Ecological calculation method for non-connected rivers

Abstract

The invention discloses a non-connected river ecological calculation method, and belongs to the field of river ecological calculation, and the method comprises the steps: simulating river environments in different connected states through constructing a multifunctional experiment water tank system, and collecting hydrodynamic force, water quality and biological multi-dimensional parameters; establishing a hydrodynamic force-water quality-water ecology coupling model to realize synchronous calculation of physical, chemical and biological processes; a non-connectivity index is innovatively proposed, and river non-connectivity features are quantified from four dimensions of longitudinal, transverse, vertical and time. According to the method, the defects of a traditional method in the aspects of dynamic water environment simulation, multi-dimensional non-connectivity representation and multi-process coupling are overcome, the transportation-retention process of the phosphorus element under the conditions of manual intervention and rainfall runoff can be accurately analyzed, and a reliable technical means is provided for ecological influence assessment of channel improvement engineering and river ecosystem management.

Description

Technical Field

[0001] This invention belongs to the field of river ecological computing, and in particular relates to a method for ecological computing of non-connected rivers. Background Technology

[0002] Currently, river ecological assessment methods are mostly focused on well-connected river systems, and studies on the transport and retention processes of nutrients such as phosphorus mainly rely on static water body experiments or simplified models. Existing technologies typically obtain water quality parameters through field monitoring or laboratory simulations and use single indicators (such as phosphorus concentration or suspended solids content) to assess river health. Some methods attempt to incorporate hydrodynamic conditions, but fail to effectively integrate biological processes and multidimensional non-connected characteristics. Furthermore, traditional models often ignore the asynchronous impact of human interventions (such as dams and channel hardening) on ​​material transport processes, resulting in limited accuracy and applicability of river ecological assessments in the context of climate change and intensified human activities.

[0003] However, existing technologies still have significant problems: First, there is a lack of systematic experimental simulations of phosphorus flux changes in dynamic water environments, making it difficult to quantify hydrodynamic-biological-sediment interactions; second, the multidimensional characteristics of disconnected rivers (longitudinal, lateral, vertical, and temporal disconnection) are not fully considered, making it impossible to accurately describe the decoupling phenomenon of material transport processes; third, existing models often treat physical, chemical, and biological parameters in isolation, failing to achieve multi-process coupled calculations, resulting in large biases when predicting the impact of human intervention and rainfall events on phosphorus retention. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for ecological computation of disconnected rivers, comprising:

[0005] The experimental flume simulated the river environment, and sampling points were set up in the actual river to collect water and sediment samples.

[0006] Based on the water and sediment samples, hydrodynamic parameters, water quality parameters, and biological parameters were measured.

[0007] Based on the hydrodynamic parameters, water quality parameters, and biological parameters, the transport flux and retention of phosphorus in the river are calculated.

[0008] Construct a coupled hydrodynamic-water quality-aquatic ecology model to integrate the mutual influences of physical, chemical and biological processes;

[0009] Based on the transport flux and retention of phosphorus, the disconnectivity index is calculated using the coupled model to analyze the material transport processes in the river ecosystem.

[0010] Optionally, the experimental water tank includes a water tank, a water supply system, a sample collection system, and a data recording system. The water tank is divided into multiple compartments by partitions to simulate connected and disconnected sections of a river.

[0011] The experimental water tank is equipped with an inlet, an outlet, and multiple sampling holes, and the water flow conditions are adjusted by a flow control valve.

[0012] Optionally, collecting water and sediment samples includes embedding pore water samplers at the inlet, bends, and outlet of the experimental water tank, and placing thermometers in the sediment and water;

[0013] Multiple sampling points were set up along the river section in the actual river to collect surface water samples and sediment samples.

[0014] Optionally, measuring hydrodynamic parameters includes using an acoustic Doppler current meter to measure velocity distribution and turbulence intensity, and analyzing boundary layer development;

[0015] Based on the velocity distribution and turbulence intensity, estimate the sediment suspension and interface elevation changes.

[0016] Optionally, measuring water quality parameters includes observing the diffusion flux of phosphorus at the sediment-water interface using thin-film diffusion gradient technology, and measuring the concentrations of total phosphorus, total dissolved phosphorus, total particulate phosphorus, and total suspended particulate matter.

[0017] Optionally, measuring biological parameters includes measuring biological activity using an online chlorophyll analyzer and combining it with data on benthic communities in sediments to analyze the impact of biosorption on phosphorus flux.

[0018] Optionally, the non-connectivity index is a dimensionless index calculated for water flow, total suspended particulate matter, total dissolved phosphorus and total particulate phosphorus respectively;

[0019] Based on the value of the non-connectivity index, the retention degree and transport amount of matter in the river channel are analyzed.

