Investigating the potential use of Sentinel-1 data for monitoring wetland water level changes in China's Momoge National Nature Reserve

Yueqing Chen; Sijia Qiao; Guangxin Zhang; Y Jun Xu; Liwen Chen; Lili Wu

doi:10.7717/peerj.8616

Investigating the potential use of Sentinel-1 data for monitoring wetland water level changes in China's Momoge National Nature Reserve

PeerJ. 2020 Feb 17:8:e8616. doi: 10.7717/peerj.8616. eCollection 2020.

Authors

Yueqing Chen^#^{1

2

3}, Sijia Qiao², Guangxin Zhang¹, Y Jun Xu⁴, Liwen Chen¹, Lili Wu^#^{2

3}

Affiliations

¹ Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, Jilin, China.
² School of Geographic Sciences, Xinyang Normal University, Xinyang, Henan, China.
³ Key Laboratory for Synergistic Prevention of Water and Soil Environmental Pollution, Xinyang Normal University, Xinyang, Henan, China.
⁴ School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, America.

^# Contributed equally.

Abstract

Background: Interferometric Synthetic Aperture Radar (InSAR) has become a promising technique for monitoring wetland water levels. However, its capability in monitoring wetland water level changes with Sentine-1 data has not yet been thoroughly investigated.

Methods: In this study, we produced a multitemporal Sentinel-1 C-band VV-polarized SAR backscatter images and generated a total of 28 interferometric coherence maps for marsh wetlands of China's Momoge National Nature Reserve to investigate the interferometric coherence level of Sentinel-1 C-VV data as a function of perpendicular and temporal baseline, water depth, and SAR backscattering intensity. We also selected six interferogram pairs acquired within 24 days for quantitative analysis of the accuracy of water level changes monitored by Sentinel-1 InSAR. The accuracy of water level changes determined through the Sentinel-1 InSAR technique was calibrated by the values of six field water level loggers.

Results: Our study showed that (1) the coherence was mainly dependent on the temporal baseline and was little affected by the perpendicular baseline for Sentinel-1 C-VV data in marsh wetlands; (2) in the early stage of a growing season, a clear negative correlation was found between Sentinel-1 coherence and water depth; (3) there was an almost linear negative correlation between Sentinel-1 C-VV coherence and backscatter for the marsh wetlands; (4) once the coherence exceeds a threshold of 0.3, the stage during the growing season, rather than the coherence, appeared to be the primary factor determining the quality of the interferogram for the marsh wetlands, even though the quality of the interferogram largely depends on the coherence; (5) the results of water level changes from InSAR processing show no agreement with in-situ measurements during most growth stages. Based on the findings, we can conclude that although the interferometric coherence of the Sentinel-1 C-VV data is high enough, the data is generally unsuitable for monitoring water level changes in marsh wetlands of China's Momoge National Nature Reserve.

Keywords: Backscatter; Interferometric coherence; Interferometric synthetic aperture radar (InSAR); Momoge National Nature Reserve; Sentinel-1; Water level; Wetland.

Grants and funding

This research was funded by the National Key R & D Program of China (grant number 2017YFC0406003) the National Natural Science Foundation of China (grant number 41701395, 41877160 and 41671476) the Featured Institute Project 4, the Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (grant number IGA-135-05) and the Nanhu Scholars Program for Young Scholars of XYNU. During the preparation of the article, Yijun Xu received funding support from a U.S. Department of Agriculture Hatch Fund project (project number: LAB94459). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.