A water conservation capacity calculation and simulation method based on RCCC-WBM hydrological model

Abstract

The present invention discloses a water conservation calculation simulation method based on the RCCC-WBM hydrological model, including: collecting hydrological and meteorological data in the study basin, calculating the monthly average precipitation, temperature and water surface evaporation, and inputting them into the model; using the RCCC-WBM model to calculate the multi-year average soil moisture content, actual evapotranspiration, surface runoff, snowmelt runoff and underground runoff in the study basin; according to the monthly scale water conservation calculation formula and the annual scale water conservation calculation formula, respectively calculating the water conservation of the basin on the monthly scale and the annual scale. The water conservation calculation formula proposed in the present invention can effectively avoid the negative value problem in the water conservation assessment, and the dynamic process of the water conservation of the basin can be calculated through the state variables and intermediate output results of the RCCC-WBM model. The water conservation calculation method provided by the present invention has fewer requirements on input data and parameters, and has a better simulation effect on the hydrological process.

Description

Technical Field

[0001] The invention relates to the technical field of ecohydrological simulation, and in particular to a water conservation calculation simulation method based on an RCCC-WBM hydrological model. Background Art

[0002] Water conservation is an important service function of watershed ecology, and plays a vital role in improving the quality of terrestrial ecosystems and river ecological environment. The definition of water conservation function has gone through several stages of development. At first, it was believed that the role of forests in conserving water sources was to promote the uniform entry of water into water sources and to supplement water sources when they were short of water; later, the ecological service functions of forests were gradually expanded, covering the role of forests in regulating runoff, redistributing precipitation, purifying water quality, and the comprehensive impact on soil and water conservation. The water conservation function has thus differentiated into two definitions, narrow and broad. The narrow water conservation function only focuses on a specific function such as the amount of precipitation intercepted by the forest or the amount of runoff regulation. The broad water conservation function can be summarized as the direct and indirect effects of forest hydrological processes on all abiotic factors. Due to differences in research purposes and different understandings of the concept, different scholars have different focuses on the study of water conservation capacity. Most of them believe that water conservation capacity is mainly composed of soil layer, litter layer and canopy layer; some scholars believe that canopy layer and litter layer play a smaller role, and soil layer is the main performance layer. Based on the existing literature, water conservation function is defined as the water retention capacity of an ecosystem under specific time and conditions, which is related to regional climate, soil, vegetation and other factors. The water conservation capacity of a basin is not only consumed by basin evapotranspiration and serves the land surface ecology, but also can replenish river runoff, regulate the annual distribution of runoff, and provide a relatively stable water source for regional industrial and agricultural development.

[0003] The assessment methods of water conservation mainly include traditional hydrological methods and hydrological model methods. Traditional hydrological methods focus on experiments, and the results are relatively accurate, but they are mostly based on point scales and cannot reflect the spatial distribution well. With the continuous development of watershed hydrological simulation technology, hydrological model methods have been widely used in large-scale water conservation research, such as the InVEST model in the existing literature 1: Liu Tao et al. Analysis of water conservation function of Jungar Banner based on InVEST and FLUS models [J]. Journal of Grassland, 2023: 1-13. The InVEST model is limited by its principles and can only be used for water conservation assessment at multi-year and annual scales. It lacks applicability to multi-scale assessments, and its input data mostly relies on empirical parameters. In addition, the data requirements are difficult to obtain, the uncertainty of the model is high, and it is difficult to provide high-precision water conservation assessments. For example, the SWAT model in the existing literature 2: Lin Feng et al. Multi-time scale analysis of water conservation in forest-discontinuous watersheds based on the SWAT model [J]. Acta Geographica Sinica, 2020, 75(05): 1065-78, the water conservation calculated by the SWAT model based on the water balance principle is actually the increase in water conservation in the watershed period, rather than the state quantity in the period, and negative values ​​will appear at different scales, which is inconsistent with the definition of water conservation. Although these two methods are detailed and comprehensive, they both have the problem of complex and diverse inputs and difficult data acquisition, which to a certain extent limits the application and promotion of this method in water conservation evaluation. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the input of the prior art is complex and diverse and the data is difficult to obtain, and to propose a water conservation calculation simulation method based on the RCCC-WBM model.

