New paper on streamflow response to forest management and increasing precipitation extremes

CoweetaDr. Charley Kelly, a former lab member and now with the Division of Forestry and Natural Resources, West Virginia University, had a paper accepted in Geophysical Research Letters this week.  The study re-examines several paired watershed studies from the Coweeta Hydrologic Lab, but focuses on high flows, low flows, and interactions with precipitation patterns.

Abstract: Increases in extreme precipitation events of floods and droughts are expected to occur worldwide. The increase in extreme events will result in changes in streamflow that are expected to affect water availability for human consumption and aquatic ecosystem function. We present an analysis that may greatly improve current streamflow models by quantifying the impact of the interaction between forest management and precipitation. We use daily long-term data from paired watersheds that have undergone forest harvest or species conversion. We find that interactive effects of climate change, represented by changes in observed precipitation trends, and forest management regime, significantly alters expected streamflow most often during extreme events, ranging from a decrease of 59% to an increase of 40% in streamflow, depending upon management. Our results suggest vegetation might be managed to compensate for hydrologic responses due to climate change to help mitigate effects of extreme changes in precipitation.

Kelly, C. N., K. J. McGuire, C. F. Miniat, and J. M. Vose (2016), Forest management changes streamflow response to increasing precipitation extremes, Geophysical Research Letters, 43, doi:10.1002/2016GL068058.

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Carrie Jensen awarded CUAHSI Pathfinder Fellowship

Congratulations to Carrie on being selected for a CUAHSI 2015 Pathfinder Fellowship.  Carrie’s proposal titled, “Stream network expansion and contraction dynamics in headwater catchments throughout the Appalachian Highlands,” will be supported by CUAHSI (Consortium of Universities for the Advancement of Hydrologic Science, Inc.), which will provide her with an opportunity to enhance her dissertation project to include the Fernow Experimental Forest as field site.  This summer she will spend several weeks at Fernow mapping stream channels allowing her to add the Allegheny Mountain section of the Appalachian Plateau physiographic province to field sites throughout the Appalachian Highlands.  Carrie recently presented preliminary data from this project at the American Geophysical Union fall meeting in December.

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Special Issue in Hydrological Processes on tracer advances

HPcoverSpecial Issue Tracer Advances Reviews

Tracer advances in catchment hydrology (pages 5135–5138) Kevin J. McGuire and Jeffrey J. McDonnell

Ecohydrological separation in wet, low energy northern environments? A preliminary assessment using different soil water extraction techniques (pages 5139–5152) Josie Geris, Doerthe Tetzlaff, Jeffrey McDonnell, James Anderson, Graeme Paton and Chris Soulsby

A preliminary assessment of water partitioning and ecohydrological coupling in northern headwaters using stable isotopes and conceptual runoff models (pages 5153–5173) Doerthe Tetzlaff, James Buttle, Sean K. Carey, Marjolein H. J. van Huijgevoort, Hjalmar Laudon, James P. McNamara, Carl P. J. Mitchell, Chris Spence, Rachel S. Gabor and Chris Soulsby

Established methods and new opportunities for pore water stable isotope analysis (pages 5174–5192) Matthias Sprenger, Barbara Herbstritt and Markus Weiler

Stable water isotopes suggest sub-canopy water recycling in a northern forested catchment (pages 5193–5202) Mark B. Green, Bethany K. Laursen, John L. Campbell, Kevin J. McGuire and Eric P. Kelsey

Tracking residence times in hydrological systems: forward and backward formulations (pages 5203–5213) Paolo Benettin, Andrea Rinaldo and Gianluca Botter

Velocities, celerities and the basin of attraction in catchment response (pages 5214–5226) Keith Beven and Jess Davies

Advancing tracer-aided rainfall–runoff modelling: a review of progress, problems and unrealised potential (pages 5227–5240) Christian Birkel and Chris Soulsby

Transit time distributions, legacy contamination and variability in biogeochemical 1/fα scaling: how are hydrological response dynamics linked to water quality at the catchment scale? (pages 5241–5256) Markus Hrachowitz, Ophelie Fovet, Laurent Ruiz and Hubert H. G. Savenije

Using concurrent DNA tracer injections to infer glacial flow pathways (pages 5257–5274) Helen E. Dahlke, Andrew G. Williamson, Christine Georgakakos, Selene Leung, Asha N. Sharma, Steve W. Lyon and M. Todd Walter

