Japan Geoscience Union Meeting 2015

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW27] Water and material transport and cycle in watersheds: from headwater to coastal area

Sun. May 24, 2015 9:00 AM - 10:45 AM 301B (3F)

Convener:*Shinji Nakaya(Department of Civil Engineering, Faculty of Engineering, Shinshu University), Mitsuyo Saito(Graduate School of Environmental and Life Science, Okayama University), Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University), Kazuhisa Chikita(Department of Natural History Sciences, Faculty of Science, Hokkaido University), Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Masahiro Kobayashi(Forestry and Forest Products Research Institute), Seiko Yoshikawa(Narional Institute for Agro-Environmental Sciences), Noboru Okuda(Research Institute for Humanity and Nature), Chair:Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University)

10:15 AM - 10:30 AM

[AHW27-06] Seasonal variation of the stratified structure in agricultural reservoirs and its effect on the nutrient cycle

*Kenji OKUBO1, Mitsuyo SAITO1, Ryohei FUNAOKA1, Shin-ichi ONODERA2, Guangzhe JIN2, Yutaka MARUYAMA2, Daiki ARITOMI2 (1.Okayama Univ., 2.Grad., Hiroshima Univ.)

Agricultural reservoirs have been used as important water resources in agriculture areas of little rain. Intensive agriculture increases the load of nutrients to surface water and groundwater, which usually causes serious eutrophication and phytoplankton blooms in small-scale reservoirs. For sustainable water use in agricultural areas, it is important to evaluate the cycles of water and nutrient in reservoirs. We aimed to examine on the seasonal variation of the stratified structure in agricultural reservoirs and its effect on the nutrient cycle. The seasonal variation of the stratification was examined using the multi-depths water temperature variation in the 4 ponds located on an island which is highly influenced by agricultural activity. DO, Chlorophyll-a, light photon, nutrients data were used for the evaluation of ecosystem condition. Water temperature was clearly different between the surface layer and the bottom layer from early spring to early autumn in some reservoirs characterized by relatively deep bathymetry or groundwater inflow from the bottom, which indicates that the thermal stratification was formed. Vertical profiles of Chlorophyll-a and DO show the significant seasonal variations from spring to winter period. However, these pattern were unique in the pond influenced by groundwater inflow.