A Satellite Imagery Approach to Monitor Turbidity and Total Suspended Sediments in Green Bay, WI
Abstract
Fox River is a major source of land-based pollutants, nutrients, and sediment that flows into the southern Green Bay (GB). GB supplies one-third of the total nutrient loading to Lake Michigan. This can play a significant role in the biological functioning of the Bay and development of managerial scenarios. To name a few, it can degrade the quality of the aquatic life, add to the costs for treatment processes, and reduce coastal quality. Water quality evaluation is a time consuming and costly process. Spaceborne imagery data provides a cheap and valuable source of information as an alternative for field monitoring of the water resources. Sediment is an optically active variable; hence; remote sensing techniques can be utilized to estimate Total Suspended Sediments (TSS) and Turbidity (TU) of water. In this study, we developed relationships between remote sensing imagery data with daily in situ measurements of TSS and TU in the summers of 2011 to 2014. Surface reflectance (SR) values obtained from Band 1 of MYD09GQ dataset-a level 2 product of MODerate Resolution Imaging Spectroradiometer (MODIS). This band covers SR between 620 and 670nm, in which, the wavelength is sensitive to mineral suspended matters most. After elimination of days with cloud contamination, 118 pairs of data remained for analysis. Several possible functions were tested and exponential function was the best estimator of the SR-TSS and SR-TU relationships with R2 values of 0.8269 and 0.8688, respectively. We then used 2014 data to validate the proposed functions. The model was able to estimate TSS and TU with NRMSE values of 0.36 and 0.30. It indicates that the model can be well-applied to predict TSS and TU within a reasonable margin of error. Then, equations were used to map the spatiotemporal dynamics of sediment in GB. Area of the plume ranges between 12 to 180 km2 while 50% of the time the area of the turbid plume is more than 106 km2. Expectedly, the concentration of sediment is much higher near the Fox River mouth. It suggests that the main source of sediment in the southern GB is river discharge, even though other factors such as wind driven wave, gyres, and circulation affect the TSS concentration. The proposed approach can be extended to other coastal regions of the Great Lakes and provides a framework to study pollution transportation in coastal areas.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMGC23B1066K
- Keywords:
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- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY;
- 4217 Coastal processes;
- OCEANOGRAPHY: GENERAL