Evaluation of the declining groundwater levels of the coastal aquifers of Guyana


Groundwater abstractions globally are increasing resulting in degradation of groundwater quantities and qualities. In Guyana 90% of the population lives along the coast which accounts for approximately 10% of the total land mass. Groundwater is the main source of domestic consumption and as such results in an elevated pressure on this resource and reported decline in groundwater levels. The aim of this project is to establish the cause of decline in groundwater levels, and whether this is attributed to a change in climate, specifically rainfall within the recharge area, or increased abstraction rate. Rainfall and groundwater level data were analysed using R2 trend analysis while recharge was calculated using a simple recharge equation and evaporation data derived from the ERA-40 reanalysis data set and use of the Thornthwaite equation. The impacts of recharge and abstraction are evaluated using Groundwater Modelling Software MODFLOW. It was accepted that the aquifer was connected to the rivers within the basin as well as the Atlantic Ocean. The high variability in rainfall over this region and the reported continuous decline in groundwater levels suggest there may be an additional reason for this decline. Current abstraction rates in comparison to the storage capacity of the recharge area did not suggest that there should be decline in groundwater sources. While abstraction rates continue to increase it is the proximity of wells that raises alarms as these can be found within a thin strip along the coast and banks of rivers. In addition to this, with connectivity to the ocean and extensive cones of depression, the possibility of saline intrusion increases and poses a threat to this precious resource.


Angela Franklin