download pdf - Institut für Umweltphysik - Ruprecht-Karls-Universität ...

156 CHAPTER 4. AQUATIC SYSTEMS
4.1.3 A multi tracer study to investigate the groundwater in the Odenwald
region
Participating scientists Ronny Friedrich, Werner Aeschbach-Hertig, Bernhard Leßmann (HLUG),
Guido Vero (HLUG)
Abstract Three sampling campaigns where performed during 2003, 2004 and 2005 in the Odenwald
region. With this multi tracer study (noble gases, 3 H, δ 18 O, δ 2 H, SF6, CFCs) we want to investigate
the age structure, mixing ratios and recharge areas of the groundwater in this region. First results
show groundwater ages of a few years up to older than 40 years.
Figure 4.3: Stable isotope data (δ 18 O, δ 2 H) of the campaign in 2003. Isotopic signatures of samples
from the crystalline part (1), the sandstone part (2) and from the ”Hanau-Seeligenstädter-Senke” (4)
are concentrated in separate groups, whereas samples from ”Hessisches Ried” (3) scatter over the
whole range.
Background The Odenwald region is one of
the main recharge areas for groundwater of
the surrounding areas (Hessisches Ried, Hanau-
Seligenstädter Senke). These areas are very important
for freshwater extraction. Therefore we
want to investigate the groundwater in the Odenwald
to study residence times and mixing ratios
of the groundwater, define regions of groundwater
recharge and understand the groundwater inflow
from the Odenwald to the surrounding areas.
Funding This work is done in cooperation with
the ”Hessisches Landesamt für Umwelt und Geologie”
Wiesbaden.
Methods and results To study the groundwater
we use different stable and radioactive gasand
isotope tracers summarized as ”environmental
tracers” such as 2 H, 18 O, 3 H, noble gases and
SF6. 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). SF6 and 3 H- 3 He are
used to date the groundwater.
Comparing the results of these two independent
dating methods we see that dating with SF6 is not
possible in the crystalline region of the Odenwald.
We assume that SF6 is influenced by a natural
source in the subsurface. Data from the 3 H- 3 He
method give robust groundwater ages in the range
of some years to values higher than 40 years. By
using the stable isotope data it is possible to distinguish
between groundwater from different areas
of the Odenwald. That will help us to define flow
paths of the groundwater from the Odenwald to
the surrounding areas. Additionally the isotopic
signatures show that the groundwater was formed
by ”annual” precipitation and not only in winteror
summertime.
Outlook/Future work Until today we have
analyzed all samples from the campaign in 2003.
Measuring the samples from 2004 and 2005 should
give us information about seasonal changes in
groundwater flow.
Main publication Friedrich et al. [2004]