308
Anna Avila
catchment with climatic change, but also, on the contrary, that base cation
concentrations and alkalinity tended to increase. In Mediterranean areas
drier than the TM9 catchment, but having similar vegetation and lithology, it
is relatively common for calcite to be precipitated along the riverbank under
certain conditions, even in catchments entirely underlain by silicate bedrock
such as Montseny and Prades (Pinol and Avila 1992). The increased concentrations simulated for a warmer scenario, with either more or less rain, were
not high enough to either pose serious problems for the water quality or
reach the calcite saturation equilibria for the Montseny catchment.
21.4 Application of MAGIC to Prades
MAGIC was applied to the Avic catchment of Prades (Chap. 2) with the principal aim of testing whether MAGIC, created for catchments in northern
latitudes with a regime of high rainfall, high pollutant loads, acid rain, and
soil and water acidification, was able to reproduce the hydrochemical behaviour for Prades, a semi-arid environment, receiving non-acidic deposition, with high soil base saturation and with highly mineralized streamwaters
(Bellot et al. 1994). While no acidification was expected for the Avic catchment, the interest was on the calibration procedure itself and the reproduction of historical sequences accounting for the changes in atmospheric deposition and forestry practices between 1845 and 1985.
The parameters used in the calibration are shown in Table 21.2, and the
fitted streamwater chemistry is shown in Table 21.4. Data for atmospheric
Table 21.4. Observed (7-year means) and modelled fits for
streamwater chemistry at Avic (Prades). Ion concentrations in
J.1eq L- 1 • The difference between observation and model fit for
Ca2+ is justified by the fact that some calcite precipitates when
water passes from soil to stream
Observed
Model fit
Ca 2 +
2574
3569
Mg'+
564
564
Na+
509
509
K+
44.4
44.7
NH4+
10
10
SO/658
657
ct
281
282
N031.6
1.6
pH
7.59
7.7
Alkalinity
3745
3746
SBC
3872
4687
SAA
953
953
SBC, Sum of base cations; SAA, sum of strong acid anions.
Anna Avila
catchment with climatic change, but also, on the contrary, that base cation
concentrations and alkalinity tended to increase. In Mediterranean areas
drier than the TM9 catchment, but having similar vegetation and lithology, it
is relatively common for calcite to be precipitated along the riverbank under
certain conditions, even in catchments entirely underlain by silicate bedrock
such as Montseny and Prades (Pinol and Avila 1992). The increased concentrations simulated for a warmer scenario, with either more or less rain, were
not high enough to either pose serious problems for the water quality or
reach the calcite saturation equilibria for the Montseny catchment.
21.4 Application of MAGIC to Prades
MAGIC was applied to the Avic catchment of Prades (Chap. 2) with the principal aim of testing whether MAGIC, created for catchments in northern
latitudes with a regime of high rainfall, high pollutant loads, acid rain, and
soil and water acidification, was able to reproduce the hydrochemical behaviour for Prades, a semi-arid environment, receiving non-acidic deposition, with high soil base saturation and with highly mineralized streamwaters
(Bellot et al. 1994). While no acidification was expected for the Avic catchment, the interest was on the calibration procedure itself and the reproduction of historical sequences accounting for the changes in atmospheric deposition and forestry practices between 1845 and 1985.
The parameters used in the calibration are shown in Table 21.2, and the
fitted streamwater chemistry is shown in Table 21.4. Data for atmospheric
Table 21.4. Observed (7-year means) and modelled fits for
streamwater chemistry at Avic (Prades). Ion concentrations in
J.1eq L- 1 • The difference between observation and model fit for
Ca2+ is justified by the fact that some calcite precipitates when
water passes from soil to stream
Observed
Model fit
Ca 2 +
2574
3569
Mg'+
564
564
Na+
509
509
K+
44.4
44.7
NH4+
10
10
SO/658
657
ct
281
282
N031.6
1.6
pH
7.59
7.7
Alkalinity
3745
3746
SBC
3872
4687
SAA
953
953
SBC, Sum of base cations; SAA, sum of strong acid anions.