基于多源卫星数据的三峡库区水体悬浮物浓度遥感监测

Remote Sensing Monitoring of Suspended Solids Concentration in the Three Gorges Reservoir Area Based on Multi-source Satellite Data

悬浮物浓度是评价水体水质及区域生态环境的重要参数之一。利用2020年5月长江三峡库区与长寿湖水体实测悬浮泥沙浓度及同步光谱数据,对照Landsat-8、Sentinel-2、GF-1三类卫星遥感影像数据,分析了不同卫星仿真波段与不同波段组合下离水光谱反射率与水体悬浮物浓度相关关系,筛选得到长江三峡水体悬浮物敏感波段,并尝试率定其有效参数区间。采用线性、指数、多项式等多种数理统计回归方法,分别建立三类卫星对应的反演模型,对比不同卫星可用于三峡库区悬浮泥沙浓度遥感反演监测的最优模型,选出一个最佳模型用于长江三峡库区的水体悬浮泥沙浓度遥感监测。结果表明:(1)三类卫星数据中近红外/绿光的波段组合与悬浮泥沙浓度均具有最显著的相关性,其中Landsat-8的相关系数为0.7713(P<0.001),Sentnel-2为0.7734(P<0.001),GF-1为0.7300(P<0.001);(2)三类卫星的最佳回归模型均为线性模型,模型R2均超过0.60以上,方程F检验均通过99%置信区间,说明常用的三类卫星均可以有效应用于三峡水体悬浮物的监测。但结合长江三峡水体特征、模型验证精度、时空分辨率以及数据获取难易程度等因素,认为Sentinel-2卫星数据最适于三峡地区水体悬浮物的业务性应用监测;(3)长江三峡悬浮泥沙浓度整体呈现江岸高于江心,下游高于上游的趋势,夏季浓度明显高于春季,在7、8月水量增多、洪涝频繁情形下悬浮泥沙浓度整体显著增加;5月长江干流区域悬浮泥沙浓度基本在40~80 mg/L左右,江岸边的浓度有达到100 mg/L左右的情况,7、8月悬浮泥沙浓度维持在80~120 mg/L左右,下游地区甚至达到了160 mg/L以上。而处于支流内陆湖泊性质的长寿湖水体,悬浮泥沙浓度呈现湖岸边高于湖心的分布特点,悬浮泥沙含量不同时期的波动变化较小,长江干流洪涝发生对其影响较小,5、7、8月湖中浓度基本在40~80 mg/L左右,湖岸有出现浓度达到110 mg/L的情况。

Suspended solids concentration is one of the important parameters to evaluate water quality and regional ecological environment.Based on the measured suspended sediment concentration and synchronous spectral data of the Three Gorges Reservoir area and Changshou Lake in May 2020,and compared with the landsat-8,sentinel-2 and GF-1 satellite remote sensing image data,this paper analyzes the correlation between the water leaving spectral reflectance and the concentration of suspended solids in the water body under different satellite simulation bands and different band combinations,selects the sensitive bands of suspended solids in the Three Gorges Reservoir area,and attempts to calibrate its effective parameter range.Using linear,exponential,polynomial and other mathematical statistical regression methods,the inversion models corresponding to three types of satellites are established respectively.The optimal models that different satellites can be used for remote sensing inversion and monitoring of suspended sediment concentration in the Three Gorges Reservoir area are compared,and an optimal model is selected for remote sensing monitoring of suspended sediment concentration in the Three Gorges Reservoir area of the Yangtze River.The results show that:(1)among the three types of satellite data,the band combination of near-infrared/green light has the most significant correlation with suspended sediment concentration,in which the correlation coefficient of landsat-8 is 0.7713(p<0.001),sentnel-2 is 0.7734(p<0.001),GF-1 is 0.7300(p<0.001);(2)The best regression models of the three types of satellites are linear models,and the model R2 is more than 0.60.The equation F test passes the 99%confidence interval,indicating that the commonly used three types of satellites can be effectively applied to the monitoring of suspended solids in the Three Gorges water body.However,combined with the characteristics of the water body in the Three Gorges of the Yangtze River,the accuracy of model verification,the spatiotemporal resolution and the difficulty of data acquisition,sentinel-2 satellite data is considered to be the most suitable for the operational application monitoring of suspended solids in the Three Gorges area;(3)The concentration of suspended sediment in the Three Gorges of the Yangtze River is higher than that in the center of the river and higher in the downstream than that in the upstream.The concentration in summer is significantly higher than that in spring.The concentration of suspended sediment increases significantly in July and August when the water volume increases and floods occur frequently;In May,the concentration of suspended sediment in the main stream of the Yangtze River was basically about 40-80 mg/L,and the concentration along the river bank reached about 100 mg/L.In July and August,the concentration of suspended sediment remained about 80-120 mg/L,and even reached more than 160 mg/L in the downstream area.As for Changshou Lake,which is an inland lake in the tributary,the suspended sediment concentration shows the distribution characteristics that the suspended sediment concentration is higher on the bank than in the center of the lake.The fluctuation of suspended sediment content in different periods is small,and the flood in the main stream of the Yangtze River has little impact on it.The concentration in the lake is basically about 40-80 mg/L in May,July and August,and the concentration on the Bank of the lake reaches 110 mgmg/L.