Drainage basin actual evapotranspiration simulation and change attribution quantitative analysis method

Abstract

The invention provides a basin actual evapotranspiration simulation and change attribution quantitative analysis method, and the method comprises the steps: determining a natural period and a human activity influence period of a basin, providing a basin actual evapotranspiration simulation method based on runoff simulation calibration model parameters based on an RCC-WBM model, simulating basin actual evapotranspiration changes in stages, and carrying out the attribution recognition. And the influence of climate change, human activity and the synergistic effect of the climate change and the human activity on the actual evapotranspiration change is quantitatively analyzed. An RCC-WBM model is utilized, staged calibration model parameters are optimized through runoff simulation, on the basis, the actual evapotranspiration process of the drainage basin in different drainage basin states (representing different human activity situations) and different climate scenes is simulated, and then the influence of climate changes, human activities and the synergistic effect of the climate changes and the human activities on the actual evapotranspiration amount of the drainage basin is recognized. The method can be more flexibly and effectively applied to specific work of watershed water resource evaluation and management.

Description

Technical Field

[0001] The invention relates to the field of hydrology, and in particular to an evapotranspiration process analysis method. Background Art

[0002] Rising temperatures and changes in precipitation will affect the actual evapotranspiration process in the basin, which in turn has a direct impact on the spatial and temporal distribution of water resources. On the other hand, with the increasing intensity of human activities, the rapid development of agricultural irrigation and changes in land use will also have a certain impact on the hydrological process in the basin. Under the influence of climate change and human activities, the measured runoff of major rivers in the world has changed to a certain extent, especially in arid and semi-arid areas. In recent decades, the measured runoff has decreased significantly compared with the previous period. Among them, the change in evapotranspiration is the most direct factor affecting the change in runoff. Scientifically clarifying the trend of the actual evapotranspiration process in the basin and the reasons for its change is an important basic work for the scientific evaluation and management of water resources.

[0003] Scientifically and accurately quantifying and evaluating the causes of changes in actual evapotranspiration in a river basin is of great significance and practical value for regional water resources evaluation, scientific river basin governance, and water resources management. Although there are instruments and equipment for water surface evaporation around the world, and there are relatively systematic studies on the changes and causes of evaporation capacity, the actual evapotranspiration process in a river basin is the most important indicator and factor that determines the status of regional water resources. At present, there is a lack of effective means to monitor and simulate the actual evapotranspiration of a river basin. At the same time, the research on the changes in the measured evapotranspiration in a river basin and its attribution is also very limited.

[0004] A watershed hydrological model is a generalization and mathematical description of the watershed hydrological cycle process. Although there are currently hundreds of watershed hydrological models used in runoff simulation and water resources assessment, differences in model structure lead to divergent expressions of the evapotranspiration module's mechanism. Evapotranspiration simulation results from different models for the same watershed often differ by orders of magnitude, seriously affecting the reliability of the results. Secondly, traditional parameter calibration relies too much on runoff observation data and lacks effective integration of evapotranspiration process observation data, resulting in significant differences in model parameters with the same effect. Thirdly, existing attribution analysis methods mostly use sensitivity test designs, which make it difficult to systematically separate the dynamic coupling effects of climate change and human activities. Summary of the invention

[0005] Purpose of the invention: This application provides a method for simulating actual evapotranspiration in a watershed and quantitatively analyzing changes in the evapotranspiration, which can decompose and quantify the impact of climate change, human activities, and the synergistic effect of the two on the changes in actual evapotranspiration in a watershed.

[0006] Technical solution: This application provides a method for simulating actual evapotranspiration in a watershed and quantitatively analyzing the attribution of changes, including the following steps:

[0007] S1. Collect long-sequence hydrological and meteorological data and human activity data in the basin since the establishment of the station, calculate the annual runoff coefficient sequence of the basin, and diagnose the mutation point of the annual runoff coefficient sequence; combined with the human activities in the basin, divide the sequence before the mutation point into the natural period, and the sequence after the mutation point into the period affected by human activities;

[0008] S2. Based on the RCCC-WBM model, the hydrological and meteorological data of the natural period and the period of human activity influence are used to drive the model to simulate the runoff process of the basin; the model parameters of the natural period and the period of human activity influence are calibrated to verify the adaptability of the model in the study basin;

