Nowadays, Directive 2000/60/CEE is the European Union's basic instrument to manage hydrologic resources in a sustainable way. Its main objectives are the progressive reduction of pollutant spills and the achievement of a good ecological quality of superficial waters. The first aspect requires registering all the spilled substances and controlling their concentration in water. In the Canary Islands, it is complicated to establish the substances to be analyzed since the inventory of pressures is not updated. Therefore, most of the very toxic compounds (Annex X) are in the Monitoring Program. Regarding the evaluation of ecological quality, biological indicators and their quality thresholds are being defined by the intercalibration exercise, which is organised among states that belong to the same ecoregion. The Canary Islands belong to the Northeast Atlantic Geographical Intercalibration Group. Although it is being attempted to consider each place's idiosyncrasy (Spain,