Rosemarie Wilson, Contributor
A satellite image showing Jamaica and Cuba.
Remote Sensing, a novel tool for monitoring the quality of Jamaica's Coastal waters
JAMAICA'S ECONOMY is heavily dependent on the tourism industry, which to a very great extent, revolves around the country's coastal resources, particularly, water. The need to preserve and promote sustainable use of these resources cannot be overstated. A primary focus of coastal water resource management should be that of implementing strategies and technologies that have the capability of rapidly detecting the presence and levels of contamination when it occurs. The technique of Remote Sensing offers good promise in the area of water quality monitoring.
WHAT IS REMOTE SENSING OF WATER QUALITY?
Remote sensing of water quality, for the purpose of this article, may be defined as the collection of information or data about the quality of a water body, from electromagnetic radiation that has interacted with the water. As the term 'remote' implies, the information is collected about the water body, without actually making physical contact with it.
Data are measured by calibrated spectro-radiometric sensors on board special environmental satellites.
HOW DOES ELECTROMAGNETIC RADIATION INTERACT WITH WATER?
As light enters a water body, it is attenuated as photons are absorbed and scattered by optically active dissolved and particulate substances in the water.
These light attenuating substances include the pigments of plants, coloured organic material (humic substances), suspended solids (plants and inorganic sediments), and the water itself. Every water body has a unique absorption spectrum, which depends on the types and quantities of light absorbing components in the water.
The extent to which the light field within, and that leaving the water change, is dependent on the extent of attenuation by absorption and scattering, which as mentioned before, depends on the quantities of the substances present in the water, and thus, the water quality. A remote sensor measures the quantity and spectral distribution of light entering and leaving a water body. The data is then interpreted based on the knowledge of the absorption characteristics of the light attenuating substances in the water. The remote sensor returns data that is then 'corrected' or 'filtered' to exclude signals that may have reached the sensor from other sources. The ultimate usefulness of the data comes when they are matched with ground-collected water-leaving radiance, and the concentrations and spectral characteristics of the water constituents.
REMOTE SENSING AND JAMAICA'S COASTAL WATERS
Research work is ongoing in the chemistry Department of the UWI, to parameterise the light attenuation processes in Black River Bay and Hunts Bay (Kingston Harbour), and to develop optical models as predictive tools for coastal water quality monitoring.
Could this work be the genesis of a space-based coastal water quality monitoring programme in Jamaica?
(See satellite image above)
Over the last two decades, a number of academic studies have been published showing the significant potential for satellite sensors to monitor water quality of the world's oceans. Significant advances which have occurred in the improvement in the calibration and spatial and spectral resolution of space-based sensors, may now allow for reliable data to be obtained on the scale of Jamaica's coastal water bodies. The United States of America's National Aeronautical and Space Agency (NASA), flies the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on-board two satellites, (Terra/morning pass and Aqua/afternoon pass) collecting water quality data continuously. These data are openly available to the scientific community, and with validation from in situ radiometric and conventional water quality measurements, may prove very valuable to water quality managers. Remote sensing offers an advantage over traditional water quality monitoring methods as it gives managers the opportunity to view many indicative water quality parameters (turbidity, total suspended solids, phytoplankton distribution, coloured dissolved organic material) over an entire water body, in near real time, without having to travel to the areas of interest.
Rosemarie Wilson is a PhD student in the Department of Chemistry.
NASA VISIBLE EARTH; HTTP://WWW.GESOURCE.AC.UK/WORLDGUIDE/HTML/IMAGE_410.HTML
