Quantitative Analysis Method for Simulation of Actual Evapotranspiration in the Basin and Attribution of Its Changes

Abstract

The present application provides a method for simulating actual evapotranspiration in a basin and quantitatively analyzing the attribution of changes, determining the natural period and the period affected by human activities in the basin, and based on the RCCC-WBM model, proposing a method for simulating actual evapotranspiration in the basin based on calibrating model parameters by runoff simulation. The changes in actual evapotranspiration in the basin are simulated in stages and the attribution is identified, and the impacts of climate change, human activities, and their combined effects on the changes in actual evapotranspiration are quantitatively analyzed. By using the RCCC-WBM model, the model parameters are calibrated in stages by optimizing runoff simulation, and on this basis, the actual evapotranspiration process in the basin under different basin states (representing different human activity situations) and different climate scenarios is simulated, and then the impacts of climate change, human activities, and their combined effects on the actual evapotranspiration in the basin are identified. This method can be more flexibly and effectively applied to the specific work of basin water resources assessment and management.

Description

Technical Field

[0001] The present invention relates to the field of hydrology, and in particular to a method for analyzing the evapotranspiration process. Background Art

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

[0003] Scientifically and accurately quantifying and evaluating the reasons for the change of the actual evapotranspiration of the basin is of great significance and practical value for regional water resources evaluation, scientific implementation of basin management and water resources management. Although there are already instrument and equipment for water surface evaporation globally, and there is a relatively systematic study on the change and reasons of evaporation capacity, the actual evapotranspiration process of the basin is the most important indicator and factor determining the regional water resources situation. At present, there is still a lack of effective means for monitoring and simulating the actual evapotranspiration of the basin. At the same time, the research on the change of the measured evapotranspiration of the basin and its attribution is also very limited.

[0004] The basin hydrological model is a generalization and mathematical description of the basin hydrological cycle process. Although there are already hundreds of basin hydrological models applied to runoff simulation and water resources evaluation and other work, however, due to the difference in model structure, there are differences in the mechanism expression of the evapotranspiration module. The evapotranspiration simulation results of different models for the same basin often show an order-of-magnitude difference, seriously affecting the reliability of the results. Secondly, the traditional parameter calibration overly relies on runoff observation data and lacks the effective integration of evapotranspiration process observation data, resulting in a significant phenomenon of different parameters having the same effect. Thirdly, the existing attribution analysis methods mostly adopt sensitivity test design and are difficult to systematically separate the dynamic coupling effect of climate change and human activities. Summary of the Invention

[0005] Object of the Invention: The present application provides a method for simulating the actual evapotranspiration of a basin and quantitatively analyzing the change attribution, which can decompose and quantify the influence of climate change, human activities, and the synergistic effect of the two on the change of the actual evapotranspiration of the basin.

[0006] Technical Solution: The present application provides a method for simulating the actual evapotranspiration of a basin and quantitatively analyzing the change attribution, including the following steps:

[0007] S1. Collect the long-term hydrometeorological data and human activity data in the basin since the self-built station was established, calculate the annual runoff coefficient sequence of the basin, and diagnose the mutation points 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 human activity influence period;

[0008] S2. Based on the RCCC-WBM model, use the hydrometeorological data of the natural period and the human activity influence period to drive the model respectively to simulate the runoff process of the basin; calibrate the model parameters of the natural period and the human activity influence period, and 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 human activity influence period, use the hydrometeorological data of the natural period and the human activity influence period to drive the RCCC-WBM model to simulate the actual evapotranspiration process of the basin under the natural period and the human activity influence respectively;

[0010] S4. Based on the simulation results of the actual evapotranspiration of the basin under the natural period and the human activity influence period, through the attribution quantification of the change amount of the basin evapotranspiration, analyze the impacts of climate change, human activities, and their combined effects on the change of the actual evapotranspiration amount.

[0011] As an implementation form, step S1 uses the mathematical statistics method to diagnose the mutation points of the annual runoff coefficient sequence, and the mathematical statistics method includes Mann-Kendall mutation test and ordered cluster analysis; among them, 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, for step S2, when using the hydrometeorological data of the natural period and the human activity influence period to drive the model, the runoff calculation formula of the RCCC-WBM model is as follows:

[0013] (1)

[0014] In the formula, is the soil water content of the basin in the (i - 1)th period, which is the state variable of the RCCC-WBM model; and are the precipitation and snow accumulation in the ith period respectively, is the temperature in the ith period, and are the thresholds for dividing temperature into snow and rain, generally taken as ±4°C; , , and are the model parameters; is the simulated runoff for the i-th time period.