[0009] S3. Based on the model parameters calibrated in the natural period and the model parameters calibrated in the period of human activities, the hydrological and meteorological data in the natural period and the period of human activities are used to drive the RCCC-WBM model to simulate the actual evapotranspiration process of the basin under the influence of natural period and human activities respectively;

[0010] S4. Based on the simulation results of the actual evapotranspiration of the basin under natural periods and periods of human activity, the impact of climate change, human activities, and the synergistic effect of the two on the changes in actual evapotranspiration is analyzed by attributing the changes in the evapotranspiration of the basin to quantitative factors.

[0011] As an implementation form, step S1 uses mathematical statistics methods to diagnose the mutation point of the annual runoff coefficient sequence, and the mathematical statistics methods include Mann-Kendall mutation test and ordered cluster analysis; wherein the ordered cluster analysis detects the year with the smallest sum of squared deviations in the annual runoff sequence and takes it as the mutation point of the annual runoff coefficient sequence.

[0012] As an implementation form, step S2 uses the hydrological and meteorological data of the natural period and the period affected by human activities to drive the model. The runoff calculation formula of the RCCC-WBM model is as follows:

[0013] (1)

[0014] In the formula, is the watershed soil moisture content in the i-1th period, which is the state variable of the RCCC-WBM model; and are the precipitation and snow accumulation in the i-th period, is the temperature in the i-th period, and These are the temperature thresholds for snow and rain, generally ±4°C; , , and are model parameters; is the simulated runoff in the i-th period.

[0015] As an implementation form, step S2 uses the Nash-Sutcliffe efficiency coefficient NSE and the relative error RE as the objective function to calibrate the RCCC-WBM model parameters under the watershed state at different periods. The objective function calculation formula is as follows:

[0016] (2)

[0017] (3)

[0018] In the formula, and are the measured and simulated average runoff, is the measured runoff, i represents the i-th period, and N is the total length of the runoff series, i.e., the total number of periods;

[0019] If the relative error RE of the runoff model is within ±5% and the Nash-Sutcliffe efficiency coefficient NSE exceeds 0.60, it is considered that the model has good adaptability in the study basin and can simulate the hydrological process of the study basin, which includes the runoff process and the actual evapotranspiration process.

[0020] As an implementation form, step S3 uses the hydrological and meteorological data of the natural period and the period affected by human activities to drive the RCCC-WBM model. The calculation formula of the actual evapotranspiration of the watershed in the model is as follows:

[0021] (4)

[0022] In the formula, and are the actual evapotranspiration and evaporation capacity of the basin in the i-th period, It can be replaced by the water surface evaporation measured by the evaporator; is the watershed soil moisture content in the i-1th period, which is the state variable of the RCCC-WBM model; and is the model parameter.

[0023] As an implementation form, the attribution and quantification of the change in basin evapotranspiration in step S4 includes the following process:

[0024] Taking the actual evapotranspiration of the basin in the natural period as the baseline value, the attribution quantification formula of the actual evapotranspiration of the basin during the period of human activity influence compared with the baseline value is as follows:

[0025] (5)

[0026] In the formula, It is the change of actual evapotranspiration in the basin during the period of human activities compared with the actual evapotranspiration in the base period, and is the total impact of climate change and human activities on the actual evapotranspiration in the basin. ; The change of actual evapotranspiration in the basin caused by climate change alone during the natural period; It is the change of actual evapotranspiration in the basin caused by changes in human activities under the natural climate conditions. It is the increment of actual evapotranspiration change in the basin caused by the synergistic driving of climate factors and human activities;

[0027] The actual evapotranspiration process simulated by using model parameters calibrated based on the natural period and meteorological data of the whole process (including the natural period and the period affected by human activities) reflects the actual evapotranspiration of the basin under the natural state. The difference between the actual evapotranspiration simulated in different periods mainly reflects the impact of changes in climate factors.

