Hydrological connectivity of hillslopes and streams: Characteristic time scales and nonlinearities

[1] Subsurface flow from hillslopes is widely recognized as an important contributor to streamflow generation; however, processes that control how and when hillslopes connect to streams remain unclear. We investigated stream and hillslope runoff dynamics through a wet-up period in watershed 10 of the H. J. Andrews Experimental Forest in the western Cascades of Oregon where the riparian zone has been removed by debris flows. We examined the controls on hillslope-stream connectivity on the basis of observations of hydrometric, stable isotope, and applied tracer responses and computed transit times for multiple runoff components for a series of storms during the wet-up phase of the 2002–2003 winter rainy season. Hillslope discharge was distinctly threshold-like with a near linear response and average quick flow ratio of 0.58 when antecedent rainfall was greater than 20 mm. Hillslope and stream stormflow varied temporally and showed strong hysteretic relationships. Event water mean transit times (8–34 h) and rapid breakthrough from applied hillslope tracer additions demonstrated that subsurface contributing areas extend far upslope during events. Despite rapid hillslope transport processes during events, soil water and runoff mean transit times during nonstorm conditions were greater than the time scale of storm events. Soil water mean transit times ranged between 10 and 25 days. Hillslope seepage and catchment base flow mean transit times were between 1 and 2 years. We describe a conceptual model that captures variable physical flow pathways, their synchronicity, threshold activation, hysteresis, and transit times through changing antecedent wetness conditions that illustrate the different stages of hillslope and stream connectivity.

[1]  Jeffrey J. McDonnell,et al.  Connectivity at the hillslope scale: identifying interactions between storm size, bedrock permeability, slope angle and soil depth. , 2009 .

[2]  R. Waring,et al.  Changes in Nitrogen Cycling at an Old-Growth Douglas-fir Site After Disturbance , 1981 .

[3]  S. P. Anderson,et al.  Unsaturated zone processes and the hydrologic response of a steep, unchanneled catchment , 1998 .

[4]  James P. McNamara,et al.  An approach to understanding hydrologic connectivity on the hillslope and the implications for nutrient transport , 2003 .

[5]  Jeffrey J. McDonnell,et al.  How does rainfall become runoff? A combined tracer and runoff transfer function approach , 2003 .

[6]  P. Troch,et al.  Development and application of a catchment similarity index for subsurface flow , 2010 .

[7]  R. J. Avanzino,et al.  Variation of rain chemistry during storms at two sites in northern California , 1979 .

[8]  Jeffrey J. McDonnell,et al.  Integrating tracer experiments with modeling to assess runoff processes and water transit times , 2007 .

[9]  J. Buttle,et al.  Isotope hydrograph separations and rapid delivery of pre-event water from drainage basins , 1994 .

[10]  Jeffrey J. McDonnell,et al.  Linking the hydrologic and biogeochemical controls of nitrogen transport in near-stream zones of temperate-forested catchments: a review , 1997 .

[11]  J. Kirchner.  A double paradox in catchment hydrology and geochemistry , 2003 .

[12]  W. Gburek,et al.  Quantifying stormflow components in a Pennsylvania watershed when 18O input and storm conditions vary , 1993 .

[13]  J. Kirchner,et al.  Catchment-scale advection and dispersion as a mechanism for fractal scaling in stream tracer concentrations , 2001 .

[14]  T. Battin.  Hydrologic flow paths control dissolved organic carbon fluxes and metabolism in an Alpine stream hyporheic zone , 1999 .

[15]  M. Mosley.  Streamflow generation in a forested watershed, New Zealand , 1979 .

[16]  J. Buttle,et al.  Runoff Production in a Forested, Shallow Soil, Canadian Shield Basin , 1995 .

[17]  K. Bencala,et al.  Hyporheic zone hydrological processes , 2000 .

[18]  R. Torres.  A threshold condition for soil‐water transport , 2002 .

[19]  James R. Sedell,et al.  Nitrogen Budget for a Small Coniferous Forest Stream , 1984 .

[20]  K. Beven,et al.  Uncertainty in hydrograph separations based on geochemical mixing models. , 2002 .

[21]  J. McDonnell,et al.  The role of hillslope hydrology in controlling nutrient loss. , 2009 .

[22]  K. Beven,et al.  TOPOGRAPHIC CONTROLS ON SUBSURFACE STORM FLOWAT THE HILLSLOPE SCALE FOR TWO HYDROLOGICALLY DISTINCT SMALL CATCHMENTS , 1997 .

[23]  James R. Hoover.  Evaluation of Flow Pathways in a Sloping Soil Cross Section , 1985 .

[24]  R. D. Harr,et al.  Water flux in soil and subsoil on a steep forested slope , 1977 .

