Dale F. Webber

The Water Quality of Kingston Harbour: Evaluating the Use of the Planktonic Community and Traditional Water Quality Indices

Abstract Kingston Harbour has been experiencing increased levels of organic pollution since initial ecological assessments in 1971. to develop a new baseline of eutrophication in the Harbour 20 years later, and determine the most appropriate indices to be used in the continued monitoring the area, the water quality of Kingston Harbour was reassessed between December 1992 and 1993, by contemporaneous sampling of traditional water column parameters and planktonic communities at 28 stations within the Harbour. Indices used for water quality assessment were temperature, salinity, light penetration, dissolved oxygen, BOD and nutrients (nitrates-N, phosphate-P and ammonia-N). Results indicated that the planktonic community provided the most reliable index of increased eutrophication and changes in water quality. While physical variables indicated little change in Harbour waters and chemical variables indicated significant but erratic changes, the planktonic community displayed the classic characteristics of eut...

Effects of flood waters on the planktonic community of the Hellshire coast, Southeast Jamaica

Between 24 May and 4 June 1986, the island of Jamaica experienced up to 635 mm of rainfall producing islandwide flooding. Planktonic communities along the south coast were studied before and after the flooding. Flood waters from Kingston Harbour flowed southwest along the Hellshire coast as far as Wreck Reef, but were confined within 4 km of the shore. Water in the bays along the lower Hellshire coast remained clear and unaffected by Harbour water, although planktonic communities there showed marked changes. The Port Royal Cays area and much of the shelf was unaffected (...)

Using the Distribution of Physicochemical Variables to Portray Reefal Bay Waters

Abstract The distributions of a variety of variables were used to characterise the physicochemical structure of inner bay waters in a reefal bay with a central channel. The aim was to describe emanations of the bay waters and the effectiveness of particular variables in depicting these emanations. In Wreck Bay—a semienclosed reefal bay located along the Hellshire south-east coast of Jamaica—distribution in temperature, salinity, dissolved oxygen, pH, and specific conductivity were used as potential indicators of the inner bay waters and their emanations. Variable profiles and contours showed that salinity and specific conductivity were found to be unreliable in characterising the bay waters because of the interruptions from numerous submarine seeps found inside and outside of the bay. However, temperature, pH, and dissolved oxygen were more robust in characterising bay waters with continuity from the inner bay, past the reef, and out to sea, even with the presence of the seeps. Surface emanations of bay waters beyond the reef were pronounced with the land-breeze regime but retarded by the entrainment of the sea breeze. Using these variables, it was evident that the reef was not effective in cutting off bay water and that inner bay waters and their characteristics persisted beyond the reef.

Understanding the Spatiotemporal Variability of Hydrological Processes for Integrating Watershed Management and Environmental Public Health in the Great River Basin, Jamaica

The demand for adequate and safe supplies of water is becoming crucial especially in the overpopulated urban centers of the Caribbean islands. Moreover, population growth coupled with environmental degradation and possible adverse impacts of land use and climate change are major factors limiting freshwater resource availability. The main objective of this study is to develop a hydrological model and analyze the spatiotemporal variability of hydrological processes in the Great River basin, Jamaica. Physically based hydrological model, Soil and Water Assessment Tool (SWAT), was calibrated and validated in the basin. Spatial distribution of annual hydrological processes, water balance components for wet and dry years, and annual hydrological water balance of the Great River basin are discussed. The basin water balance analysis indicated that surface runoff contributes more than 28 %, whereas the groundwater contributes more than 18 % of the stream flow. The water balance components differ spatially between each subbasin. The actual evapotranspiration varies between subbasins which range from 887 to 1,034 mm. The variation in evapotranspiration between subbasins is mainly due to variations in land cover. The model can be used to predict watershed responses to climate and land use changes. Hydrological water balance analysis can be used to predict the existing water resource component that can help manage water availability and predict where and when there will be water shortages. The output of water balance study can be used in irrigation potential assessment, runoff assessment, flood control, and pollution control.

The Hydrodynamic Modelling of Reefal Bays – Placing Coral Reefs at the Center of Bay Circulation

Reefal bays are a common type of bay system found along most Caribbean coasts including the Jamaican coastline. These bay systems are associated with and delimited by arching headland with sub-tending reef arms broken by a prominent channel. Traditionally, these bays are termed “semi-enclosed” as their limits are defined by the sand bar or reef partially cutting off waters behind them from open sea (Nybakken, 1997). Yet, it has been shown that circulatory patterns emanating from the lee of reef structures can persist beyond the forereef (Prager, 1991; Gunaratna et al., 1997). This raises the possibility of re-characterizing these systems where the reef is defined as the centre of a dynamic bay, inducing a continuous re-circulation of the inside waters beyond the traditional limit (Figure 1). In this study, hydrodynamic modelling, particle tracking and a novel gyre analysis method were used to assess the reefal bay’s signature spatial and temporal patterns in circulation, with the goal of characterizing the reefal bay as unique in its function. This was carried out on the Hellshire southeast coast of Jamaica where four of seven bays are typical reefal bays.