The Placencia Lagoon - Coastal Zone Management Authority and ...

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inundation during the rain season. The principal waterway, Big Creek, is fed by numerous small streams and debouches at the southernmost end of the Placencia Lagoon. The vegetation cover within this catchment includes marshlands, mangroves, grass meadows and pine ridge. It is worth pointing out that none of the watercourses that flow into the Placencia Lagoon are gauged, hence there are no time series on the discharge and water levels (Hydrology Service, 2003). However, Grimshaw (2000) purports that the combined low flow for August and Mango Creeks is 0.7 CMS. Furthermore the low flow for Jenkins and Flour Camp Creeks was estimated at 0.8 CMS. Silver Creek was estimated to have a low flow of 1.3 CMS. The ground water resources map of Belize divides the country into ten regions based on water availability and quality (Buckalew et al., 1998). The terrestrial zone of influence on the Placencia Lagoon falls into two of these regions. (1) The Placencia Peninsula and the western margin of the lagoon are classified as areas where small to large quantities of brackish to saline water are available. Also, meager to very small quantities of fresh water are available from quaternary alluvium and coastal deposits along the coast. Depth to water is 2 to 50 meters. (2) The wider extent of the terrestrial zone of influence is that part of the Central Coastal Plain composed of sandy shales, shales, claystones, mudstones, and alluvium. These deposits bear meager to moderated quantities of freshwater. Depth to water is generally less than 60 meters. Although, there is limited information about the ground water distribution in the terrestrial zone influencing the lagoon, it is envisaged that ground water might have some effects on the water budget of the Placencia Lagoon. Meteorology The Placencia Lagoon and adjacent catchments fall in a tropical climatic zone. Walker (1973), King et al. (1989, 1992) documented the rainfall distribution for Belize and indicate that the annual rainfall for the Placencia area varies between 80 inches (2032 mm) and 100 inches (3048 mm). The mean annual temperature for the region is 28°C and the mean relative humidity is 80%. The predominant winds are out of the Southeast at a mean speed of 4 knots. The Belize National Meteorological Service (BNMS) has a countrywide network of climatological stations. Station 28 located at Rum Point Inn and station 29 located at the Savannah Forest Station are the stations nearest to the Placencia Lagoon. 9
Characteristics Of The Belize Barrier Reef Lagoon The Belize Barrier Reef Lagoon is divided into the Northern and Southern Shelf Lagoons based on differences of physical, chemical, geological and biological characteristics of the area (Purdy et al., 1975; Purdy, 1974). The immediate coastal oceanographic zone that exerts influence on the Placencia Lagoon is that portion of the Southern Shelf Lagoon adjacent to the Placencia Peninsula. Bathymetry The bathymetry in the Southern Shelf Lagoon is very irregular due in part to the tectonic activity that formed the shelf in the first place (Lara, 1993). Subsequent growth of coral assemblages, the formation of incised valleys, channels and shoals also add to the complexity of the bathymetry of the southern Shelf. Seaward of the Placencia Peninsula is the Inner Channel with depths ranging from 10 –20 meters. East of the Inner Channel is the Victoria Channel with depths of 20- 30 meters. Sediments The Southern Shelf is comprised of both biogenic and terrigenous sediments. The biogenic sediment is derived from the remains of marine organisms such as corals, coralline algae and mollusk (Purdy et al., 1975; Purdy, 1974). The terrigenous material includes quartz sand, muds, and clay minerals derived from the Maya Mountains, the Central and Southern Coastal Plains (Esker, 1998). The fact that the Southern Shelf Lagoon shows high influence of terrigenous sediment highlights the influence of terrigenous material on the Placencia Lagoon, which is in closer proximity to the Central Coastal Plain. Currents Thus far there is no comprehensive study of the current patterns near the Placencia Peninsula or the Placencia Lagoon. The Watershed Reef Interconnectivity Scientific Study (2001) purports that water within the barrier reef lagoon flows predominantly from north to south at a rate of 0.05 to 0.15 m/s and rarely exceed 0.3 m/s. The Regional Monitoring and Environmental Information System component of the MBRS is in the process of completing a 3-dimensional ocean circulation model of the continental shelf of the MBRS (Ariola, 2002). In addition to this, a 2-dimensional circulation model is also being prepared. Undoubtedly, these models will enhance present knowledge about circulation patterns in Belize. Tides Tides of the Caribbean and along the Belize Barrier Reef are microtidal and of mixed semidiurnal type with a mean range of 15 cm (Kjerve, 1981). PASCO (2002) mentions that the tidal fluctuations on the windward side of the Peninsula range from 0.40 to 1.5 feet. 10
Page 2 and 3: Characterization of a Tropical Estu
Page 4 and 5: ACKNOWLEDGEMENT The preparation of
Page 6 and 7: EXECUTIVE SUMMARY There is growing
Page 8: OBJECTIVES To identify and document
Page 11 and 12: The turbidity sensor was calibrated
Page 16 and 17: Salinity The salinity of the Southe
Page 19: Major Land Use and Activities in th
Page 23 and 24: Table 2a. Shrimp Mariculture produc
Page 26 and 27: Temperature °C 30.20 30.00 29.80 2
Page 28 and 29: The salinity measurements within th
Page 30 and 31: Turbidity The mean turbidity levels
Page 32 and 33: The salinity maps presented in Appe
Page 34 and 35: CONCLUSIONS The characterization of
Page 36 and 37: Huntington, T., Dixon, H. 1997. A R
Page 38: APPENDIX I Temperature Distribution
Page 48: Abbreviations and Notations BNMS Be

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