[25]  Jeffrey J. McDonnell,et al.  Scale effects on headwater catchment runoff timing, flow sources, and groundwater‐streamflow relations , 2004 .

[26]  P. Troch,et al.  A tale of two isotopes: differences in hydrograph separation for a runoff event when using δD versus δ18O , 2009 .

[27]  Ross Woods,et al.  The changing spatial variability of subsurface flow across a hillside , 1996 .

[28]  C. T. Haan,et al.  Subsurface flow responses of a small forested catchment in the Ouachita mountains , 1992 .

[29]  Jeffrey J. McDonnell,et al.  Threshold relations in subsurface stormflow: 1. A 147‐storm analysis of the Panola hillslope , 2006 .

[30]  J. A. Vomocil,et al.  Perched water tables on hillsides in western Oregon: I. Some factors affecting their development and longevity. , 1982 .

[31]  W. V. Verseveld,et al.  Hydro-biogeochemical coupling at the hillslope and catchment scale , 2007 .

[32]  J. Buttle,et al.  Infiltration and soil water mixing on forested and harvested slopes during spring snowmelt, Turkey Lakes Watershed, central Ontario , 2005 .

[33]  J. McDonnell,et al.  A review and evaluation of catchment transit time modeling , 2006 .

[34]  Kevin J. McGuire,et al.  Topographic controls on shallow groundwater dynamics: implications of hydrologic connectivity between hillslopes and riparian zones in a till mantled catchment , 2010 .

[35]  J. Kirchner.  Getting the right answers for the right reasons: Linking measurements, analyses, and models to advance the science of hydrology , 2006 .

[36]  P. Sollins,et al.  The Internal Element Cycles of an Old‐Growth Douglas‐Fir Ecosystem in Western Oregon , 1980 .

[37]  D. Weyman,et al.  MEASUREMENTS OF THE DOWNSLOPE FLOW OF WATER IN A SOIL , 1973 .

[38]  M. Tani.  Runoff generation processes estimated from hydrological observations on a steep forested hillslope with a thin soil layer , 1997 .

[39]  Shoji Noguchi,et al.  Stormflow generation in steep forested headwaters: a linked hydrogeomorphic paradigm , 2000 .

[40]  D. Greenland.  Regional context of the climate of H.J. Andrews Experimental Forest, Oregon , 1994 .

[41]  H. Gholz,et al.  Early vegetation recovery and element cycles on a clear-cut watershed in western Oregon , 1985 .

[42]  Keith Beven,et al.  Riparian control of stream-water chemistry: Implications for hydrochemical basin models , 1998 .

[43]  James M. Buttle,et al.  Hydrologic coupling of slopes, riparian zones and streams: an example from the Canadian Shield , 2004 .

[44]  S. P. Anderson,et al.  Subsurface flow paths in a steep, unchanneled catchment , 1997 .

[45]  P. Vidon,et al.  Landscape controls on the hydrology of stream riparian zones , 2004 .

[46]  F. M. McCorison,et al.  Initial effects of clearcut logging on size and timing of peak flows in a small watershed in western Oregon , 1979 .

[47]  M. Bonell,et al.  SELECTED CHALLENGES IN RUNOFF GENERATION RESEARCH IN FORESTS FROM THE HILLSLOPE TO HEADWATER DRAINAGE BASIN SCALE 1 , 1998 .

[48]  H. Laudon,et al.  Oxygen 18 fractionation during snowmelt: Implications for spring flood hydrograph separation , 2002 .

[49]  D. Burns.  Stormflow‐hydrograph separation based on isotopes: the thrill is gone — what's next? , 2002 .

[50]  Keith Beven,et al.  The role of bedrock topography on subsurface storm flow , 2002 .

[51]  J. Nash,et al.  River flow forecasting through conceptual models part I — A discussion of principles☆ , 1970 .

[52]  J. McDonnell,et al.  A hydrometric and geochemical approach to test the transmissivity feedback hypothesis during snowmelt , 1999 .

[53]  P. Troch,et al.  Characterizing the response of a catchment to an extreme rainfall event using hydrometric and isotopic data , 2008 .

[54]  Jeffrey J. McDonnell,et al.  Quantifying the relative contributions of riparian and hillslope zones to catchment runoff , 2003 .

[55]  Keith Beven,et al.  Hydrological processes—Letters. Topographic controls on subsurface storm flow at the hillslope scale for two hydrologically distinct small catchmetns , 1997 .

[56]  P. Smart,et al.  An evaluation of some fluorescent dyes for water tracing , 1977 .

[57]  M. Sivapalan,et al.  Hydrological connectivity of upland-riparian zones in agricultural catchments: Implications for runoff generation and nitrate transport , 2006 .