[0020] Optionally, the hydrodynamic-water quality-aquatic ecology coupled model simulates the transport and retention process of phosphorus in rivers by synchronously updating the physical, chemical and biological parameters in the water body, and analyzes the material transport characteristics under different artificial intervention conditions based on the non-connectivity index.

[0021] On the other hand, the present invention also provides an electronic device including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0022] On the other hand, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] This invention establishes a computational framework for the synchronous updating of physical, chemical, and biological processes by constructing a coupled hydrodynamic-water quality-aquatic ecology model, effectively solving the problem of isolated parameter processing in traditional methods. By designing an experimental flume system capable of simulating multi-connectivity states, it achieves precise measurement of phosphorus flux changes under dynamic water conditions, compensating for the limitations of static experiments. The innovatively proposed disconnectivity index quantifies the disconnectivity characteristics of rivers from four dimensions: longitudinal, lateral, vertical, and temporal, accurately characterizing the asynchronous nature of material transport processes under human intervention. This method significantly improves the prediction accuracy of phosphorus transport and retention processes under the dual influences of climate change and human activities, providing reliable technical support for the ecological impact assessment of projects such as waterway improvement, and overcoming the limitations of existing technologies in dynamic hydrological condition simulation and multi-dimensional disconnectivity analysis. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0026] Figure 1 This is a design diagram of the experimental apparatus according to an embodiment of the present invention;

[0027] Figure 2 This is a comparison diagram of cross-sectional flow velocities in an embodiment of the present invention;

[0028] Figure 3 This is a graph showing the change of TP concentration over time under different hydrodynamic conditions according to an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram showing the location of the Qingshuihe silt-trapping dam and sampling points according to an embodiment of the present invention;

[0030] Figure 5 This is a spatial variation diagram of TP, TDP, TPP, and TSS concentrations in an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram showing the daily retention amount and retention rate of phosphorus in the silt trap section (from 1# to 3#) according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram illustrating the material transport process between connected and disconnected rivers according to an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram of the non-connectivity index model according to an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram illustrating the calculation of the non-connectivity index model in an embodiment of the present invention;

[0035] Figure 10 This is a schematic diagram illustrating the variation of different material transport-retention processes with rainfall in different seasons according to an embodiment of the present invention;

[0036] Figure 11 This is a schematic diagram illustrating the changes in the non-connectivity index of different substances in different seasons according to an embodiment of the present invention;

[0037] Figure 12 This is a schematic diagram illustrating the relationship between the non-connectivity index and total phosphorus retention in an embodiment of the present invention. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0040] Example 1

[0041] This embodiment provides a method for ecological computation of non-connected rivers, including:

[0042] The experimental flume simulated the river environment, and sampling points were set up in the actual river to collect water and sediment samples.

[0043] Based on the water and sediment samples, hydrodynamic parameters, water quality parameters, and biological parameters were measured.

[0044] Based on the hydrodynamic parameters, water quality parameters, and biological parameters, the transport flux and retention of phosphorus in the river are calculated.

[0045] Construct a coupled hydrodynamic-water quality-aquatic ecology model to integrate the mutual influences of physical, chemical and biological processes;

[0046] Based on the transport flux and retention of phosphorus, the disconnectivity index is calculated using the coupled model to analyze the material transport processes in the river ecosystem.

[0047] Phosphorus flux research can be used to establish river water quality ecological models, providing theoretical basis and research tools for studying river ecosystems and addressing river blackening, odor, and eutrophication. Limited by the complex observation conditions in river channels and increasing human intervention, previous phosphorus flux research has focused on lakes and still water experiments, lacking studies on phosphorus flux in dynamic water environments. This is a key difference between river phosphorus flux research and lake phosphorus flux research. Studying phosphorus flux at the interface between river sediments and overlying water bodies is of great significance for the study of river ecosystems, which are influenced by hydrodynamic, sedimentary, water quality, and biological environments.

[0048] An indoor rotary flume experiment was conducted to investigate the effects of hydrodynamics, sediment, water quality, and organisms on phosphorus flux. The experimental setup consisted of four parts: a water tank, water supply, sample collection, and data recording. The water tank was constructed of plexiglass on all sides and bottom, with an outer diameter of 160 cm, a width of 100 cm, and a height of 50 cm. Inside the tank, three plexiglass partitions, each 130 cm long, 0.05 m wide, and 0.5 m high, divided the tank into four equal sections. An inlet and outlet were located on the left side of the tank, with flow control valves installed at both the inlet and outlet. Five × four circular openings were located on the right side of the tank, each fitted with a flow control valve. Total phosphorus concentrations (TPCs) of 0.5–0.7 mg / L were measured by collecting pore water samples. Using tap water as the overlying water, the TPC concentration was measured to be approximately 0.15 mg / L. Pore ​​water samplers were vertically embedded in the middle and bottom of the sediments at the inlet, bend, and outlet of the test section, and thermometers were installed in both the sediments and the water. The relationships between fine-grained sediment transport and phosphorus flux under dam hydrodynamic conditions were investigated; the relationship between biosorption in sediments and phosphorus flux; the relationship between channel hardening and phosphorus flux; and the relationship between sediment wet-dry history and phosphorus flux.

