The relationships between the river water chemistry and the wetland
coverage are shown in Figure 7. Riverine dFe and DOC concentrations
clearly increased with the wetland coverage (dFe:r2 = 0.66, DOC: r2 =
0.46). In contrast, riverine EC exponentially decreased with wetland
coverage (EC: r2 = 0.45). In addition to these
findings, we found that riverine dFe concentration had a strong positive
correlation with DOC concentration (r2 = 0.63),
and a negative correlation with EC (r2 = 0.74).
Since EC is an index showing how much dissolved ion components are
present in the water, these results strongly suggest that wetland
(Mari ) supplies dFe- and DOC-rich and mineral-poor groundwater to
rivers (see Discussion 4.2).