Site Characterization of the
Jülicher Zwischenscholle area
for the PEGASE project
Mihail Ciocanaru, Rainer Harms, Olaf Nitzsche, Andreas Englert, Harry Vereecken
Forschungszentrum Jülich, Germany
1. Introduction
The Jülicher Zwischenscholle test area, located in North Rhine – Westfalia (Germany), is one
of the six test areas studied within the PEGASE project and belongs to the larger
Zwischenscholle area (Fig. 1). The six sites reflect different hydrogeological conditions and
land use strategies within the EU.
The Jülicher area was chosen from the following reasons:
1. good knowledge of the hydrogeological situation (e.g. reflected in the high density of
wells);
2. the presence of the test site Krauthausen, providing detailed information at field scale;
3. the possibility to conduct additional field experiment at the test site Krauthausen, allowing
a combined analysis of pesticides transport in soil and groundwater ;
4. the presence of different stack holders (e.g. water works, farmers and water users);
5. the Jülicher Zwischenscholle contains several protection areas designed to safeguard
groundwater quality;
6. presence of pesticides in the groundwater.
2. Geology
The Zwischenscholle area is situated in the Lower Rhine Embayment (Fig. 1). This is the tectonic lengthening of the Dutch Rift Valley. Since Tertiarian times, the Lower Rhine Embayment is an area of subsidence. The base are Variscian folded sediments of Devonian and Carboniferous times. Since the subsidence started, up to 1200m Tertiary and up to 100 m Quaternary sediments had been deposited. The stratigraphic sequence of the Tertiary (Fig. 2) shows
an interlocking of terrestrial and marine sediments. These sediments consist of fine and coarse
sand, gravel, clay, and lignite coal. The Quaternary sediments in the southern part of the Lower Rhine Embayment are mainly fluvial deposits of the Rhine/Maas river system. In the northern part, push moraines and aqueoglacial deposits of the Saale inland ice are added.
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Fig. 1 – Geo-structural map of Lower Rhine Embayment (Lingelbach, 1996)
Fig. 2 – Geological cross-section through the Lower Rhine Embayment (Lingelbach, 1996)
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Fig. 3 – Geological map of the Jülicher Zwischenscholle area (Lingelbach, 1996)
The Lower Rhine Embayment is divided into several parts by mainly south-east - north-west
directed faults. The Zwischenscholle area is bounded by the Rurscholle on the south-west and
the Erftscholle on the north-east (Fig. 1). The bounding faults are called Rurrand fault
Rurrand Verwerfung) and Rursprung (Fig. 3). The Zwischenscholle area is lowered against
the Erftscholle but lifted against the Rurscholle. Tectonic activities in the Lower Rhine Embayment are still ongoing and have resulted in some historic and recent earthquakes with
magnitudes up to 5.8.
3. Soil
In the Zwischenscholle area we can find mainly (Fig. 4): Braunerde, Parabraunerde, Gley,
Pseudogley, Auenboden (for a translation of the German soil types we refer to the Arbeitskreis für Bodensystematik der Deutschen Bodenkundlichen Gesellschaft, 1998).
In the south-eastern part of the region (Hambach, Niederzier) Braunerde are predominant,
while in the north-western part Brauner Auenboden dominate. In the middle part of the region
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we can find predominantly Pseudogley, Parabraunerde and Braunerde. Along the Rur river we
find Niedermoor.
Fig. 4 – Soil map of the Jülicher Zwischenscholle area (from Geologische Landesamt
Nordrhein-Westfalen, 1976)
4. Land Use
The area is characterized by forest and agricultural land use (Fig. 5). The western part, which
includes the research center area, is mainly covered by deciduous forest. Minor parts are
found with mixed forest, coniferous forest, and urban land use. The eastern part is dominated
by agricultural land use. The main crop is sugar beat with an annual turning of winter wheat,
winter barley, and winter rye. Minor crops are corn, potatoes and oat. The predominantly used
fertilizer is urea. As pesticides are mainly used: Isoproturon, Oxydemeton-methyl, Metamitron, Cycloat, Bifenox, Triflusulfuron-Methyl, Fluroxypyr, Carbendazim, Epoxiconazol,
Fenpropimorph, Kresoxim-methyl, Metribuzin and Ethofumesat.
