A method and system for determining a brackish water intertidal zone of an estuary wetland

Abstract

The application provides a method and system for determining a brackish water interaction zone of an estuary wetland, the method comprising: obtaining water depth data and salinity data of a plurality of sampling points in a region to be studied; constructing a salinity-water depth relationship model according to the water depth data and the salinity data of the plurality of sampling points; obtaining distances of a reference point from each of the sampling points along a tidal current direction and salinity data of the plurality of sampling points, and constructing a salinity-tidal current distance relationship model; obtaining tidal data, and determining a boundary of a brackish water interaction zone of the wetland in the region to be studied by using the salinity-water depth relationship model and the salinity-tidal current distance relationship model; and determining a range of the brackish water interaction zone of the estuary wetland in the region to be studied according to the boundary of the brackish water interaction zone of the wetland. The salinity-water depth relationship model and the salinity-tidal current distance relationship model are constructed, so that a dynamic boundary of the brackish water interaction zone of the estuary wetland can be determined, and the determination accuracy of the range of the brackish water interaction zone of the estuary wetland is improved.

Description

Technical Field

[0001] This invention relates to the field of dynamic boundary simulation, and in particular to a method and system for determining the brackish water interaction zone in estuary wetlands. Background Technology

[0002] The varying brackish water conditions of estuarine wetlands determine their respective wetland functions, and the ecological protection, restoration, and management of these wetlands must take into account the brackish water interaction zones of the estuarine wetlands of rivers flowing into the sea. Rivers flowing into the sea are increasingly influenced by ocean tides before reaching the ocean, and different zones can be defined based on the strength of these tidal influences. For example... Figure 1 The maximum distance that tidal waves can influence is the tidal boundary (tidal wave line). Above the tidal boundary, there is no influence from ocean tides. The farthest point upstream of the tidal current, i.e., the farthest point reached by the tide, is the tidal boundary, which is also the location of the highest spring tide line. The area between the tidal boundary and the tidal boundary is the near-mouth section. The near-mouth section is only affected by tidal waves, and the water flow is unidirectional. Because there is no seawater inflow, the river water is all freshwater, forming the freshwater area of ​​the estuarine wetland. According to the definition of wetlands in the 1971 Ramsar Convention, estuarine wetlands include shallow seas with a depth not exceeding 6 meters at low tide. The area from the low tide line to the near-mouth with a depth not exceeding 6 meters is covered by seawater and is part of the saline area of ​​the estuarine wetland. Between the high tide line and the low tide line, the tidal influence is frequent, and the area is periodically submerged by seawater every day. The surface water is mainly seawater with a high salinity, forming the terrestrial part of the saline area of ​​the estuarine wetland. It is evident that the boundary between fresh and brackish water in estuary wetlands is constantly changing due to the influence of tides, which increases the difficulty of determining the extent of the brackish water interaction zone in estuary wetlands. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for determining the brackish water interaction zone of estuary wetlands, which can determine the dynamic boundary of the brackish water interaction zone of estuary wetlands and improve the accuracy of determining the range of the brackish water interaction zone of estuary wetlands.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A method for determining the brackish water interaction zone in an estuarine wetland includes:

[0006] Acquire water depth data from multiple sampling points in the area to be studied;

[0007] Acquire salinity data from multiple sampling points in the area under study;

[0008] A salinity-water depth relationship model was constructed based on water depth data and salinity data from multiple sampling points.

[0009] Determine reference points in the area to be studied;

[0010] Obtain the distances between the reference point and each of the sampling points along the current direction;

[0011] Based on the distances between the reference points and each of the sampling points along the tidal current direction, and the salinity data of multiple sampling points, a salinity-tidal current distance relationship model is constructed.

[0012] Acquire tidal data for the area under study;

[0013] Based on the tidal data, the boundary of the wetland brackish water interaction zone in the study area is determined using the salinity-water depth relationship model and the salinity-tidal distance relationship model. The boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the upper boundary of the adjacent brackish water zone.

[0014] Based on the boundary of the brackish water interaction zone of the wetland, the extent of the brackish water interaction zone of the estuarine wetland in the area to be studied is determined.

[0015] Optionally, both the salinity-water depth relationship model and the salinity-tidal current distance relationship model are S-shaped Logistic models.

[0016] Optionally, determining the boundary of the brackish water interaction zone in the area under study based on the tidal data, using the salinity-depth relationship model and the salinity-tidal distance relationship model, specifically includes:

[0017] Based on the tidal data in the area under study, determine the maximum tidal level line, minimum tidal level line, and tidal wave line of the area under study;

[0018] The tidal wave line is defined as the boundary of the adjacent freshwater zone of the brackish water interaction zone;

[0019] Based on the maximum tide level, the upper boundary of the adjacent brackish water zone of the brackish water interaction zone is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0020] Based on the minimum tide level, the lower boundary of the adjacent brackish water zone of the brackish water interaction zone is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0021] Optionally, determining the upper boundary of the adjacent brackish water zone of the brackish water interaction zone based on the maximum tide level line, using the salinity-depth relationship model and the salinity-tidal current distance relationship model, specifically includes:

[0022] Obtain water depth data at multiple maximum tide points along the maximum tide line;

[0023] Obtain the distances between the reference points and each of the maximum tide points along the direction perpendicular to the tidal current;

[0024] Based on the water depth data of multiple maximum tide points, the salinity data of multiple maximum tide points are determined using the salinity-water depth relationship model.

[0025] Based on the salinity data of multiple maximum tide points, the salinity-tidal current distance relationship model is used to determine the distances between the reference point and each of the maximum tide points along the tidal current direction.

[0026] Based on the coordinates of the reference point, the distance between the reference point and each of the maximum tide points along the tidal current direction, and the distance between the reference point and each of the maximum tide points along the tidal current direction perpendicular to the tidal current direction, the coordinates of a plurality of maximum tide points are determined;

[0027] The curves fitted by multiple maximum tidal points are used as the upper boundary of the adjacent brackish water zone of the freshwater-brine interaction zone.

