66
Peter Stille and Graham Shields
CJ
E
~
r
~u
i/)
GI r ~
:
~---G2s I
I
J
5m
i
!
!
-I0
0
I0
20
30
Distonce from river bonk (m)
Fig. -1.13. Radon dating of groundwater. Groundwater residence time between Glatt fiver
and observation wells G I-G5. (Hoehn and yon Gunten 1989)
Sample G3 suggests a longer residence time, which may imply some exchange
with water from deeper levels. The balance between river and groundwater
exchange as well as the rate of exchange between the two systems can also be
estimated with the help of the oxygen isotope system. The study of Stichler et al.
(1986) carried out on the River Danube near Passau illustrates this well. Due to
the lack of groundwater, river water, which makes its way into the uppermost
layers of the groundwater table, is used as drinking water. Water chemistry must
be constantly monitored and it is of the utmost importance that the rate of
exchange between river and groundwater be known. Fig 4.14 gives the localities
of investigation springs. Spring OW contains pure groundwater that has not
experienced exchange with the river Danube. The other springs contain water that
is affected by exchange with river water to various extents. Fig. 4.15 shows this
exchange between river and groundwater schematically. Variations in oxygen
isotopic composition are displayed for OW and the Danube between 1980-1982 in
Fig. 4.16. From this we can detect significantly different isotopic compositions for
the various water systems. Groundwater clearly shows higher 8*80 values than
river water. Annual fluctuations can be recognized for Danube river water but
these fluctuations do not manifest themselves in groundwater. The isotope
characteristics of groundwater and Danube river water can be explained as
follows: 1. Groundwater is more strongly enriched in tdO than river water as it de
rives from pre-Alp precipitation, which is less strongly fractionated than the true
Alpine precipitation which is the source of the river water.
Peter Stille and Graham Shields
CJ
E
~
r
~u
i/)
GI r ~
:
~---G2s I
I
J
5m
i
!
!
-I0
0
I0
20
30
Distonce from river bonk (m)
Fig. -1.13. Radon dating of groundwater. Groundwater residence time between Glatt fiver
and observation wells G I-G5. (Hoehn and yon Gunten 1989)
Sample G3 suggests a longer residence time, which may imply some exchange
with water from deeper levels. The balance between river and groundwater
exchange as well as the rate of exchange between the two systems can also be
estimated with the help of the oxygen isotope system. The study of Stichler et al.
(1986) carried out on the River Danube near Passau illustrates this well. Due to
the lack of groundwater, river water, which makes its way into the uppermost
layers of the groundwater table, is used as drinking water. Water chemistry must
be constantly monitored and it is of the utmost importance that the rate of
exchange between river and groundwater be known. Fig 4.14 gives the localities
of investigation springs. Spring OW contains pure groundwater that has not
experienced exchange with the river Danube. The other springs contain water that
is affected by exchange with river water to various extents. Fig. 4.15 shows this
exchange between river and groundwater schematically. Variations in oxygen
isotopic composition are displayed for OW and the Danube between 1980-1982 in
Fig. 4.16. From this we can detect significantly different isotopic compositions for
the various water systems. Groundwater clearly shows higher 8*80 values than
river water. Annual fluctuations can be recognized for Danube river water but
these fluctuations do not manifest themselves in groundwater. The isotope
characteristics of groundwater and Danube river water can be explained as
follows: 1. Groundwater is more strongly enriched in tdO than river water as it de
rives from pre-Alp precipitation, which is less strongly fractionated than the true
Alpine precipitation which is the source of the river water.