3 research outputs found
Catchment-scale vulnerability assessment of groundwater pollution from diffuse sources using the DRASTIC method : a case study
The catchment-scale groundwater vulnerability assessment that delineates zones representing different
levels of groundwater susceptibility to contaminants from diffuse agricultural sources has become an important
element in groundwater pollution prevention for the implementation of the EUWater Framework Directive (WFD).
This paper evaluates the DRASTIC method using an ArcGIS platform for assessing groundwater vulnerability in
the Upper Bann catchment, Northern Ireland. Groundwater vulnerability maps of both general pollutants and
pesticides in the study area were generated by using data on the factors depth to water, net recharge, aquifer media,
soil media, topography, impact of vadose zone, and hydraulic conductivity, as defined in DRASTIC. The mountain
areas in the study area have “high” (in 4.5% of the study area) or “moderate” (in 25.5%) vulnerability for general
pollutants due to high rainfall, net recharge and soil permeability. However, by considering the diffuse agricultural
sources, the mountain areas are actually at low groundwater pollution risk. The results of overlaying the maps of
land use and the groundwater vulnerability are closer to the reality. This study shows that the DRASTIC method is
helpful for guiding the prevention practices of groundwater pollution at the catchment scale in the UK
Interdecadal variability of the Southern Ocean
The intrinsic variability of the Antarctic Circumpolar Current is investigated using an idealized wind-driven model. The model uses three quasigeostrophic layers, with steady wind stress forcing, and no diabatic effects. Despite the idealized nature of the model, the simulations display a robust mode of low-frequency variability in the flow. It is demonstrated that this variability is dependent upon the explicit simulation of the dynamics of mesoscale eddies. As such, the variability is sensitive to stratification, horizontal viscosity, bottom stress, and topography. The energetic balance of the variability is diagnosed, and a driving mechanism is proposed that involves positive feedback between the generation of eddies through baroclinic instability and the dynamics of the mean circulation.<br/