Remote Sensing Evaluation of Total Suspended Solids Dynamic with Markov Model: A Case Study of Inland Reservoir across Administrative Boundary in South China.

Shuisen Chen,Jinyue Chen,Hui Zhou,Jing Zhao,Yong Xue,Fujie Zhang,Chongyang Wang

doi:10.3390/s20236911

Abstract

Accurate and quantitative assessment of the impact of natural environmental changes and human activities on total suspended solids (TSS) concentration is one of the important components of water environment protection. Due to the limits of traditional cross-sectional point monitoring, a novel water quality evaluation method based on the Markov model and remote sensing retrieval is proposed to realize the innovation of large-scale spatial monitoring across administrative boundaries. Additionally, to explore the spatiotemporal characteristics and driving factors of TSS, a new three-band remote sensing model of TSS was built by regression analysis for the inland reservoir using the synchronous field spectral data, water quality samples and remote sensing data in the trans-provincial Hedi Reservoir in the Guangdong and Guangxi Provinces of South China. The results show that: (1) The three-band model based on the OLI sensor explained about 82% of the TSS concentration variation () with an acceptable validation accuracy (), which is basically the first model of its kind available in South China. (2) The TSS concentration has spatial distribution characteristics of high upstream and low downstream, where the average TSS at 31.54 mg/L in the upstream are 2.5 times those of the downstream (12.55 mg/L). (3) Different seasons and rainfall are important factors affecting the TSS in the upstream cross-border area, the TSS in the dry season are higher with average TSS of 33.66 mg/L and TSS are negatively correlated with rainfall from upstream mankind activity. Generally, TSS are higher in rainy seasons than those in dry seasons. However, the result shows that TSS are negatively correlated with rainfall, which means human activities have higher impacts on water quality than climate change. (4) The Markov dynamic evaluation results show that the water quality improvement in the upstream Shijiao Town is the most obvious, especially in 2018, the improvement in the water quality level crossed three levels and the TSS were the lowest. This study provided a technical method for remote sensing dynamic monitoring of water quality in a large reservoir, which is of great significance for remediation of the water environment and the effective evaluation of the river and lake chief system in China.

Highlights

Total suspended solids (TSS) are essential carriers of organic matter such as nitrogen and phosphorus and their movement and migration play a significant role in the process of global material cycling and change [1]
This study provided a technical method for remote sensing dynamic monitoring of water quality in a large reservoir, which is of great significance for remediation of the water environment and the effective evaluation of the river and lake chief system in China
It reflects the changes in water quality by the trend analysis of the Markov model since the local implementation of the river chief system of China in 2016

Summary

Introduction

Total suspended solids (TSS) are essential carriers of organic matter such as nitrogen and phosphorus and their movement and migration play a significant role in the process of global material cycling and change [1]. Reservoirs are one of the most important sources of drinking water for human beings. They are rich in biodiversity and play a decisive role in improving and regulating the surrounding ecological environment. The reservoir gradually accumulates suspended matter at different water levels, which reduces the water storage capacity of the reservoir and reduces the effective storage capacity [5]. It is important for real-time monitoring and management of the aquatic environment in the reservoir area to reveal the dynamic of TSS. Since the release of the guidance for the river chief system by the General Office of the State Council of China in 2016, the research of TSS in inland water including lakes and reservoirs has been paid more lasting attention, and the associated research has been conducted by a variety of scholars, governments and social communities [6,7,8], such as the Río Tercero reservoir (Córdoba, Argentina) [6], the Mekong and Bassac Rivers [9,10], the Amazon River [11], Taihu Lake [8,12], the Yangtze River [13,14,15] and the Pearl River [16,17,18,19]

Methods

Results

Discussion

Conclusion