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

[0016] (2)

[0017] (3)

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

[0019] If the relative error RE of the runoff modulus 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. The hydrological process includes the runoff process and the actual evapotranspiration process.

[0020] As an implementation form, step S3 drives the RCCC-WBM model by using the hydrometeorological data of the natural period and the human activity influence period. The calculation formula of the actual evapotranspiration of the basin 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 time period respectively, can be replaced by the water surface evaporation measured by the evaporator; is the soil water content of the basin in the (i - 1)-th time period, which is the state variable of the RCCC-WBM model; and are the model parameters.

[0023] As an implementation form, the attribution 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 reference value, the attribution quantification formula of the actual evapotranspiration of the basin in the human activity influence period compared with the reference value is as follows:

[0025] (5)

[0026] In the formula, is the change in the actual evapotranspiration of the basin during the period affected by human activities compared to that during the reference period, and is the total impact of the combined effects of climate change and human activities on the actual evapotranspiration of the basin ; is the change in the actual evapotranspiration of the basin caused by pure climate change during the natural period; is the change in the actual evapotranspiration of the basin due to changes in human activities under the state of climate elements during the natural period, is the increment of the change in the actual evapotranspiration of the basin caused by the combined driving of climate elements and human activities;

[0027] The actual evapotranspiration process simulated through the model parameters calibrated during the natural period and the meteorological data of the whole process (including the natural period and the period affected by human activities) reflects the actual evapotranspiration situation of the basin in the natural state. The differences between the simulated actual evapotranspiration amounts in different periods mainly reflect the impact of climate element changes;

[0028] Taking the actual evapotranspiration of the basin during the natural period as the reference value, analyze the impact of climate change on the change in evapotranspiration:

[0029] (6)

[0030] In the formula, and are the average actual evapotranspiration amounts (mm) during the period affected by human activities and the natural period simulated based on the parameters during the natural period, respectively;

[0031] Taking the actual evapotranspiration of the basin during the natural period as the reference value, analyze the impact of human activities on the change in runoff:

[0032] (7)

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

[0034] and are the actual evapotranspiration processes of the basin during the natural period simulated based on the model parameters calibrated during the period affected by human activities and the natural period, respectively. Their driving climate elements are the same, both being the climate elements of the natural period of the basin. Therefore, they respectively reflect the actual evapotranspiration amounts of the basin under the same climate conditions and different human activity influence situations, and their differences reflect the impact of human activities on the actual evapotranspiration amount;

[0035] Based on formulas (5) to (7), analyze the increment of the combined effect of climate change and human activities on the change in the actual evapotranspiration of the basin:

[0036] (8)

[0037] (9)

[0038] In the formula, is the total reduction of actual evapotranspiration in the basin (mm), is the average actual evapotranspiration of the basin simulated by the model parameters calibrated based on the rate of human activity impact period and the climate elements in this period (mm), is the average actual evapotranspiration of the basin simulated by the model parameters calibrated based on 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 change of actual evapotranspiration in the basin (mm).

[0039] Beneficial effects: This application uses the RCCC-WBM model to optimize the calibration of 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 impacts of climate change, human activities, and their synergistic effects on the actual evapotranspiration of the basin. In the attribution analysis, the synergistic effect of climate-human activities is quantified, effectively realizing the dynamic decoupling of the impacts of climate change and human activities. 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 this application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0041] Figure 1 It is a schematic diagram of the method for simulating the actual evapotranspiration of the basin based on the RCCC-WBM model and quantitatively analyzing its change attribution;

[0042] Figure 2 is the measured annual runoff of Huaxian Station in the Weihe River Basin from 1955 to 1995 and its 5-year moving average process;

[0043] Figure 3 is the process of the sum of squared deviations of the measured annual runoff coefficient in the Weihe River Basin from 1955 to 1995;

[0044] Figure 4Monthly measured and simulated flow processes at the Huaxian Station on the Weihe River during the natural period (1955 - 1970) and the period affected by human activities (1971 - 1995);

[0045] Figure 5 Actual evapotranspiration processes in the Weihe River Basin under natural and human - activity - affected conditions. Specific implementation manners

[0046] To make the objectives, 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 accompanying drawings in this application.

