AGU 2014…check out this session on tracers!

McGuire is co-convening a session with Josie Geris, Daniele Penna, and Julian Klaus called “New Developments in Tracer Applications in Catchment Hydrology.”  If you are attending the meeting next week, please come to our session.  The program is available below:

Papers – Tuesday, Moscone West
3022

https://agu.confex.com/agu/fm14/meetingapp.cgi#Session/4908

 

Read more ›

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New review paper on tracers in northern catchments

HPcoverAbstract: We examine how tracer studies have enhanced our understanding of flow paths, residence times and sources of stream flow in northern catchments. We define northern catchments as non-glacial sites in the temperate conifer/boreal/permafrost zone, focussing our review mainly on sites in North America and Europe. Improved empirical and theoretical understanding of hydrological functioning has advanced the analytical tools available for tracer-based hydrograph separations, derivation of transit time distributions and tracer-aided rainfall-runoff models that are better able to link hydrological response to storage changes. However, the lack of comprehensive tracer data sets still hinders development of a generalized understanding of how northern catchments will respond to change. This paucity of empirical data leads to many outstanding research needs, particularly in rapidly changing areas that are already responding to climatic warming and economic development. To continually improve our understanding of hydrological processes in these regions our knowledge needs to be advanced using a range of techniques and approaches. Recent technological developments for improved monitoring, distributed hydrological sensor systems, more economic analysis of large sample numbers in conjunction with novel, tracer-aided modelling approaches and the use of remote sensing have the potential to help understanding of northern hydrological systems as well as inform policy at a time of rapid environmental change.

Tetzlaff, D, Buttle, J., Carey, S.K., McGuire, K., Laudon, H., Soulsby, C. 2014. Tracer-based assessment of flow paths, storage and runoff generation in northern catchments: a review, Hydrological Processes, doi: 10.1002/hyp.10412.

 

Posted in Lab news, Review paper Tagged with: , , , , ,

Paper published on mapping of hydropedologic spatial patterns

sssa-logoA paper from Cody Gillin’s master’s thesis was accepted last week.  The manuscript titled “Mapping of hydropedologic spatial patterns in a steep headwater catchment” will be published in a special issue on hydropedology in the Soil Science Society of America Journal.  This paper appears in the special issue with another paper on the same project, which was led by Rebecca Bourgault from the University of Vermont.

Gillin, C.P., Bailey, S.W., McGuire, K.J., Gannon, J.P. 2014. Mapping of hydropedologic spatial patterns in a steep headwater catchment, Soil Science Society of America Journal, doi: 10.2136/sssaj2014.05.0189.

Abstract: A hydropedologic approach can be used to describe soil units affected by distinct hydrologic regimes. We used field observations of soil morphology and geospatial information technology to map distribution of five hydropedologic soil units across a 42 ha forested headwater catchment. Soils were described and characterized at 172 locations within watershed 3, the hydrologic reference catchment for the Hubbard Brook Experimental Forest, NH. Soil profiles were grouped by presence and thickness of genetic horizons. Topographic and bedrock metrics were used in a logistic regression model to estimate the probability of soil group occurrence. Each soil group occurred under specific settings that influence subsurface hydrologic conditions. The most important metrics for predicting soil groups were Euclidean distance from bedrock outcrop, topographic wetness index, bedrock-weighted upslope accumulated area, and topographic position index. Catchment scale maps of hydropedologic units highlight regions dominated by lateral eluviation or lateral illuviation, and show that only about half the catchment is dominated by podzolization processes occurring under vertical percolation at the pedon scale. A water table map shows the importance of near-stream zones, typically viewed as variable source areas, as well as more distal bedrock-controlled zones to runoff generation. Although the catchment is steep and underlain by soils developed in coarse-textured parent material, patterns of groundwater incursion into the solum indicate that well drained soils are restricted to deeper soils away from shallow bedrock and the intermittent stream network. Hydropedologic units can be a valuable tool for informing watershed management, soil carbon accounting, and understanding biogeochemical processes and runoff generation.

