The Management of Siltation at Hillsborough Dam, Tobago

Hillsborough Dam is situated on the Hillsborough East River, 4 km north of the village of Mount St George on the island of Tobago and is owned and operated by Trinidad and Tobago Water and Sewerage Authority (WASA). The dam, commissioned in 1952, forms one of the main sources of water supply for the island of Tobago.

WASA have been concerned for a number of years that the volume of Hillsborough Dam was decreasing due to the deposition of sediment in the reservoir. In 2004 Inter-American Bank funding was obtained by the Government of Trinidad and Tobago to let a contract for the feasibility study and detailed design for desilting and rehabilitation works at Hillsborough Dam, Tobago. The project was carried out between January and August 2005.

The paper describes the investigations that were carried out to determine the extent of siltation, discusses the causes of siltation, describes methods proposed for desilting the reservoir, outlines the environmental legislation and discusses issues related to the disposal of silt. The paper concludes with proposed methods for future reservoir and catchment management.

• Introduction

• Geology of the Study Area

• Extent of Siltation

• Causes of Siltation

• Proposed Method of Desilting

• Environmental Legislation

• Silt Disposal Issues

• Proposals for Future Catchment Management

• Acknowledgments

• References