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Urban regions in the area consist of small villages (Stteternich, Hambach, Niederzier,
Krauthausen, Selgersdorf), a network of larger and smaller motorways, and the area of the
research center.
Open pit mining activities are found outside the Zwischenscholle area but have no direct influence on the PEGASE investigation area.
Fig. 5 – Land use map of the Jülicher Zwischenscholle area (Lingelbach, 1996)
5. Hydrogeology
The first (unconfined or semi confined) aquifer (Fig. 6) consists of Quaternary Rhine and
Maas sand and gravel sediments (Klosterman, 1992). The base of the aquifer is build by the
Reuver clay. The aquifer thickness varies from 15 m in the south-west to 35 m in the northeast (Fig. 7). The main groundwater flow direction is from south-west to north-east. The first
aquifer is in direct contact with small local creeks and the Rur river. Regions with leakage
effects from the lower confined aquifer (between 45 and 120 m thick) are found on the
Rurrand fault (Rurrand Verwerfung). The Rurrand fault is assumed to be a natural no flux
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boundary, whereas the Rursprung fault shows a hydraulic connection between the
Zwischenscholle area and the Rurscholle area.
The mean hydraulic conductivity of the aquifer varies between 5  10 4 m/s and 5  10 3 m/s.
The mean hydraulic gradient is 0.002. The porosity varies between 20 and 30% (Lahmeyer
International, 1984).
Fig. 6 – Hydrogeological map of the Jülicher Zwischenscholle area (from Lingelbach, 1996)
The southern part of the area is used by the research center for the withdrawal of drinking
water from shallow wells (Fig. 6, well cluster around 020224 and 020226). For this purpose
two water supply wells are used. The yearly totally amount of water withdrew by these two
wells is of 33.000 m3.
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Fig. 7 – Lithological profiles from different groundwater measurement points within the
Jülicher Zwischenscholle area
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6. Groundwater chemistry
Water samples were available from monitoring wells and public supply wells screened over
the whole investigation area (Lingelbach, 1996). Sampling was done accordingly to the following german standards: DVWK Regel 128, DIN 38402-T13, DIN 38402-T21, DIN 38405T19, DIN 38406-T22. Most of the wells are screened in aquifer 1, which is the investigated
aquifer within PEGASE (Fig. 7). Some of the wells reach the deeper aquifer 2 and can be
used for comparative purposes. Chemical composition of the groundwater was determined by
following procedures:

ion chromatography for anions except HCO3- ;

titration for HCO3- ;

atomic adsorption spectroscopy for cations.
Iron and manganese were stabilized by adding 0.5 mL/L HNO3 to the tested samples. Due to
that fact, only the total concentration could be measured, not the redox state.
For most of the wells an additional screening of electrochemical parameters (pH, EH, conductivity, and temperature) is done regularly. Average concentrations of the most important species in the groundwater bellow areas used for forest, agriculture and urban settlements are
given in table 1.
The dominating ions are Ca2+ and HCO3- in all regions of aquifer 1. Magnesium and sodium
are also found but in minor concentrations. The anion concentrations show a clear influence
of agricultural use in the whole area. Sulfate, chloride and nitrate concentrations are significantly higher in aquifer 1 than in aquifer 2. Highest concentrations can be found in the region
under agricultural use. Magnesium and partly sodium show also a high concentration, potassium does not. One could expect also a higher potassium concentration due to the use of KCl,
K2SO4, and K 2 SO4  MgSO4 fertilizers. The low natural background of the potassium concentration in combination with a high selectivity for ion exchange of potassium may be one reason for that low concentrations.