Posted in Lab news, Research paper Tagged with: , , , ,

2014 AGU presentations

AGU_logoHere are the AGU presentation titles from the group this year:

Benettin, P., Kirchner, J., McGuire, K., Rinaldo, A., Botter, G., 2014. Linking tracers and travel time distributions: the emergence of age mixing patterns, Abstract H21L-01, Fall Meeting, AGU, Dec. 15-19, San Francisco, CA (Invited)

Gannon, J., McGuire, K., Bailey, S., Shanley, J., 2014. Simply active, or contributing too? Investigating the hydrologic connectivity of shallow water tables in a headwater catchment, Abstract H31I-0756, Fall Meeting, AGU, Dec. 15-19, San Francisco, CA (Invited)

Klaus, J., Chun, K., McGuire, K., McDonnell, J., 2014. A new non-parametric framework to determine time-variant catchment transit times and their distributions, Abstract H23L-1041, Fall Meeting, AGU, Dec. 15-19, San Francisco, CA

McGuire, K., Bailey, S., Gannon, J., Likens, G., Buso, D., Torgersen, C., Lowe, W., 2014. Multi-Scale Variations in Streamwater Chemistry and Hydropedological Implications for Hotspot Development, Abstract H14E-03, Fall Meeting, AGU, Dec. 15-19, San Francisco, CA (Invited)

Morse, J., Duran, J., Morillas, L., Roales, J., Bailey. S., McGuire, K., Groffman, P., 2014. Searching for hot spots and hot moments of soil denitrification in northern hardwood forests, Abstract H14E-04, Fall Meeting, AGU, Dec. 15-19, San Francisco, CA

Weiler, M., McGuire, K., Stahl, K., 2014. A Reanalysis of Forest Disturbance Impacts on Streamflow, Abstract H12D-02, Fall Meeting, AGU, Dec. 15-19, San Francisco, CA

Posted in Lab news, Meetings

New paper about how forests lose nitrogen through shallow groundwater flowpaths

WS3_weir

This weir, a place in a stream where a wall controls the flow of water, measures stream flow and dissolved chemical exports from Watershed 3 at the Hubbard Brook Experimental Forest in New Hampshire, where the research took place (photo credit: JP Gannon).

In a paper published in the Proceedings of the National Academy of Sciences, McGuire working with a team from the Hubbard Brook Ecosystem Study found clear evidence of nitrogen loss through denitrification in isolated shallow groundwater patches in a small watershed. The findings were somewhat of a surprise because denitrification has been so difficult to measure at Hubbard Brook even though deposition and export relationships suggested that denitrification may have been a factor in the decline of nitrate concentrations observed in streamwater. The paper significance statement and abstract are below. The paper is also available now in PNAS early edition.

Significance:

Denitrification is the most poorly understood process in the terrestrial N cycle. As a result, terrestrial N budgets are wildly unbalanced and our ability to address global nitrogen pollution is fundamentally constrained. Denitrification is controlled by multiple factors, often exhibiting extraordinary variation in time and space, especially in terrestrial environments. Temperate forests regularly receive much larger inputs of precipitation N than they export in streamwater. The fate of the rest has been elusive. We present stable isotope measurements revealing extensive evidence of denitrification from temper- ate-forest shallow groundwater in midsummer, even as concurrent measurements of streamwater show little sign of denitrification. These measurements support the importance of a disputed nitrogen removal process and its occurrence at a previously missed time and location.

Abstract:

Despite decades of measurements, the nitrogen balance of tem- perate forest catchments remains poorly understood. Atmospheric nitrogen deposition often greatly exceeds streamwater nitrogen losses; the fate of the remaining nitrogen is highly uncertain. Gaseous losses of nitrogen to denitrification are especially poorly documented and are often ignored. Here, we provide isotopic evidence (δ15NNO3 and δ18ONO3) from shallow groundwater at the Hubbard Brook Experimental Forest indicating extensive denitrification during midsummer, when transient, perched patches of saturation developed in hillslopes, with poor hydrological connectivity to the stream, while streamwater showed no isotopic evidence of denitrification. During small rain events, precipitation directly contributed up to 34% of streamwater nitrate, which was otherwise produced by nitrification. Together, these measurements reveal the importance of denitrification in hydrologically disconnected patches of shallow groundwater during midsummer as largely overlooked control points for nitrogen loss from temperate forest catchments.

