Evaluation Of Water Environment Carrying Capacity Based On Hyperspectral Data Modeling

The ecological environment protection is related to the national economy and the people’s livelihood.Since 18 th CPC National Congress,it has risen to the national strategy.Therefore,under the background of ecological civilization construction,grasping the bearing capacity of regional water environment is particularly important to the formulation of regional sustainable development policy.The evaluation of water environment carrying capacity should grasp the water environment and its changes in the study area.The main method is to analyze the water quality monitoring data with timeliness,macro accuracy and periodicity.At present,the water environment monitoring system in our country is mainly based on the traditional layout sampling laboratory analysis.But the traditional method has many defects,such as input-output ratio is low,affected by weather conditions,natural environment and other factors,resulting in the acquisition range data is small and slow also does not have the periodicity.Relatively speaking,hyperspectral inversion technology can overcome the many shortcomings,the experimental cost reduced,significantly improve the timeliness and has very strong periodicity,is an important supplement to conventional water quality monitoring,providing a new technical method for regional water environment monitoring and bearing capacity.Relatively speaking,hyperspectral inversion technology can overcome the many shortcomings,reduce the experimental cost,significantly improve the timeliness and has strong periodicity.It is an important supplement to conventional water quality monitoring,providing a new technical method for regional water environment monitoring and bearing capacity.This paper takes the Pengshan District of Meishan as the research area,based on the measured hyperspectral data and Landsat 8 satellite remote sensing data OLI,and based on the comparison of traditional wavelet threshold denoising algorithm,proposed an improved spectral data denoising algorithm based on new threshold function,and sthdied the coupled modeling of two-dimensional convection diffusion equation and water quality hyperspectral inversion model by using the processed hyperspectral data.Chlorophyll a(Chl-a),total nitrogen(TN)and total phosphorus(TP)were selected as the object of study.A coupling model of water quality inversion based on hyperspectral data was established,and the water environment carrying capacity of Pengshan district was evaluated.The evaluation results were verified and analyzed.The main research contents and conclusions are as follows:(1)Remote sensing image and hyperspectral remote sensing data denoising technology based on wavelet new threshold method.According to study the satellite remote sensing images and water measured hyperspectral data characteristics,and based on the theoretical results of wavelet threshold denoising of I.M.Johnstone and D.L.Dohono.By choosing the appropriate wavelet basis function and wavelet decomposition scale,a new threshold function for spectral data denoising in this paper is constructed.Compared with the previous soft and hard threshold,this function has the advantages of convenient calculation,superior mathematical characteristics and clear physical meaning.The simulation results show that the new threshold function is very effective to remove the random noise.This method is introduced to display the results in Penshan region OLI image noise and water measured hyperspectral data processing,the new wavelet threshold function can better improve the signal and image processing effect and effectively improve the snr.(2)The analysis of water spectral characteristics based on Hyperspectral features.The spectra experiments of TN and TP in laboratory show that the trend of spectral reflectance increases with the increase of TP and TN concentration in water,and the reflectance peaks of different responses are generated.The sensitive reflection peaks of TN are located at 715 nm and 805 nm,and the sensitive reflection peaks of TP are located at 540 nm and 680 nm,and the correlation between the reflectance and the concentration of the original spectral data is significant.By analyzing the spectral reflectance characteristics of planktonic algae,three prominent reflection peaks can be found.The three peaks were located near about 580 nm,about 700 nm and 800 nm,there are two obvious absorption peak at 675 nm and 750 nm.In general,the overall spectral reflectance of phytoplankton is low under the influence of water body;the overall waveform and characteristic position are consistent with the hyperspectral spectrum of terrestrial green vegetation.(3)Coupled modeling of two dimensional convection diffusion equation and water quality hyperspectral inversion model.Hyperspectral Characteristics Analysis based on laboratory and field waters.The hyperspectral inversion model of water quality was established by using reflectance sensitive band method and WCI index method,and the model was verified to verify its reliability.On this basis,a two-dimensional convection diffusion water quality model is introduced,which is coupled with the hyperspectral inversion model of water quality,and the spectral reflectance equation is discretized and solved by finite difference method,and constructed a solution model of spectral reflectance based on spatial position.A new method of water quality model modeling for Pengshan district was established,and the water spectral reflectance simulation was carried out for the main rivers of Pengshan area,and the validity of the model was verified.(4)Evaluation and verification of water environment carrying capacity in Pengshan district.Taking township(town)as the basic evaluation unit,according to the general method and steps of water environment carrying capacity index construction,the evaluation index system of county scale water environment carrying capacity including 9 evaluation indexes is constructed.The verified water quality coupled inversion model is applied to the simulation calculation of water quality of main rivers in Pengshan district.According to the simulation results,the water environment capacity,water environment comprehensive trophic state index,water environment pollution index and other water environment carrying capacity evaluation indexes were calculated.On this basis,the Delphy-Comprehensive index method was used to evaluate the water environment carrying capacity of Pengshan district,and a set of water environment carrying capacity evaluation system based on remote sensing technology is developed.Compared with the reference results,the reliability of the research evaluation technology was verified.In summary,this study has further improved the evaluation model of water environmental carrying capacity at County scale.This technical route and research results will provide important technical reference and guidance for the evaluation of water environment carrying capacity of rivers in other regions.