[0047] This application provides a method for simulating actual evapotranspiration in a basin and quantitatively analyzing the attribution of changes, as Figure 1 shown, including the following steps:

[0048] S1. Collect long - term hydrometeorological 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 method of ordered clustering to diagnose the mutation points 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 - activity situation 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, use the meteorological data of the natural period and the period affected by human activities to drive the model respectively to simulate the runoff process of the basin. Taking the Nash - Sutcliffe efficiency coefficient NSE and the relative error RE as the objective functions, calibrate the model parameters of the natural period and the period affected by human activities, and verify the adaptability of the model in the study basin;

[0050] S3. Propose a method for simulating actual evapotranspiration in the basin based on the runoff - simulation - calibrated model parameters. Based on the model parameters calibrated in the natural period and the model parameters calibrated in the period affected by human activities, use the meteorological data of the whole process (natural period + period affected by human activities) to drive the RCCC - WBM model to simulate the actual evapotranspiration processes in the basin under natural and human - activity - affected conditions respectively;

[0051] S4. Propose a quantitative calculation formula for analyzing the attribution of changes in basin evapotranspiration. Based on the simulation results of actual evapotranspiration in the basin under natural and human - activity - affected conditions, analyze the impacts of climate change, human activities, and their synergistic effects on the changes in actual evapotranspiration.

[0052] This method is based on the annual runoff coefficient series. The research period is divided into a natural period and a period affected by human activities. A method for simulating the actual evapotranspiration of a basin based on calibrating model parameters through runoff simulation is proposed, as well as a method for identifying the attribution of changes in actual evapotranspiration in the basin based on phased simulation, to quantitatively analyze the impacts of climate change, human activities, and their combined effects on the changes in actual evapotranspiration.

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

[0054] (1) Collect the hydrometeorological data of the Weihe River Basin from 1955 to 1995, including: runoff, precipitation, water surface evaporation, and air temperature; collect the human activity data in the basin, including literature data such as water conservancy projects, land use data, and water consumption data.

[0055] Analyze the measured annual runoff process of Huaxian Station. As Figure 2 shown, calculate the annual runoff coefficient series based on the annual runoff (mm) of Huaxian Station and the average annual precipitation (mm) of the basin area. Use the sequential clustering analysis method to calculate the sum of squared deviations series of the annual runoff coefficient. As Figure 3 shown, it can be found from the figure that the sum of squared deviations reaches the minimum value in 1970. Therefore, the mutation point of the annual runoff coefficient series is diagnosed as 1970.

[0056] According to the mutation year 1970 of the annual runoff coefficient and the human activity situation in the basin, determine that the natural period and the period affected by human activities of the basin are 1955 - 1970 and 1971 - 1995 respectively.

[0057] (2) Based on the RCCC - WBM model, use the hydrometeorological data of the natural period and the period affected by human activities to drive the model respectively to simulate the basin runoff process. Taking the Nash - Sutcliffe efficiency coefficient NSE and the relative error RE as the objective functions, calibrate the model parameters of the natural period and the period affected by human activities (Table 1) to verify the adaptability of the model in the research basin:

[0058] Table 1 Calibrated model parameters and statistics of runoff simulation effects in the natural period and the human activity period

[0059] The Nash-Sutcliffe efficiency coefficient NSE for the runoff simulation of the Huaxian Station on the Weihe River during the natural period (1955 - 1970) was 0.77, and the relative error RE of the multi-year average simulation was -0.34%; the Nash-Sutcliffe efficiency coefficient NSE for the runoff simulation during the period affected by human activities (1971 - 1995) was 0.66, and the relative error RE of the multi-year average simulation was -0.31%. During the natural period ( Figure 4 a) and the period affected by human activities ( Figure 4 b), the simulation and the measured runoff process fit well. It shows that the model has good adaptability in the Weihe River Basin and can be used to simulate the runoff and the actual evapotranspiration process of the basin under natural conditions and the situation affected by human activities.