See also news stories by:

VTnews

The Cornell Chronicle

Posted in Lab news, Research paper Tagged with: , , , , , ,

Welcome Ray!

Ray Lee

A new Ph.D. student, Ray Lee, joined our lab this week.  Ray recently completed his M.S. at San Diego State University in geography and studied environmental and resource economics and philosophy during his undergraduate program at UC-Davis.  Ray will be working on a project based at the Coweeta Hydrologic Lab in North Carolina.  Welcome to Blacksburg!

Posted in Lab news

New paper by Gannon on organizing groundwater regimes and response thresholds by soils

JP Gannon had a paper accepted this week in Water Resources Research titled “Organizing groundwater regimes and response thresholds by soils: A framework for understanding runoff generation in a headwater catchment.”

Here’s the abstract: A network of shallow groundwater wells in a headwater catchment at the Hubbard Brook Experimental Forest in New Hampshire, USA was used to investigate the hydrologic behavior of five distinct soil morphological units. The soil morphological units were hypothesized to be indicative of distinct water table regimes. Water table fluctuations in the wells were characterized by their median and interquartile range of depth, proportion of time water table was present in the solum, and storage-discharge behavior of subsurface flow. Statistically significant differences in median, interquartile range, and presence of water table were detected among soil units. Threshold responses were identified in storage-discharge relationships of subsurface flow, with thresholds varying among soil units. These results suggest that soil horizonation is indicative of distinct groundwater flow regimes. The spatial distribution of water table across the catchment showed variably connected/disconnected active areas of runoff generation in the solum. The spatial distribution of water table and therefore areas contributing to stormflow is complex and changes depending on catchment storage.

Key points:

  • Soil horizonation is indicative of distinct water table fluctuations
  • Threshold storage-discharge relationships vary among hydropedological soil units
  • Spatial patterns of runoff generation are linked to soil horizonation and thresholds in catchment storage
Posted in Lab news, Research paper Tagged with: , , , ,

Variable source area concept…Hewlett 1961

I recently obtained a digital copy of Hewlett’s 1961 description of the variable source area concept.  This document, which is part of an annual report of the US Forest Service Southeastern Forest Experiment Station and at the time was based out of Asheville, NC, is regarded as the first publication of the concept in English.  There were simultaneous works published in France (Cappus 1960) and Japan (Tsukamoto 1961), but Hewlett’s version is often credited as the first.  While this 1961 report is not my favorite description of the variable source area concept, it is probably the most difficult to find and that is why I am posting it here (I think copyright is not an issue since it is a federal report).  I prefer the description by Tom Dunne from Kirkby’s Hillslope Hydrology book, but apparently Hewlett did not agree that version.  Anyway, it’s a shame that Hewlett (or Cappus or Tsukamoto) did not explicitly publish his ideas in a peer-review journal in the early 1960s.

Posted in Research paper

Welcome Carrie and Amy

We have two new students in the lab!  Carrie Jensen and Amy Gondran.

Welcome!

Posted in Lab news

New paper on urban soil rehabilitation

STE_coverYujuan Chen just had her third paper published from her dissertation.  Yujuan is now with the Food and Agriculture Organization in Rome Italy.

Chen, Y., Day, S.D., Wick, A.F., McGuire, K.J. 2014. Influence of urban land development and subsequent soil rehabilitation on soil aggregates, carbon, and hydraulic conductivity, Science of The Total Environment, 494-495: 329–336, 10.1016/j.scitotenv.2014.06.099.

Paper highlights:

  • Urban land development reduces soil macroaggregates and permeability.
  • Can subsurface soil rehabilitation with compost mitigate these effects?
  • Soil rehabilitation does not measurably enhance aggregate formation within 5 years.
  • Soil rehabilitation does improve subsurface hydraulic conductivity.
  • Urban soil ecosystem service provision is strongly management dependent.

 

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