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.
Acknowledgements
The David Lamb Memorial Scholarship awarded by the Washington State Lake Protection Association (WALPA) to RSM covered a portion of the geochemical analyses.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This project was funded by the joint venture agreement [No. 10-JV-11221634–252] between USDA Forest Service Rocky Mountain Research Station and the University of Idaho.
Supplemental data
Supplemental data for this article can be accessed http://dx.doi.org/10.1080/10256016.2015.1008468http://dx.doi.org/10.1080/10256016.2015.1008468.