[0028] Optionally, determining the lower boundary of the adjacent saline zone of the brackish water interaction zone based on the minimum tidal level line, using the salinity-depth relationship model and the salinity-tidal current distance relationship model, specifically includes:

[0029] Obtain water depth data for multiple minimum tide points on the minimum tide line;

[0030] Obtain the distances between the reference points and each of the minimum tide points along the direction perpendicular to the tidal current;

[0031] Based on the water depth data of multiple minimum tide points, the salinity data of multiple minimum tide points are determined using the salinity-water depth relationship model.

[0032] Based on the salinity data of multiple minimum tide points, the salinity-tidal current distance relationship model is used to determine the distances between the reference point and each of the minimum tide points along the tidal current direction.

[0033] Based on the coordinates of the reference point, the distances between the reference point and each of the minimum tide points along the tidal current direction, and the distances between the reference point and each of the minimum tide points along the tidal current direction perpendicular to the tidal current direction, the coordinates of a plurality of minimum tide points are determined;

[0034] The curves fitted by multiple minimum tidal points are used as the lower boundary of the adjacent brackish water zone of the brackish water interaction zone.

[0035] A system for determining the brackish water interaction zone in estuarine wetlands includes:

[0036] The sampling point water depth data acquisition module is used to acquire water depth data from multiple sampling points in the area under study.

[0037] The sampling point salinity data acquisition module is used to acquire salinity data from multiple sampling points in the area under study.

[0038] The salinity-water depth relationship model construction module is used to construct a salinity-water depth relationship model based on water depth data and salinity data from multiple sampling points.

[0039] A reference point determination module is used to determine reference points in the area to be studied.

[0040] The first distance acquisition module is used to acquire the distances between the reference point and each of the sampling points along the current direction;

[0041] The salinity-tidal current distance relationship model construction module is used to construct a salinity-tidal current distance relationship model based on the distance between the reference point and each of the sampling points along the tidal current direction, as well as the salinity data of multiple sampling points.

[0042] The tidal data acquisition module is used to acquire tidal data in the area under study.

[0043] The boundary determination module is used to determine the boundary of the wetland brackish water interaction zone in the area to be studied based on the tidal data, using the salinity-water depth relationship model and the salinity-tidal current distance relationship model; the boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the upper boundary of the adjacent brackish water zone of the wetland brackish water interaction zone.

[0044] The module for determining the extent of the brackish water interaction zone in estuary wetlands is used to determine the extent of the brackish water interaction zone in the area to be studied based on the boundary of the brackish water interaction zone.

[0045] Optionally, both the salinity-water depth relationship model and the salinity-tidal current distance relationship model are S-shaped Logistic models.

[0046] Optionally, the boundary determination module specifically includes:

[0047] The tidal line determination unit is used to determine the maximum tidal line, minimum tidal line, and tidal wave line of the area under study based on the tidal data in the area under study.

[0048] A freshwater zone boundary determination unit is used to determine that the tidal wave line is the freshwater zone boundary of the brackish water interaction zone.

[0049] The unit for determining the upper boundary of the adjacent saline water zone is used to determine the upper boundary of the adjacent saline water zone of the brackish water interaction zone based on the maximum tide level line, the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0050] The unit for determining the lower boundary of the adjacent saline water zone is used to determine the lower boundary of the adjacent saline water zone of the brackish water interaction zone based on the minimum tide level line, the salinity-water depth relationship model, and the salinity-tidal current distance relationship model.

[0051] Optionally, the unit for determining the upper boundary of the adjacent saline water zone specifically includes:

[0052] The maximum tide point water depth data acquisition subunit is used to acquire water depth data of multiple maximum tide points on the maximum tide line;

[0053] The second distance acquisition subunit is used to acquire the distance between the reference point and each of the maximum tide points along the direction perpendicular to the tidal current.

[0054] The maximum tide point salinity data determination subunit is used to determine the salinity data of multiple maximum tide points based on the water depth data of multiple maximum tide points and using the salinity-water depth relationship model.

[0055] The third distance determination subunit is used to determine the distances between the reference point and each of the maximum tide points along the tidal current direction based on the salinity data of multiple maximum tide points and the salinity-tidal current distance relationship model.

[0056] The maximum tide point coordinate determination subunit is used to determine the coordinates of multiple maximum tide points based on the coordinates of the reference point, the distance between the reference point and each maximum tide point along the tidal current direction, and the distance between the reference point and each maximum tide point along the tidal current direction perpendicular to the tidal current direction.

[0057] The upper boundary determination sub-unit of the adjacent saline water zone is used to determine the upper boundary of the adjacent saline water zone of the brackish water interaction zone by fitting the curves of multiple maximum tidal points.

[0058] Optionally, the unit for determining the lower boundary of the adjacent saline water zone specifically includes:

[0059] The minimum tide level water depth data acquisition subunit is used to acquire water depth data of multiple minimum tide levels on the minimum tide line;

[0060] The fourth distance acquisition subunit is used to acquire the distances between the reference point and each of the minimum tide points along the direction perpendicular to the tidal current.

[0061] The minimum tide point salinity data determination subunit is used to determine the salinity data of multiple minimum tide points based on the water depth data of multiple minimum tide points and using the salinity-water depth relationship model.

[0062] The fifth distance determination subunit is used to determine the distances between the reference point and each of the minimum tide points along the tidal current direction based on the salinity data of multiple minimum tide points and the salinity-tidal current distance relationship model.

[0063] The coordinate determination subunit of the minimum tide point is used to determine the coordinates of multiple minimum tide points based on the coordinates of the reference point, the distance between the reference point and each minimum tide point along the tidal current direction, and the distance between the reference point and each minimum tide point along the tidal current direction perpendicular to the tidal current direction.

[0064] The lower boundary determination sub-unit of the adjacent saline water zone is used to determine the lower boundary of the adjacent saline water zone of the brackish water interaction zone by fitting the curves of multiple minimum tidal points.