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

[0006] Step 1: Collect hydrological and meteorological data in the study basin, including monthly precipitation, temperature, water surface evaporation, and runoff depth, calculate the monthly average precipitation, temperature, and water surface evaporation, and input them into the RCCC-WBM model;

[0007] Step 2: Analyze and study the interdecadal variation characteristics and annual distribution characteristics of the basin's hydrological and meteorological elements, including surface average precipitation, water surface evaporation, temperature and runoff depth, and determine the initial values ​​of the model's key parameters based on the basin's hydrological and meteorological characteristics;

[0008] Step 3: Use the RCCC-WBM model to simulate and calculate the multi-year average soil moisture content, actual evapotranspiration, surface runoff, snowmelt runoff and groundwater runoff in the basin;

[0009] Step 4: Calculate the water conservation capacity of the basin on a monthly and annual scales according to the monthly and annual water conservation calculation formulas based on the multi-year average soil moisture content, groundrunoff and actual evapotranspiration obtained through simulation.

[0010] Model output: The study of multi-scale water conservation capacity of the basin and related key variables is the core variable in the water cycle process. The key variables are soil moisture content, surface runoff, groundrunoff, snowmelt runoff and actual evapotranspiration.

[0011] Furthermore, the calculation formula for the monthly water conservation capacity in step 4 is:

[0012]

[0013] Where: W mi For the i Monthly water conservation capacity of the basin during the period; S i-1 and S i Respectively i The soil moisture content of the watershed at the beginning and end of the time period can be obtained by monitoring the measured data or by simulating and calculating the watershed hydrological model; AE mi and EP mi Respectively i Actual monthly evapotranspiration and monthly evaporation capacity of the basin during the period; Q gmi For the i The monthly underground runoff depth of the watershed during the period represents the soil moisture content that replenishes the river runoff through the outflow of the soil layer; k e、 k g、 S max are parameters, namely evaporation coefficient, groundwater runoff coefficient and maximum soil water storage capacity, which can be obtained by optimizing the basin hydrological model.

[0014] The above calculation formula is based on the definition of water conservation capacity and is constructed in combination with the RCCC-WBM model principle.

[0015] From the above, it can be seen that water conservation capacity includes two parts: one is the state variable of the basin, that is, soil moisture content S i , which represents the amount of soil moisture and is affected by factors such as precipitation and soil texture; the other part is the support amount of water conservation ecological service function AE mi + Q gmi ,in, AE mi The evapotranspiration that supports the land surface ecosystem service functions in the basin, Q gmi The underground runoff is deep to replenish river runoff and serve the river ecology.

[0016] Furthermore, the annual scale water conservation capacity calculation formula in step 4 is:

[0017]

[0018] Where: W aj For the j Annual water conservation capacity of the basin during the year period; S j For the j The soil moisture content of the watershed at the end of the annual period (i.e., the end of December) can be obtained by monitoring the measured data or by simulating and calculating the watershed hydrological model; AE aj and Q gaj Respectively j The actual annual evapotranspiration and annual groundwater depth in the basin in 2018 are calculated from the current year ( j Actual monthly evapotranspiration AE mji Heyue underground runoff depth Q gmji The cumulative calculation is shown in formula (3) and formula (4).

[0019] The RCCC-WBM model is a watershed hydrological model developed and gradually improved by the team of the Climate Change Research Center of the Ministry of Water Resources. The model is based on the principle of water balance and simulates the hydrological cycle of the watershed. The model inputs include: average temperature of the watershed surface, precipitation, evaporation of the water surface (evaporation capacity) and measured runoff depth. The measured runoff depth is used to construct the objective function for model parameter calibration. The model includes 5 parameters, namely, maximum soil water storage capacity S max , surface runoff coefficient K s , underground runoff coefficient K g , snowmelt runoff coefficient K sn and evaporation coefficient K e The model can output simulated runoff depth, actual evapotranspiration, soil moisture, and three runoff components (surface runoff depth, snowmelt runoff depth, and underground runoff depth). It has many advantages, such as simple structure, fewer parameters, and easy access to input data. This method is based on the RCCC-WBM model structure. By adding water conservation calculation and output modules, the model can simulate and calculate the water conservation capacity of the basin.

[0020] Beneficial effects of the present invention:

[0021] The water conservation capacity calculation method provided by the present invention has fewer requirements on input data and parameters, and has a better simulation effect on hydrological processes. The simulated water conservation capacity has a clear physical meaning and can effectively summarize the water conservation body and conservation function of the basin.

[0022] Compared with the SWAT model, the water conservation calculation formula proposed in the present invention can effectively avoid the negative value problem in water conservation assessment. The dynamic process of water conservation in the basin can be calculated through the state variables and intermediate output results of the RCCC-WBM model.

