Freshwater - Drivers and pressures (Germany)
The main sources of water pollution by nutrients and other pollutants are agriculture, municipal wastewater treatment plants, rainwater drainage from towns and cities, and industrial plants. However, water pollution caused by point-source discharges from wastewater treatment has fallen considerably. Currently development of treatment plants focussed on pollutants that cannot be degraded, including many pharmaceutical products and pesticides. Diffuse discharges of agricultural nutrients and pesticides and of heavy metals and organic substances from urban areas and transport are now the most important material pollutants of Germany’s inland waters. For the biotic communities of inland waters, structural loss is seen as an even bigger problem since it leads to the disappearance of entire habitats (see 2.2). For groundwater pollution, the removal of nitrogen resulting from the use of nitrate fertilisers and farmyard manure and leaching from pesticides is of paramount importance.
The nitrogen surplus determined from the total nitrogen balance is an indicator of potential discharges of nitrogen compounds into groundwater, surface waters and the air. It is calculated from the difference between nitrogen flows into agriculture and nitrogen flows exported from it. The figures given here are averages for Germany. In order to offset annual weather-dependent variations beyond anyone’s control, a sliding three-year average is taken for the middle year in each case.
Since 1993 the nitrogen surplus in the three-year average has fallen from 115 kg/ha and year to 105 kg/ha and year (see figure), corresponding to a reduction of 9 %. Overall, in the period from 1993 to 2007, just under a third of the target reduction by 2010 had been achieved. The reduction in the early 1990s was not because nitrogen was used more efficiently, rather because of the decline in the livestock population in the new Länder. In the past five years the average annual reduction in the balance has been less than 2 %, whereas it needed to decrease 10% a year between 2008 and 2010 for the target to be reached. The 2007 amendment to the Fertilisers Regulation introduced mandatory operational ceilings for the surplus of each farm. Further efforts to improve nitrogen use are needed.
Diffuse sources of nitrogen are always at a maximum where too many livestock are being kept on sites where there is a risk of leaching.
Nitrogen and phosphorus discharges into surface waters
In 2005 nitrogen discharges into surface waters stood at 565 kt/a, a reduction of 465 kt/a or 45% from the reference year of 1985 (see figure below). This meant that the internationally agreed target of halving nitrogen discharges into the oceans between 1985 and 2000 had still not been reached by 2005. Nitrogen discharges from point sources – municipal wastewater treatment plants and industrial dischargers – fell by 76 % between 1985 and 2005, reducing the proportion of the total discharge accounted for by point sources in 2005 to 18 %. This was largely due to more efficient wastewater treatment: in contrast, nitrogen discharges from diffuse sources fell by only 24%.
At 48 %, discharges through groundwater were overall the dominant entry route in 2005. Discharges into surface waters through erosion and atmospheric deposition accounted for only a small proportion of the total discharges – 2 % each.
Phosphorus discharges into surface waters nationwide stood at some 23 kt/a in 2005 (see figure below), a drop of around 58 kt/a – 71 % from the reference year of 1985. The target of halving phosphorus discharges into the oceans has thus been met in all river areas.
The reduction in phosphorus discharges is also largely due to the reduction in discharges from point sources – 86 %. However, despite this huge reduction, at 35 % of the total in 2005, discharges from point sources were still the most dominant entry route. Diffuse phosphorus discharges were reduced by only 29 %. The majority of this was accounted for by the 71 % reduction in discharges from urban areas, including combined sewer system overflows, rain discharges from separated sewer systems and wastewater from households not connected to a municipal treatment plant or sewer system.
Of the diffuse sources of phosphorus the main discharges are from erosion with 22 % of the total, followed by 20 % of discharges through groundwater.
Heavy metal discharges into surface waters
Heavy metal discharges into surface waters in Germany fell considerably between 1983 and 2005.
The targets set by the international marine conventions of reducing discharges of chromium, copper, nickel and zinc by 50 % and of cadmium, mercury and lead by 70 % from 1985 levels had been achieved or surpassed by 2005, with the sole exception of nickel, a very high percentage of which is geo-genic and unavoidable. The reductions in individual metals range from 47 % for nickel to 91 % for mercury, and are mainly the result of drastic reductions in point source industrial discharges, ranging from 89 % for lead to 99 % for mercury. Measures taken by industry to meet stricter statutory requirements have played a decisive part in these environmental improvements, as has the reduction in industrial activity in the new Länder since 1990.
In 2005 industrial discharges were responsible for only a very small proportion of the total discharge, ranging from 3% for nickel to 8 % for chromium.
Point source discharges from municipal wastewater treatment plants continued to be high, but in 2005 water pollution was dominated by discharges from diffuse sources that varied from 56 % for cadmium to 84 % for lead.
The main diffuse pathways were erosion, groundwater inflows and urban areas – particularly from sewer systems and residents not connected to mains sewers – that accounted for varying proportions of the heavy metals. Erosion discharges mainly involved chromium (62%) and lead (48%).
For nickel the main discharge – 45 %, – was geo-genic, through groundwater. A high percentage of the discharges, other than of nickel and chromium, into surface waters also comes from urban areas. This includes discharges from combined and separate sewer systems which account for particularly high proportions of the total discharge for zinc (39 %), copper (31 %) and lead (22 %). Since a significant proportion of the precipitation runoff in combined systems goes to wastewater treatment plants, such systems are preferable to separate systems as far as heavy metals are concerned (see figures 3 and 4).
Use of water resources
The main user groups – industry, including thermal power plants; public water supply; and agriculture – together took around 32 billion m³ from groundwater and surface water supplies in 2007.
Water extraction has been declining for years in all sectors, but the demand for water from thermal power stations has fallen the most.
At present the water demand from private households accounts for around 16 % of the total extracted; industry is responsible for the largest share of the demand with 84 %, over 73% of which is taken by thermal power plants, mainly for cooling, while just under 27% is needed by the mining and manufacturing industries for production processes. Water extraction for agriculture is not significant in Germany.
The total volume of 32.1 billion m³ represents less than 20 % of the potential water supply, in other words more than 80 % of the water supply is unused at present. The figure below shows the percentages of the main water users in proportion to the potential supply.