Assessment of current water pollution loads in Europe: estimation of gridded loads for use in global water quality models

A methodology for estimating the loading of pollutants to water courses across all of pan-Europe, an area reaching to the River Don in the east and including some Mediterranean rim countries in the near east and North Africa is presented. Loadings come from point (domestic effluent, manufacturing discharge and urban runoff) and diffuse (scattered settlements and land use) sources. The loads have been calculated on a countrywide basis using readily available data held by national and international bodies. These loads are downscaled to the grid cells (5 × 5′) used in the model. The paper illustrates the general framework for making these calculations using biochemical oxygen demand (BOD) and total dissolved solids (TDS), and estimated loads for periods representing 1990, 1995, 2000 and 2005 are presented as maps. According to the model, in 2005, annual BOD loads came mostly from domestic effluent (3 Mt) and diffuse sources (5 Mt, mainly attributed to livestock). Manufacturing, urban runoff and scattered settlements contributed annual loads of 0.33, 0.15 and 1.2 Mt, respectively. For TDS, annual manufacturing loads were 65 Mt and annual domestic loads 28 Mt. Diffuse loadings (36 Mt) came from irrigated land and therefore showed a different spatial pattern from BOD. The total annual diffuse load of TDS was 56 Mt. Scattered settlements contributed only 9.6 Mt to the total pan-European load. Some limited comparison of the loads estimated in this study for BOD with those estimated by others for countries and large catchments in the area has been carried out.