Hidrológiai Közlöny, 2017 (97. évfolyam)

2017 / 3. szám - TRANSNATIONAL EFFORTS - Kovács Ádám: Agricultural development and good water status in the Danube River Basin - A contradiction?

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Adám Kovács: Agricultural development and good water status in the Danube River Basin - A contradiction?

river loads at sub-catchment outlets taking into account in- stream retention processes. Scenarios for implementing control measures can be developedat the catchment scale and their effectiveness in terms of emission and river load reduction can be assessed.

Model input dataset has been updated for the reference period 2009-2012 and the model has been validated against measured river loads. Model results have been analysed to identify regional scale emission hot-spots within the DRB and to better understand the main pathways and sources of nutrient emissions and their proportions.

RESULTS AND DISCUSSION

Results

The basin-wide nutrient emissions entering the surface water bodies are 605,000 tons per year total N and 38,500 tons per year total P for the reference period (.ICPDR

2015). Pathway and source apportionment of the total emissions is presented in Figure 1 and Figure 2. Diffuse pathways clearly dominate the total releasesby 84% (N) and 67% (P). For N, subsurface flow (base flow and interflow) is the most important diffuse pathway with a proportion of 54%. In case of P, soil erosion (32%) and urban runoff (18%) generate the highest emissions. Regarding the sources, agriculture (N: 42%, P: 28%) and urban water management (N: 25%, P: 51%) are responsible for the majority of the nutrient emissions. The recently (2005-2015) transported fluxes are 460,000 tons per year total N and 25,000 tons per year total P (ICPDR 2016a), which are still considerably higher than those of the early 1960ies which represent river loads under low pressures (IWAG 2005). This indicates a further load reduction potential that might be exploited for the benefit of the Black Sea (N: 35%, P: 20%). This would require a further decrease of both, the point source and diffuse emissions generated in the DRB.

Direct atmospheric deposition • Overland flow

9 Soil erosion

Tile drainage flow 9 Groundwater flow

9 Urban runoff

9 Point sources

9 Agriculture (fertilisers) Agriculture (atm. deposition) 9 Urban water management Other areas 9 Natural background

Figure 1. Share of sources in the overall total Nemissions in the DRB for 2009-2012; on the left: pathways, on the right: sources

(Source: ICPDR 2015)

Direct atmospheric deposition 9 Overland flow

9 Soil erosion

Tile drainage flow 9 Groundwater flow

9 Urban runoff

9 Point sources

9 Agriculture • Urban water management 9 Other areas 9 Natural background

Figure 2. Share of sources in the overall total P emissions in the DRB for 2009-2012; on the left: pathways, on the right: sources

(Source: ICPDR 2015)

Country contributions can be seen in Figure 3. Germany and Slovenia produce the highest area-specific N emissions in the basin. Regarding the source areas, rural areas have a principal role in nitrogen emission generation. Urban water management is still an im- portantsource, especially in the new and non-EU MS. In case of P, Serbia generatesthe highest area-specific P emission rates. Upstream countries show similar contribution of theurban and agricultural areas. Movingdown- stream in the basin urban areas become more dominant indicating the high potential to improve wastewater treatment by introducing P removal. The importance of

the urban sources is strong particularly in themiddle basin.

Comparing recently calculated the emission figures to those reported in the 1st DRBMP (ICPDR 2009) for the reference year 2005,remarkable decrease is visible. The N and P emissions from urban waste water treatment plants significantly declined by 32% and 45%, respec- tively.Diffuse emissions also substantially dropped due to both, the low agricultural intensity inmany countries and the measures implemented (TN: 8%, TP: 28%). The total N emissions decreased by 12% in comparison to the 1st DRBMP whilst total P emissions declined by 34%.