title: Isotope hydrology and baseflow geochemistry in natural and human-altered watersheds in the Inland Pacific Northwest, USA.
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 δ(2)H = 7.42·δ(18)O + 0.88 (n = 316; r(2) = 0.97). Isotope compositions exhibited a strong temperature-dependent seasonality. Despite this seasonal variation, the stream δ(18)O variation was small. A significant regression (τ = 0.11D(-1.09); r(2) = 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.
authors.affiliation: a Waters of the West - Water Resources Program, University of Idaho , Moscow , ID , USA.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Sánchez-Murillo
authors.forename: Erin S
authors.initials: ES
authors.lastname: Brooks
authors.forename: William J
authors.initials: WJ
authors.lastname: Elliot
authors.forename: Jan
authors.initials: J
authors.lastname: Boll
mesh_terms: D003903:Deuterium / Q000032:analysis*; D062070:Hydrology; D007061:Idaho; D008962:Models, Theoretical; D010103:Oxygen Isotopes / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D014861:Washington; D014867:Water / Q000032:analysis*
chemical_list: D010103:Oxygen Isotopes; D014867:Water; D003903:Deuterium
keywords: baseflow geochemistry; hydrogen-2; isotope hydrology; mean transit times; natural and human-altered watersheds; oxygen-18; watershed management