[0028] Taking the actual evapotranspiration of the basin in the natural period as the benchmark value, the impact of climate change on evapotranspiration change is analyzed:

[0029] (6)

[0030] In the formula, and are the average actual evapotranspiration (mm) during the human activity impact period and the natural period simulated based on the natural period parameters;

[0031] Taking the actual evapotranspiration of the basin during the natural period as the benchmark value, the impact of human activities on runoff changes is analyzed:

[0032] (7)

[0033] In the formula, is the average actual evapotranspiration of the basin during the natural period simulated based on the parameters of the period affected by human activities (mm);

[0034] and They are the actual evapotranspiration process of the basin in the natural period simulated by the model parameters calibrated based on the period of human activity influence and the natural period, respectively. Their driving climate factors are the same, which are all climate factors of the basin in the natural period. Therefore, the two reflect the actual evapotranspiration of the basin under the same climate conditions and different situations of human activity influence, and their difference reflects the impact of human activities on the actual evapotranspiration.

[0035] Based on formula (5) to formula (7), the increment of actual evapotranspiration change in the basin due to the synergistic effect of climate change and human activities is analyzed as follows:

[0036] (8)

[0037] (9)

[0038] In the formula, is the total amount of actual evapotranspiration reduction in the basin (mm), is the average actual evapotranspiration of the basin simulated based on the model parameters calibrated during the period of human activities and the climate elements of that period (mm), is the average actual evapotranspiration of the basin simulated based on the model parameters calibrated in the natural period and the climate elements in the natural period (mm), is the increment of the impact of the synergistic effect of climate change and human activities on the actual evapotranspiration change in the basin (mm).

[0039] Beneficial effects: This application uses the RCCC-WBM model to optimize the model parameters in stages through runoff simulation. On this basis, it simulates the actual evapotranspiration process of the basin under different basin states (representing different human activity situations) and different climate scenarios, and then identifies the impact of climate change, human activities and the synergy of the two on the actual evapotranspiration of the basin. In the attribution analysis, the synergy of climate-human activities is quantified, and the dynamic decoupling of climate change and human activity impacts is effectively achieved. This method can be more flexibly and effectively applied to the specific work of basin water resources evaluation and management, effectively improving the accuracy of attribution identification, and providing reliable technical support for the refined management of basin water resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 Schematic diagram of the simulation of actual evapotranspiration in the basin based on the RCCC-WBM model and the quantitative analysis method of its change attribution;

[0042] Figure 2 The measured annual runoff and its five-year sliding average process from 1955 to 1995 at Huaxian Station in the Weihe River Basin;

[0043] Figure 3 It is the sum of squares of the measured annual runoff coefficients in the Weihe River Basin from 1955 to 1995;

[0044] Figure 4The measured and simulated monthly flow processes of the Weihe River Huaxian Station during the natural period (1955-1970) and the period of human activity influence (1971-1995);

[0045] Figure 5 It is the actual evapotranspiration process in the Weihe River Basin under natural conditions and conditions affected by human activities. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application.

[0047] This application provides a method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its changes. Figure 1 As shown, the following steps are included:

[0048] S1. Collect long-sequence hydrological and meteorological data and human activity data in the basin since the establishment of the station, calculate the annual runoff coefficient sequence of the basin, and use the ordered clustering method to diagnose the mutation point of the annual runoff coefficient sequence by detecting the year when the sum of squared deviations of the annual runoff sequence is the smallest; combined with the human activities in the basin, divide the sequence into the natural period (the period before the mutation year) and the period affected by human activities (the period after the mutation year);

[0049] S2. Based on the RCCC-WBM model, the meteorological data of the natural period and the period affected by human activities are used to drive the model to simulate the runoff process of the basin. The Nash-Sutcliffe efficiency coefficient NSE and relative error RE are used as the objective function to calibrate the model parameters of the natural period and the period affected by human activities to verify the adaptability of the model in the study basin.

[0050] S3. A simulation method for the actual evapotranspiration of a watershed based on the model parameters calibrated by runoff simulation is proposed. Based on the model parameters calibrated in the natural period and the model parameters calibrated in the period of human activity impact, the RCCC-WBM model is driven by the meteorological data of the whole process (natural period + period of human activity impact) to simulate the actual evapotranspiration process of the watershed under the natural state and under the influence of human activities respectively.

[0051] S4. A quantitative calculation formula for attributing changes in basin evapotranspiration is proposed. Based on the simulation results of actual evapotranspiration in the basin under natural conditions and human activity conditions, the impact of climate change, human activities, and the synergistic effect of the two on changes in actual evapotranspiration is analyzed.