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Table 1 – Average concentrations for different land use regions found in 1992 (Lingelbach,
1996) and electrochemical parameters in aquifer 1 and 2
Ion
Ca2+
Mg2+
Na+
K+
NH4+
Fetot
Mntot
HCO3SO42ClNO3NO2PH
Cond. [µS/cm]
Temp[°C]
Eh [mV]
*
agric.use aqu. 1
mg/L Mmol/L
2.925
117
0.827
20.1
0.874
20.1
0.086
3.35
0.000
0.00
0.014
0.77
0.002
0.11
2.066
126
1.667
160
2.817
100
0.828
59.6
0.000
0.02
forest aqu. 1
Mg/L mmol/L
2.180
87.2
0.704
17.1
1.013
23.3
0.058
2.27
0.005
0.09
0.201
11.2
0.019
1.03
2.098
128
1.448
139
2.152
76.4
0.449
32.3
0.000
0.02
6.65
972
11.2
188
6.41
776
10.3
170
urban use aqu. 1
mg/L
mmol/L
2.323
92.9
0.683
16.6
1.022
23.5
0.072
2.83
0.001
0.02
0.008
0.43
0.005
0.30
2.033
124
1.344
129
2.501
88.8
0.540
38.9
0.002
0.09
6.50
781
13.5
125
forest aqu. 2
Mg/L mmol/L
1.420
56.8
0.453
11.0
0.770
17.7
0.074
2.88
*
N.D.
N.D.
0.072
4.00
0.005
0.27
N.D.
N.D.
0.485
46.6
0.679
24.1
0.000
0.0
N.D.
N.D.
6.77
448
N.D. – No Data
The pH value for all regions ranges between 6.5 and 7. The electrical conductivity is in direct
correlation with the ionic strength of each solution. Due to the described measurement procedure, iron and manganese could be determined only as a sum parameter. However, from the
redox and pH state of the well waters, it can be assumed, that iron is found as Fe2+ and manganese as Mn2+. Both concentrations are high in the first aquifer underlying the forest region,
iron is also found in high concentration in aquifer 2 (forest region). A significant reduction of
nitrate is not found in the unconfined aquifer.
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7. Krauthausen test site
The Krauthausen test site is situated approximately 7 km southeast from the research center in
Jülich, Germany (Fig. 6). Here the uppermost semiconfined strongly heterogeneous aquifer is
investigated in detail. The Krauthausen test site was established in 1993 within the framework
of EU project "Critical parameters governing the mobility and fate of pesticides in
soil/aquifer systems: An experimental and modeling study based on coherent interpretation of
transport parameters and physico-chemical characteristics measured at multiple scales". To
examine the impact of aquifer heterogeneity on solute transport, 72 wells were installed at the
site.
Fig. 8 – Generalized stratigraphic sequence for the Krauthausen test site
The drillings reach a depth of maximally 22 m. From these drillings a generalized stratigraphic sequence was derived (Fig. 8).
The investigated aquifer at the test site Krauthausen is situated between 1.5 and 10.5 m below
surface (Fig. 8). The aquifer is covered by a 1.5 thick alluvial material in which a stagnic pod-
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zoluvisol developed (Jacques D. et al., 1998). Below the alluvial material is an inter-bedding
of clay, silt and fine sand.
The clay and silt content of the aquifer sediments varies between 0.5 % and 7.5 %, the mean
total porosity is 26 % with a standard deviation of 7 %. The mean cation exchange capacity is
0.44 meq/100g. The mean clay content amounts to 2.3 %. The mean specific surface is 0.7
m2/g (Englert et al., 2000; Vereecken et al., 2000).
The groundwater flow is parallel to the length of the Krauthausen test site with a mean gradient of 0.2 %. The groundwater table varies from 1 m to 3 m below surface. At high groundwater tables ( < 1.5 m) the aquifer is semiconfined. At lower groundwater tables the aquifer is
semi-unconfined. This variation in the groundwater table causes a time dependent change in
the specific storage coefficient (S) within one magnitude. At high groundwater table situations
S amounts to 7.7  10 4 , at low groundwater table situations S amounts to 10  10 2 . The mean
hydraulic conductivity amounts to 3.8  10 3 m/s (Englert et al., 2000; Vereecken et al., 2000).
