What is GREAT-ER |  GREAT-ER Output |  Application Examples |  Model Validation |  What's Next? |  Colour Coded River Maps Concentration Profiles Aggregated PEC's Colour Coded River Maps GREAT-ER's direct output provides Predicted Environmental Concentrations linked to a river network, which are visualised as colour coded digital river maps using a Geographic Information System (GIS). To capture natural variability, the predicted concentrations are represented as statistical distributions. The GIS tools allow identification of any locations within a region where site-specific PEC values may be exceed the PNEC (i.e. 'hot spots'). GREAT-ER does not model general water quality, but WQ maps can be overlain onto the simulation output to correlate chemical emissions with actual water quality and ecosystem health. Top of Page Concentration Profiles Profiles of Predicted Environmental Concentrations (PECs) through the studied catchment can be generated for any selected probability level (e.g. PECmean or PEC90%). Such profiles clearly illustrate chemical emissions and fate from a river's headwaters down to its mouth, and can be used to compare model predictions with monitoring data. Top of Page Aggregated PECs (Predicted Environmental Concentrations) New concepts have been developed to aggregate geo-referenced model results into a spatially averaged PEC, which is representative of the river basin under study. PEC definitions developed within GREAT-ER: GREAT-ER can generate PECinitial which comes from the distribution of concentrations in the river stretch below each emission point. This corresponds to the PEClocal concept used in the EU Technical Guidance Document. GREAT-ER can also generate PECcatchment by incorporating the concentration distributions in each river stretch in the catchment. This corresponds to the PECregional concept used in the EU Technical Guidance Document. Top of Page