[0052] Based on the annual runoff coefficient series, this method divides the study period into the natural period and the period affected by human activities. A method for simulating the actual evapotranspiration of a watershed based on the runoff simulation calibration model parameters is proposed. Based on the attribution identification method of the actual evapotranspiration change in the watershed based on the staged simulation, the impact of climate change, human activities, and the synergistic effect of the two on the change of actual evapotranspiration is quantitatively analyzed.

[0053] This example takes the Weihe River Basin as an example and uses the method of the present invention to simulate the actual evapotranspiration of the basin and quantitatively analyze the change attribution. The Weihe River is a first-level tributary of the Yellow River. The basin area above Huaxian Station is 106,498 km 2 , the specific analysis steps are as follows:

[0054] (1) Collect hydrological and meteorological data in the Weihe River Basin from 1955 to 1995, including runoff, precipitation, evaporation and temperature; collect data on human activities in the basin, including water conservancy projects, land use data, water consumption data and other literature.

[0055] Analyze the annual runoff process measured at Huaxian Station, such as Figure 2 As shown in Figure 2, the annual runoff coefficient sequence is calculated based on the annual runoff volume (mm) of Huaxian Station and the average annual precipitation (mm) of the basin area. The sequence clustering analysis method is used to calculate the deviation square sum sequence of the annual runoff coefficient, as shown in Figure 2. Figure 3 As shown in the figure, it can be found that the sum of squared deviations reaches its minimum value in 1970. Therefore, the mutation point of the diagnostic annual runoff coefficient series is 1970.

[0056] According to the sudden change year of annual runoff coefficient in 1970 and the human activities in the basin, it was determined that the natural period and the period influenced by human activities in the basin were 1955-1970 and 1971-1995 respectively.

[0057] (2) Based on the RCCC-WBM model, the model was driven by hydrological and meteorological data in the natural period and the period affected by human activities to simulate the runoff process in the basin. The Nash-Sutcliffe efficiency coefficient NSE and relative error RE were used as the objective function to calibrate the model parameters in the natural period and the period affected by human activities (Table 1) to verify the adaptability of the model in the study basin:

[0058] Table 1 Model parameters and runoff simulation results calibrated during natural and human activity periods

[0059] The Nash-Sutcliffe efficiency coefficient NSE of the runoff simulation at the Huaxian Station of the Weihe River during the natural period (1955-1970) is 0.77, and the average relative error RE of the simulation over many years is -0.34%; the Nash-Sutcliffe efficiency coefficient NSE of the runoff simulation during the period of human activity impact (1971-1995) is 0.66, and the average relative error RE of the simulation over many years is -0.31%. Figure 4 a) and the period of human activities ( Figure 4 The simulation of b) fits well with the measured runoff process, which shows that the model has good adaptability in the Weihe River Basin and can be used to simulate the runoff and actual evapotranspiration process of the basin under natural conditions and under the influence of human activities.

[0060] (3) Based on the model parameters calibrated during the natural period (1955-1970) and the model parameters calibrated during the period of human activity influence (1971-1995) (Table 1), the RCCC-WBM model was driven by the meteorological data of the entire period (1955-1995) to simulate the actual evapotranspiration process of the basin under the natural state and under the influence of human activities, respectively. Figure 5 shown.

[0061] (4) A method for attributing the changes in actual evapotranspiration in a watershed based on staged simulation is proposed. Based on the actual evapotranspiration process of the watershed under natural conditions and under the influence of human activities, the impact of climate change, human activities, and the synergistic effect of the two on the changes in actual evapotranspiration is analyzed:

[0062] Taking the natural period (1955-1970) as the base period, the actual evapotranspiration of the basin simulated under the natural conditions in the base period (1955-1970) and the period affected by human activities (1971-1995) were 512.5 mm and 496.8 mm respectively. The impact of climate change on the actual evapotranspiration of the basin was -15.7 mm, indicating that the actual evapotranspiration of the basin decreased due to reduced precipitation and increased temperature.