[0065] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0066] This invention provides a method and system for determining the brackish water interaction zone in an estuarine wetland. The method includes: acquiring water depth data from multiple sampling points in the area to be studied; acquiring salinity data from multiple sampling points in the area to be studied; constructing a salinity-water depth relationship model based on the water depth and salinity data from multiple sampling points; determining a reference point in the area to be studied; acquiring the distances between the reference point and each sampling point along the tidal current direction; constructing a salinity-tidal current distance relationship model based on the distances between the reference point and each sampling point along the tidal current direction and the salinity data from multiple sampling points; acquiring tidal data in the area to be studied; determining the boundary of the brackish water interaction zone in the area to be studied using the salinity-water depth relationship model and the salinity-tidal current distance relationship model based on the tidal data; the boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the upper boundary of the adjacent brackish water zone; and determining the extent of the brackish water interaction zone in the area to be studied based on the boundary of the brackish water interaction zone. This invention, by constructing a salinity-water depth relationship model and a salinity-tidal current distance relationship model, can determine the dynamic boundary of the brackish water interaction zone in estuary wetlands, thereby improving the accuracy of determining the extent of the brackish water interaction zone in estuary wetlands. Attached Figure Description

[0067] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 This is a schematic diagram of the dynamic boundary of the brackish water interaction zone in the prior art;

[0069] Figure 2 This is a flowchart illustrating the method for determining the brackish water interaction zone in estuary wetlands according to an embodiment of the present invention.

[0070] Figure 3 This is a diagram showing the layout of sampling points at the Yellow River Delta estuary in an embodiment of the present invention.

[0071] Figure 4 is a schematic diagram showing the variation of river water salinity in the Yellow River Delta estuary area with water depth in the study area, water depth in the brackish water interaction zone, and distance of the brackish water interaction zone from the reference point in an embodiment of the present invention; Figure 4(a) is a schematic diagram showing the variation of river water salinity in the Yellow River Delta estuary area with water depth in the study area in an embodiment of the present invention; Figure 4(b) is a schematic diagram showing the variation of river water salinity in the Yellow River Delta estuary area with water depth in the brackish water interaction zone in an embodiment of the present invention; Figure 4(c) is a schematic diagram showing the variation of river water salinity in the Yellow River Delta estuary area with distance of the brackish water interaction zone from the reference point in an embodiment of the present invention.

[0072] Figure 5 This is a schematic diagram of the spatial distribution of salinity in the Yellow River Delta estuary wetlands, as described in this embodiment of the invention.

[0073] Figure 6 This is a schematic diagram of the tidal changes in Dongying Port, Yellow River Delta throughout 2018, as described in this embodiment of the invention.

[0074] Figure 7 This is a schematic diagram illustrating the changes in salinity of river water in the brackish water interaction zone at the highest and lowest tide levels in an embodiment of the present invention.

[0075] Figure 8 This is a schematic diagram of the boundary of the brackish water interaction zone of the estuary wetland outside the river channel in an embodiment of the present invention;

[0076] Figure 9 is a schematic diagram of the distribution and dynamic boundary range of the brackish water interaction zone of the Yellow River estuary wetland in an embodiment of the present invention; Figure 9(a) is a schematic diagram of the distribution range of the brackish water interaction zone of the Yellow River estuary wetland in an embodiment of the present invention; Figure 9(b) is a schematic diagram of the boundary of the brackish water interaction zone of the Yellow River estuary wetland at the highest tide level in an embodiment of the present invention; Figure 9(c) is a schematic diagram of the boundary of the brackish water interaction zone of the Yellow River estuary wetland at the lowest tide level in an embodiment of the present invention. Detailed Implementation

[0077] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0078] The purpose of this invention is to provide a method and system for determining the brackish water interaction zone of estuary wetlands, which can determine the dynamic boundary of the brackish water interaction zone of estuary wetlands and improve the accuracy of determining the range of the brackish water interaction zone of estuary wetlands.

[0079] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0080] like Figure 2 This invention provides a method for determining the brackish water interaction zone in estuary wetlands, comprising:

[0081] Step 201: Obtain water depth data from multiple sampling points in the area to be studied;

[0082] Step 202: Obtain salinity data from multiple sampling points in the area to be studied;

[0083] Step 203: Construct a salinity-water depth relationship model based on water depth data and salinity data from multiple sampling points;

[0084] Step 204: Determine reference points in the area to be studied;

[0085] Step 205: Obtain the distances between the reference point and each sampling point along the power flow direction;

[0086] Step 206: Based on the distances between the reference point and each sampling point along the tidal current direction, and the salinity data of multiple sampling points, construct a salinity-tidal current distance relationship model;

[0087] Step 207: Obtain tidal data in the area to be studied;

[0088] Step 208: Based on tidal data, use the salinity-water depth relationship model and the salinity-tidal distance relationship model to determine the boundary of the wetland brackish water interaction zone in the area to be studied; the boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the upper boundary of the adjacent brackish water zone of the wetland brackish water interaction zone.

[0089] Step 209: Determine the extent of the brackish water interaction zone of the estuary wetland in the area to be studied based on the boundary of the brackish water interaction zone of the wetland.

[0090] Among them, the salinity-water depth relationship model and the salinity-tidal current distance relationship model are both S-shaped Logistic models.

[0091] Step 208 specifically includes:

[0092] Based on the tidal data in the area to be studied, determine the maximum tidal level line, minimum tidal level line, and tidal wave line of the area to be studied;

[0093] The tidal wave line is determined to be the boundary of the adjacent freshwater zone in the brackish water interaction zone;

[0094] Based on the maximum tide level, the upper boundary of the adjacent brackish water zone in the brackish water interaction zone is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0095] Based on the minimum tide level, the lower boundary of the adjacent brackish water zone in the brackish water interaction zone is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0096] Specifically, based on the maximum tide level, the upper boundary of the adjacent brackish water zone in the brackish water interaction zone is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model. This includes:

[0097] Obtain water depth data at multiple maximum tide points along the maximum tide line;

[0098] Obtain the distances from the reference points to each maximum tide point along the direction perpendicular to the tidal current;

[0099] Based on the water depth data of multiple maximum tide points, the salinity data of multiple maximum tide points were determined using a salinity-water depth relationship model.

[0100] Based on the salinity data of multiple maximum tide points, the distances between the reference points and each maximum tide point along the tidal current direction are determined using the salinity-tidal current distance relationship model.

