Calculation of Natural Background Levels, Threshold
Total Page:16
File Type:pdf, Size:1020Kb
DRAFT Calculation of natural background levels, threshold values and dilution for groundwater according to the proposed methodology in the groundwater body “Southern Vienna Basin” in Austria Claudia Schramm, Andreas Scheidleder, Dietmar Müller, Franko Humer, Irene Zieritz, Johannes Grath, Irmgard Plank, Günter Eisenkölb UMWELTBUNDESAMT – Federal Environmental Agency Austria SUMMARY In the frame of the EU project BRIDGE the Austrian groundwater body “GK100024 Southern Vienna Basin” was chosen as a case study within WP4. In a first step the groundwater body was characterised. Groundwater itself, drinking water and surface water were found to be relevant receptors in the Southern Vienna Basin. According to the proposed tiered approach (Deliveralbe D15) natural background levels (tier 1), receptor based threshold values (tier 2) and dilution with surface water (tier 3) was acquired. Drinking water quality standards and ecotoxicological standards were used as reference values. Attenuation of pollutants due to (bio)geochemical reactions (tier 4) was not considered in the Austrian case study. Abbreviations WFD: Water Framework Directive GWD: Draft Groundwater Directive NBL: Natural Background Level TV: Threshold Value LOD: Limit of Detection LOQ: Limit of Quantification DWD: Drinking Water Directive DF: Dilution Factor EQS: Environmental Quality Standard REF: Reference Value not av.: not available 1 CONTENT OF THE CASE STUDY REPORT AUSTRIA SUMMARY ..................................................................................................................... 1 1. Introduction ................................................................................................................ 3 2. CHARACTERISATION OF THE GROUNDWATER BODY ................................ 3 2.1 Physical and hydrogeological description........................................................................... 3 2.1.1 Geographical boundaries .............................................................................................. 3 2.1.2 Climate.......................................................................................................................... 4 2.1.3 Water balance ............................................................................................................... 4 2.1.4 Geology......................................................................................................................... 5 2.1.5 Hydrogeology ............................................................................................................... 5 2.2 Identification of pressures ................................................................................................... 8 2.2.1 Groundwater abstraction............................................................................................... 8 2.2.2 Artificial recharge......................................................................................................... 8 2.2.3 Pollution........................................................................................................................ 9 2.3 Conceptual model................................................................................................................ 9 2.4 Natural background levels – national approach ................................................................ 10 2.5 Review of impacts............................................................................................................. 11 2.5.1 Monitoring network (groundwater and surface water) ............................................... 11 2.5.2 Effects of abstraction on groundwater quantity .......................................................... 11 2.5.3 Effects of abstraction on groundwater quality............................................................ 11 2.5.4 Effects of abstraction on dependent ecosystems......................................................... 12 2.5.5 Effects of artificial recharge........................................................................................ 12 2.5.6 Effects of pollutant pressures on groundwater quality................................................ 12 2.5.7 Effect of groundwater induced pollutant pressures on dependent ecosystems ........... 13 2.5.8 Pollutants selected for threshold methodology evaluation ......................................... 13 3. THRESHOLD VALUES TO ASSESS THE CHEMICAL STATUS OF THE GROUNDWATER................................................................................................... 13 3.1 Application and evaluation of the proposed threshold methodology ................................ 13 3.1.1 Tier 1: Assessing the Natural Background Levels (NBLs) with the proposed pre- selection method ......................................................................................................... 13 3.1.2 Tier 2a Option 1: Calculation of Threshold Values for the receptor Groundwater itself .................................................................................................................................... 16 3.1.3 Tier 2a Option 2: Calculation of Threshold Values with the maximum permissible addition (MPA) approach for the receptor groundwater itself.................................... 18 3.1.4 Calculation of the dilution factor for the receptor surface water ................................ 20 4. CONCLUSIONS ...................................................................................................... 22 4.1 Comments and conclusion on BRIDGE data pre-selection and NBL estimation ............. 22 4.2 Comments and conclusion on the selection of Reference (REF) values........................... 22 4.3 Comments and conclusion on the derivation of threshold values (TVs)........................... 23 4.4 GENERAL CONCLUSION.............................................................................................. 23 5. REFERENCES......................................................................................................... 23 2 1. Introduction The “Southern Vienna Basin” is located in the south-east of Vienna. It contains one of the largest groundwater reservoirs in Europe, the so called “Mitterndorfer Senke” and is hence of utter importance for the drinking water supply the eastern part of Austria. According to Art. 5 of the Water Framework Directive the groundwater body GK100024 Southern Vienna Basin has not been reported to be at risk. Nevertheless water abstractions and agriculture are a relevant pressure in the Southern Vienna basin. Contaminated sites put a risk the groundwater quality of the Southern Vienna Basin, mainly due to chlorinated hydrocarbons. 2. CHARACTERISATION OF THE GROUNDWATER BODY 2.1 Physical and hydrogeological description 2.1.1 Geographical boundaries The Southern Vienna Basin is a single, shallow groundwater body. The mean altitude is 235 meters above sea level (adria), ranging from 133 up to 494 meters. The total area of the Southern Vienna Basin is 1228 km 2. The maximal length and width is 72 and 30 km, respectively. More than 85% of the area is situated in the federal province Lower Austria (1048 km 2), the rest in the area of the province and city of Vienna (173 km 2) and a small area of 7 km 2 belongs to the Province of Burgenland. The groundwater body belongs to the Sub river basin “Donau unterhalb Jochenstein (DUJ) [PL100004]” and the river basin “Donau [EZ100002]”. It is part of the ecoregion for rivers and lakes “11.Hungarian Lowlands” and partly “4. Alps” and the ecoregion for coastal waters “7. Black Sea”. 3 Fig. 1: Map of the groundwater body GK100024 Southern Vienna Basin 2.1.2 Climate The mean annual air temperature in the Southern Vienna Basin is 8 to 10 °C. The average of the annual precipitation is about 570 mm. In the southern part of the groundwater body values up to 700 mm can be reached. The seasonality of the monthly precipitation shows its maxima in June in the central and southern part of the Southern Vienna Basin. In the northern part the maxima of the monthly precipitation occurs in July. 2.1.3 Water balance The climatic water balance in the groundwater body is mainly negative according to data from 1961 to 1990. Only the south-western part of the Southern Vienna Basin and narrow bands along the rivers show a positive water balance. The mean annual potential evapotranspiration in the Southern Vienna Basin is between 625 and 650 mm. The mean annual actual evapotranspiration ranges from 400 mm in the northern part of the case study area up to 625 mm in the south (using water balance data). The mean annual depth of runoff in the case study area is less than 250 mm (using water balance data). Table 1: Annual average in mm of water balance components Precipitation ETP pot. ETP act. Runoff 500 - 700 mm 625 - 650 mm 400 - 625 mm 0 - 250 mm 4 2.1.4 Geology The Southern Vienna Basin was formed as a pull-apart basin between the Alps and the Karpat mountain range. It was filled during tertiary times by thick, mainly marine sediments. Above these quaternary fluviatile channel and basin sediments can be found. The sandy gravel formations of the Pleistocene are relevant water resources. The so called “Mitterndorfer Senke” for example has a length of approximately 50 km and a width ranging from 15 to 20 km and is one of the largest groundwater reservoirs in Europe. Upper confining layers in the Southern Vienna Basin are siltic humic top soils. At the western fringe of the basin middle till coarse grained water-bearing Pannonian sediments are present. 2.1.5