation of the ecological water demand of natural vegetation in arid areas and describing the ecological water demand of ecological vegetation in arid areas.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for quantitatively calculating the ecological water demand of natural vegetation in arid areas based on a remote sensing evapotranspiration model, comprising the following steps:

[0008] Step 1: Collection of basic data of the study area:

[0009] Collect basic data of the study area, including meteorological radiation data, land use and vegetation cover data, actual evapotranspiration observation data, regional hydrological data and economic and social development data;

[0010] Step 2: Collection and processing of long-term satellite remote sensing data:

[0011] S201, collects long-term satellite remote sensing data, including multi-source satellite remote sensing data such as Landsat8, Sentinel 2, Terra / Aqua MODIS, and Sentinel 3;

[0012] S202, based on the long-time satellite remote sensing data collected in S21, calculating the biophysical parameters of the regional underlying surface; the underlying surface biophysical parameters include normalized vegetation index, leaf area index, surface albedo, snow area data and underlying surface land cover data;

[0013] Step 3, calculation of regional actual evapotranspiration based on the model ensemble:

[0014] S301, constructing an evapotranspiration model set, which includes three models, namely, SEBS model, ETEML model and ETMAL model;

[0015] S302, based on the basic data of the study area collected in step 1 and the regional underlying surface biophysical parameters obtained in step 2, the actual evapotranspiration data of the study area are calculated using the evapotranspiration model set constructed in S301;

[0016] Step 4, Actual evapotranspiration assessment and verification:

[0017] Use the actual evapotranspiration observation data in the study area collected in step 1 to evaluate the actual evapotranspiration data of the study area calculated in step 3, and select the best actual evapotranspiration data to carry out calculation and analysis in subsequent steps;

[0018] Step 5, calculation of regional reference evapotranspiration ratio:

[0019] Using the optimal actual evapotranspiration data obtained in step 4, the regional reference evapotranspiration ratio is calculated using the following formula:

[0020]

[0021] Where Ref is the regional reference evapotranspiration ratio, ET is the optimal actual evapotranspiration data, and ET o is the reference evapotranspiration;

[0022] Step 6, calculation of blue water evapotranspiration of natural vegetation:

[0023] The actual evapotranspiration in the study area is supplied by runoff blue water and precipitation green water;

[0024] S60 1, by calculating the effective precipitation to characterize the contribution of precipitation green water supply to evapotranspiration, the parameterization method is used for calculation in arid areas:

[0025]

[0026] Where P eff is the effective precipitation, P is the monthly precipitation;

[0027] S602, based on the calculation of effective precipitation, use the following formula to calculate blue water evapotranspiration:

[0028] ET blue =ET m -P eff

[0029] In the formula, ET m is the monthly evapotranspiration, ET blue For blue water evaporation;

[0030] Step 7, correction of blue water evapotranspiration of natural vegetation based on water balance:

[0031] The blue water evapotranspiration obtained in step 6 is corrected in combination with the water balance. Based on the regional hydrological data and economic and social development data collected in step 1, the blue water evapotranspiration is corrected based on the water consumption calculated by the water balance:

[0032]

[0033] ETR blue =ε×ET wb

[0034] In the formula, ∑ET blue is the total regional blue water evapotranspiration, ET wb is the total regional blue water consumption calculated based on the water balance method, ETR blue is the corrected blue water evapotranspiration; ε is the blue water evapotranspiration correction coefficient;

[0035] Step 8, calculation of blue water evapotranspiration coefficient of natural vegetation:

[0036] Based on the corrected blue water evapotranspiration in step 7, the blue water evapotranspiration coefficient of natural vegetation is calculated:

[0037]

[0038] In the formula, ET m is the monthly evapotranspiration, K blue is the blue water evapotranspiration coefficient;

[0039] Step 9, calculation of ecological water demand of natural vegetation:

[0040] Based on the blue water evapotranspiration coefficient calculated in step 8, the ecological water requirement of natural vegetation is calculated:

[0041] ET xu =ET m，o ×Ref m ×K blue

[0042] In the formula, ET xu is the ecological water requirement of natural vegetation in the study area, ET m，o is the monthly reference evapotranspiration, Ref m is the monthly reference evapotranspiration ratio, K blue is the blue water evapotranspiration coefficient.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The present invention designs a quantitative calculation method for the ecological water demand of natural vegetation in arid areas, and particularly designs a calculation method for the ecological water demand of natural vegetation based on a remote sensing evapotranspiration model. On the basis of accurately describing the water consumption status of natural ecological vegetation, the method realizes the segmentation calculation of the water consumption sources of natural ecological vegetation, and constructs a quantitative calculation method for the ecological water demand in arid areas based on remote sensing evapotranspiration water consumption data, which can more accurately and reliably describe the ecological water demand of ecological vegetation in arid areas.