[0101] Based on the coordinates of the reference point, the distance between the reference point and each maximum tide point along the tidal current direction, and the distance between the reference point and each maximum tide point along the tidal current direction perpendicular to the tidal current direction, the coordinates of multiple maximum tide points are determined.

[0102] The curves fitted by multiple maximum tidal points are used as the upper boundary of the adjacent brackish water zone of the freshwater-brine interaction zone.

[0103] Specifically, based on the minimum tidal level, the lower boundary of the adjacent brackish water zone in the brackish water interaction zone is determined using the salinity-depth relationship model and the salinity-tidal current distance relationship model. This includes:

[0104] Obtain water depth data at multiple minimum tide points along the minimum tide line;

[0105] Obtain the distances from the reference point to each minimum tide point along the direction perpendicular to the tidal current;

[0106] Based on the water depth data of multiple minimum tide points, the salinity data of multiple minimum tide points were determined using a salinity-water depth relationship model.

[0107] Based on the salinity data of multiple minimum tide points, the distances between the reference point and each minimum tide point along the tidal current direction are determined using the salinity-tidal current distance relationship model.

[0108] Based on the coordinates of the reference point, the distance between the reference point and each minimum tide point along the tidal current direction, and the distance between the reference point and each minimum tide point along the tidal current direction perpendicular to the tidal current direction, the coordinates of multiple minimum tide points are determined.

[0109] The curve fitted by multiple minimum tidal points is used as the lower boundary of the adjacent brackish water zone of the brackish water interaction zone.

[0110] The dynamic boundary of the brackish water interaction zone is determined using the following steps:

[0111] (1) Based on the salinity analysis results of surface water monitoring sampling points in the field, the spatial pattern of surface water salinity distribution in the study area was constructed using the natural neighbor interpolation model.

[0112] (2) Based on the monitoring data of surface salinity of rivers, a salinity-depth model of river water in the brackish water interaction zone was constructed. The relationship between the salinity of river water in the brackish water interaction zone and the distance to the reference point was established with the Xintan Floating Bridge as the reference point.

[0113] (3) Based on the tidal data with a period of 1 year, determine the maximum tidal level, minimum tidal level, and mean high tide level of the Yellow River Delta estuary. By constructing a salinity-depth model of the river in the brackish water interaction zone, simulate the boundary and range of the river's brackish water interaction zone at the maximum and minimum tidal levels.

[0114] (4) Combine the geomorphological elevation data of the study area to determine the seawater inundation range of the estuarine wetland on land at the maximum and minimum tide levels, and obtain the boundary and range of the brackish water interaction zone of the wetland on land.

[0115] (5) Overlay the freshwater and saltwater interaction zones of the river and wetland on land to construct the dynamic boundary and range of the freshwater and saltwater interaction zone of the Yellow River Delta estuary wetland.

[0116] Surface water sampling point layout:

[0117] To obtain information on surface water salinity, a total of 191 surface water monitoring sampling points were set up in the Yellow River Delta estuary area. Figure 3 The study area included 23 nearshore sampling points, 33 river sampling points, and 135 surface water sampling points in wetlands outside river channels. Sampling was conducted in July 2018 and June 2019, and the salinity of the 0-20cm water samples was analyzed in-situ using a DDBJ-350 conductivity meter (Shanghai Instrument & Electronics Scientific Instruments Co., Ltd.). Based on the surface water salinity analysis results, the study area was determined to be approximately 685.92 km². 2 It covers the freshwater area, brackish water interaction area and saline water area of ​​the Yellow River Delta estuary wetland.

[0118] Natural neighbor interpolation:

[0119] Natural neighbor interpolation is an interpolation method based on Delaunay triangulation and Voronoi diagrams. It calculates the interpolation result of a point based on the contribution rate of each natural neighbor to the point to be interpolated. Assume that point x has M natural neighbors, namely p1, p2, ..., p... MThe formula for natural neighbor interpolation is as follows:

[0120]

[0121] Where f(x) is the interpolation value of the point x to be interpolated; f(p i ) is a natural neighbor p i The value at; w i Represents the natural neighbor p i The weighting coefficient.

[0122] W i Determined by the following formula:

[0123]

[0124] Among them, a i Let a(x) be the area of ​​the Thiessen polygon containing the sample point involved in the interpolation, and let a(x) be the area of ​​the Thiessen polygon containing the point x to be interpolated. i ∩a(x) represents the area where the two intersect.

[0125] Geomorphological elevation data and tidal monitoring data:

[0126] Based on aerial elevation DEM (2011-2016) data of the eastern Yellow River Delta provided by the Shandong Provincial Bureau of Surveying and Mapping, merging, extraction, and geometric correction were performed to obtain an elevation map of the Yellow River Estuary wetlands. Tidal variations in the Yellow River Delta were measured using tidal monitoring data from Dongying Port throughout 2018, with a monitoring frequency of once per hour.

[0127] The sea surface elevation was calculated using Dongying Port tide data to determine the extent of land submerged at different tide levels. Current topographic maps in my country use the 1985 Yellow Sea Elevation Datum as the reference surface, the Dongying Port tide datum as the theoretical depth datum (0.90m below local sea level), and the Yellow Sea Elevation Datum is 0.397m high. The sea surface elevation at the corresponding tide levels was then calculated.

[0128] Results and Analysis:

[0129] Spatial distribution of salinity in the Yellow River Delta estuary wetlands:

[0130] As shown in Figure 4, (in Figure 4, 1.31E8 is scientific notation, representing 1.13 x 10⁸) 8The salinity of the Yellow River Delta estuary wetlands ranges from 0.40 to 26.67 g / L. Specifically, the salinity of the river itself (from Xintan Floating Bridge to the Yellow River-Blue River boundary) ranges from 0.48 to 16.80 g / L, with an average of 1.24 ± 3.06 g / L. At a depth of 6 meters, the salinity reaches 26.67 g / L. Upstream from Xintan Floating Bridge, the salinity of the surface water decreases only slightly, reaching approximately 0.38 g / L at Jianlin Floating Bridge, classifying it as a freshwater wetland. The salinity of the wetlands outside the river channel ranges from 0.40 to 18.30 g / L, with an average of 11.20 ± 7.61 g / L. The surface salinity of the Bohai Sea near the Yellow River estuary at depths of 6-16m varies little, with a salinity range of 26.67-29.17 g / L and an average of 27.92 ± 0.64 g / L.

