CN-121579611-B - Quantitative evaluation method for influence of river basin ecological system pattern change on wading function

Abstract

The invention discloses a quantitative assessment method for influence of a river basin ecological system pattern change on wading functions, which comprises the steps of constructing a SWAT model, dividing a river basin discretization and hydrologic response unit HRU, setting parameters and operating the model, calibrating and verifying the model, replacing forest, grassland and wetland ecological system types in land utilization data with bare lands, operating the river basin hydrologic model again, carrying out river basin hydrologic process simulation under different land utilization scenes to obtain corresponding rainfall, evapotranspiration, runoff depth, water yield and river channel runoff, calculating river basin water conservation quantity, obtaining water yield, calculating a standardized runoff index through river channel runoff quantity, and counting the number of flood/drought occurrence months. The method can quantitatively evaluate the influence of the pattern change of the main natural ecological system on the conservation effect, the water production effect, the flood regulation and drought relief effect of the water source of the river basin, and provide theoretical support for scientific management, protection and restoration measures of the ecological system of the river basin.

Inventors

• WANG BIAO
• WU YANFENG
• ZHANG GUANGXIN

Assignees

• 中国科学院东北地理与农业生态研究所

Dates

Publication Date

20260512

Application Date

20251128

Claims (6)

1. 1. The quantitative evaluation method for influence of the change of the pattern of the river basin ecological system on the wading function is characterized by comprising the following steps of: Firstly, constructing a SWAT model, and preparing topographic data, land utilization data, soil data and meteorological data; performing drainage basin discretization and hydrological response unit HRU division; parameter setting and model operation are carried out; Calibrating and verifying the model; replacing forest, grassland and wetland ecosystem types in the land utilization data with bare land by using an MATLAB tool, and running the SWAT model again; Step three, performing SWAT process simulation under the ecological utilization situations of forests, grasslands and wetlands according to the SWAT model, and obtaining corresponding rainfall, evapotranspiration, runoff depth, water yield and river channel runoff based on different SWAT process simulation results; Calculating the conservation amount of the river basin water source based on the water balance principle, directly obtaining the water yield through a model output result, calculating a standardized runoff index through the river channel runoff amount, and counting the number of months when flood/drought occurs; in the fourth step, the first step is performed, The SWAT model water source conservation amount calculating method comprises the following steps: WC = P - E - R Wherein WC is the water source conservation quantity of unit area, P, E, R is the average precipitation quantity of unit area, the actual evaporation quantity of unit area and the radial flow depth of unit area; The SWAT model calculates the water production WYLD based on the following formula: WYLD = Q surf + Q gw + Q lat - Q loss Wherein Q surf is surface runoff mm, Q gw is the contribution mm of groundwater to runoff, Q lat is the contribution mm of lateral flow, and Q loss is the transmission loss mm in HRU; the quantitative evaluation method for flood regulation and drought relief effect comprises the following steps: Carrying out Huo Lin river basin drought and flood identification by calculating a standardized runoff index, wherein the standardized runoff index data SRI calculation method comprises the following steps: Assuming that the runoff x of the river is in a certain period of time, the gamma distribution probability density function is: In the formula, As a function of the shape parameter(s), The scale parameter is used to determine the scale parameter, The accumulation rate of the runoff x with a certain time scale is as follows: the runoff data output by the SWAT model RCH file has 0 value, so a mixed distribution function is adopted, and the formula is as follows: Conversion to a standard normal distribution: Wherein, the Is an inverse function of the standard normal distribution.
2. 2. The quantitative evaluation method for influence of river basin ecosystem pattern change on wading function according to claim 1, wherein in the first step, the terrain data, land utilization data, soil data and meteorological data are respectively: the topographic data is that a digital elevation model is used for extracting river basin boundaries, river networks, sub-river basin division and calculating gradient topographic features; The data are obtained from USGS and SRTM channels, and are subjected to projection conversion and noise removal pretreatment; Land utilization data, namely, interpreting from a remote sensing image, and reclassifying according to a classification system embedded in the SWAT model after obtaining the land utilization data; soil data, namely, soil type and physical and chemical attribute data thereof are needed, the data come from soil investigation or a soil database, and a soil attribute database needed by a SWAT model is established; Weather data, which is key to driving the model operation, includes daily precipitation, maximum/minimum air temperature, solar radiation, wind speed, relative humidity, and the SWAT model uses weather generators to generate missing weather data.
3. 3. The method for quantitatively evaluating the influence of a change in the pattern of a watershed ecosystem on a wading function according to claim 1, wherein in the first step, the SWAT model adopts a "sub-watershed-hydrologic response unit" two-stage discretization method to treat the spatial heterogeneity of the watershed, wherein, Dividing the whole research river basin into a plurality of sub-river basins based on the DEM through the steps of filling the depression, calculating the water flow direction, accumulating the confluence area, extracting the river network and dividing the river basin; the hydrological response unit defines that HRU is further divided according to the combination of land utilization type, soil type and gradient grade in each sub-flow domain; The HRUs are the basic computational units of the SWAT model, each HRU is considered as a uniform region with the same soil utilization, soil and slope characteristics, the model is first independently hydrodynamically calculated on each HRU, and then summarized to sub-watershed and watershed dimensions.
4. 4. The quantitative assessment method for influence of river basin ecosystem pattern change on wading function according to claim 1, wherein in the first step, parameters are set, which comprises setting vegetation growth parameters including canopy height and root depth for different land utilization types, setting hydrologic parameters including saturated water conductivity and field water holding capacity for different soil types, and setting agricultural management measures including fertilization, irrigation and cultivation parameters; The SWAT model is provided with a plurality of default parameter databases, including a soil database and a vegetation growth database, and is adjusted according to the actual conditions of a research area; and (3) model operation, namely after all parameter setting is completed and a model input file is generated, the SWAT model can be operated to perform simulation calculation, and the start-stop time and the time step of simulation can be set.
5. 5. The quantitative evaluation method for influence of river basin ecological system pattern change on wading function according to claim 1, wherein in the first step, parameter calibration is performed by firstly performing parameter sensitivity analysis, identifying runoff curve number CN and soil evaporation compensation coefficient ESCO, and then optimizing the parameters; Model verification, namely fixing the calibrated parameters, and using another section of independent observation data operation model which does not participate in calibration to evaluate the simulation effect; the evaluation index comprises commonly used model performance evaluation indexes including Nash-Sattklift efficiency coefficient NSE, decision coefficient R2 and gram Lin Xiaolv coefficient KGE, wherein the model simulation effect is better when NSE, R2 and KGE are close to 1, R 2 , NSE and KGE have the following calculation formulas: Wherein r is the pearson correlation coefficient of the measured value and the analog value, the variability ratio of the alpha analog value and the measured value, the average value ratio of the beta analog value and the measured value; the calculation formulas of r, alpha and beta are as follows: In the formula 、 、 、 K are measured diameter flow m 3 /s, measured diameter flow average value m 3 /s, simulated diameter flow m 3 /s, simulated diameter flow average value m 3 /s and time sequence length respectively.
6. 6. The quantitative assessment method for influence of river basin ecosystem pattern change on wading function according to claim 1, wherein in the second step, before using MATLAB to replace forest, grassland and wetland ecosystem types in land use data with unused land, the land use data needs to be reclassified by using Acrgis software, and the steps are as follows: (1) Preparing data, namely ensuring that land utilization data are in a grid format, and if the original data are vector surfaces, firstly using a conversion tool to carry out rasterization; (2) Opening the tool, in ArcToolbox, navigating to SPATIAL ANALYST Tools- > Reclass- > RECLASSIFY; (3) Setting parameters: An input grid for selecting land utilization grid data; reclassifying a field that stores the original land type code; remapping, namely directly modifying New values in Reclassification tables; (4) Running, clicking OK to execute operation.