The groundwater is a bicarbonate rich water with high concentrations of nitrate caused by
intensive agricultural land use. The pH value amounts to 6.7, the EH value varies between
250 and 300 mV. The content of solved oxygen amounts to 7.7 mg/l (Englert et al., 2000; Vereecken et al., 2000).
In the last years, extensive research concerning the transport of LiBr, uranin and NaBr was
conducted at the test site and documented in literature (Englert et al., 2000; Döring U., 1997;
Döring U. et al., 1999; Neuendorf O., 1996; Vereecken et al., 1999; Vereecken et al., 2000).
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References
Arbeitskreis für Bodensystematik der Deutschen Bodenkundlichen Gesellschaft (1998) – Systematik der Böden und der Bodenbildenden Substrate Deutschlands. Mitt. Dt. Bodenkund. Ges., 86, 1-180.
Döring U. (1997) – Transport der reaktiven Stoffe Eosin, Uranin und Lithium in einen heterogenen Grundwasserleiter. Internal report, Forschungszentrum Jülich.
Döring U., Jaekel U., Neuendorf O., Seidemann R., Vereecken H. (1999) – Analysis of reactive solute transport in a heterogeneous aquifer. 3. Characterization of sorption heterogenity and its impact on solute transport. Internal report, Forschungszentrum Jülich.
Englert A., Hashagen U., Jaekel U., Nitzsche O., Schwarze H., Vereecken H. (2000) –
Transport vor gelösten Stoffen im Grundwaser – Untersuchungen am Testfeld
Krauthausen. Grundwasser, 3, 115-124.
Geologische Landesamt Nordrhein-Westfalen (1976) – Bodenkarte von Nordrhein-Westfalen
1:50000, L 5104 – Düren. Krefeld.
Jacques D., Kim D.-J., Diels J., Vanderborght J., Vereecken H. and Feyen J. (1998) – Analysis of steady state chloride transport through two heterogeneous field soils. Water Resour. Res., 34, 2539-2550.
Klosterman J. (1983) – Die Geologie der Venloer Scholle (Niederrhein). Geol. Jb., Bd. A66,
Hanover, 3-115.
Klosterman J. (1992) – Das Quartär der Niederrheinischen Bucht. Geologische Landesamt
Nordrhein-Westfalen, Krefeld.
Lahmeyer International (1984) – Standortgutachten Geologie, Hydrogeologie und Bodenmechanik. Jülich.
Lingelbach M. (1996) – Untersuchung und statistische Auswertung der Grundwasserbeschaffenheit auf der Jülicher Zwischenscholle der Niederrheinischen Bucht von
1975 und 1992. Diplomaarbeit, Ruprecht-Karls-Universität, Heidelberg.
Neuendorf O. (1996) – Numerische 3-D Simulation des Stofftransportes in einen heterogenen
Aquifer. Dissertation RWTH Aachen.
Schneider H. & Thiele S. (1965) – Geohydrologie des Erftgebietes. Ministerium für
Ernährung, Landwirtschaft und Forsten des Landes Nordrhein-Westfalen, Düsseldorf.
Vereecken H., Jaekel U., Esser O., Nitzsche O. (1999) – Solute transport analysis of bromide, uranin and LiCl using breakthrough curves from aquifer sediment. J. Contaminant
Hydrol., 39, 7-34.
Vereecken H., Doring U., Hardelauf H., Jaekel U., Hashagen U., Neuendorf O., Schwarze H.,
R. Seidemann H. (2000) – Analysis of solute transport in a heterogeneous aquifer: the
Krauthausen field experiment. J. Contaminant Hydrol., 45, 329-358.
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