The community and roadway of the Salmon Point Fishing Village in Westmoreland, were flooded as ponds in the community overflowed their banks as a result of heavy rains associated with Hurricane Wilma. - Photo by Junior Grandison
There are three major sources of freshwater to the sea: rainwater from the atmosphere, river and groundwater from the land. Rivers are often thought to be the major source, but in some regions groundwater and atmospheric sources can be of considerable importance.
More than 70 per cent of Jamaica's base rocks are limestone which contain huge aquifers. Aquifers are basically underground lakes containing massive supplies of groundwater. These aquifers are connected to the sea via underground 'rivers', and the groundwater from the land can be released along the coast as 'submarine groundwater discharge'.
Jamaica has many rivers flowing on the surface, but did you know that there are many underground 'rivers' flowing to the coast? They are found particularly in the northern parishes of the Island. You may ask yourself, "Why is this important?" Well, our activities on land affect our coastlines. When we dump waste in the ground, pollutants, such as bacteria and compounds of nitrogen and phosphorus, can enter the groundwater and be transported to the coast. Not only does this contaminate our potable water ,but it may also put our beaches and coastal habitats, such as coral reefs, at risk.
Excessive nutrients
A study of the amount of nitrogen and phosphorus reaching Discovery Bay, St. Ann, in the submarine groundwater discharge was recently concluded at the UWI Discovery Bay Marine Laboratory. Nitrogen and phosphorus are important plant nutrients, essential for the growth of plants. When plants die these nutrients are released back to the environment and can then be reused by other growing plants. However, when we discharge large amounts of waste into our sewers and landfills, excessive amounts of these nutrients can get into our ground and surface waters and finally reach the coast. Using too much fertiliser (plant nutrients, including nitrogen and phosphorus) contributes to this problem.
It has been suggested over many years that excessive amounts of nutrients reaching our coastal waters have contributed to the degradation of our coral reefs. The recently-completed study at Discovery Bay showed that the amounts of nitrogen and phosphorus reaching the bay through submarine groundwater discharge are not unnaturally high and, thus, unlikely to be major contributors to the degradation of the reef in that area. However, Discovery Bay is on an area of the Island with a small and dispersed population. Underground rivers near densely populated areas (Montego Bay, Ocho Rios, Kingston, Port Antonio, for example) may well be carrying heavier loads and contributing to the pollution of the coastal waters. We need to be monitoring our coastal waters to find out if we are contaminating them and if so, change our ways to avoid that.
Contributed by Debbie-Ann Gordon-Smith, a Ph.D. student.