[0131] The hydrodynamic processes of rivers in the estuary region are complex due to the influence of ocean tides. Studies have shown that the tidal boundary and current boundary of the Yellow River channel are located 20 km and 10 km from Lanmensha, respectively {Chen Zhangrong, 1988#208}. This study selected the location of the Xintan Floating Bridge (119°09′25.4551″E, 37°45′35.9317″N, salinity 0.48 g / L), 17.04 km from Lanmensha, as a reference point to analyze the relationship between surface salinity and water depth in the brackish water interaction zone up to a depth of 6 m. Using sampling and analysis data from 2018, a salinity-depth model of the river in the brackish water interaction zone was constructed. The model analysis results show that the variation of salinity with water depth in the brackish water interaction zone (water from Lanmensha to a depth of 6 m) conforms to the S-shaped Logistic model (R... 2 =0.98), the water depth at the barrier sandbar is relatively shallow at 1.25m, increasing to 3.8m towards the sea with a salinity of 0.60g / L. At a depth of 6m, the salinity increases to 26.67g / L. According to the model calculation, the freshwater interface (salinity 0.50g / L) in the brackish water interaction zone of the Yellow River estuary occurs at a depth of 3.90m, and the saline interface (salinity 18.00g / L) occurs at a depth of 5.51m. Therefore, the water depth range of the brackish water interaction zone in the Yellow River channel is 3.90-5.51m. To verify the accuracy of the model simulation, measured data from 2019 were used for validation, based on the coefficient of determination (R²). 2 Based on the results of (=0.99) and root mean square error (0.52), the simulation effect is accurate and highly reliable.

[0132] In the brackish water transition zone, river salinity increases extremely rapidly with distance, and its variation pattern conforms to the S-shaped Logistic model (R²). 2=0.99), the salinity of the river water is 0.48 g / L at the Lanmensha location and 16.80 g / L at the yellow-blue water boundary, with a distance of approximately 2.10 km between the two. Based on the formula, the freshwater and saline water interfaces in the Yellow River estuary are located 18.08 km and 19.27 km from the Xintan Floating Bridge, respectively, which means the width of the freshwater-saline water interaction zone in the Yellow River channel is approximately 1.19 km.

[0133] The salinity of the terrestrial wetlands outside the Yellow River channel varies considerably (average 11.20±7.61 g / L). Freshwater wetlands are relatively small in distribution, mainly consisting of saline water areas and brackish water transition zones. The salinity of surface water shows a trend of gradually increasing from the Yellow River channel to the nearshore area.

[0134] The spatial pattern of wetland salinity distribution in the study area was constructed using ArcGIS through natural neighbor interpolation. Figure 5 Analysis results indicate that the freshwater wetlands of the Yellow River Delta estuary are mainly distributed along the current Yellow River channel and floodplains, as well as oxbow lakes formed by the Yellow River's course changes, with a total area of ​​approximately 16.06 km². 2 This area accounts for only 2.34% of the study area. The brackish water zone is located outside the freshwater zone to the upper part of the intertidal zone, including the former course of the Yellow River and scattered irrigation areas, with a total area of ​​approximately 295.66 km². 2 This accounts for 43.11% of the study area. The saline zone is mainly distributed in the middle and lower intertidal zone and the subtidal zone with a depth of less than 6 meters. It also includes salt ponds within the study area, covering an area of ​​approximately 374.20 km². 2 This accounts for 54.55% of the study area.

[0135] Boundary extent of the brackish water interaction zone in the Yellow River Delta estuary wetlands:

[0136] Salinity variations in the Yellow River Delta estuary wetlands are primarily controlled by tidal level changes. This study utilized 2018 annual tidal level monitoring data from Dongying Port in the Yellow River Delta. Figure 6 Analysis was conducted. Results showed that the highest tide level of the year was 177 cm, occurring at 23:00 on July 14th; the lowest tide level of the year was 8 cm, occurring at 21:00 on January 3rd; and the tide level on July 1st, at the sampling time in the brackish water interaction zone (10:00-11:00), was 71 cm. Based on the water depth at each sampling point, water depth data for the highest and lowest tide levels were obtained. The salinity data for each sampling point at the highest and lowest tide levels was simulated using a salinity-depth model of the river in the brackish water interaction zone. Analysis of the distance relationship between the river salinity in the brackish water interaction zone and the reference point at the highest and lowest tide levels showed that… Figure 7At the highest tide, the freshwater and saltwater interfaces in the brackish water interaction zone were located 17.68 km and 18.21 km from the Xintan Floating Bridge, respectively, with a width of only 0.53 km. At the lowest tide, the freshwater and saltwater interfaces were located 18.26 km and 19.99 km from the Xintan Floating Bridge, respectively, with a width of 1.73 km. This indicates that during ocean tidal rise, the compression and lifting effect of seawater on river freshwater gradually intensifies, leading to a gradual decrease in the width of the brackish water interaction zone in the Yellow River Delta estuary wetlands. The zone's width ranges from 0.53 km to 1.73 km. Simultaneously, the boundaries of the brackish water interaction zone shift inland along the river, with the maximum shifts of the freshwater and saltwater interfaces being 0.58 km and 1.78 km, respectively.

[0137] The land portion of the Yellow River estuary wetlands outside the river channel is mainly composed of saline water areas and brackish water transition zones, with very little freshwater distribution, consisting only of oxbow lakes formed by the Yellow River's course changes. Figure 5 Therefore, this study focuses on the dynamic boundary of the brackish water interaction zone in the terrestrial part of the riverine wetland, analyzing the brackish water interface that is periodically submerged due to tidal fluctuations. Based on aerial elevation DEM (2011-2016) data of the eastern Yellow River Delta provided by the Shandong Provincial Bureau of Surveying and Mapping, an elevation map of the Yellow River Estuary wetland was drawn after merging, extraction, and geometric correction. The water surface elevation at corresponding tidal levels was obtained through conversion, thus yielding the seawater boundary line and its submerged range at the highest tide level (177cm), average high tide level (130cm), lowest tide level (8cm), and the tide level (71cm) during the sampling period in the brackish water interaction zone. Figure 8 ).

