Water movement in upland humid watersheds from the soil surface to the stream is often described using the concept of translatory flow1,2, which assumes that water entering the soil as precipitation displaces the water that was present previously, pushing it deeper into the soil and eventually into the stream2. Within this framework, water at any soil depth is well mixed and plants extract the same water that eventually enters the stream. Here we present water-isotope data from various pools throughout a small watershed in the Cascade Mountains, Oregon, USA. Our data imply that a pool of tightly bound water that is retained in the soil and used by trees does not participate in translatory flow, mix with mobile water or enter the stream. Instead, water from initial rainfall events after rainless summers is locked into small pores with low matric potential until transpiration empties these pores during following dry summers. Winter rainfall does not displace this tightly bound water. As transpiration and stormflow are out of phase in the Mediterranean climate of our study site, two separate sets of water bodies with different isotopic characteristics exist in trees and streams. We conclude that complete mixing of water within the soil cannot be assumed for similar hydroclimatic regimes as has been done in the past3,4.
Subscribe to Journal
Get full journal access for 1 year
only $15.58 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Hewlett, J. D. & Hibbert, A. R. in Forest Hydrology (eds Sopper, W. E. & Lull, H. W.) 275–291 (Pergamon, 1967).
Horton, J. H. & Hawkins, R. H. Flow path of rain from soil surface to water table. Soil Sci. 100, 377–383 (1965).
Bruijnzeel, L. A. (De)forestation and dry season flow in the tropics: A closer look. J. Tropical Forest Sci. 1, 229–243 (1989).
Govind, A., Chen, J. M. & Ju, W. Spatially explicit simulation of hydrologically controlled carbon and nitrogen cycles and associated feedback mechanisms in a boreal ecosystem. J. Geophys. Res. 114, G02006 (2009).
Bates, C. G. First results in the streamflow experiment Wagon Wheel Gap, Colorado. J. Forestry 19, 402–408 (1921).
Bosch, J. M. & Hewlett, J. D. A review of catchment experiments to determine the effect of vegetation changes on water yield and evapotranspiration. J. Hydrol. 55, 3–23 (1982).
Jones, J. A. Hydrologic processes and peak discharge response to forest removal, regrowth, and roads in 10 small experimental basins, western Cascades, Oregon. Wat. Resour. Res. 36, 2621–2642 (2000).
Jones, J. A. & Grant, G. E. Peak flow responses to clear-cutting and roads in small and large basins, western Cascades, Oregon. Wat. Resour. Res. 32, 959–974 (1996).
Alila, Y., Kuras, P. K., Schnorbus, M. & Hudson, R. Forests and floods: A new paradigm sheds light on age-old controversies. Wat. Resour. Res. 45, W08416 (2009).
McDonnell, J. J. et al. Moving beyond heterogeneity and process complexity: A new vision for watershed hydrology. Wat. Resour. Res. 43, W07301 (2007).
Dawson, T. E. & Ehleringer, J. R. Streamside trees that do not use streamside water. Nature 350, 335–337 (1991).
Bond, B. J. et al. The zone of vegetation influence on baseflow revealed by diel patterns of streamflow and vegetation water use in a headwater basin. Hydrol. Process. 16, 1671–1677 (2002).
Seibert, J. & McDonnell, J. J. On the dialog between experimentalist and modeler in catchment hydrology: Use of soft data for multicriteria model calibration. Wat. Resour. Res. 38, 1241 (2002).
Clark, I. D. & Fritz, P. Environmental Isotopes in Hydrogeology (Lewis, 1997).
Dansgaard, W. Stable isotopes in precipitation. Tellus 4, 436–468 (1964).
West, A. G., Patrickson, S. J. & Ehleringer, J. R. Water extraction times for plant and soil materials used in stable isotope analysis. Rapid Commun. Mass Spectrometry 20, 1317–1321 (2006).
Harr, R. D. Water flux in soil and subsoil on a steep forested slope. J. Hydrol. 33, 37–58 (1977).