[0049] The experimental setup consists of four parts: a water tank, a water supply system, a sample collection system, and a data recording system.

[0050] The water tank is made of plexiglass on all sides and bottom. The outer dimensions of the tank are 160cm long, 100cm wide, and 50cm high. Inside the tank, three plexiglass partitions, each 130cm long, 0.05m wide, and 0.5m high, divide the tank into four equal parts. An inlet and outlet are located on the left side of the tank, with flow control valves installed at both the inlet and outlet. Five x four circular openings are provided on the right side of the tank, each for a flow control valve. See the attached dimensions for the tank dimensions. Figure 1 .

[0051] The experimental water tank is divided into four equal-volume parts (called compartments) by partitions. This design has two advantages:

[0052] (1) A waterway with a maximum effective length of 6m is formed by the staggered arrangement of partitions to simulate a river. (2) The four compartments of the water tank can be filled with sediments, benthic plants or microorganisms of different particle sizes to improve experimental efficiency.

[0053] Layered leachate outlets will be installed on the sidewalls of the water tank to collect samples of overlying water and pore water from the sediment layer. It is planned to install one outlet at the midpoint of the long side of the tank and four outlets at equal intervals along the short side, for a total of ten outlets. Each of these ten outlets will be equipped with an independent control valve for selective use. The location and spacing of the outlets will be determined based on the water volume and the tank material, with a designed spacing of no more than 0.1m, meaning at least five outlets in total.

[0054] The experimental methods specifically include:

[0055] Surface sediments from a river channel were collected and placed at the bottom of the two middle test sections of an experimental flume, then manually smoothed. The sediment thickness within the flume did not exceed half the flume's height, i.e., the sediment thickness ranged from 0 to 0.25 m. The distance between the surface of the overlying water and the top of the flume was not less than 0.05 m, i.e., the depth of the overlying water ranged from 0.2 to 0.45 m. The total internal volume of the flume was 0.725 m³ (minus the volume occupied by the partitions).

[0056] Pore ​​water samplers were installed vertically in the middle and at the bottom of the sediment at the inlet, bend, and outlet of the test section, and thermometers were installed in the sediment and water respectively.

[0057] After the water in the tank was filled to the experimental elevation, the circulation pump was started. The flow velocity distribution at a depth of 0.05 m from the sidewall and 20% of the water surface was measured using an ADV at flow velocities of 0.05 m / s and 0.25 m / s, respectively. The distribution of turbulence intensity and boundary layer development in the tank were analyzed.

[0058] (1) Hydrodynamic measurement parameters and observation scheme:

[0059] Advanced flow velocity (ADV) was used to measure the flow velocity at 0.05 m from the bottom and at 20% of the water surface. Four time series were measured: at 0.05 and 0.25 m / s, at 0.05 m above the mud surface, and at 20% of the water depth. Each time series was sampled at a frequency of 25 Hz for at least 330 seconds. The results were used for spectral analysis to calculate the velocity fluctuations within the flume.

[0060] (2) Sediment measurement parameters and observation scheme:

[0061] ADV was used to measure water turbidity and estimate sediment suspension. Changes in the elevation of the overlying water-sediment interface were recorded.

[0062] (3) Water quality measurement parameters and observation plan:

[0063] There are two methods: ① using soil pore water; ② using thin-film diffusion gradient technology (hereinafter referred to as DGT technology).

[0064] The diffusion model method is a method for calculating phosphorus diffusion flux at the sediment-water interface using Fick's first law. Thin-film diffusion gradient technology (DGT) is a high-resolution in-situ passive sampling technique established by Professor Davison in the UK in 1994, capable of obtaining in-situ spatial distribution information of available states such as free ions. Zhang et al. developed a ferrihydrite gel DGT using ferrihydrite as the diffusion layer binding phase, which was successfully applied to the profile distribution analysis of active phosphorus in sediment pore water. Subsequently, Ding et al. developed Zr-oxide DGT based on previous research, effectively increasing the DGT capacity and extending the monitoring results from a one-dimensional scale to a two-dimensional scale. This study uses Zr-oxide DGT for high-resolution observation of phosphorus at the sediment-water interface and combines it with the diffusion model method to quantitatively estimate the phosphorus diffusion flux in Hongfeng Lake sediments.

