PDF(Sci-hub)
Abstract：
This study aims to develop an empirical model from Landsat data series to monitor the water salinity of coastal Bangladesh efficiently. Such a model can substitute expensive conventional techniques for assessing remote water quality. A set of equations connecting sensors 5 TM and 8 OLI were generated using multiple regression analysis. Radiometric and atmospheric corrections were carried out to enhance the quality of satellite images. Total 13 compositions of different bands including blue, green and red were considered to find the Coefficient of Determination (r2) with the field level EC (electrical conductivity) values collected from 74 sampling locations. Salinity data mainly EC values of coastal water were collected from primary and secondary sources. Considering the r2 values, significant band compositions were identified and then employed to generate linear equations. Such equation for Landsat 5 TM could detect water salinity (i.e. EC) accurately of around 82%. Similarly, the r2 value for Landsat 8 OLI was found as 0.76 that can confirm the applicability of Landsat data series to detect the change of salinity level of coastal water for a long period. The availability of coastal water was delineated by NDWI whereas salinity level was assessed using the developed equations for the year 2001 and 2019. Interestingly, it was observed that coastal areas having lower level of EC almost vanished whereas those of having higher level of EC were increased significantly between 2001 and 2019. Such increase in coastal water salinity is the result of combined effects of climatic and anthropogenic factors, which can pose a considerable risk to the coastal inhabitants including freshwater scarcity, food insecurity, and health hazard.
摘要：
本研究旨在从Landsat数据系列中开发一个经验模型，以有效地监测孟加拉国沿海的水盐度。这种模型可以代替昂贵的常规技术来评估远程水质。使用多元回归分析生成连接传感器5TM和8OLI的一组方程。进行了辐射和大气校正，以提高卫星图像的质量。总共13种不同波段的成分，包括蓝色，绿色和红色被认为是用从74个采样位置收集的场水平EC(电导率)值找到测定系数(r2)。盐度数据主要是从主要和次要来源收集的沿海水的EC值。考虑到r2值，确定了重要的条带组成，然后用于生成线性方程。Landsat5TM的这种方程可以准确检测约82%的水盐度(即EC)。同样，Landsat8OLI的r2值为0.76，可以证实Landsat数据系列长期检测沿海水域盐度水平变化的适用性。NDWI描述了沿海水的可用性，而盐度水平则使用2001年和2019年的已开发方程进行评估。有趣的是,据观察,2001年至2019年间,EC水平较低的沿海地区几乎消失,而EC水平较高的沿海地区则显著增加.沿海水盐度的这种增加是气候和人为因素综合影响的结果，这可能对沿海居民构成相当大的风险，包括淡水短缺，粮食不安全，和健康危害。