[0023] The water conservation process of a river basin simulated by the method of the present invention can provide a reference for ecological protection and water resources management of the river basin. The method of the present invention, combined with future climate change scenarios, can simulate the trend of water conservation in the river basin in the future, which can provide scientific support for ecological protection and water resources planning of the river basin. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the decadal process of monthly average precipitation, water surface evaporation, air temperature and runoff depth in the Xiangjiang River Basin from 1960 to 2010, where a) is precipitation, b) is water surface evaporation, c) is air temperature, and d) is runoff depth;

[0025] Figure 2 It is the multi-year average annual distribution of monthly average precipitation, water surface evaporation, temperature and runoff depth in the Xiangjiang River Basin from 1960 to 2010, where a) is precipitation, b) is water surface evaporation, c) is temperature, and d) is runoff depth;

[0026] Figure 3 This is a structural framework diagram of the multi-scale water conservation calculation simulation method based on the RCCC-WBM model;

[0027] Figure 4 This is a comparison of the runoff depth process measured and simulated monthly at Xiangtan Station from 1960 to 2010;

[0028] Figure 5 is the multi-year average value obtained by model simulation in the Xiangjiang River Basin from 1960 to 2010, where a) is the actual evapotranspiration, b) is the soil moisture content, and c) is the runoff components;

[0029] Figure 6 a) is the annual scale water conservation change process of the Xiangjiang River Basin; b) is the multi-year average annual distribution process;

[0030] Figure 7 This is the monthly scale water conservation capacity change process of the Xiangjiang River Basin year by year. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are described in detail in conjunction with the accompanying drawings and embodiments: The following embodiments are only used to explain the present invention and are not used to limit the application scope of the present invention.

[0032] Example

[0033] The calculation of water conservation capacity is illustrated by taking the Xiangjiang River in the Yangtze River Basin as an example. The Xiangjiang River Basin belongs to the Yangtze River Dongting Lake water system and is the largest river in Hunan Province. The basin area above Xiangtan Station is 81,638 square kilometers. The multi-scale water conservation capacity calculation simulation method based on the RCCC-WBM model includes constructing a multi-scale water conservation capacity calculation formula based on the key output variables of the RCCC-WBM hydrological model. The key output variables include soil moisture, surface runoff, groundwater runoff, snowmelt runoff and actual evapotranspiration; based on the simulation results of the RCCC-WBM model, the multi-scale water conservation capacity of the study basin is calculated and output.

[0034] like Figure 3 The figure shows the structural framework of the multi-scale water conservation calculation and simulation method based on the RCCC-WBM model, where the input of the model is the monthly average surface precipitation, temperature and water surface evaporation, and the output of the model is the multi-scale water conservation capacity, actual evapotranspiration, soil moisture, surface runoff, snowmelt runoff and groundrunoff.

[0035] The specific calculation process is as follows:

[0036] Step 1: Collect the monthly precipitation, temperature, water surface evaporation and monthly measured runoff depth data of Xiangjiang River Basin from 1960 to 2010 at Xiangtan Station, calculate the monthly average precipitation, temperature and water surface evaporation, and input them into the RCCC-WBM model;

[0037] Step 2: Analyze the interdecadal variation characteristics of meteorological and hydrological elements in the Xiangjiang River Basin, including surface average precipitation, surface evaporation, temperature and runoff depth, as follows: Figure 1 The multi-year average annual distribution characteristics of meteorological and hydrological elements in the Xiangjiang River Basin are analyzed, as shown in a), b), c), and d). Figure 2 The average annual precipitation in the Xiangjiang River Basin is about 1500 mm, the average annual runoff depth is about 800 mm, the runoff coefficient is about 0.5, and the annual distribution of rainfall and runoff is similar. It is a typical humid area. The surface runoff coefficient and soil water storage capacity are both larger than the default values. According to the results of the analysis of the rainfall and runoff characteristics of the basin, the initial value of the surface runoff coefficient simulated by the model is set to 0.5, and the initial value of the maximum soil water storage capacity is set to 300 mm.

[0038] Step 3: Since the actual value of water conservation is difficult to obtain, the Nash-Sutcliffe model efficiency coefficient NSE and relative error RE are used as the objective function. The RCCC-WBM model parameters are calibrated using the 36-year data from Xiangtan Station from 1960 to 1995, and the 15-year measured runoff depth data from 1996 to 2010 are used for verification. The calibration method uses the SCE-UA automatic calibration algorithm, with the Nash efficiency coefficient closest to 1 as the objective function, and the optimal value is found within a reasonable parameter range. The calibrated parameter results are then input into the verification period for effect verification. (1) If the model can accurately simulate the evolution characteristics of runoff over a long time scale, it proves that the model has a good generalization of the entire eco-hydrological process of the basin and can be used to calculate the water conservation capacity of the basin. When NSE is greater than 70% and the relative error is less than 5%, the model simulation is considered to be relatively accurate.

