An oxygen isotope study of seasonal trends in soil water fluxes at two sites along a climate gradient in Washington state (USA)

Isotopically‐depleted late Pleistocene groundwater in Columbia River Basalt aquifers: Evidence for recharge of glacial Lake Missoula floodwaters?

“…[11] Paleogroundwaters in the CRBAs have radiocarbon ages from 6.5 k to 33.3 k yrs BP and low d 18 O values (−18.9 to −16.7‰; Figure 2), compared to modern mean annual precipitation (−15.9‰) [Robertson and Gazis, 2006]. These Late Pleistocene waters may have been sourced from paleoprecipitation or Missoula flood recharge.…”

HESS Opinions "A perspective on isotope versus non-isotope approaches to determine the contribution of transpiration to total evaporation"

“…A conventional method for partitioning evaporation is the combination of hydrometric measurements such as sap flow to measure transpiration rate with other methods to calculate total evaporation (Kelliher et al, 1992;Herbst et al, 1996;Roupsard et al, 2006;Mitchell et al, 2009;Cavanaugh et al, 2011). Soil evaporation is then calculated from the difference of total evaporation and transpiration with the assumption that canopy evaporation is a small component and can be neglected.…”

“…Soil evaporation is then calculated from the difference of total evaporation and transpiration with the assumption that canopy evaporation is a small component and can be neglected. More recent methods analyze the isotopic composition of liquid water and water vapor (e.g., Yepez et al, 2003;Ferretti et al, 2003;Williams et al, 2004;Xu et al, 2008;Lai et al, 2006;Robertson and Gazis, 2006;Wang et al, 2010;Sutanto et al, 2012;Jasechko et al, 2013). This method has become common since measurements of stable isotopologues in precipitation and water vapor are relatively easy and robust.…”

Data-model comparison of soil–water δ 18 O at a temperate site in N. Spain with implications for interpreting speleothem δ 18 O

“…The steep slope defined by our soil-water data on a D/H vs. δ 18 O diagram ( Figure 6) and the absence of significant departures from the Local Meteoric Water Line (LMWL; Figure 6) provides little evidence for evaporative isotopic enrichment of soil-waters prior to recharge at this temperate site, in contrast with results from drier sites (Hsieh et al, 1998;Robertson and Gazis, 2006). This validates results from Bradley et al (2010), where evaporation is found to be negligible at relatively temperate and wet sites.…”

“…In some semi-arid regions, these effects have been invoked to explain some of the observed δ 18 O variability in cave drip-waters (Ayalon et al, 1998;Cuthbert et al, 2014). By contrast, comparatively little data are available for seasonal δ 18 O sw variability in temperate regions (Robertson and Gazis, 2006;Gehrels et al, 1998). The evolution of δ 18 O sw at temperate sites is likely to differ from that at arid and semi-arid sites because a positive soil-water balance may exist for much of the year and evaporative effects are consequently less important.…”