[0063] Under the influence of human activities, the actual evapotranspiration of the basin in the simulated baseline period (1955-1970) is 530.9 mm. Since the actual evapotranspiration of the basin simulated under natural conditions is 512.5 mm, the impact of human activities on the actual evapotranspiration of the basin is 18.4 mm, indicating that the actual evapotranspiration of the basin has increased due to the variability of vegetation and the influence of other human activities.

[0064] Under the influence of human activities, the actual evapotranspiration of the basin during the simulated human activity influence period is 515.9 mm. Compared with the actual evapotranspiration of 512.5 mm in the natural state of the baseline period, the actual evapotranspiration of the basin increased by 3.4 mm due to the synergistic effects of climate change and human activities. Combining the respective effects of climate change and human activities on the actual evapotranspiration of the basin, the incremental effect of the synergistic effect of climate change and human activities on the change in the actual evapotranspiration of the basin is 0.7 mm, indicating that the reduction in precipitation and the increase in temperature have further increased the impact of human activities on the actual increase in evapotranspiration in the basin.

[0065] The following conclusions can be drawn from the above analysis:

[0066] (1) The measured runoff at Huaxian Station in the Weihe River Basin showed a decreasing trend from 1955 to 1995, and the measured runoff series suddenly changed in 1970. The study period can be divided into the natural period (1955-1970) and the period affected by human activities (1971-1995).

[0067] (2) Taking the natural period (1955-1970) as the base period, the actual evaporation in the basin increased by 3.4 mm during the period of human activities. Among them, human activities increased the actual evapotranspiration in the basin by 18.4 mm, climate change decreased the actual evapotranspiration in the basin by 15.7 mm, and the synergistic effect of human activities and climate change increased the change in actual evapotranspiration in the basin by 0.7 mm.

[0068] (3) Due to the limitation of monitoring technology, it is still difficult to directly monitor the actual evapotranspiration process at the basin scale. The actual evapotranspiration of the basin is an important part of the basin hydrological cycle. Therefore, the present invention proposes a basin hydrological evapotranspiration calculation method based on runoff simulation, which can be used in practical work such as basin water resources evaluation. The basin evapotranspiration process under a changing environment will be affected by factors such as climate change and human activities on the underlying surface. Clarifying the attribution of evapotranspiration changes can provide an important basis for basin management. The present invention proposes an attribution analysis method for the actual evapotranspiration of the basin based on segmented simulation, which quantifies the contribution of climate change, human activities, and the synergistic effect of the two to the change in the actual evapotranspiration of the basin.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its changes, characterized in that: The following steps are involved: S1. Collect long-sequence hydrological and meteorological data and human activity data in the basin since the establishment of the station, calculate the annual runoff coefficient sequence of the basin, and diagnose the mutation point of the annual runoff coefficient sequence; combined with the human activities in the basin, divide the sequence before the mutation point into the natural period, and the sequence after the mutation point into the period affected by human activities; S2. Based on the RCCC-WBM model, the hydrological and meteorological data of the natural period and the period of human activity influence are used to drive the model to simulate the runoff process of the basin; the model parameters of the natural period and the period of human activity influence are calibrated to verify the adaptability of the model in the study basin; S3. Based on the model parameters calibrated in the natural period and the model parameters calibrated in the period of human activities, the hydrological and meteorological data in the natural period and the period of human activities are used to drive the RCCC-WBM model to simulate the actual evapotranspiration process of the basin under the influence of natural period and human activities respectively; S4. Based on the simulation results of the actual evapotranspiration of the basin under natural periods and periods of human activity, the impact of climate change, human activities, and the synergistic effect of the two on the changes in actual evapotranspiration is analyzed by attributing the changes in the evapotranspiration of the basin to quantitative factors.

2. The method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its change attribution according to claim 1 is characterized in that: Step S1 uses mathematical statistics methods to diagnose the mutation point of the annual runoff coefficient sequence, and the mathematical statistics methods include Mann-Kendall mutation test and ordered cluster analysis; wherein the ordered cluster analysis detects the year with the smallest sum of squared deviations in the annual runoff sequence and takes it as the mutation point of the annual runoff coefficient sequence.

