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CN-121999237-A - Method, equipment, medium and program for judging wet land flooding state of grid scale

CN121999237ACN 121999237 ACN121999237 ACN 121999237ACN-121999237-A

Abstract

The invention relates to a grid scale wetland flooding state judging method, equipment, medium and program, which are used for constructing a linear relation model of subgrid groundwater level and topography index, representing a critical flooding state by taking the subgrid groundwater level as 0, acquiring a topography index value at the moment based on the linear relation model as a topography index threshold value of subgrid flooding, calculating the flooding area occupation ratio of each grid based on the subgrid flooding state, constructing a fitting model of grid average groundwater level and flooding area occupation ratio, acquiring a wetland image and grid average groundwater level in the image, and acquiring the grid flooding area occupation ratio of the wetland based on the fitting model. The method can couple the groundwater level change and the subgrid terrain heterogeneity characteristic on the grid scale, realize a new technical scheme for finely judging the flooding state of the wetland, and make up the defect of the existing hydrologic model in the expression capacity of the flooding space of the wetland.

Inventors

  • Hou Yuyu
  • Zhu Qiuan
  • FANG XIUQIN
  • JIN JIAXIN

Assignees

  • 河海大学

Dates

Publication Date
20260508
Application Date
20251218

Claims (10)

  1. 1. The method for judging the wet land flooding state of the grid scale is characterized by comprising the following steps of: constructing sub-grid groundwater level and topography index The method comprises the steps that (1) a critical flooding state is represented by taking the underground water level of a subgrid as 0, and a terrain index value at the moment is obtained based on the linear relation model to serve as a terrain index threshold value of subgrid flooding; calculating the flooding area occupation ratio of each grid based on the flooding state of the subgrid, wherein the grid is composed of a plurality of subgrids; constructing a fitting model of the grid average underground water level and the water flooding area occupation ratio; and acquiring the land topography space data of the to-be-studied area, calculating the grid average ground water level, and acquiring the grid flooding area occupation ratio of the land based on the fitting model.
  2. 2. The method of claim 1, wherein the flooding status of the subgrid is determined based on: setting a water flooding minimum threshold value for the subgrid; And taking the maximum value of the topographic index threshold value and the lowest flooding threshold value of each subgrid as a judging threshold value, and judging that the subgrid is in a flooding state when the topographic index of the subgrid is not smaller than the judging threshold value.
  3. 3. The method of claim 1, wherein the fitted model is of the form: ; Wherein, the Fitting parameters; The average ground water level of the grid; and the water flooding area ratio of the fitted grid is calculated.
  4. 4. The method of claim 1, further comprising setting a flooding minimum threshold for the subgrid; For each subgrid, judging that the subgrid is in a flooding state when the topography index of the subgrid is not less than the lowest flooding threshold value; And acquiring the flooding area occupation ratio based on the fitting model, and taking smaller values of the flooding area occupation ratio acquired by the model and the maximum potential flooding area occupation ratio as the actual flooding area occupation ratio of the grid.
  5. 5. A method according to claim 1 or 3, characterized in that the fitting parameters of the fitting model are obtained on the basis of: setting a water flooding minimum threshold value for the subgrid, setting a parameter range for the water flooding minimum threshold value and soil parameters, and constructing a plurality of groups of parameter combinations in the parameter range, wherein the soil parameters select an exponential decay coefficient of the saturated water conductivity of the soil along with the change of depth; Each group of parameter combination is subjected to assumption of a series of grid average underground water levels, corresponding grid flooding area occupation ratios are obtained under the assumption of water levels, a plurality of groups of water level-area occupation ratio sample points are formed, and fitting is carried out based on the sample points, so that a fitting model is obtained; Substituting the actually measured daily underground water level sequence into the fitting model to obtain the daily wetland flooding area ratio, and carrying out fitting parameter evaluation by using a true value to obtain the best fitting parameter combination.
  6. 6. The method of claim 1, further comprising obtaining a grid flooding area duty cycle of a yearly scale based on the grid flooding area duty cycle data of the yearly scale, comprising: acquiring a time sequence of the daily wetland flooding area occupation ratio; Sliding the time sequence based on an N-day sliding window, wherein the minimum occupied area of the wetland flooding area in the N-day sliding window is used as a smooth value of the sliding window, N is the preset sliding window size, and N=30 is preferable; and taking the maximum value of the annual smooth value sequence as the annual wet grid flooding area ratio.
  7. 7. The method of claim 6, wherein the sliding take on values in a segment take on values as follows: ; in the formula, The minimum value of N days of sliding is given, T is the time number of the current date in the total number of days, and T is the total number of days.
  8. 8. A computer device comprising a memory, a processor and a computer program stored on the memory, characterized in that the processor executes the computer program to carry out the steps of the method according to any one of claims 1 to 7.
  9. 9. A computer readable storage medium having stored thereon a computer program/instruction, which when executed by a processor, implements the steps of the method according to any of claims 1 to 7.
  10. 10. A computer program product comprising computer programs/instructions which, when executed by a processor, implement the steps of the method of any of claims 1 to 7.

