Results of LTER4
Studies of hydrology during the previous years have produced new insights by examining
upstream disturbance and vegetation effects on stream flow responses. Forest harvest was
found to increase the magnitude of peak flows in small basins and, possibly, in larger
basins (Jones and Grant 1996, Jones 2000). The increases are greatest for small, frequent
storms (Jones and Grant 2001a, b). These findings have sparked analysis by others
(Thomas and Megahan 1998, Beschta et al. 2000). Roads also lead to increases of peak
flows (Wemple et al. 1996, Wemple 1998) and modify landscape-scale response to floods
due to their ability to extend the drainage network (Wemple et al. 2001). Rain-on-snow
flood events were analyzed, showing distinctive behaviors of types of event related to
precipitation-landscape interactions (Perkins 1997). An LTER intersite study evaluated
temporal behavior of long-term hydrologic data from Andrews as well as data from
Caspar Creek, Coweeta, Hubbard Brook, and Luquillo (Post et al. 1998). These five sites
have distinct time scales of precipitation-stream flow coupling (Post & Jones 2001) and
differ markedly in their long-term response to forest harvest, highlighting the influence of
soil reservoirs on hydrologic response.
References
Beschta, R. L.; Pyles, M. R.; Skaugset, A. E.; Surfleet, C. G. 2000. Peakflow responses to
forest practices in the western cascades of Oregon, USA. Journal of Hydrology 233: 102120.
Jones, J. A. 2000. Hydrologic processes and peak discharge response to forest removal,
regrowth, and roads in 10 small experimental basins, western Cascades, Oregon. Water
Resources Research 36(9): 2621-2642.
Jones, J. A.; Post, D. A. 1999. Ecological hydrology--intersite comparison of long-term
streamflow records from forested basins in Oregon, New Hampshire, North Carolina, and
Puerto Rico. LTER The Network News 12(2): 10, 15.
Jones, J. A.; Grant, G. E. 1996. Peak flow responses to clear-cutting and roads in small
and large basins, western Cascades, Oregon. Water Resources Research 32(4): 959-974.
Jones, J. A.; Grant, G. E. 2001a. Comment on "Peak flow responses to clear-cutting and
roads in small and large basins, western Cascades, Oregon: a second opinion" by R.B.
Thomas and W.F. Megahan. Water Resources Research 37(1): 175-178.
Jones, J. A.; Grant, G. E. 2001b. Comment on "Peak flow responses to clear-cutting and
roads in small and large basins, western Cascades, Oregon" by J.A. Jones and G.E. Grant.
Water Resources Research. 37(1): 179-180.
Jones, J. A.; Swanson, F. J.; Wemple, B. C.; Snyder, K. U. 2000. Effects of roads on
hydrology, geomorphology, and disturbance patches in stream networks. Conservation
Biology 14(1): 76-85.
Jones, J. A.; Swanson, F. J. 2001. Hydrologic inferences from comparisons among small
basin experiments. Hydrological Processes 15: 2363-2366.
Perkins, R. M. 1997. Climatic and physiographic controls on peakflow generation in the
western Cascades,Oregon. Oregon State University. 190 p. Ph.D. dissertation.
Post, D. A.; Grant, G. E.; Jones, J. A. 1998. New developments in ecological hydrology
expand research opportunities. EOS, Transactions, American Geophysical Union 79(43):
517-526.
Post, D.A.; Jones, J.A. 2001. Hydrologic regimes of forested, mountainous, headwater
basins in New Hampshire, North Carolina, Oregon, and Puerto Rico. Advances in Water
Resources 24(9-10): 1195-1210.
Thomas, R. B.; Megahan, W. F. 1998. Peak flow responses to clear-cutting and roads in
small and large basins, western Cascades, Oregon: a second opinion. Water Resources
Research 34(12): 3393-3403.
Wemple, B. C.; Jones, J. A.; Grant, G. E. 1996. Channel network extension by logging
roads in two basins, western Cascades, Oregon. Water Resources Bulletin 32(6): 11951207.
Wemple, B. C.; Swanson, F. J.; Jones, J. A. 2001. Forest roads and geomorphic process
interactions, Cascade Range, Oregon. Earth Surface Processes and Landforms 26: 191204.
Wemple, B. C. 1998. Investigations of runoff production and sedimentation on forest
roads. Oregon State University. 168 p. Ph.D. dissertation.
Plan for LTER 5
Hydrology. The objective of our hydrologic studies in LTER 5 will be to
understand how hydrologic processes interact with land use, climate change, and natural
disturbance. We will continue to analyze 50-yr records of stream flow from small
watersheds, Lookout Creek, and Blue River, and will conduct short-term process studies
using tracers, water aging techniques, and a continuation of ongoing hydrologic modeling
efforts. We will also examine how the hydrologic cycle is affected by vegetation at
multiple temporal scales – from diel fluxes in discharge resulting from sap flow dynamics
to decadal changes associated with climate change and natural disturbance (see
Ecophysiology Component).
To better understand the routing and timing of water delivery and solute fluxes,
we plan to reinvigorate process studies of water storage and transport in soils and
hillslopes. Using hillslope tracer tests, we will examine how the physical properties of
the deep soil profile influence water storage and release, and relate these properties to the
observed soil moisture retention curve. Hillslope hydrologic behavior will be
characterized using the distribution of residence times of subsurface water in hillslopes.
Process studies using isotopic tracers, including 18O, will allow us to determine when
water is isotopically “young” or “old,” revealing the role of fast versus slow flowpaths.
Conservative tracer analyses (Haggerty et al. in press, Wondzell submitted) will
characterize residence time distributions in channels with different character (e.g.,
bedrock, alluvial). These studies will contribute to mechanistic understanding of the
influences of storm, seasonal, and interannual precipitation flowpaths on stream flow
chemistry and provide a foundation for our small watershed integration.
We will continue to examine the processes that influence the behavior of floods,
such as those observed in 1996. Using modeling and retrospective analysis, we will
explore hypothesized alternative explanations for the emergent behavior evident in rainon-snow floods: (1) spatial coherence of small basin discharge peaks (Perkins 1997), (2)
replacement of old growth with young stands (Jones & Grant 1996), (3) spatial coherence
of snowmelt (Marks et al. 1998), (4) arrangement of road-stream connections (Jones et al.
2000), and (5) flood routing. Our retrospective analysis will benefit from ongoing
modeling efforts conducted by collaborators in Sweden (Seibert) and Germany
(Uhlenbrook).