[0065] (4) Biometric parameters and observation scheme: an online chlorophyll analyzer was used;

[0066] (5) Dynamic water environment: The dynamic water environment is divided into low-speed (0.05m / s), medium-speed (0.1m / s) and high-speed (0.25m / s) flow environments.

[0067] First, a sediment sample (10 cm thick) was laid at the bottom of the test section of the water tank. Water was slowly poured in to the experimental elevation (35 cm depth). The flow rate of the water tank was set using a circulation pump. After the flow rate stabilized, water samples were collected at three sampling points: the water surface, the middle of the water body (both horizontally and vertically), the mud-water interface, the middle of the sediment (both horizontally and vertically), and the bottom of the sediment. The above sampling was repeated every 24 hours, for a total of two times.

[0068] Three flow rate experiments were completed, and a total of 135 samples were obtained.

[0069] (6) Artificial dams:

[0070] The artificial dam experiment is divided into two types: dam drainage and weir drainage, corresponding to the two states of fully open and partially open water-blocking devices.

[0071] First, a sediment sample (10cm thick) was laid at the bottom of the test section of the water tank. A water-blocking device was set up in front of the test section, and water was slowly poured in to the experimental elevation (water depth 35cm). The water-blocking device and the circulation pump were turned on. After the flow rate stabilized, water samples and surface soil samples were collected at three sampling points: the water surface, the middle of the water body, the mud-water interface, the middle of the sediment, and the bottom of the sediment. A total of 18 samples were collected to complete the two drainage experiments, with a total of 36 samples collected.

[0072] (7) Changes in humidity:

[0073] The wet-dry variation was divided into short-term and long-term variations. The short-term variation cycle was one day. First, a sediment sample (10 cm thick) was laid at the bottom of the test section of the flume. Water was slowly added to the experimental elevation (35 cm depth). Fifteen water samples were collected at three sampling points: the water surface, the middle of the water body (both horizontal and vertical centers), the mud-water interface, the middle of the sediment (both horizontal and vertical centers), and the bottom of the sediment. This sampling was repeated every four hours, twice, resulting in two batches of 30 samples. Then, the water was slowly drained to the mud-water interface. After settling, six water samples were collected at the middle and bottom of the sediment at the three sampling points, resulting in two batches of 12 samples. Finally, water was slowly added to the experimental elevation. After settling for eight hours, 15 water samples were collected at the three sampling points: the water surface, the middle of the water body (both horizontal and vertical centers), the mud-water interface, the middle of the sediment (both horizontal and vertical centers), and the bottom of the sediment.

[0074] The total phosphorus concentration was measured to be 0.5-0.7 mg / L by collecting pore water samples. Using tap water as the overlying water body, the total phosphorus concentration in the tap water was measured to be approximately 0.15 mg / L. Sediments and overlying water are expected to be sent for testing to measure the following parameters: (1) sediment particle size; (2) sediment water content; (3) sediment particle analysis; (4) sediment permeability coefficient; (5) water-soluble salts in sediments and water bodies; (6) water-soluble and acid-soluble sulfates in sediments and water samples; (7) total nitrogen in sediments and water samples; (8) ammonia nitrogen in sediments and water samples; (9) nitrite ammonia in sediments and water samples; (10) nitrate ammonia in sediments and water samples; (11) redox potential of sediments; (12) organic carbon in sediments and water samples; (13) organic matter in sediments and water samples; (14) organic phosphorus in sediments and water samples; (15) benthic community in sediments; (16) content of hydrolyzable metals in sediments.

[0075] This study investigates the relationship between the transport of fine-grained sediment and phosphorus flux under dam hydrodynamic conditions; the relationship between biosorption in sediments and phosphorus flux; the relationship between channel hardening and phosphorus flux; and the relationship between sediment wet-dry variation history and phosphorus flux.

[0076] like Figures 2-3 As shown, the changes in phosphorus concentration in the water with different hydrodynamic intensities were observed using a controlled experimental tank. Hydrodynamic intensity is represented by the intensity of water turbulence. Artificial structures were placed at the bottom of the tank to simulate the weakening of substrate hydrodynamics caused by benthic emergent plants. The experimental results showed that the hydrodynamic intensity of the group with benthic plants (Group A) was lower than that of the group without benthic plants (Group B).

[0077] The changes in the average total phosphorus concentration in the water at different times after the start of the experiment showed that, in the short term (within 5 hours of the experiment), hydrodynamic changes had little effect on the total phosphorus concentration. However, in the long term (after 5 hours of the experiment), hydrodynamic changes had a significant effect on the total phosphorus concentration (increasing by up to 3 times).