[0039]

[0040] In the formula: In the formula: MAR sim is the average simulated runoff depth, MAR obs is the measured average runoff depth, Q SIMi is the simulated runoff depth, Q REi is the measured runoff depth, N is the total length of the runoff series, i.e. the total number of time periods, is the average value of the measured runoff depth.

[0041] In this embodiment, the NSE in the rate period and the verification period are 0.89 and 0.88, and the RE is 2.4% and -0.25%, respectively. Figure 4 The results show that the RCCC-WBM model has good adaptability to the simulation of hydrological processes in the Xiangjiang River Basin.

[0042] The RCCC-WBM model was used to simulate the multi-year average soil moisture content, actual evapotranspiration, surface runoff, snowmelt runoff and groundwater runoff in the Xiangjiang River Basin from 1960 to 2010. Figure 5 .

[0043] Step 4: Based on the simulated average soil moisture content, groundwater runoff and actual evapotranspiration of the basin over many years, the water conservation capacity at the monthly and annual scales of the basin is calculated according to formula (1) and formula (2), respectively, and the annual and monthly changes of the water conservation capacity are analyzed, as follows: Figure 6 As shown in a and b, the annual change process of the monthly scale is as follows Figure 7 The simulated dynamic change process of water conservation capacity in the Xiangjiang River Basin shows an overall increasing trend.

[0044] From the above steps, it can be seen that the water conservation calculation method based on the RCCC-WBM hydrological model provided by the present invention has less requirements for data. Although the model structure is simple and the parameters are few, it has a good simulation effect on the hydrological process and is easy to promote and apply. The calculation formula proposed by the present invention can effectively avoid the negative value problem in the water conservation assessment. From the perspective of the conservation body and conservation function goal orientation, the water conservation state quantity of the basin at different times is calculated. The state quantity will not have a negative value, and the water conservation function of the basin can be evaluated more scientifically and simply. This calculation method is more in line with common sense and more convenient for evaluation and comparison.

[0045] As above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention defined in the appended claims.

Claims

1. A water conservation capacity calculation and simulation method based on the RCCC-WBM hydrological model, characterized by: The following steps are involved: Step 1: Collect hydrological and meteorological data in the study basin, including monthly precipitation, temperature, water surface evaporation, and runoff depth, calculate the monthly average precipitation, temperature, and water surface evaporation, and input them into the RCCC-WBM model; Step 2: Analyze and study the hydrological and meteorological elements of the basin, including the interdecadal variation characteristics and annual distribution characteristics of the average precipitation, water surface evaporation, temperature and runoff depth, and determine the initial values ​​of the key parameters of the model; Step 3: Use the RCCC-WBM model to simulate and calculate the multi-year average soil moisture content, actual evapotranspiration, surface runoff, snowmelt runoff and groundwater runoff in the basin; Step 4: Based on the multi-year average soil moisture content, groundrunoff and actual evapotranspiration obtained by simulation, the monthly and annual water conservation capacity calculation formulas are used to calculate the water conservation capacity of the basin on a monthly and annual scales, respectively.

2. The water conservation capacity calculation simulation method based on the RCCC-WBM hydrological model according to claim 1 is characterized in that: The calculation formula for monthly water conservation capacity in step 4 is: Where: W mi For the i The monthly scale water conservation capacity of the basin is studied in the time period; S i-1 and S i Respectively i The watershed soil moisture content at the beginning and end of the period; AE mi and EP mi Respectively i Monthly actual evapotranspiration and monthly evaporation capacity for the time period; Q gmi For the i Monthly subsurface runoff depth in the watershed during the period; k e、 k g、 S max They are evaporation coefficient, groundwater runoff coefficient and maximum soil water storage capacity respectively.

3. The water conservation capacity calculation simulation method based on the RCCC-WBM hydrological model according to claim 1 is characterized in that: The calculation formula for annual water conservation capacity in step 4 is: Where: W aj For the j Annual scale water conservation capacity; S j For the j The soil moisture content in the watershed at the end of the annual period, i.e., at the end of December; AE aj and Q gaj Respectively j The actual annual evapotranspiration and annual groundwater runoff depth in the year are calculated from j Actual monthly evapotranspiration AE mji Heyue underground runoff depth Q gmji The cumulative calculation is shown in formula (3) and formula (4).

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