Future climate scenarios project lower precipitation rates
on a mean annual basis, but increased rates for winter months
for the study area. On the other hand, both evaporation and
transpiration fluxes increase, due to rising air temperatures.
This increase is compensated for by a decrease in the drainage
flux and groundwater recharge. As a result, groundwater
levels decline and the annual discharge of the Keersop stream
decreases under all future climate scenarios, by 26% to 46%. In
conclusion, climate change leads to an intensification of irrigation
practices, lower groundwater levels due to increased
evapotranspiration and a slowing-down of the groundwater
system.
Climate change leads to lower Cd and Zn concentrations
for most of the year as a result of lower groundwater levels.
Combined with lower discharge rates, the decrease of Cd and
Zn mass loads through the surface water system is even more
pronounced. This is in accordance with the predicted and
observed response of solute transport to drier conditions
(Rozemeijer and Broers, 2007; Rozemeijer et al., 2010) and
the observed changes in total concentration of some heavy
metals (i.e. lead, chrome, mercury and cadmium) under low
flow conditions (Van Vliet and Zwolsman, 2008).
Thanks to the drier conditions projected for future climate
a positive impact of climate change is projected on a limited
aspect of surface water quality. The contamination of the
subsurface is sustained and Cd and Zn will further accumulate,
month
Cd [ g/L]
2
b
4 6 8 10 12
0.0 0.2 0.4 0.6 0.8 1.0
Mean Cd concentration
baseline
ARPEGE
RACMO_H
RCAO_E
RCAO_H
REMO_H
HAD_P_H
HIRHAM_E
HIRHAM_H
month
Zn [ g/L]
2 4 6 8 10 12
0 10 20 30 40 50
Mean Zn concentration
μ μ a
Fig. 11. Monthly mean Cd (a) and Zn (b) concentrations in the Keersop
stream, for the baseline scenario and eight future climate scenarios.
A. Visser et al. / Journal of Contaminant Hydrology 127 (2012) 47–64 61