[0138] To obtain as much surface water salinity data as possible towards the sea, sampling of the land portion outside the river channel was conducted during low tide. Analysis of land water samples from 2018 and 2019 showed that the salinity of surface water near the waterline was greater than 20.00 g / L (range 20.06 g / L-23.55 g / L), indicating that the area submerged by seawater was a saline zone. Therefore, the highest tide level (177 cm) waterline was used as the upper boundary of the saline lateral movement boundary of the freshwater-saltwater interaction zone. Where a seawall was present, the seawall was used as the upper boundary of the saline lateral movement boundary of the freshwater-saltwater interaction zone. Further analysis revealed that the 18.00 g / L salinity isoplethora of the land portion of the wetland outside the river channel was within the 71 cm tide level waterline at the time of sampling. Figure 8The 71cm tide level falls between the average high tide level (130cm) and the lowest tide level (8cm). This area is in the tidal range daily on average. Therefore, even at the lowest tide level, the surface water towards the sea along the 18g / L salinity isoline is still above 18g / L due to the influence of seawater retained on the surface. Monitoring results show that when the tide level is below 71cm, the average salinity near the 18g / L isoline is 17.81±0.41g / L. Therefore, the 18g / L isoline is used as the lower boundary of the saline water lateral movement boundary in the brackish water interaction zone. Due to the influence of topography, the range of the saline water lateral movement boundary in the brackish water interaction zone varies considerably in the terrestrial part of the wetland outside the river channel. The dynamic boundary of the study area ranges from 0.28 to 4.27 km, with an average of 1.59 ± 0.88 km. Specifically, the dynamic boundary in the northern part of the study area ranges from 0.31 to 3.01 km, with an average of 1.71 ± 0.72 km, while the dynamic boundary in the southern part ranges from 0.62 to 4.27 km, with an average of 1.55 ± 0.86 km. Due to the influence of the dike, the dynamic boundary in the eastern part of the study area fluctuates the most, ranging from 0.28 to 3.46 km, with an average of 1.55 ± 1.06 km.

[0139] Dynamic boundary of the brackish water interaction zone in the Yellow River Delta estuary wetlands:

[0140] Using ArcGIS, the saline, freshwater, and brackish water transition zones under the conditions of lowest and highest tide levels in the study area were superimposed to obtain the dynamic boundary of the brackish water transition zone (Figure 9). The total area of ​​the study area is approximately 685.92 km². 2 Of which, the land area is 391.05 km². 2 The sea area is 294.87 km². 2 These account for 57.01% and 42.99% of the study area, respectively. If the area of ​​the saline water zone is included, the Yellow River Delta estuary wetland has the largest saline water zone, approximately 381.16–511.64 km². 2 This area accounts for 55.57%-74.59% of the study area. Within the terrestrial area, the brackish water interaction zone has the largest area (148.84-289.64 km²). 2 Saline-alkali land, accounting for 38.06%-74.07% of the land area, is mainly distributed in the land areas outside the Yellow River channel that are not covered by seawater at the highest tide level. The saline-alkali land area ranges from 86.28 to 216.77 km². 2 It accounts for 22.06%-55.43% of the land area. Freshwater areas are the smallest (approximately 15.12-25.44 km²). 2 These saline-alkali landforms, accounting for only 3.87%-6.51% of the land area of ​​the study region, are mainly distributed within the Yellow River channel and oxbow lakes formed by the Yellow River's course changes. Further analysis revealed that the dynamic boundary of the freshwater-saline water interaction zone in the study region is relatively large, with a total area of ​​approximately 140.80 km². 2(Covering 36.01% of the land area), with approximately 92.68% located on the saltwater side and only 7.32% on the freshwater side. The dynamic boundary on the freshwater side of the brackish water interaction zone is mainly due to the difference in the backwater effect of seawater on the freshwater in the river channel during tidal cycles, causing the brackish water interface to move. This also affects the change in the width of the river surface, resulting in the periodic transition between the freshwater and brackish water interfaces. The formation of the dynamic boundary on the saltwater side of the brackish water interaction zone is the result of the combined effects of tidal forces and land topography. The land elevation in the study area is relatively low (2-3m near the coast), with a flat terrain and an average slope of 1‰-1.5‰. The area of ​​land periodically covered by seawater during tidal cycles is relatively large; therefore, the dynamic range of the brackish water interaction zone boundary mainly occurs on the saltwater side. Due to the obstruction of dikes, the dynamic boundary range of the brackish water interaction zone in the southeast is irregularly distributed.

[0141] Furthermore, the present invention also provides a system for determining the brackish water interaction zone of estuary wetlands, comprising:

[0142] The sampling point water depth data acquisition module is used to acquire water depth data from multiple sampling points in the area under study.

[0143] The sampling point salinity data acquisition module is used to acquire salinity data from multiple sampling points in the area under study.

[0144] The salinity-water depth relationship model construction module is used to construct a salinity-water depth relationship model based on water depth data and salinity data from multiple sampling points.

[0145] The reference point determination module is used to determine reference points in the area to be studied.

[0146] The first distance acquisition module is used to acquire the distances between the reference point and each sampling point along the power flow direction;

[0147] The salinity-tidal current distance relationship model construction module is used to construct a salinity-tidal current distance relationship model based on the distance between the reference point and each sampling point along the tidal current direction, as well as the salinity data of multiple sampling points.

[0148] The tidal data acquisition module is used to acquire tidal data in the area under study.

[0149] The boundary determination module is used to determine the boundary of the wetland brackish water interaction zone in the study area based on tidal data, using the salinity-water depth relationship model and the salinity-tidal distance relationship model. The boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the upper boundary of the adjacent brackish water zone.

