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4.1. GROUNDWATER AND PALEOCLIMATE 123
4.1.3 A multi tracer study to investigate the groundwater in the Odenwald
region
Ronny Friedrich (participating scientists: Werner Aeschbach-Hertig, Bernhard Leßmann (HLUG),
Guido Vero (HLUG), Rolf Kipfer (IGMR))
Abstract Three sampling campaigns where performed during 2003, 2004 and 2005 in the Odenwald
region (Germany). This multi tracer study (noble gases, 3 H, δ 18 O, δ 2 H, SF6, 222 Rn) investigates the
age structure, mixing ratios and recharge areas of the groundwater in this region.
S F 6 a g e [y r b . 2 0 0 5 ]
4 0
3 5
3 0
2 5
2 0
1 5
1 0
5
0
0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0
3 H / 3 H e a g e [y r b . 2 0 0 5 ]
c ry s t.
re e d
s a n d s t.
H S d e p r.
Figure 4.4: Comparison of ages obtained by SF6 and 3 H- 3 He of samples from 2005. Different symbols
reflect geological origin (⊙ = crystalline rocktype, ⋄ = Hessian reed, ∆ = sandstone rocktype, ∇ =
Hanau-Seeligenstaedter depression). Arrows indicate ages older than 40 years. Samples above the
1:1 line indicate mixing between old (tracer free) and young (tracer bearing) groundwater. Samples
below 1:1 line could be influenced by natural SF6. Especially samples from the crystalline part are
influenced.
Background The mountainous Odenwald region
in the federal state of Hessia (Germany) is
one of the main local recharge areas for groundwater
of the surrounding depressions, where substantial
extraction for public water supply takes
place. Therefore we investigate the groundwater
in the Odenwald to study residence times and mixing
ratios, define regions of groundwater recharge
and understand the groundwater inflow from the
Odenwald to the surrounding areas.
Methods and results This study includes different
stable and radioactive gas and isotope tracers
such as 2 H, 18 O, 3 H, noble gases, 222 Rn and
SF6 . Based on the stable isotope data it is possible
to distinguish between groundwater from different
areas of the Odenwald. This will help us to
define source regions for the groundwater in the
surrounding areas. Additionally the isotopic signatures
show that the groundwater was formed
by ”annual” precipitation and not only in winteror
summertime. Noble gases (He, Ne, Ar, Kr,
Xe) can be used in principle to calculate recharge
temperatures or the infiltration altitudes (above
sea level) of recharge areas. Furthermore noble
gases give important information to correct other
gas tracers for so called ”excess air” that oversaturates
gases in groundwater (see Kipfer et al.
[2002] for a review of the methods). Comparing
the results of the two independent dating methods
- SF6 and 3 H- 3 He - we found that dating with
SF6 is not possible in the crystalline region of the
Odenwald. The results indicate that SF6 is influenced
by a natural source in the subsurface that
varies with lithology (see Busenberg & Plummer
[2000]). 222 Rn and radiogenic 4 He data from part
of the wells seem to be related to the natural SF6,
consistent with the idea of radiochemical SF6 production
in rocks supported by radiochemical reactions.
Data from the 3 H- 3 He method give robust
groundwater ages in the range of some years to
values higher than 40 years. Furthermore, regions
where mixing of old and young groundwater occurred
can be distinguished.
Outlook/Future work Data analysis is still in
progress. Comparing tracer results with hydrogeological
and hydrochemical data should lead to a
better system description.
Funding This work is done in cooperation with
the ”Hessisches Landesamt für Umwelt und Geologie”
Wiesbaden.
Main publication Friedrich et al. [2006]