Assessing groundwater sources and their association with reservoir water using stable hydrogen and oxygen isotopes: a case study of the Taipei Basin, northern Taiwan

The purpose of this isotopic study is to identify groundwater sources in Taipei Basin (TPB) and their association with water of the Feitsui Reservoir (FTR), northern Taiwan. To this end, water samples including precipitation, catchment surface water, TPB groundwater, FTR water, and catchment surface water of FTR were analyzed for stable hydrogen and oxygen isotope compositions (δ2H and δ18O). Isotopic results support previous reports that Dahan Stream and Xindian Stream waters are the major recharge sources of TPB groundwater. These recharge regions are located along the southern border of the TPB. Further, isotopic evidence finds that water from the southern hills catchment area of the TPB also recharges TPB groundwater, and most importantly, indicates that TPB groundwater is highly related to FTR water. However, for caution’s sake, future comprehensive study is needed to confirm hydrological connectivity between the FTR water and TPB groundwater.