[0060] Based on the model parameters calibrated during the natural period (1955 - 1970) and the model parameters calibrated during the period affected by human activities (1971 - 1995) (Table 1), using the meteorological data of the whole process (1955 - 1995) to drive the RCCC-WBM model, the actual evapotranspiration processes of the basin under natural conditions and under the influence of human activities are respectively simulated, as Figure 5 shown.

[0061] (4) A method for identifying the attribution of changes in the actual evapotranspiration of the basin based on phased simulation is proposed. Based on the actual evapotranspiration processes of the basin under natural conditions and under the influence of human activities during the natural period and the period affected by human activities, the impacts of climate change, human activities, and their combined effects on the changes in actual evapotranspiration are analyzed:

[0062] Taking the natural period (1955 - 1970) as the reference period, the actual evapotranspiration of the basin simulated during the reference period (1955 - 1970) and the period affected by human activities (1971 - 1995) under natural conditions 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 due to the decrease in precipitation and the increase in temperature, the actual evapotranspiration of the basin decreased.

[0063] Under the state affected by human activities, the actual evapotranspiration of the basin simulated during the reference period (1955 - 1970) was 530.9 mm. Since the actual evapotranspiration of the basin simulated under natural conditions was 512.5 mm, therefore, the impact of human activities on the actual evapotranspiration of the basin was 18.4 mm, indicating that due to the variability of vegetation and the influence of other human activities, the actual evapotranspiration of the basin increased.

[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 reference period, due to the combined influence of climate change and human activities, the actual evapotranspiration of the basin increases by 3.4 mm. Considering the respective impacts of climate change and human activities on the actual evapotranspiration of the basin, the incremental impact of the combined action of climate change and human activities on the change in actual evapotranspiration of the basin is 0.7 mm, indicating that the decrease in precipitation and the increase in temperature further enhance the impact of human activities on the actual evapotranspiration of the basin.

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

[0066] (1) The measured runoff of Huaxian Station in the Weihe River Basin showed a decreasing trend from 1955 to 1995. The measured runoff series had a mutation in 1970, dividing the research period into a natural period (1955 - 1970) and a human activity influence period (1971 - 1995).

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

[0068] (3) Limited by monitoring technology, it is currently difficult to directly monitor the actual evapotranspiration process at the basin scale. Since the actual evapotranspiration of the basin is an important part of the basin hydrological cycle, the present invention proposes a method for calculating the hydrological evapotranspiration of the basin based on runoff simulation, which can be used in practical work such as basin water resources evaluation. The evapotranspiration process of the basin under changing environments will be affected by factors such as climate change and changes in the underlying surface (human activities, etc.). Clarifying the attribution of evapotranspiration changes can provide an important basis for basin management. The present invention proposes a method for analyzing the attribution of actual evapotranspiration of the basin based on segmented simulation, quantifying the contributions of climate change, human activities, and their combined action to the change in 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 and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate 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 basin and quantitatively analyzing the attribution of changes, characterized in that It includes the following steps: S1. Collect long-term hydrometeorological data and human activity data in the basin since the self-built station, calculate the annual runoff coefficient sequence of the basin, and diagnose the mutation points of the annual runoff coefficient sequence; combine the human activity conditions in the basin, divide the sequence before the mutation point into the natural period, and divide the sequence after the mutation point into the human activity influence period; S2. Based on the RCCC-WBM model, use the hydrometeorological data of the natural period and the human activity influence period to drive the model respectively to simulate the runoff process of the basin; calibrate the model parameters of the natural period and the human activity influence period, and 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 human activity influence period, use the hydrometeorological data of the natural period and the human activity influence period to drive the RCCC-WBM model to simulate the actual evapotranspiration process of the basin under the natural period and human activity influence respectively; S4. Based on the simulation results of the actual evapotranspiration of the basin under the natural period and the human activity influence period, through the attribution quantification of the change amount of the basin evapotranspiration, analyze the impacts of climate change, human activities, and their synergistic effects on the change of the actual evapotranspiration amount: Taking the actual evapotranspiration amount of the basin in the natural period as the reference value, the attribution quantification formula of the actual evapotranspiration of the basin in the human activity influence period compared with the reference value is as follows: （5） In the formula, is the change in the actual evapotranspiration of the basin during the human activity influence period compared to the actual evapotranspiration during the reference period, and is the total impact of the combined action of climate change and human activities on the actual evapotranspiration of the basin ; is the change in the actual evapotranspiration of the basin caused by pure climate change during the natural period; is the change in the actual evapotranspiration of the basin caused by changes in human activities under the climate element state during the natural period, is the increment of the change in the actual evapotranspiration of the basin caused by the combined driving of climate elements and human activities; The actual evapotranspiration process simulated through the model parameters calibrated in the natural period and the meteorological data of the whole process reflects the actual evapotranspiration situation of the basin in the natural state. The differences between the actual evapotranspiration amounts simulated in different periods mainly reflect the impacts of climate element changes; Taking the actual evapotranspiration amount of the basin in the natural period as the reference value, analyze the impact of climate change on the change of the evapotranspiration amount: （6） In the formula, and are the average actual evapotranspiration of the human activity influence period and the natural period simulated based on the natural period parameters, respectively; Taking the actual evapotranspiration amount of the basin in the natural period as the reference value, analyze the impact of human activities on the change of the evapotranspiration amount: （7） In the formula, is the average actual evapotranspiration of the natural period simulated based on the parameters of the human activity influence period; and are the actual evapotranspiration processes of the basin during the natural period simulated by the model parameters calibrated based on the human activity impact period and the natural period, respectively. Their driving climate elements are the same, both being the climate elements of the basin during the natural period. Therefore, the two respectively reflect the actual evapotranspiration of the basin under the same climate conditions and different human activity impact situations, and their differences reflect the impact of human activities on the actual evapotranspiration; Based on formulas (5) to (7), analyze the increment of the synergistic effect of climate change and human activities on the change of the actual evapotranspiration amount of the basin: （8） （9） In the formula, is the total reduction of actual evapotranspiration in the basin, is the average actual evapotranspiration of the basin simulated by the model parameters calibrated during the human activity impact period and the climate elements of that period, is the average actual evapotranspiration of the basin simulated by the model parameters calibrated during the natural period and the climate elements of the natural period, is the increment of the impact of the combined action of climate change and human activities on the change of actual evapotranspiration in the basin.

