Water Quality and Sediment Behaviour of the Future: Predictions for the
21st Century (Proceedings of Symposium HS2005 at IUGG2007, Perugia, July
2007). IAHS Publ. 314, 2007, 108-116.
Effect of frequent storms on nutrient discharge in a
mountainous coastal catchment, western Japan
Shin-ichi Onodera1, Misa Sawano1, Mitsuyo Saito2 & HIDEHIRO TAKAHASHI3
1 Graduate School of Integrated Arts and Sciences, Hiroshima
University, 1-7-1, Kagamiyama, Higashi-Hiroshima,
Hiroshima, Japan
sonodera@hiroshima-u.ac.jp
2 JSPS research fellowship, Graduate School of Biosphere Sciences, Hiroshima University, Higashi-Hiroshima, 7398521, Japan
3 National Agricultural Research Center for Western Region, Fukuyama, 7218514, Japan
Abstract In order to forecast
the variation of nutrient load with climate change, the long-term change in
rainfall and its effect on river runoff in a study catchment were investigated
and related to change in nutrient discharge to the ocean. In the study area
there has been a decreasing rainfall trend for 40 years but the frequency
of large rainfall events has remained constant. The annual runoff decreased by 60
mm in the last 40 years, but large annual runoff amounts were observed in years
with large rainfall events. The nutrient discharge also reflected the rainfall and
runoff trends. DN load has increased in the long term, while in drought years
DP load has increased, reflecting the dominant groundwater contribution with
significantly higher DP concentrations in such conditions.
Key words groundwater; heavy storm event; nutrient discharge; river