Rationale - what it means and why it is an important measure
Water bodies (ground water and surface water) in close proximity to urban areas are often very important sources for drinking water consumption. Nevertheless, water resources are under threat from many human activities and, in several parts of the continent, human health, welfare and economic development are constrained by a lack of sufficient water of good quality.
The most important source of organic matter in rivers is wastewater. The main source of nitrate is generally diffuse pollution from agriculture.
How it is compiled, what data are needed
The quality of rivers and streams is measured as the Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD); these are not directly comparable. Phosphorus in water is measured as either total or dissolved phosphorus. Nitrogen is measured as the total of nitrate and ammonium. All measurements are taken as the average of annual means.
Measurements and units
The quality of rivers and streams (BOD (mgO2/l); P (ug/l); N (mg/l))
Possible temporal and spatial format
trend charts, maps
Reference to methodology resources
EEA, 1995. Europe's Environment: The Second Assessment. Copenhagen.
To improve water quality in the streams.
Targets, benchmarks, reference values
Europe: The Urban Wastewater Directives (91/271/EEC), the Nitrate Directives (91/676/EEC), EU Action Programme's proposal for a Water Framework Directive.
There are several action plans for specific water bodies that establish target limits; for example, the Rhine Action Plan and the Danube Action Plan.
References to examples of application
Water quality on surface streams in Prague (Czech Republic): http://www.ceroi.net/reports/prague/charts/2-01.gif