HR: 0800h
AN: H11D-0331    [Abstracts]
TI: Vertical Recharge of a Confined Aquifer in the Fish Farming Area
AU: * Chia, Y
EM: ypc@ntu.edu.tw
AF: Department of Geosciences, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Liou, W
AF: Department of Geosciences, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Lee, T
AF: Department of Geosciences, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei, 106 Taiwan
AU: Chiu, Y
AF: Department of Geosciences, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei, 106 Taiwan
AB: The rate of vertical groundwater recharge into a confined aquifer is often difficult to estimate due to poor information about confining beds and local pumping activities. Previous studies on a confined aquifer in the coastal plain of Taiwan suggested that its groundwater is primarily recharged laterally from the eastern highland. However, heavy rainfalls that cause all water wells to cease pumping and a widespread recovery of groundwater levels provide an unusual opportunity to re-examine the traditional concept of recharge process. Monitoring records during every heavy rainfall show that groundwater level rises in the fish farming area are far greater than those in the surrounding area. The abnormal rises imply the existence of a rapid cross-formational downward groundwater flow into the confined aquifer. We developed a 3-D finite-element groundwater flow model, based on core log, well log, and measured hydraulic parameters, to simulate the recovery process of groundwater levels during heavy rainfalls. Study results indicate that downward flow provides the major source of groundwater recharge in the fish farming area, while lateral flow provides the major recharge outside the area. Thousands of water wells developed in the fish farming area have been considered to be potential conduits for vertical recharge. The rapid vertical flow not only changes the conceptual model of regional groundwater flow system but poses a potential threat to the groundwater quality in the confined aquifer.
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting