Isotope hydrology and baseflow geochemistry in natural and human-altered watersheds in the Inland Pacific Northwest,USA |
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| Authors: | Ricardo Sánchez-Murillo Erin S Brooks William J Elliot Jan Boll |
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| Institution: | 1. Waters of the West – Water Resources Program, University of Idaho, Moscow, ID, USA;2. Chemistry Department, Universidad Nacional, Heredia, Costa Ricasanc7767@vandals.uidaho.edu;4. Department of Biological and Agricultural Engineering, University of Idaho, Moscow, ID, USA;5. USDA Forest Service Rocky Mountain Research Station, Moscow, ID, USA;6. Department of Biological and Agricultural Engineering, University of Idaho, Moscow, ID, USA |
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| Abstract: | This study presents a stable isotope hydrology and geochemical analysis in the inland Pacific Northwest (PNW) of the USA. Isotope ratios were used to estimate mean transit times (MTTs) in natural and human-altered watersheds using the FLOWPC program. Isotope ratios in precipitation resulted in a regional meteoric water line of δ2H?=?7.42·δ18O?+?0.88 (n?=?316; r2?=?0.97). Isotope compositions exhibited a strong temperature-dependent seasonality. Despite this seasonal variation, the stream δ18O variation was small. A significant regression (τ?=?0.11D?1.09; r2?=?0.83) between baseflow MTTs and the damping ratio was found. Baseflow MTTs ranged from 0.4 to 0.6 years (human-altered), 0.7 to 1.7 years (mining-altered), and 0.7 to 3.2 years (forested). Greater MTTs were represented by more homogenous aqueous chemistry whereas smaller MTTs resulted in more dynamic compositions. The isotope and geochemical data presented provide a baseline for future hydrological modelling in the inland PNW. |
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| Keywords: | baseflow geochemistry hydrogen-2 isotope hydrology mean transit times natural and human-altered watersheds oxygen-18 watershed management |
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