A crucial aspect of environmental policy is to review and assess human impacts of all types. GIS plays an important role in achieving this task when monitoring and analyzing the adverse environmental impact on water bodies, such as lakes, rivers, and bays. For example, a GIS can facilitate an evaluation of pollution sources by generating reports and managing data about polluters, results of measurements, reference materials providing classification of hazardous groups, and concentrations of hazardous substances in a specific river or an entire aquatic system. A GIS can also provide the tools to identify the most hazardous contaminants with regard to ecological regulations and contribute to effective decision making to ensure that natural resources are preserved and utilized correctly.