[0078] Phosphorus transport and retention processes in rivers under human intervention are a fundamental component of the material cycle in river ecosystems and a key indicator of their health. This study focuses on an artificially intervened section of a mountain river, including a natural section, a section with a check dam, and a hardened section. Four monitoring points were established in the river to study the spatial characteristics of total phosphorus, dissolved phosphorus, particulate phosphorus, and suspended solids transport and retention processes, and to evaluate phosphorus transport and retention under human intervention.

[0079] Next, sample collection and on-site observation were conducted. Four sampling points were set up along the Qingshui River section with the check dam, labeled 1#, 2#, 3#, and 4#. Point 1# was located 0.4 km upstream of the check dam in a natural river section; point 2# was located on the dam itself; point 3# was located downstream of the dam; and point 4# was located 1.4 km downstream of the dam. The sampling point locations are detailed below. Figure 4 The sampling period was from late April to mid-to-late August 2019. During rainfall, surface water samples were collected at four sampling points within 24 hours during and after rainfall. During non-rainfall periods, surface water samples were collected at the four sampling points every three days. All sampling points used 2.5 L plexiglass water samplers. A total of 104 water samples were collected during the observation period, with 26 samples collected from each sampling point.

[0080] After the water samples were brought back to the laboratory, total phosphorus (TP) was measured directly. Water samples filtered through a 0.45 μm glass fiber membrane were used to measure total dissolved phosphorus (TDP), and the membrane itself was used to measure total suspended particulate matter (TSS). Water samples were stored at 4°C for no more than 30 hours before analysis. TP, TDP, and TSS were analyzed using standard methods.

[0081] The daily phosphorus retention (MR) in the river section is calculated using Equation 1, and the daily retention rate (RP) is calculated using Equation 2.

[0082] (1)

[0083] (2)

[0084] Among them, M in It is the phosphorus flux in the inflow section of the river, M out This refers to the phosphorus flux in the outflow section, M. 1# M represents the phosphorus flux at sampling point #1, in t / d. R A positive value indicates that phosphorus is retained in that river section, MR A negative value indicates that phosphorus has flowed out of that section of the river.

[0085] Table 1

[0086]

[0087] The average concentrations and dispersion of TP, TPP, TDP, and TSS at each sampling point are shown in Table 1 and 2. Figure 5 It can be seen that the average concentrations of TP, TPP, and TSS downstream of the dam (3#) are significantly lower than those upstream of the dam (1#). The average concentration of TDP does not change significantly between 1# and 3#. The average concentrations of TP, TPP, and TSS upstream of the dam (2#) are the highest among all sampling points. The average concentrations of TP, TPP, and TSS downstream of the dam (3#) are about 50% of those upstream of the dam (2#). This indicates that the dam has a significant retention effect on sediment and particulate phosphorus, but no significant retention effect on dissolved phosphorus. The concentration changes of TP, TPP, and TSS from upstream (1#) to downstream (3#) show that the dam affects the transport-retention process of phosphorus in the longitudinal direction of the river. That is, the distribution of phosphorus concentration in the longitudinal direction of the river does not meet the concentration index change of continuous rivers, but is close to the concentration abrupt change model of discontinuous rivers. Looking at the proportion of TPP in TP at each sampling point, #2 has the largest proportion, #1 is slightly larger than #3, and #4 has the smallest proportion. From #1 to #3, the proportion of TPP in TP decreases by 0.9%, and from #3 to #4, the proportion of TPP in TP decreases by 21.4%. Looking at the proportion of TDP in TP at each sampling point, #2 has the smallest proportion, #1 is slightly smaller than #3, and #4 has the largest proportion. From #1 to #3, the proportion of TDP in TP increases by 0.9%, and from #3 to #4, the proportion of TPP in TP increases by 21.4%.

[0088] Table 2

[0089]

[0090] Using Equations 1 and 2, the daily retention (MR) and daily retention rate (RP) of TP, TPP, and TDP in river sections 1 through 3 were calculated. On average, 29.7% and 30% (5.54 kg and 4.87 kg respectively) of TP and TPP flowing into the check dam section from section 1 were retained within the check dam daily, while an average of 30% (0.28 kg) of TDP flowed out of the check dam daily. The absolute values ​​of the daily retention of TP and TPP were greater than those of TDP, but the absolute value of the daily retention rate of TDP was greater than that of TP and TPP. The calculation results show that 60% of the daily retention of TDP is positive, occurring entirely during non-rainy periods; 40% of TDP is negative, occurring entirely during rainy periods. 80% of the daily retention of TPP is positive, occurring during both rainy and non-rainy periods; 20% of TPP is negative, occurring entirely during rainy periods. As rainfall ends, the daily retention of TDP and TPP increases daily. The changes in TDP and TPP during rainfall periods are quite complex. Generally speaking, the greater the rainfall intensity, the lower the daily retention of TDP and TPP; the longer the rainfall duration, the lower the daily retention of TDP and TPP. Comparing the daily retention rates of TDP and TPP, rainfall events have a more significant impact on TDP.

