Hung I. Lin

An approach to evaluate groundwater recharge from streamflow and groundwater records

To assess groundwater recharge, this study provided a composite method combining the recession-curve-displacement method and water-table fluctuation method. First, the initial recharge reference value was determined using the water-table fluctuation method. The corresponding groundwater discharge was then determined from the recharge reference value using the recession-curve-displacement method. Furthermore, the recession segment of the match between groundwater discharge and streamflow was computed. The recharge reference value was repeatedly adjusted to achieve a good fit with the recession segment for groundwater discharge and streamflow, thereby attaining the final groundwater recharge using the proposed method. Finally, the groundwater recharge of the Lanyang Creek basin in Taiwan was estimated as a case study. A comparison of recession-curve-displacement method and proposed composite method are presented. Estimation results show that the number of recharge events, recharge timing of these events, groundwater recharge events that satisfy recession theory, and range of transmissivity can be obtained using the proposed composite method. Comparison results demonstrate that the number of groundwater recharge events obtained with the composite method was greater than that acquired with the recession-curvedisplacement method. However, the annual recharge and seasonal recharge obtained with the recession-curve-displacement method and composite method were close.

GIS and SBF for estimating groundwater recharge of a mountainous basin in the Wu River watershed, Taiwan

The temporal and spatial distributions of precipitation are extremely uneven; so, careful management of water resources in Taiwan is crucial. The long-term overexploitation of groundwater resources poses a challenge to water resource management in Taiwan. However, assessing groundwater resources in mountainous basins is challenging due to limited information. In this study, a geographic information system (GIS) and stable base-flow (SBF) techniques were used to assess the characteristics of groundwater recharge considering the Wu River watershed in central Taiwan as a study area. First, a GIS approach was used to integrate five contributing factors: lithology, land cover/land use, lineaments, drainage, and slope. The weights of factors contributing to the groundwater recharge were obtained from aerial photos, geological maps, a land use database, and field verification. Second, the SBF was used to estimate the groundwater recharge in a mountainous basin scale. The concept of the SBF technique was to separate the base-flow from the total streamflow discharge in order to obtain a measure of groundwater recharge. The SBF technique has the advantage of integrating groundwater recharge across an entire basin without complex hydro-geologic modelling and detailed knowledge of the soil characteristics. In this study, our approach for estimating recharge provides not only an estimate of how much water becomes groundwater, but also explains the characteristics of a potential groundwater recharge zone.