Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Poster

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

[A-HW23] Residence time of groundwater / surface water and water / mass cycle processes in watershed

Thu. May 24, 2018 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Maki Tsujimura(Faculty of Life and Environmental Sciences, University of Tsukuba), Shigeru Mizugaki(PWRI Public Works Research Institute), Masanori Katsuyama(京都大学農学研究科, 共同), Maksym Gusyev(International Centre for Water Hazard Risk Management, Public Works Research Institute)

[AHW23-P05] The impact of clogging layer on groundwater flow pattern beneath streambed by using numerical method

*HUNG-YEN LIN1, Shao-Yiu Hsu1 (1.National Taiwan University)

Keywords:Clogging layer, Inflitration rate, Groundwater flow

In Taiwan, steep mountain streams could be cut off during dry seasons, which impacts the rivers’ ecosystem. The stream cut-off can be related to the high streambed percolation since the streambed usually consists of coarse sand with high permeability. Studies have shown that the sediment deposited on the streambed forming a thin layer with lower hydraulic conductivity, which is referred to as the ”clogging layer”. The layer significantly affects the infiltration or percolation rate beneath the stream bed. In this study, we quantified the effects of the clogging layer on the infiltration rate and the groundwater flow pattern beneath the stream bed by numerical simulations and lysimeter experiments. Our simulations showed that a lowering of the groundwater table turned connected surface water-groundwater into disconnected when the streambed covered by a clogging layer. Once the surface water and groundwater was disconnected, an unsaturated zone appeared in the aquifer beneath the streambed, and the infiltration rate reached to the maximum rate. Our simulation also showed that the occurrence of the clogging layer significantly changed the patterns of groundwater flow beneath the stream bed. It can influence substantially on the residence times of groundwater and the transport of nutrients between surface and subsurface water.