[0150] The module for determining the extent of the brackish water interaction zone in estuary wetlands is used to determine the extent of the brackish water interaction zone in the area to be studied based on the boundary of the brackish water interaction zone.

[0151] Specifically, both the salinity-water depth relationship model and the salinity-tidal current distance relationship model are S-shaped Logistic models.

[0152] The boundary determination module specifically includes:

[0153] The tidal line determination unit is used to determine the maximum tidal line, minimum tidal line, and tidal wave line of the area under study based on the tidal data in the area under study.

[0154] The adjacent freshwater zone boundary determination unit is used to determine the boundary of the adjacent freshwater zone where the tidal wave line is a brackish water interaction zone.

[0155] The upper boundary determination unit of the adjacent saline water zone is used to determine the upper boundary of the adjacent saline water zone in the brackish water interaction zone based on the maximum tide level line, using the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0156] The lower boundary determination unit for the adjacent saline water zone is used to determine the lower boundary of the adjacent saline water zone in the brackish water interaction zone based on the minimum tide level line, using the salinity-water depth relationship model and the salinity-tidal current distance relationship model.

[0157] Specifically, the unit defining the upper boundary of the adjacent saline water zone includes:

[0158] The maximum tide point water depth data acquisition subunit is used to acquire water depth data of multiple maximum tide points on the maximum tide line;

[0159] The second distance acquisition sub-unit is used to acquire the distance between the reference point and each maximum tide point along the direction perpendicular to the tidal current.

[0160] The maximum tide point salinity data determination subunit is used to determine the salinity data of multiple maximum tide points based on the water depth data of multiple maximum tide points and using the salinity-water depth relationship model.

[0161] The third distance determination subunit is used to determine the distance between the reference point and each maximum tide point along the tidal current direction based on the salinity data of multiple maximum tide points and the salinity-tidal current distance relationship model.

[0162] The maximum tide point coordinate determination subunit is used to determine the coordinates of multiple maximum tide points based on the coordinates of a reference point, the distance between the reference point and each maximum tide point along the tidal current direction, and the distance between the reference point and each maximum tide point along the tidal current direction perpendicular to the tidal current direction.

[0163] The upper boundary determination sub-unit of the adjacent saline water zone is used to fit the curve of multiple maximum tidal points as the upper boundary of the adjacent saline water zone in the brackish water interaction area.

[0164] Specifically, the unit for determining the lower boundary of the adjacent saline water zone includes:

[0165] The minimum tide level water depth data acquisition subunit is used to acquire water depth data of multiple minimum tide levels along the minimum tide line;

[0166] The fourth distance acquisition sub-unit is used to acquire the distance between the reference point and each minimum tide point along the direction perpendicular to the tidal current.

[0167] The minimum tide point salinity data determination subunit is used to determine the salinity data of multiple minimum tide points based on the water depth data of multiple minimum tide points and using the salinity-water depth relationship model.

[0168] The fifth distance determination subunit is used to determine the distances between the reference point and each minimum tide point along the tidal current direction based on the salinity data of multiple minimum tide points and the salinity-tidal current distance relationship model.

[0169] The coordinate determination subunit of the minimum tide point is used to determine the coordinates of multiple minimum tide points based on the coordinates of a reference point, the distance between the reference point and each minimum tide point along the tidal current direction, and the distance between the reference point and each minimum tide point along the tidal current direction perpendicular to the tidal current direction.

[0170] The lower boundary determination sub-unit of the adjacent saline water zone is used to fit the curve of multiple minimum tidal points as the lower boundary of the adjacent saline water zone in the brackish water interaction area.

[0171] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0172] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for determining the brackish water interaction zone in an estuary wetland, characterized in that, The method includes: Acquire water depth data from multiple sampling points in the area to be studied; Acquire salinity data from multiple sampling points in the area under study; A salinity-water depth relationship model was constructed based on water depth data and salinity data from multiple sampling points. Determine reference points in the area to be studied; Obtain the distances between the reference point and each of the sampling points along the current direction; Based on the distances between the reference points and each of the sampling points along the tidal current direction, and the salinity data of multiple sampling points, a salinity-tidal current distance relationship model is constructed. Acquire tidal data for the area under study; Based on the tidal data, the boundary of the wetland brackish water interaction zone in the study area is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model. The boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the lower boundary of the adjacent brackish water zone. Based on the boundary of the brackish water interaction zone of the wetland, the extent of the brackish water interaction zone of the estuary wetland in the area to be studied is determined. The step of determining the boundary of the brackish water interaction zone in the study area based on the tidal data, using the salinity-water depth relationship model and the salinity-tidal current distance relationship model, specifically includes: Based on the tidal data in the area under study, determine the maximum tidal level line, minimum tidal level line, and tidal wave line of the area under study; The tidal wave line is defined as the boundary of the adjacent freshwater zone of the brackish water interaction zone; When there is a sea dike, the sea dike is used as the upper boundary of the adjacent brackish water zone of the brackish water interaction zone. When there is no sea dike, the upper boundary of the adjacent brackish water zone of the brackish water interaction zone is determined according to the maximum tide line, using the salinity-water depth relationship model and the salinity-tidal current distance relationship model. Based on the minimum tide level, the lower boundary of the adjacent brackish water zone of the brackish water interaction zone is determined using the salinity-water depth relationship model and the salinity-tidal current distance relationship model. Based on the maximum tide level, the upper boundary of the adjacent brackish water zone of the brackish water interaction zone is determined using the salinity-depth relationship model and the salinity-tidal current distance relationship model, specifically including: Obtain water depth data at multiple maximum tide points along the maximum tide line; Obtain the distances between the reference points and each of the maximum tide points along the direction perpendicular to the tidal current; Based on the water depth data of multiple maximum tide points, the salinity data of multiple maximum tide points are determined using the salinity-water depth relationship model. Based on the salinity data of multiple maximum tide points, the salinity-tidal current distance relationship model is used to determine the distances between the reference point and each of the maximum tide points along the tidal current direction. Based on the coordinates of the reference point, the distance between the reference point and each of the maximum tide points along the tidal current direction, and the distance between the reference point and each of the maximum tide points along the tidal current direction perpendicular to the tidal current direction, the coordinates of a plurality of maximum tide points are determined; The curves fitted by the multiple maximum tidal points are used as the upper boundary of the adjacent brackish water zone of the freshwater-brine interaction zone. Both the salinity-water depth relationship model and the salinity-tidal current distance relationship model are S-shaped Logistic models; The step of determining the lower boundary of the adjacent brackish water zone of the brackish water interaction zone based on the minimum tide level line, using the salinity-depth relationship model and the salinity-tidal current distance relationship model, specifically includes: Obtain water depth data for multiple minimum tide points on the minimum tide line; Obtain the distances between the reference points and each of the minimum tide points along the direction perpendicular to the tidal current; Based on the water depth data of multiple minimum tide points, the salinity data of multiple minimum tide points are determined using the salinity-water depth relationship model. Based on the salinity data of multiple minimum tide points, the salinity-tidal current distance relationship model is used to determine the distances between the reference point and each of the minimum tide points along the tidal current direction. Based on the coordinates of the reference point, the distances between the reference point and each of the minimum tide points along the tidal current direction, and the distances between the reference point and each of the minimum tide points along the tidal current direction perpendicular to the tidal current direction, the coordinates of a plurality of minimum tide points are determined; The curves fitted by multiple minimum tidal points are used as the lower boundary of the adjacent brackish water zone of the brackish water interaction zone.