[0091] Rainfall-runoff processes have a significant impact on phosphorus transport and retention in mountain rivers. The time interval, duration, and intensity of rainfall-runoff processes affect the particle size and phosphorus speciation of suspended particulate matter in rivers, thus determining the amount and distance of suspended particulate matter and phosphorus transported in the river channel. Figure 6 It can be seen that the retention of TP, TDP, and TPP by the dam is significantly affected by rainfall-runoff. Under no-rainfall conditions, the retention amounts of TP, TDP, and TPP at the dam section are all positive. However, statistical analysis of phosphorus retention and retention rate at the dam (1#-3#) during different rainfall events (see Table 3) reveals that the percentages of events with positive retention amounts of TP, TDP, and TPP at the dam are 63.6%, 9%, and 81.8%, respectively. This indicates that the rainfall-runoff process reduces the retention effect of the dam on TP, TDP, and TPP.

[0092] Silt traps have varying impacts on the transport-retention characteristics of TDP and TPP during different rainfall events. Rainfall generally leads to TDP release from the silt trap area (i.e., daily retention is less than zero). During periods of continuous rainfall (from July 16th to July 29th), TDP release initially increases and then decreases with increasing rainfall duration. During periods of discontinuous rainfall, TDP release increases with increasing rainfall intensity. Comparatively, continuous rainfall is more likely to release TDP, while short-duration heavy rainfall can cause extreme values ​​in TDP release. For example, on July 18th and June 20th, the rainfall duration and intensity were similar, but the former was during continuous rainfall while the latter was during discontinuous rainfall; the former resulted in a greater TDP release than the latter.

[0093] Rainfall generally reduces the retention effect of sediment-trapping dams on total phosphorus (TP), but the amount of TPP retained by dams varies greatly across different rainfall events. Continuous rainfall significantly reduces the amount of TPP retained in the dam area, and the amount of TPP retained increases with rainfall intensity. In discontinuous rainfall, the retention process of TPP by sediment-trapping dams is more complex; some rainfall events cause TPP to be released from the dam area (i.e., negative daily retention), while others cause TPP to be retained in the dam area (i.e., positive daily retention).

[0094] During rainfall events, the retention effect of sediment-trapping dams on total phosphorus (TP) is influenced by both total precipitation (TDP) and total precipitation (TPP). The effect varies greatly during discontinuous rainfall and little during continuous rainfall, similar to the variation pattern of TPP.

[0095] Table 3

[0096]

[0097] The observations revealed a clear statistical pattern: along the longitudinal direction of the river, the average concentrations of TP, TPP, and TSS first increased and then decreased, while the average concentration of TDP first decreased and then increased. This longitudinal distribution pattern of phosphorus concentration does not conform to the general exponential variation pattern of rivers. This distribution pattern stems from a comprehensive response of the river ecosystem to the alteration of river topography, hydrological conditions, and hydrodynamic processes by silt-trapping dams. Natural river sections, silt-trapping dam sections, and hardened river sections have created different landscape structures in the Qingshui River, which influence phosphorus transport, retention, and biological exchange processes within the river.

[0098] Silt-trapping dams alter river topography, hydrology, and hydrodynamic processes, causing significant particulate matter deposition and sedimentation on the dam surface. Since TPP retention primarily occurs through particulate sedimentation, silt-trapping dams have a significant retention effect on TPP. In contrast, TDP retention primarily occurs through particulate adsorption and biological uptake. The high sediment content near the dam inhibits aquatic growth, thus the dams have no significant TDP retention effect. The average concentrations of TPP and TSS initially increase and then decrease from upstream of the dam (1#) to upstream of the dam (2#) and downstream of the dam (3#). After being impounded by the dam, the average concentrations of TPP and TSS decrease by 50%. Meanwhile, the average concentration of TDP steadily decreases, and the TDP retention rate is lower than that of TPP.

[0099] The retention effect of silt-trapping dams on total phosphorus (TP) is not only reflected in the sedimentation process above the dam, but also in the shallows formed below the dam, which significantly retain total phosphorus (TPP) and total salinity (TSS). Due to the protection provided by the dam, the shallows below are not only protected from excessive hydrodynamic erosion, but also from being covered by excessive fine-grained sediment in high-sediment-laden water bodies. Simultaneously, they receive a certain amount of water and nutrients, making them suitable habitats for aquatic organisms. The vegetation types upstream and downstream of the dam reveal that the upstream natural river section is diluted grassland, the sedimentation area above the dam lacks vegetation, while the area below the dam has grassland and forests. After passing through the shallows below the dam, the average concentration of TPP decreased by 50%, while the average concentration of TDP increased by 20%.