Description

Method, equipment, medium and program for judging wet land flooding state of grid scale Technical Field The invention belongs to the technical field of hydrological data processing, and particularly relates to a method, equipment, medium and program for judging a wet land flooding state of a grid scale. Background The wetland is a typical hydrologic-ecological coupling system, and the flooding state is commonly controlled by a plurality of factors such as precipitation, terrain, soil properties, groundwater level, and evapotranspiration process. Whether the wetland is flooded or not and the spatial distribution pattern of flooding not only directly influence the regional water circulation process, but also have important influence on the carbon circulation, the biological habitat and the ecological system service function. Therefore, in hydrologic simulation and ecological evaluation, accurate determination of the flooded condition of the wetland is one of basic technical problems. At present, in the simulation research of the wetland hydrologic process, a distributed or semi-distributed hydrologic model, such as SWAT, TOPMODEL, various land process models and the like, is widely adopted. Such models typically use grid units or sub-basin units as basic computational units and groundwater levels, soil moisture content or runoff as key hydrologic state variables to numerically model the surface-to-groundwater hydrologic process. However, the output result of such models is mostly the average groundwater level or average water-containing state of the individual grid or sub-basin scale, which essentially belongs to the "hydrologic state description in the sense of spatial averaging". For a geomorphic unit with strong spatial heterogeneity characteristic of a wetland, flooding tends to occur first at a low-lying catchment location, while areas with high Gao Chenglve or large gradients may not be flooded even under the same average groundwater level conditions. That is, inside the same hydrological model grid, the groundwater level and the flooded state have a significant sub-grid scale difference in space. However, the existing hydrologic model generally lacks the capability of describing the micro-topography differences inside the grid unit, and is difficult to describe the key problem of whether different positions in the same grid are flooded. In the prior art, partial researches try to adopt a ground water level threshold method or a soil saturation judging method, and ground water level or water content output by a hydrologic model is directly used as a judging basis for whether the wetland is flooded or not, but the method usually uses whether the average ground water level of the grid exceeds a certain empirical threshold value or not as a criterion, so that the whole grid is simply divided into a full-flooded state or a non-flooded state. The method ignores the difference of the relief and confluence inside the grid, easily causes excessive generalization or missed judgment of the flooding range of the wetland, and is difficult to reflect the spatial distribution characteristics of the flooding plaque of the real wetland. In addition, although the topography factors such as topography index, catchment area and the like are introduced into the part of the distributed hydrologic model to characterize the distribution characteristics of the runoff production and the saturated region, most of related researches focus on a runoff formation mechanism instead of taking the wet land flooding state judgment as a direct target, and the result is always output in the form of source region proportion or the saturation region proportion in the statistical sense, so that the precise quantitative expression of the grid scale wet land flooding area proportion is difficult to realize. Therefore, the existing wetland flooding judgment technology based on the hydrologic model has the following defects: Firstly, only the average hydrologic state of grid or sub-basin scale can be obtained, and the local flooding difference of sub-grid scale is difficult to reflect; secondly, the wet land flooding judgment depends on an empirical threshold value, and a quantitative constraint mechanism of groundwater level-topography coupling is lacked; thirdly, the result of 'grid scale flooding area ratio' which can be in one-to-one correspondence with the remote sensing flooding area is difficult to directly output, so that the accuracy verification and application of the model result are limited. Disclosure of Invention The first object of the present invention is to overcome the above-mentioned drawbacks of the prior art, and to provide a method for determining a flooding condition of a wet land on a grid scale. In order to achieve the above purpose, the invention adopts the following technical scheme: A method for determining a wet land flooding state of a grid scale, the method comprising: constructing sub-grid groundwater level and to