2. The method for simulating actual evapotranspiration in a basin and quantitatively analyzing the attribution of changes according to claim 1, characterized in that In step S1, the mutation points of the annual runoff coefficient sequence are diagnosed by using mathematical statistics methods, and the mathematical statistics methods include Mann-Kendall mutation test and ordered cluster analysis; among them, the ordered cluster analysis determines the year with the minimum sum of squared deviations in the annual runoff sequence as the mutation point of the annual runoff coefficient sequence.

3. The method for simulating actual evapotranspiration in a basin and quantitatively analyzing the attribution of changes according to claim 1, wherein In step S2, when using the hydrometeorological data of the natural period and the human activity influence period to drive the model, the runoff calculation formula of the RCCC-WBM model is as follows: （1） In the formula, is the basin soil water content at the i- 1st time period, which is a state variable of the RCCC-WBM model; and are the precipitation and snow accumulation amounts at the ith time period respectively, i is the air temperature at the and are the thresholds for temperature-based snow and rain division respectively; , , and are model parameters; is the simulated runoff at the i time period.

4. The method for simulating actual evapotranspiration in a river basin and quantitatively analyzing the attribution of changes according to claim 1 or 3, characterized in that 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 basin state in different periods. The calculation formula of the objective function is as follows: （2） （3） Wherein, and are the measured and simulated average runoff volumes respectively, is the measured runoff volume, i represents the i th time period, N is the total length of the runoff series, i.e., the total number of time periods; If the relative error of runoff modulus RE 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 processes in the study basin, including the runoff process and the actual evapotranspiration process.

5. The method for simulating actual evapotranspiration in a river basin and quantitatively analyzing the attribution of changes according to claim 1, wherein In step S3, when using the hydrometeorological data of the natural period and the human activity influence period to drive the RCCC-WBM model, the calculation formula of the actual evapotranspiration amount of the basin of the model is as follows: （4） In the formula, and are respectively the actual evapotranspiration and evaporation capacity of the basin in the i time period, and can be replaced by the water surface evaporation measured by the evaporator; is the soil water content of the basin in the i- 1st time period and is the state variable of the RCCC-WBM model; and are model parameters.

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