[0100] Rainfall-runoff processes significantly impact phosphorus transport and retention in mountain rivers. The time interval, duration, and intensity of these processes influence phosphorus retention by check dams. The Qingshui River exhibits a distinct water level cycle: during the spring snowmelt season, water levels rise, increasing river velocity and flow; as the snowmelt season ends, rainfall decreases, water levels drop, river velocity and flow decrease, and localized river flow interruptions form ponds or even dry up; during the summer flood season, short-duration or continuous rainfall causes rapid water level rises, reconnecting ponds and dried-up riverbeds; in autumn and winter, rainfall decreases, water levels drop until the following spring snowmelt season, when water levels rise again. This study spanned from the end of the snowmelt season to the end of the flood season.

[0101] Following the snowmelt season, the drop in water levels leads to the formation of a series of isolated ponds in the river channel. These ponds can persist for days, weeks, or even months, depending on the rainfall runoff process. The ponds are typically anoxic or anaerobic environments, and studies have shown that anaerobic conditions favor the release of phosphates from sediments into the water. The phosphorus content and biogeochemical processes in the sediments also change dramatically due to desiccation; field studies in different types of aquatic ecosystems have shown that sediment desiccation leads to a decrease in phosphorus binding capacity. Therefore, rainfall during this period facilitates short-distance transport of TDP and TPP while reducing the retention effect of sediment-trapping dams on both. After the rainfall ends, the retention of both by sediment-trapping dams gradually recovers.

[0102] During the summer flood season, rainfall increases hydrological connectivity, leading to a rapid recovery of surface biological activity in rivers

[24] , resulting in nutrient-rich flood peaks, and a large amount of TDP and TPP are transported downstream; on the other hand, the rising water level and flow velocity above the dams reduce the retention effect of the dams on phosphorus. In most mountain rivers, TDP mainly comes from the subsurface flow zone

[26] and previously dried sediments. The duration of drying strongly affects the release of TDP and TPP from debris and sediments after rewetting. Therefore, under the influence of continuous rainfall during the flood season, the retention of TPP in the dams first increases and then decreases, while the retention of TDP in the dams first decreases and then increases. Continuous rainfall reduces the retention of TPP in the dams and increases the release of TDP from the dams. When the rainfall stops, the retention effect of the dams on TPP and TDP slowly recovers.

[0103] In general, the phosphorus retention effect of sediment-trapping dams weakens with increasing rainfall. When daily rainfall exceeds 56 mm, the retention effect of sediment-trapping dams on TPP and TDP becomes ineffective, and a large amount of TPP and TDP is transported from the sedimentation area above the dam to the downstream. During continuous rainfall, the retention effect of sediment-trapping dams on TDP becomes ineffective.

[0104] To better describe river morphology under the dual effects of climate change and human activities, we propose the concept of "disconnected rivers".

[0105] like Figure 7 As shown, a non-connected river is a river whose flow has ceased or whose riverbed has dried up for a period of time or in a certain space. Its non-connectivity has four dimensions:

[0106] (1) Longitudinal non-connected (between the upstream and downstream of the river);

[0107] (2) Laterally disconnected (between the river channel and the riverbank);

[0108] (3) Vertically disconnected (between river water and groundwater or between river water and atmosphere);

[0109] (4) Time is not connected (between months, seasons or years).

[0110] The concept of "non-connected rivers" can refer to a section of a river or the entire watershed. It is an extension of the traditional concept of "seasonal rivers" and includes rivers that have stopped flowing or disappeared due to human activities.

[0111] In "disconnected rivers," the processes of water flow, sediment transport, and nutrient transport are decoupled, exhibiting significant asynchronicity. — The mechanism by which disconnectivity affects material transport processes.

[0112] like Figure 8-9As shown, aquatic ecology is based on the interaction between organisms and the environment. It simulates the ecological state of surface water by analyzing species populations, such as algal blooms, endangered species protection, and aquatic ecosystem restoration. The disconnectivity index is used to characterize different material transport processes in surface water. The disconnectivity index is a dimensionless index; the smaller the value, the greater the amount of material transported from upstream to downstream (the less material remains in a certain part of the river channel), and vice versa. Many factors influence material transport processes in rivers, including flow velocity, flow rate, chemical reaction rate, and sedimentation-suspension processes. A coupled hydrodynamic-water quality-aquatic ecology model was constructed, achieving synchronous updates and mutual influences of physical, chemical, and biological parameters in the water body. The unique "disconnectivity index" solves the problem of solving the coupled hydrodynamic-water quality-aquatic ecology model.

[0113] The Disconnectivity Index (DCI) is a dimensionless index. The smaller the value, the weaker the disconnectivity and the smaller the amount of material retained; conversely, the stronger the disconnectivity and the larger the amount of material retained.