Description

Quantitative evaluation method for influence of river basin ecological system pattern change on wading function Technical Field The invention relates to the technical field of hydrology and water resources, in particular to a quantitative evaluation method for influence of a river basin ecological system pattern change on wading functions. Background The hydrologic function is taken as an important component of the ecological function, refers to the core capability of the ecological system for regulating and controlling the water circulation based on the processes of physics, chemistry, biology and the like through the structure of the ecological system, and is the basis for maintaining ecological balance and guaranteeing sustainable utilization of water resources. The degradation of the ecological system can directly weaken the transpiration effect, reduce the soil infiltration capacity, destroy the regional hydrologic cycle process, lead the precipitation not to be effectively intercepted or infiltrated, lead to large amount of surface runoffs to be formed in a short time, lead to the expansion of flood scale and increase of frequency, simultaneously reduce the soil infiltration capacity, lead to insufficient groundwater supply, reduce river base flow, reduce regional water conservation capacity, reduce available water resources, obviously increase drought occurrence frequency and intensity, and finally lead to regional water resource shortage crisis such as urban water shortage, agricultural yield reduction and the like. As global climate change is exacerbated and regional human activity effects continue to increase, the "additive effect" of both is accelerating the degradation of the ecosystem, simplifying structures (e.g., decreasing species abundance), and impairing its ecological functional integrity (e.g., impaired biodiversity maintenance, impaired soil and water conservation). Therefore, the quantitative evaluation of the influence of the change of the pattern of the ecological system on the hydrologic function of the river basin has important practical significance for maintaining the ecological safety of the river basin, preventing flood and reducing disaster, preventing drought and resisting drought and realizing sustainable utilization of water resources. Water conservation is a key indicator reflecting the health of the ecosystem and is defined as the ability of the ecosystem to maintain water reserves within a specific space-time range. The main functions of water conservation include water supply guarantee, flood peak reduction, water and soil conservation, water environment maintenance and the like. To understand the water conservation effect of the basin ecology system in depth, the water conservation amount (which refers to the amount of water stored by the ecology system in a certain period of time) can be calculated to quantitatively evaluate the water conservation effect. In recent years, although research on the hydrologic function of the ecosystem has been significantly progressed, most of the research has focused on evaluation of a single hydrologic function (such as conservation of water source) but has not fully reflected the complex hydrologic function of the ecosystem. In fact, only calculating the single index of the water conservation amount cannot intuitively embody the key roles of the ecological system in aspects of water production, flood regulation, drought relief and the like. These insights limit our full understanding of the multi-hydrologic functions of the ecosystem and also affect the scientificity of water resource management decisions. Therefore, a comprehensive evaluation framework is needed to be established, and various hydrologic functions such as water conservation, water production, flood regulation and drought relief are brought into a unified analysis system, so that multiple functions of the ecological system in water resource management are evaluated more comprehensively, and a more scientific theoretical basis is provided for sustainable management of regional water resources. There have been studies to evaluate the time-varying characteristics of water conservation or water production capacity, often by means of a hydrological model, or to analyze the effect of returning the cultivation counter-forest to the overall water conservation in the flow field. However, the problems and defects existing in the prior art are as follows: (1) Most studies have focused on the assessment of single hydrologic functions (e.g., water conservation) and have failed to fully reflect the complex hydrologic functions of the ecosystem. In fact, only calculating the single index of the water conservation amount cannot intuitively embody the key roles of the ecological system in aspects of water production, flood regulation, drought relief and the like; (2) In natural situations, the influence of the coverage change of the river basin ecological system on the river basin hyd