Estimating flow and recharge rates of groundwater in western Taiwan using radiocarbon and tritium

The Choushuichi alluvial-fan delta is the largest groundwater system in Taiwan. The coastal area of this fan delta has recently suffered severe land subsidence and sea-water intrusion due to overpumping of groundwater. To study the hydrogeological character of proper water-resource management, an intensive program of geological and water monitoring through well drilling and sampling has been undertaken. At present, radiocarbon dating and/or tritium analysis for samples from >70 boreholes has been completed. The clearly defined position of ''bomb-tritium front'' allows the groundwater flow and recharge rates of the confined aquifer to be calculated with confidence at <10 m yr(-1) and 9.0 x 10(8) m(3) yr(-1), respectively. The flow velocities of the confined aquifer have also accelerated remarkably due to much pumping during the last decades.