Modeling of Chlorophyll-a and Eutrophication Indicators in the Dubai Creek Area using Remote Sensing

Abstract

The last few decades have witnessed an increase in the frequency and magnitude of the occurrences of algal blooms in coastal regions. A high increase in the levels of nutrients (phosphorus and nitrogen) in the water column leads to excessive algal growth, known as eutrophication. The presence of a large amount of algae normally turns water green or red in the case of Harmful Algal Blooms (HABs). Chlorophyll-a is the main indicator of algal blooms and its concentrations are used as indicators of the scale of an algal bloom. Nutrients have a major impact over algal blooms. Dubai Creek is a salt water body located in Dubai, UAE which divides the city into Bur Dubai and Deira. Due to high levels of human activities surrounding the creek, there have always been eutrophication concerns given the levels of nutrients in the creek. In the last few years, remote sensing algorithms have been developed to monitor algae in water bodies by mapping chlorophyll-a concentrations. The aim of this study was to map chlorophyll-a in the Dubai Creek from WorldView-2 imagery (high resolution satellite images) and to explore the relationship between chlorophyll-a and other eutrophication indicators. A geometrically and atmospherically corrected Worldview-2 image and in-situ data have been utilized to map chlorophyll-a in the creek. A spectral model was developed to retrieve chlorophyll-a concentrations from the WorldView-2 multispectral image. The model showed an R-squared value of 0.82 with in-situ chlorophyll-a data. Another model was developed for the relationship between the levels of spectral chlorophyll-a and total nitrogen and phosphates, which showed an R-squared value of 0.97. The developed models are to be used in the mapping of chlorophyll-a, total nitrogen, and phosphates without the need for expensive in-situ monitoring efforts since they will provide values of these parameters everywhere in the creek.