[0045] 2. The quantitative calculation method of ecological water demand of natural vegetation in arid areas described in the present invention, wherein the evapotranspiration model is mainly based on a model that can reflect the water stress of the underlying surface, and an evapotranspiration model set is constructed to realize the accurate estimation of regional evapotranspiration water consumption, and the contribution of precipitation to natural vegetation water consumption is eliminated in combination with the effective precipitation calculation method suitable for arid areas, and the total blue water consumption of natural vegetation is obtained. The blue water consumption of natural vegetation calculated by remote sensing is corrected in combination with the total evapotranspiration of regional water balance, and the blue water consumption data that meets the water balance and maintains the spatial pattern of remote sensing evapotranspiration is obtained, and then the blue water consumption coefficient is calculated. In combination with the regional evapotranspiration ratio and the blue water consumption coefficient, a calculation framework for the ecological water demand of natural vegetation in arid areas is constructed, which can accurately and reliably characterize the ecological water demand of ecological vegetation in arid areas. The method not only has the practicality and operability of regional application, but also can serve the business application fields such as water resources management, ecological protection and restoration, watershed water resources planning and water resources optimization allocation in arid areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0047] Figure 1 It is a schematic flow chart of the quantitative calculation method of the ecological water requirement of natural vegetation in arid areas according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] Example 1

[0049] This embodiment provides a method for quantitatively calculating the ecological water demand of natural vegetation in arid areas based on a remote sensing evapotranspiration model, comprising the following steps:

[0050] Step 1: Collection of basic data of the study area:

[0051] Collect basic data of the study area, including meteorological radiation data, land use and vegetation cover data, actual evapotranspiration observation data, regional hydrological data and economic and social development data.

[0052] The meteorological radiation data include daily meteorological and radiation observation data, including: daily temperature, wind speed, atmospheric pressure, precipitation, air humidity and solar radiation data;

[0053] The land use and vegetation cover data include: regional land use data and regional vegetation type data based on satellite remote sensing interpretation, which are used to verify subsequent model results;

[0054] The actual evapotranspiration observation data are observation data based on lysimeters or flux observation stations in the study area;

[0055] The regional hydrological data and economic and social development data include: runoff data within the study area and water volume data cited in the regional economic and social development, which are mainly used to calculate the actual regional evapotranspiration based on the water balance method, as well as the verification and correction of subsequent model results.

[0056] Step 2: Collection and processing of long-term satellite remote sensing data:

[0057] S201 collects long-term satellite remote sensing data, including multi-source satellite remote sensing data such as Landsat8, Sentinel 2, Terra / Aqua MODIS, and Sentinel 3.

[0058] Specifically, Landsat8 and Sentinel 2 meet the requirements for regional evapotranspiration calculations with a resolution better than 30 meters, and MODIS remote sensing product data meet the requirements for evapotranspiration calculations with a resolution of 500 meters. The data download address for EOS / MODIS satellite products is: https: / / modis.gsfc.nasa.gov / data / dataprod / .

[0059] This embodiment uses MODIS remote sensing data as an example to illustrate the technical solution of the present invention.

[0060] S202, based on the long-time satellite remote sensing data collected in S21, calculating the regional underlying surface biophysical parameters; the underlying surface biophysical parameters include normalized vegetation index, leaf area index, surface albedo, snow area data and underlying surface land cover data.

