Bio
Geoffrey Marshall is a hydrogeologist by training who has worked in the water sector for over 27 years. He attended St. Jago High School from 1990-1997, and then worked as a Hydrology Technician at the Water Resources Authority of Jamaica from September 1997-August 1998. He then attended Washington and Lee University in Lexington, Virginia USA from Sept 1998 to June 2002, where he graduated with dual degrees: a Bachelor of Science in Geology and a Bachelor of Arts in Computer Science. After this, he attended the New Mexico Institute of Mining and Technology in Socorro, New Mexico USA from September 2002 to May 2005, and graduated in December 2005 with a Masters of Science Degree in Hydrology. In February 2006, he returned to Jamaica and re-joined the Water Resources Authority as a Hydrogeologist starting in March 2006. Since that time, he has served as a Hydrogeologist in the Planning and Investigations Unit from 2006-2014, then as the Senior Hydrologeologist in charge of the Permits and Licenses Unit (2014-2016), then Chief Hydrologist in charge of the Planning and Investigations Unit (2016-2022). Currently, Mr. Marshall serves as the Deputy Managing Director with oversight responsibility for the WRA’s Technical Branch.
Mr. Marshall has also served as the WRA Staff Representative at the Jamaica Civil Service Association from 2016-2022, and was a member of the JCSA Executive Committee from 2019-2024. He is a Justice of the Peace, a Distinguished Toastmaster, and a trained Mediator and Restorative Justice Practitioner.
Abstract
The Miocene/Eocene karstic limestone aquifers form substantial portions of groundwater resource storage in Jamaica, and are highly vulnerable to anthropogenic activities in their watersheds. Groundwater fluxes follow complex subsurface karstic structures, often bypassing surface-morphological divides. A prominent example is the Rio Bueno sub-WMU of the Dry Harbour Mountains Hydrologic Basin, where recharge primarily occurs through sinking streams and rainfall infiltration via fissures and sinkholes in the basin’s central areas. The groundwater is discharged near the coast through risings such as Dornoch Head (Rio Bueno headwaters) and Pear Tree Bottom wetlands.
Significantly deteriorating ambient water quality levels in groundwater and surface water throughout the Rio Bueno sub-WMU do indicate anthropogenic impacts from various causes. The definitions of recharge areas and travel times for groundwater flow and sinking streams throughout the sub-WMU are crucial for sustainable water resources management. The use of dye-trace and stable isotope hydrology techniques can provide more clarity on source water provenance and flow dynamics in the sub-WMU.
As such, the WRA conducted a series of monitoring exercises of various spring, river, sinks, wells and rainfall sources in the sub-WMU between 2017 to 2023 utilizing stable isotopes (2H and 18O), tritium and chemistry data, along with dye trace injections (fluorescein, rhodamine and eosine) to more precisely delineate the groundwater and streamflow dynamics in this sub-WMU. The results confirmed previously known connections, revealed previously unknown connections, and indicated the main recharge contributions to streamflow, as well as the presence of significant groundwater resources potentially recharged by extreme precipitation events (among other findings). The results of these studies can be used to guide future actions for source water protection, development and management in the sub-WMU, such as the establishment of Water Quality Control Zones as per the Water Resources Act.