3. The method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its change attribution according to claim 1 is characterized in that: In step S2, the model is driven by hydrological and meteorological data in the natural period and the period affected by human activities. The runoff calculation formula of the RCCC-WBM model is as follows: （1） In the formula, is the watershed soil moisture content in the i-1th period, which is the state variable of the RCCC-WBM model; and are the precipitation and snow accumulation in the i-th period, is the temperature in the i-th period, and These are the temperature thresholds for snow and rain, generally ±4°C; , , and are model parameters; is the simulated runoff in the i-th period.

4. The method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its change attribution according to claim 1 or 3, characterized in that: In step S2, the Nash-Sutcliffe efficiency coefficient NSE and relative error RE are used as the objective function to calibrate the RCCC-WBM model parameters under the watershed conditions at different periods. The objective function calculation formula is as follows: （2） （3） In the formula, and are the measured and simulated average runoff, is the measured runoff, i represents the i-th period, and N is the total length of the runoff series, i.e., the total number of periods; If the relative error RE of the runoff model is within ±5% and the Nash-Sutcliffe efficiency coefficient NSE exceeds 0.60, it is considered that the model has good adaptability in the study basin and can simulate the hydrological process of the study basin, which includes the runoff process and the actual evapotranspiration process.

5. The method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its change attribution according to claim 1 is characterized in that: In step S3, the hydrological and meteorological data of the natural period and the period affected by human activities are used to drive the RCCC-WBM model. The calculation formula of the actual evapotranspiration of the watershed in the model is as follows: （4） In the formula, and are the actual evapotranspiration and evaporation capacity of the basin in the i-th period, It can be replaced by the water surface evaporation measured by the evaporator; is the watershed soil moisture content in the i-1th period, which is the state variable of the RCCC-WBM model; and is the model parameter.

6. The method for simulating actual evapotranspiration in a watershed and quantitatively analyzing its change attribution according to claim 1, characterized in that: Step S4: Quantification of the change in basin evapotranspiration The process includes: Taking the actual evapotranspiration of the basin in the natural period as the baseline value, the attribution quantification formula of the actual evapotranspiration of the basin during the period of human activity influence compared with the baseline value is as follows: （5） In the formula, It is the change of actual evapotranspiration in the basin during the period of human activities compared with the actual evapotranspiration in the base period, and is the total impact of climate change and human activities on the actual evapotranspiration in the basin. ; The change of actual evapotranspiration in the basin caused by climate change alone during the natural period; It is the change of actual evapotranspiration in the basin caused by changes in human activities under the natural climate conditions. It is the increment of actual evapotranspiration change in the basin caused by the synergistic driving of climate factors and human activities; The actual evapotranspiration process simulated by using the model parameters calibrated based on the natural period and the meteorological data of the whole process reflects the actual evapotranspiration of the basin under the natural state. The difference between the actual evapotranspiration simulated in different periods mainly reflects the impact of the change of climate elements. Taking the actual evapotranspiration of the basin in the natural period as the benchmark value, the impact of climate change on evapotranspiration change is analyzed: （6） In the formula, and are the average actual evapotranspiration in the human activity impact period and the natural period simulated based on the natural period parameters; Taking the actual evapotranspiration of the basin during the natural period as the benchmark value, the impact of human activities on runoff changes is analyzed: （7） In the formula, is the average actual evapotranspiration of the basin during the natural period simulated based on the parameters of the period affected by human activities; and They are the actual evapotranspiration process of the basin in the natural period simulated by the model parameters calibrated based on the period of human activity influence and the natural period, respectively. Their driving climate factors are the same, which are all climate factors of the basin in the natural period. Therefore, the two reflect the actual evapotranspiration of the basin under the same climate conditions and different situations of human activity influence, and their difference reflects the impact of human activities on the actual evapotranspiration. Based on formula (5) to formula (7), the increment of actual evapotranspiration change in the basin due to the synergistic effect of climate change and human activities is analyzed as follows: （8） （9） In the formula, is the total amount of actual evapotranspiration reduction in the basin, is the average actual evapotranspiration of the basin simulated based on the model parameters calibrated during the period of human activities and the climate elements of that period, is the average actual evapotranspiration of the basin simulated based on the model parameters calibrated in the natural period and the climate elements in the natural period, It is the increment of the impact of the synergistic effect of climate change and human activities on the actual evapotranspiration change in the basin.

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