Discussion
This study has demonstrated that water quality in the
Xiangxi River is strongly related to land use. The forest
dominated region has low concentrations of most nutrient
variables except COD, whereas the agricultural subwatershed
has high concentration of NO3N, TN, Alk., and
Hardness. This pattern of good water quality in forested
areas and high concentrations of nitrogen in agricultural
areas has been demonstrated in many related studies
(Hunsaker and Levine 1995; Allan 2004). The high concentration
of COD in forest region may be caused by high
levels of terrestrial organic matter (branches and leaves)
enter into river channel. The region downstream of the
urban area has high concentrations of NH3N, NO2N, PO4P
and TP, which may be a result of point source discharges of