Sensing Images for Assessing the Minimum Ecological Flux by Automatically Extracting River Surface Width

Wenting Xu,Xuelei Wang,Xiaoyong Chen,Yue Yao,Mingxiu Wang,Qian Wang,Wei Huang,Fangfang Zhang,Junsheng Li,Qian Shen

doi:10.3390/rs12182899

Abstract

Global warming and economic development have intensified the evaporation and exploitation of river waters, resulting in reduced global river runoff. In minimum ecological flux management, objective determination of the minimum ecological flux and evaluation of whether a river complies with standards are urgently required. Satellite remote sensing allows for rapid, large-scale, and dynamic monitoring. Herein, the Tangmazhai cross-section of the Taizi River was analyzed using the Chinese Gaofen (GF) series satellite that comprises panchromatic multi-spectral sensors and the Sentinel-2 multi-spectral images to automatically extract the water surface width. We applied the Normalized Difference Water Index (NDWI)-Iterative Self-Organizing Data Analysis Technique Algorithm (ISODATA) to 225 cloudless scenes from January 2015 to November 2019. We proposed a method to evaluate the minimum ecological flux using water surface width. The river surface width at this location increased from January 2015 to November 2019, and all widths exceeded the minimum river surface water width for the month. The degree of the minimum ecological flux guarantee was determined to be satisfactory. Because there are less clouds and rain in the North China than South China, our results may be used for evaluating the degree of minimum ecological flux guarantee of many river sections in the north China through monthly monitoring.

Highlights

With the continuous development of society and economy, humans continue to exploit rivers in addition to constructing many water conservancy projects, deteriorating the ecological environment of rivers [1]
The minimum river surface width corresponds to the minimum ecological water level, and the minimum ecological water level corresponds to the minimum ecological flux
(2) To improve the accuracy and efficiency of water body extraction, we selected the Iterative Self-Organizing Data Analysis Technique Algorithm (ISODATA) method, which can automatically divide the water body or determine the threshold value, so that the water body information is automatically extracted from the batches before the river surface width is extracted

Summary

Introduction

With the continuous development of society and economy, humans continue to exploit rivers in addition to constructing many water conservancy projects, deteriorating the ecological environment of rivers [1]. Water surface width can be extracted from MODIS [7,8], medium-resolution (Landsat) satellite data [9], JERS-1 [10], and other optical remote sensing images. The remote sensing images were used to realize an automatic method for extracting river surface width, and the width of the river surface at the cross-section of Tangmazhai Station from January 2015 to December 2019 was monitored. This method will be of great significance for assessing river surface width both in the observation area and globally. TThhee mmaaiinn ssttrreeaamm wwaass 441133 kkmm lloonngg aanndd rruunnss eeaasstt––wweesstt,, flfloowwiinngg tthhrroouugghh iimmppoorrttaanntt hhyyddrroollooggiiccaall ssttaattiioonnss,, ssuucchh aass XXiiaaoosshhii SSttaattiioonn,, BBeennxxii SSttaattiioonn,, LLiiaaooyyaannggSSttaattioionn, ,XXiaioaolilninzizSi tSattaiotino,na,nadnTdanTgamngamzhaazihSatiatSiotant,ioann,dafinndalfliynianlltyo LiniatoodLoinaogdBoanygofBtahye oBfohthaei SBeoahaalionSgeathealDoanlgiaothReiveDra(lFiaigourRei1v)e.rTh(Feicgruorses-s1e)c.tioTnheof cthroesrsi-vseerctaitoTnanogfmtahzehariiHveyrdraotloTgaicnaglmStaaztihoani iHs ythderorleosgeiacraclhStaarteiaonofisotuhre srteusdeayr, cwhhairceha iosfboeutwr seteundy1,2w2◦h3i2ch24is” baentdwe1e2n2◦15212°3362”′E24, ′′anandd4112◦22°2541”′3a6n′′Ed, 4a1n◦d22411°22”′2N4,′′aannddb4e1lo°2n2g′1s2t′′oNth, eanpdlabinelroivnegrs atroetah[e17p]l.aAinccriovredrinagretao[t1h7e].sAhacpcoerodfinthgetroivtehrebsehda, ptheeorfivtheer craivnebrbeeddi,vtihdeedrivinetrocfaonubr ecadteivgiodreidesi:nWtoafnoduerricnagte,gborrainecsh: iWnga,ncduerrvinegd,, banradnscthrianigg,hctu[1rv8]e.dA, amnodnsgtrtahiegmht, s[1tr8a]i.gAhtmroivnegrsthareemt,hsetsraimigphltesrtivaenrds aarree ethaseystiomsptuledsyt.aTnhdearreeacehasayt tthoestsuecdtyio. nThateTraenagchmaazt hthaei Ssteacttiioonnoant TTaainzgi Rmiavzehrawi aSstasteiolenctoendTaasiazisRtriaviegrhwt raivs esre.lected as a straight river

Data Source

Deffiinition of River Surface width

Accuracy Evaluation

Conclusions