[0114] By calculating the flow disconnectivity index (flow-DCI), total suspended particulate matter disconnectivity index (TSS-DCI), total dissolved phosphorus disconnectivity index (TDP-DCI), and total particulate matter disconnectivity index (TPP-DCI) near the dam, it was found that the dam has different interception effects on suspended particulate matter, dissolved phosphorus, and particulate phosphorus in the same rainfall process. The disconnectivity index shows that the dam does not intercept water (flow-DCI≈1). When phosphorus is retained in the dam area, the particulate matter disconnectivity index (TSS-DCI) is positively correlated with the retention of total particulate phosphorus (TPP), but not with total dissolved phosphorus (TPP). Reducing the disconnectivity of suspended particulate matter will simultaneously increase the discharge of both TDP and TPP.

[0115] like Figure 10-12 As shown, the transport and retention processes of different forms of phosphorus in the dam area are significantly affected by rainfall and runoff processes. During non-rainfall periods, the dam retains sediment but does not impede water.

[0116] During the rainfall period, a large amount of sediment from upstream enters the dam area with the water. It may accumulate in the dam area or overflow the dam and flow downstream.

[0117] Sand-trapping dams exhibit varying retention efficiencies for water, sediment, and different forms of phosphorus.

[0118] The transport and retention processes of different forms of phosphorus in the dam area of ​​the sand-trapping dam are significantly affected by the rainfall and runoff processes.

[0119] When phosphorus is retained in the dam area, the particulate non-connectivity index (TSS-DCI) is positively correlated with the amount of total particulate phosphorus (TPP) retained, but not with the amount of total dissolved phosphorus (TPP).

[0120] Reducing the non-connectivity of suspended particulate matter will simultaneously increase the discharge of both TDP and TPP.

[0121] On the other hand, this embodiment also provides an electronic device, including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0122] On the other hand, this embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0123] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for ecological computation of disconnected rivers, characterized in that, include: The experimental flume simulated the river environment, and sampling points were set up in the actual river to collect water and sediment samples. Based on the water and sediment samples, hydrodynamic parameters, water quality parameters, and biological parameters were measured. Based on the hydrodynamic parameters, water quality parameters, and biological parameters, the transport flux and retention of phosphorus in the river are calculated. Construct a coupled hydrodynamic-water quality-aquatic ecology model to integrate the mutual influences of physical, chemical and biological processes; Based on the transport flux and retention of phosphorus, the disconnectivity index is calculated using the coupled model to analyze the material transport processes in the river ecosystem.

2. The method according to claim 1, characterized in that, The experimental water tank includes a water tank, a water supply system, a sample collection system, and a data recording system. The water tank is divided into multiple compartments by partitions to simulate the connected and disconnected sections of a river. The experimental water tank is equipped with an inlet, an outlet, and multiple sampling holes, and the water flow conditions are adjusted by a flow control valve.

3. The method according to claim 1, characterized in that, Water and sediment samples were collected by burying pore water samplers at the inlet, bends and outlet of the experimental water tank, and by placing thermometers in the sediment and water. Multiple sampling points were set up along the river section in the actual river to collect surface water samples and sediment samples.

4. The method according to claim 1, characterized in that, The measurement of hydrodynamic parameters includes using an acoustic Doppler current meter to measure velocity distribution and turbulence intensity, and analyzing boundary layer development; Based on the velocity distribution and turbulence intensity, estimate the sediment suspension and interface elevation changes.

5. The method according to claim 1, characterized in that, The water quality parameters measured included observing the diffusion flux of phosphorus at the sediment-water interface using thin-film diffusion gradient technology, and measuring the concentrations of total phosphorus, total dissolved phosphorus, total particulate phosphorus, and total suspended particulate matter.

6. The method according to claim 1, characterized in that, The measurement of biological parameters included measuring biological activity using an online chlorophyll analyzer and combining it with data on benthic communities in sediments to analyze the impact of biosorption on phosphorus flux.

7. The method according to claim 1, characterized in that, The non-connectivity index is a dimensionless index calculated separately for water flow, total suspended particulate matter, total dissolved phosphorus, and total particulate phosphorus; Based on the value of the non-connectivity index, the retention degree and transport amount of matter in the river channel are analyzed.

8. The method according to claim 1, characterized in that, The hydrodynamic-water quality-aquatic ecology coupled model simulates the transport and retention process of phosphorus in rivers by synchronously updating the physical, chemical and biological parameters in the water body, and analyzes the material transport characteristics under different artificial intervention conditions based on the non-connectivity index.

9. An electronic device comprising a memory, a processor, and a computing program stored in the memory and executable on the processor, characterized in that, When the processor executes the computing program, it implements the method of any one of claims 1-8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1-8.

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