Soil Water Chemistry
249
17.5 Relationship Between Soil Water
and Streamwater Chemistries
The chemistry of the soil water at both sites was quite different from that of
the streamwater (Fig. 17.5). During baseflow, groundwater is the major
source feeding the stream. This water is enriched with rock weathering
products, with high alkalinity, and base cation concentrations. Soil water
chemistry is expected to contribute to the stormflow composition to some
extent. The streamwater of the Avic catchment at Prades is more mineralized
than that from the TM9 catchment in Montseny (PHiol et al. 1992), coinciding
with the results found in the soil water concentrations from both sites. Calcium was the major cation in Prades streamwaters, whereas at Montseny Na+
and Ca 2 + codominate in streamwater.
At Montseny, all analyzed ions except Na+ were higher in soil water than in
both the baseflow and th~ stormflow (Fig. 17.5). In addition, the mean ion
3500
3000
~ 2500
C' 2000
~
::l.
1500
+
.... WOO
co
u 500
0
700
600
- ~
if
400
::l. 300
+",
200
Z
100
0
_
Gravitational
c:::::J Soil olution
~ Streamwaler
500,-----------------,
400 -
-:.J
300
if
::l. 200
+
~ 100
In
O~~ .n~n.~~~~I ~~~
MONTSENY
PRADES
1200 , - - - - - - - - - - ,
WOO
~ 800
[600
200
O--'-...... ~-='"-----'-.u ...... ""'-----'
Fig. 17.5. Water chemistry profiles from gravitational soil water below forest floor to streamwater at Prades and Montseny. Volume-weighted means are given for gravitational water and
streamwater, and arithmetic means for soil solution. Baseflow and stormflow at Montseny are
for the TM9 catchment (from Avila et al. 1995). Streamwater at Prades is for the Avic catchment
(from Pinol and Avila 1992)