Selker, J. S., Keller, C. K. & McCord, J. T. Vadose Zone Processes (Lewis, 1999).
Gouet-Kaplan, M., Tartakovsky, A. & Berkowitz, B. Simulation of the interplay between resident and infiltrating water in partially saturated porous media. Wat. Resour. Res. 45, W05416 (2009).
Gazis, C. & Feng, X. A stable isotope study of soil water: Evidence for mixing and preferential flow paths. Geoderma 119, 97–111 (2004).
Gardner, W. R. Some steady state solutions of the unsaturated moisture flow equations with application to evaporation from a water table. Soil Sci. 85, 228–232 (1958).
Brooks, J. R., Meinzer, F. C., Warren, J. M., Domec, J. C. & Coulombe, R. Hydraulic redistribution in a Douglas-fir forest: Lessons from system manipulations. Plant Cell Environ. 29, 138–150 (2006).
Warren, J. M., Meinzer, F. C., Brooks, J. R. & Domec, J. C. Vertical stratification of soil water storage and release dynamics in Pacific Northwest coniferous forests. Agric. For. Meteorol. 130, 39–58 (2005).
Domec, J. C., Warren, J. M., Meinzer, F. C., Brooks, J. R. & Coulombe, R. Native root xylem embolism and stomatal closure in stands of Douglas-fir and ponderosa pine: Mitigation by hydraulic redistribution. Oecologia 141, 7–16 (2004).
McGuire, K. J. et al. The role of topography on catchment-scale water residence time. Wat. Resour. Res. 41, W05002 (2005).
Bundt, M., Jaggi, M., Blaser, P., Siegwolf, R. & Hagedorn, F. Carbon and nitrogen dynamics in preferential flow paths and matrix of a forest soil. Soil Sci. Soc. Am. J. 65, 1529–1538 (2001).
Asano, Y., Compton, J. E. & Church, R. M. Hydrologic flowpaths influence inorganic and organic nutrient leaching in a forest soil. Biogeochem. 81, 191–204 (2006).
Dawson, T. E. in Stable Isotopes and Plant Carbon–Water Relations (eds Ehleringer, J. R., Hall, A. E. & Farquhar, G. D.) 465–496 (Academic, 1993).
Kennedy, V. C., Zellweger, G. W. & Avanzino, R. J. Variation of rain chemistry during storms at two sites in northern California. Wat. Resour. Res. 15, 687–702 (1979).
This work was supported by the US Environmental Protection Agency. This manuscript has been subjected to the Environmental Protection Agency’s peer and administrative review, and it has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. This research was conducted at the H. J. Andrews Experimental Forest, and we thank USDA Forest Service Pacific Northwest Research Station, Oregon State University and the Willamette National Forest for their support of this research facility. H.B. thanks the Oregon State University Institute for Water and Watersheds and the Ford Foundation for financial support. We thank G. Heinz and M. Johnson for help in field work, W. Rugh and K. Rodecap for isotopic analysis, and J. Selker, D. Williams, L. Hopp and R. Ozretich for helpful comments on an earlier draft of this manuscript.
The authors declare no competing financial interests.
About this article
Cite this article
Renée Brooks, J., Barnard, H., Coulombe, R. et al. Ecohydrologic separation of water between trees and streams in a Mediterranean climate. Nature Geosci 3, 100–104 (2010). https://doi.org/10.1038/ngeo722
Journal of Geophysical Research: Biogeosciences (2020)
Vadose Zone Journal (2020)
The role of deep vadose zone water in tree transpiration during drought periods in karst settings – Insights from isotopic tracing and leaf water potential
Science of The Total Environment (2020)
Calibration method affects the measured δ 2 H and δ 18 O in soil water by direct H 2 O liquid –H 2 O vapour equilibration with laser spectroscopy
Hydrological Processes (2020)
Bound and mobile soil water isotope ratios are affected by soil texture and mineralogy, whereas extraction method influences their measurement
Hydrological Processes (2020)