[0061] Specifically, the normalized vegetation index, leaf area index and surface albedo can be obtained through the Terra / Aqua MODIS satellite remote sensing data products. The normalized vegetation index is calculated using the latest 6.1 version of the MODIS surface reflectance data product (MOD09GA.061). The leaf area index is obtained using the latest 6.1 version of the MODIS leaf area index and photosynthetically active radiation data product (MCD15A3H.061). The albedo can be obtained through the latest 6.1 version of the MODIS surface albedo data product (MCD43A3.061). Daily 500-meter resolution snow area data can be obtained through the MODIS snow data product (MOD10A1). The underlying land cover data can be obtained through the MODIS surface cover data (MCD12Q1.061) product. Step 3, calculation of regional actual evapotranspiration based on the model set:

[0062] Based on the collection and processing of regional long-term satellite remote sensing data, the actual evapotranspiration of the region can be calculated based on the remote sensing evapotranspiration model. At present, although the evapotranspiration model based on remote sensing has made great progress, some evapotranspiration models lack consideration of water stress in arid areas and have certain errors in arid areas. In this regard, the present invention prefers a model method that can truly depict the evapotranspiration of arid areas, constructs an evapotranspiration model set, and is used to estimate the actual evapotranspiration data of the region. The specific method is:

[0063] S301, constructing an evapotranspiration model set, which includes three models, namely, the SEBS model, the ETEML model and the ETMAL model.

[0064] Model 1 selects the SEBS model, which is an energy balance algorithm based on remote sensing data and is used to estimate atmospheric turbulent fluxes and daily surface evaporation. References to the SEBS model can be found in [Su, Z. (2002). The Surface Energy Balance System (SEBS) for estimation of turbulent heat fluxes. Hydrology & Earth System Sciences 6, pp. 85-99.].

[0065] Model 2 selects the ETEML model. The ETEML model is a two-layer remote sensing evapotranspiration model based on theoretical feature space, using surface temperature as one of the main drivers of the model. References to the ETEML model can be found in [Yongmin Yang, Hongbo Su, Renhua Zhang, Jing Tian, ​​Lu Li, An enhanced two-source evapotranspiration model for land (ETEML): Algorithm and evaluation, Remote Sensing of Environment, Volume 168, 2015, Pages 54-65, https: / / doi.org / 10.1016 / j.rse.2015.06.020.].

[0066] Model 3 selects the ETMAL model. The ETMAL model uses the key information of short-wave infrared sensitivity to the underlying surface moisture characteristics to construct a single-layer model that describes the underlying surface moisture stress information. References to the ETMAL model can be found in [Yang, Yongmin & Long, Aihua & Zhang, Ji & Liu, Hongxin. (2021). An Evapotranspiration Model for Arid Land to Estimate Water Loss in Hotan River Basin. 3725-3728.10.1109 / IGARSS47720.2021.9553521.].

[0067] S302, based on the basic data of the study area collected in step 1 and the regional underlying surface biophysical parameters obtained in step 2, the actual evapotranspiration data of the study area are calculated using the evapotranspiration model set constructed in S301.

[0068] Step 4, Actual evapotranspiration assessment and verification:

[0069] Using the actual evapotranspiration observation data in the study area collected in step 1, the actual evapotranspiration data of the study area calculated in step 3 were evaluated using the Nash efficiency coefficient, root mean square error and variation, and the optimal actual evapotranspiration data were selected to carry out the calculation and analysis in the subsequent steps.

[0070] Use the observation data based on lysimeters or flux observation stations in the study area collected in step 1 to evaluate remote sensing evapotranspiration; if there is a lack of actual observation data in the study area, data from neighboring areas or literature surveys can be collected to evaluate the remote sensing evapotranspiration model.

[0071] Step 5, calculation of regional reference evapotranspiration ratio:

[0072] Using the optimal actual evapotranspiration data obtained in step 4, the regional reference evapotranspiration ratio is calculated using the following formula:

[0073]

[0074] Where Ref is the regional reference evapotranspiration ratio, ET is the optimal actual evapotranspiration data, and ET o is the reference evapotranspiration.

[0075] The reference evapotranspiration ET o The calculation is done using the following formula:

[0076]

[0077] Among them, E.T. ois the reference evapotranspiration (), Δ is the slope of the temperature and saturated water vapor pressure curve (kPa / ℃), γ is the humidity calculation constant (kPa / ℃), R n and G are the net radiation (MJ / m 2 ) and soil heat flux (MJ / m 2 ), T is the air temperature (℃), e s and e a are the saturated water vapor pressure and actual water vapor pressure (kPa) respectively, and U2 is the wind speed at 2 meters (m / s).

[0078] Step 6, calculation of blue water evapotranspiration of natural vegetation:

[0079] At present, my country's water resources allocation mainly focuses on the optimal allocation of runoff blue water resources. The actual evapotranspiration in the study area is supplied by runoff blue water and precipitation green water. It is necessary to characterize the precipitation green water part and then calculate the blue water evapotranspiration.

