Use of stable water isotopes to identify hydrological processes of meteoric water in montane catchments

This study analyzes the stable isotopic compositions of hydrogen and oxygen (δ2H, δ18O) in montane meteoric waters including precipitation and stream water of central Taiwan to identify hydrological processes in montane catchments. Results of precipitation demonstrate that monsoon and altitude effects are two principal processes affecting δ and deuterium excess (dE) values of inland precipitation in central Taiwan. Furthermore, slope and intercept values of summer and winter local meteoric water line are modified by secondary evaporation effects such as moisture recycling and raindrop evaporation. Additionally, stream water's results indicate that differences in δ values among stream waters reflect isotopic altitude effect whereby lower values are more evident in stream water originating from high‐elevation catchments than low‐elevation catchments. Comparison of the isotopic results between precipitation and stream water indicates that summer precipitation containing recycled moisture is the most important water source for the studied stream waters and indicates that catchment effect and base flow contribution are the two major hydrological processes affecting mountain stream hydrology. The hydrological processes identified by the isotopic study re‐stress the important role of forests in mountain hydrology. Copyright © 2015 John Wiley & Sons, Ltd.