2. A system for determining the brackish water interaction zone in estuary wetlands, characterized in that, The system for implementing the method for determining the brackish water interaction zone of an estuary wetland as described in claim 1, comprises: The sampling point water depth data acquisition module is used to acquire water depth data from multiple sampling points in the area under study. The sampling point salinity data acquisition module is used to acquire salinity data from multiple sampling points in the area under study. The salinity-water depth relationship model construction module is used to construct a salinity-water depth relationship model based on water depth data and salinity data from multiple sampling points. A reference point determination module is used to determine reference points in the area to be studied. The first distance acquisition module is used to acquire the distances between the reference point and each of the sampling points along the current direction; The salinity-tidal current distance relationship model construction module is used to construct a salinity-tidal current distance relationship model based on the distance between the reference point and each of the sampling points along the tidal current direction, as well as the salinity data of multiple sampling points. The tidal data acquisition module is used to acquire tidal data in the area under study. The boundary determination module is used to determine the boundary of the wetland brackish water interaction zone in the area to be studied based on the tidal data, using the salinity-water depth relationship model and the salinity-tidal current distance relationship model; the boundary includes the boundary of the adjacent freshwater zone, the upper boundary of the adjacent brackish water zone, and the lower boundary of the adjacent brackish water zone of the wetland brackish water interaction zone. The module for determining the extent of the brackish water interaction zone in estuary wetlands is used to determine the extent of the brackish water interaction zone in the area to be studied based on the boundary of the brackish water interaction zone. The boundary determination module specifically includes: The tidal line determination unit is used to determine the maximum tidal line, minimum tidal line, and tidal wave line of the area under study based on the tidal data in the area under study. A freshwater zone boundary determination unit is used to determine that the tidal wave line is the freshwater zone boundary of the brackish water interaction zone. The unit for determining the upper boundary of the adjacent saline water zone is used to determine the upper boundary of the adjacent saline water zone of the brackish water interaction zone based on the maximum tide level line, the salinity-water depth relationship model and the salinity-tidal current distance relationship model. The unit for determining the lower boundary of the adjacent saline water zone is used to determine the lower boundary of the adjacent saline water zone of the brackish water interaction zone based on the minimum tide level line, the salinity-water depth relationship model and the salinity-tidal current distance relationship model. The unit for determining the upper boundary of the adjacent saline water zone specifically includes: The maximum tide point water depth data acquisition subunit is used to acquire water depth data of multiple maximum tide points on the maximum tide line; The second distance acquisition subunit is used to acquire the distance between the reference point and each of the maximum tide points along the direction perpendicular to the tidal current. The maximum tide point salinity data determination subunit is used to determine the salinity data of multiple maximum tide points based on the water depth data of multiple maximum tide points and using the salinity-water depth relationship model. The third distance determination subunit is used to determine the distances between the reference point and each of the maximum tide points along the tidal current direction based on the salinity data of multiple maximum tide points and the salinity-tidal current distance relationship model. The maximum tide point coordinate determination subunit is used to determine the coordinates of multiple maximum tide points based on the coordinates of the reference point, the distance between the reference point and each maximum tide point along the tidal current direction, and the distance between the reference point and each maximum tide point along the tidal current direction perpendicular to the tidal current direction. The upper boundary determination sub-unit of the adjacent saline water zone is used to fit the curves of multiple maximum tidal points as the upper boundary of the adjacent saline water zone of the freshwater-saltwater interaction zone. Both the salinity-water depth relationship model and the salinity-tidal current distance relationship model are S-shaped Logistic models; The unit for determining the lower boundary of the adjacent saline water zone specifically includes: The minimum tide level water depth data acquisition subunit is used to acquire water depth data of multiple minimum tide levels on the minimum tide line; The fourth distance acquisition subunit is used to acquire the distances between the reference point and each of the minimum tide points along the direction perpendicular to the tidal current. The minimum tide point salinity data determination subunit is used to determine the salinity data of multiple minimum tide points based on the water depth data of multiple minimum tide points and using the salinity-water depth relationship model. The fifth distance determination subunit is used to determine the distances between the reference point and each of the minimum tide points along the tidal current direction based on the salinity data of multiple minimum tide points and the salinity-tidal current distance relationship model. The coordinate determination subunit of the minimum tide point is used to determine the coordinates of multiple minimum tide points based on the coordinates of the reference point, the distance between the reference point and each minimum tide point along the tidal current direction, and the distance between the reference point and each minimum tide point along the tidal current direction perpendicular to the tidal current direction. The lower boundary determination sub-unit of the adjacent saline water zone is used to determine the lower boundary of the adjacent saline water zone of the brackish water interaction zone by fitting the curves of multiple minimum tidal points.

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