[0080] S60 1, by calculating the effective precipitation to characterize the contribution of precipitation green water supply to evapotranspiration, the parameterization method is used for calculation in arid areas:

[0081]

[0082] Where P eff is the effective precipitation, P is the monthly precipitation;

[0083] S602, based on the calculation of effective precipitation, use the following formula to calculate blue water evapotranspiration:

[0084] ET blue =ET m -P eff

[0085] In the formula, ET m is the monthly evapotranspiration, which is obtained by accumulating the evapotranspiration on a daily or 8-day scale; ET blue It is the evaporation of blue water.

[0086] Step 7, correction of blue water evapotranspiration of natural vegetation based on water balance:

[0087] Due to the errors in remote sensing evapotranspiration calculation, the blue water evapotranspiration calculated above may not necessarily meet the water balance. Therefore, it is necessary to correct the blue water evapotranspiration obtained in step 6 in combination with the water balance. Based on the regional hydrological data and economic and social development data collected in step 1, the blue water evapotranspiration is corrected based on the water consumption calculated by the water balance:

[0088]

[0089] ETRblue =ε×ET wb

[0090] In the formula, ∑ET blue is the total regional blue water evapotranspiration, ET wb is the total regional blue water consumption calculated based on the water balance method, ETR blue is the corrected blue water evapotranspiration; ε is the blue water evapotranspiration correction coefficient.

[0091] Step 8, calculation of blue water evapotranspiration coefficient of natural vegetation:

[0092] Based on the corrected blue water evapotranspiration in step 7, the blue water evapotranspiration coefficient of natural vegetation is calculated:

[0093]

[0094] In the formula, ET m is the monthly evapotranspiration, K blue is the blue water evapotranspiration coefficient.

[0095] Step 9, calculation of ecological water demand of natural vegetation:

[0096] Based on the blue water evapotranspiration coefficient calculated in step 8, the ecological water requirement of natural vegetation is calculated:

[0097] ET xu =ET m，o ×Ref m ×K blue

[0098] In the formula, ET xu is the ecological water requirement of natural vegetation in the study area, ET m，o is the monthly reference evapotranspiration (mm / month), Ref m is the reference evapotranspiration ratio at the monthly scale, which is calculated by averaging the reference evapotranspiration ratio at the daily scale or the 8-day scale; K blue is the blue water evapotranspiration coefficient.

[0099] Application examples:

[0100] Taking the lower reaches of the Hotan River as an example, the ETMAL model and method described in Example 1 of the present application were used to estimate the evapotranspiration of the Hotan River basin. Since the ETMAL model uses a water stress index combined with short-wave infrared, it can accurately reflect the spatial pattern of evapotranspiration in the Hotan River. The interval water consumption calculated using the water balance method for the lower reaches of the Hotan River was 627 million cubic meters, and the interval evapotranspiration water consumption rate estimated by the ETMAL model described in Example 1 of the present application was 694 million cubic meters. The difference between the water balance result and the result based on remote sensing actual evapotranspiration estimation is about 10%, indicating that the actual evapotranspiration estimation result based on remote sensing is more reliable. The actual evapotranspiration based on remote sensing is corrected based on the water balance evapotranspiration result, and then the ecological water demand of natural vegetation in the lower reaches of the Hotan River is calculated. According to calculations, using a 2-3 km buffer zone along the river channel to divide the distribution area of ​​the main ecological corridor downstream, the ecological water demand in the interval is 463 million cubic meters, and the water consumption due to evaporation in the river channel is 129 million. After deducting the 129 million in the river channel, the ecological water demand outside the interval river channel is 334 million cubic meters.