[58]  M. Sklash.  Environmental isotope studies of storm and snowmelt runoff generation , 1990 .

[59]  Jeffrey J. McDonnell,et al.  Modeling Base Flow Soil Water Residence Times From Deuterium Concentrations , 1991 .

[60]  D. A. Lietzke,et al.  Hydrogeochemical processes controlling subsurface transport from an upper subcatchment of Walker Branch watershed during storm events. 1. Hydrologic transport processes , 1991 .

[61]  D. W. Ranken.  Hydrologic properties of soil and subsoil on a steep, forested slope , 1974 .

[62]  P. Sollins,et al.  Nitrogen and carbon solution chemistry of an old growth coniferous forest watershed before and after cutting , 1981 .

[63]  C. Jackson,et al.  Hillslope infiltration and lateral downslope unsaturated flow , 1992 .

[64]  Ming-ko Woo,et al.  Hydrology of subarctic Canadian shield: soil-filled valleys , 2003 .

[65]  Jeffrey J. McDonnell,et al.  Threshold relations in subsurface stormflow: 2. The fill and spill hypothesis , 2006 .

[66]  G. Pinay,et al.  Linking hydrology and biogeochemistry in complex landscapes , 2004 .

[67]  Peter Lehmann,et al.  Hydrology and Earth System Sciences Rainfall Threshold for Hillslope Outflow: an Emergent Property of Flow Pathway Connectivity , 2022 .

[68]  Brian L. McGlynn,et al.  A review of the evolving perceptual model of hillslope flowpaths at the Maimai catchments, New Zealand , 2002 .

[69]  D. Weyman,et al.  THROUGHFLOW ON HILLSLOPES AND ITS RELATION TO THE STREAM HYDROGRAPH , 1970 .

[70]  A. Zuber,et al.  On the physical meaning of the dispersion equation and its solutions for different initial and boundary conditions , 1978 .

[71]  Michael N. Gooseff,et al.  Hydrologic connectivity between landscapes and streams: Transferring reach‐ and plot‐scale understanding to the catchment scale , 2009 .

[72]  Barbara J. Bond,et al.  Precision and accuracy of three alternative instruments for measuring soil water content in two forest soils of the Pacific Northwest , 2005 .

[73]  Mark S. Johnson,et al.  Storm pulses of dissolved CO2 in a forested headwater Amazonian stream explored using hydrograph separation , 2007 .

[74]  R. Harr,et al.  Movement of water through forested soils in steep topography , 1972 .

[75]  R. Sidle,et al.  Throughflow variability during snowmelt in a forested mountain catchment, coastal British Columbia, Canada , 2004 .

[76]  S. Epstein,et al.  Variation of O18 content of waters from natural sources , 1953 .

[77]  D. Genereux,et al.  Quantifying uncertainty in tracer‐based hydrograph separations , 1998 .

[78]  Kelsey J. Sinclair,et al.  The use of stream flow routing for direct channel precipitation with isotopically-based hydrograph separations: the role of new water in stormflow generation , 2003 .

[79]  André G. Roy,et al.  Revisiting Hydrologic Sampling Strategies for an Accurate Assessment of Hydrologic Connectivity in Humid Temperate Systems , 2009 .

[80]  Nobuhito Ohte,et al.  Residence times and flow paths of water in steep unchannelled catchments , 2002 .

[81]  G. Lischeid.  Combining Hydrometric and Hydrochemical Data Sets for Investigating Runoff Generation Processes: Tautologies, Inconsistencies and Possible Explanations , 2008 .

[82]  J. McDonnell,et al.  Deuterium variations in storm rainfall: Implications for stream hydrograph separation , 1990 .

[83]  Shoji Noguchi,et al.  Seasonal hydrologic response at various spatial scales in a small forested catchment, Hitachi Ohta, Japan , 1995 .

[84]  Shoji Noguchi,et al.  Flow and solute transport through the soil matrix and macropores of a hillslope segment , 1994 .

[85]  Louise J. Bracken,et al.  The concept of hydrological connectivity and its contribution to understanding runoff‐dominated geomorphic systems , 2007 .

[86]  R. Z. Whipkey.  SUBSURFACE STORMFLOW FROM FORESTED SLOPES , 1965 .

[87]  J. Welker,et al.  The role of topography on catchment‐scale water residence time , 2005 .

[88]  K. McGuire,et al.  Threshold changes in storm runoff generation at a till‐mantled headwater catchment , 2010 .

[89]  Jeffrey J. McDonnell,et al.  A rationale for old water discharge through macropores in a steep, humid catchment. , 1990 .

[90]  K. Beven,et al.  Towards identifying sources of subsurface flow: A comparison of components identified by a physically based runoff model and those determined by chemical mixing techniques , 1992 .