[0101] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, a person skilled in the art should understand that the technical solution of the present invention (such as the use of various formulas, the sequence of steps, etc.) can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A quantitative calculation method for ecological water demand of natural vegetation in arid areas based on remote sensing evapotranspiration model, characterized in that: The calculation method comprises the following steps: Step 1: Collection of basic data of the study area: Collect basic data of the study area, including meteorological radiation data, land use and vegetation cover data, actual evapotranspiration observation data, regional hydrological data and economic and social development data; Step 2: Collection and processing of long-term satellite remote sensing data: S201, collects long-term satellite remote sensing data, including multi-source satellite remote sensing data such as Landsat8, Sentinel 2, Terra / Aqua MODIS, and Sentinel 3; S202, based on the long-time satellite remote sensing data collected in S21, calculating the biophysical parameters of the regional underlying surface; the underlying surface biophysical parameters include normalized vegetation index, leaf area index, surface albedo, snow area data and underlying surface land cover data; Step 3, calculation of regional actual evapotranspiration based on the model ensemble: S301, constructing an evapotranspiration model set, which includes three models, namely, SEBS model, ETEML model and ETMAL model; S302, based on the basic data of the study area collected in step 1 and the regional underlying surface biophysical parameters obtained in step 2, the actual evapotranspiration data of the study area are calculated using the evapotranspiration model set constructed in S301; Step 4, Actual evapotranspiration assessment and verification: Use the actual evapotranspiration observation data in the study area collected in step 1 to evaluate the actual evapotranspiration data of the study area calculated in step 3, and select the best actual evapotranspiration data to carry out calculation and analysis in subsequent steps; Step 5, calculation of regional reference evapotranspiration ratio: Using the optimal actual evapotranspiration data obtained in step 4, the regional reference evapotranspiration ratio is calculated using the following formula: Where Ref is the regional reference evapotranspiration ratio, ET is the optimal actual evapotranspiration data, and ET o is the reference evapotranspiration; Step 6, calculation of blue water evapotranspiration of natural vegetation: The actual evapotranspiration in the study area is supplied by runoff blue water and precipitation green water; S601, by calculating the effective precipitation to characterize the contribution of precipitation green water supply to evapotranspiration, the following parameterization method is used for calculation in arid areas: Where P eff is the effective precipitation, P is the monthly precipitation; S602, based on the calculation of effective precipitation, use the following formula to calculate blue water evapotranspiration: AND blue =ET m -P eff In the formula, ET m is the monthly evapotranspiration, ET blue For blue water evaporation; Step 7, correction of blue water evapotranspiration of natural vegetation based on water balance: The blue water evapotranspiration obtained in step 6 is corrected in combination with the water balance. Based on the regional hydrological data and economic and social development data collected in step 1, the blue water evapotranspiration is corrected based on the water consumption calculated by the water balance: ETR blue =ε×ET wb In the formula, ∑ET blue is the total regional blue water evapotranspiration, ET wb is the total regional blue water consumption calculated based on the water balance method, ETR blue is the corrected blue water evapotranspiration; ε is the blue water evapotranspiration correction coefficient; Step 8, calculation of blue water evapotranspiration coefficient of natural vegetation: Based on the corrected blue water evapotranspiration in step 7, the blue water evapotranspiration coefficient of natural vegetation is calculated: In the formula, ET m is the monthly evapotranspiration, K blue is the blue water evapotranspiration coefficient; Step 9, calculation of ecological water demand of natural vegetation: Based on the blue water evapotranspiration coefficient calculated in step 8, the ecological water requirement of natural vegetation is calculated: AND xu =ET m,o ×Ref m ×K blue In the formula, ET xu is the ecological water requirement of natural vegetation in the study area, ET m,o is the monthly reference evapotranspiration, Ref m is the monthly reference evapotranspiration ratio, K blue is the blue water evapotranspiration coefficient.

2. The calculation method according to claim 1, characterized in that: In step 1, the meteorological radiation data includes daily meteorological and radiation observation data, specifically including: daily temperature, wind speed, atmospheric pressure, precipitation, air humidity and solar radiation data; The land use and vegetation cover data include: regional land use data and regional vegetation type data based on satellite remote sensing interpretation; The actual evapotranspiration observation data are observation data based on lysimeters or flux observation stations in the study area; The regional hydrological data and economic and social development data include: runoff data within the study area and water volume data cited in the regional economic and social development.

3. The calculation method according to claim 1, characterized in that: In step 4, the Nash efficiency coefficient, root mean square error and variation are used to evaluate the evapotranspiration data of the study area calculated in step 3.

4. The calculation method according to claim 1, characterized in that: In step 5, the reference evapotranspiration ET o The calculation is done using the following formula: Among them, E.T. o is the reference evapotranspiration, Δ is the slope of the temperature and saturated water vapor pressure curve, γ is the humidity calculation constant, R n and G are net radiation and soil heat flux respectively, T is air temperature, e s and e a are the saturated water vapor pressure and actual water vapor pressure respectively, and U2 is the wind speed at 2 meters.

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