A tracer to bridge the scales: on the value of diatoms for tracing fast flow path connectivity from headwaters to meso-scale catchments (pages 5275–5289) Julian Klaus, Carlos E. Wetzel, Núria Martínez-Carreras, Luc Ector and Laurent Pfister

Application of isotope hydrograph separation to understand contributions of stormwater control measures to urban headwater streams (pages 5290–5306) Anne J. Jefferson, Colin D. Bell, Sandra M. Clinton and Sara K. McMillan

Winter is Coming

I have been going to Coweeta every one or two weeks for the past two months to monitor sprinkling events on the soil model. Although I am measuring only one thing, water, being precise is actually very difficult. There are 5 high-resolution tipping buckets on the hillslope to measure samples of input and one large tipping bucket at the bottom of the model to measure outflow.

I experimented with placement of PVC collectors that are designed to capture spatial variability of the input by expanding the collection areas and positions of each input tipping bucket. Then I experimented with acrylic collectors, which are longer and smoother. Finally, I put specimen cups out along a grid on the model to measure input by hand. It is a dependable low-tech, high-resolution solution.

On the last trip of this year I shut down and winterized the model. That means disconnecting the water supply to the irrigation system, shutting off the reverse osmosis pump, and draining the water from the lines and water tank, all in case of a hard freeze, which is uncommon but possible. My instruments, e.g., soil probes and tensiometers, are sitting in the shed, ready for installation in an upcoming trip.


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2015 AGU presentations


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

Carrie Jensen and Kevin McGuire, Active Stream Length Dynamics in Headwater Catchments Spanning Physiographic Provinces in the Appalachian Highlands, H11E-1385, Monday Morning, Moscone South – Poster Hall

Scott Bailey, Kevin McGuire, Don Ross, Moving the Watershed Ecosystem Approach Beyond the Black Box with Sensor Technologies and New Conceptual Models, H42B-04, Thurs. 11:05 – 11:20, Moscone West – 3022

Kyle Corcoran, JP Gannon, Scott Bailey, Kevin McGuire, Mark Green, Biogeochemical Hotspots in Shallow to Bedrock Zones: Sources of Dissolved Organic Carbon (DOC) in the Appalachian Mountain Region of the Eastern USA, B51B-0424, Friday Morning, Moscone South – Poster Hall

Paolo Benettin, Pierre Queloz, Scott Bailey, Kevin McGuire, Andrea Rinaldo, Gianluca Botter, Modeling Hydrologic Transport through the Critical Zone: Lessons from Catchment-Scale and Lysimeter Studies, H51J-1522 

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New paper linking water age and solute dynamics at Hubbard Brook

Benettin_conceptual_figPaolo Benettin’s paper was just accepted, which was the result of his study abroad visit here in the lab during the fall 2013 and spring 2014.  The manuscript explores water age-dependent transport in estimating wePaoloathering-derived solute export.   The model predicts water travel time dynamics from water stable isotope data and represents geochemical dissolution at the catchment-scale as a simple first-order kinetic relationship based explicitly on the dynamic water travel time distributions. Paolo completed his dissertation last year at the University of Padova and is now a postdoc at EPFL (École polytechnique fédérale de Lausanne).

Abstract: We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to compute hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). The innovative contribution of this paper is the simulation of dissolved silicon and sodium concentration in streamflow, achieved by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key-role of water stored within the sub-soil glacial material in both the short- and long-term solute circulation. The travel time analysis provided an estimate of streamflow age distributions and their evolution in time related to catchment wetness conditions. The use of age information to reproduce a 14-year dataset of silicon and sodium stream concentration shows that, at catchment scales, the dynamics of such geogenic solutes are mostly controlled by hydrologic drivers, which determine the contact times between the water and mineral interfaces. Justifications and limitations toward a general theory of reactive solute circulation at catchment scales are discussed.

Benettin, P., Bailey, S.W., Campbell, J.L., Green, M.B., Rinaldo, A., Likens, G.E., McGuire, K.J., Botter, G., 2015. Linking water age and solute dynamics in streamflow at the Hubbard Brook Experimental Forest, NH, USA, Water Resources Research, doi: 10.1002/2015WR017552.

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New paper showing alternative source of stream dissolved organic carbon in a headwater catchment

Gannon_etal_figJP Gannon just had another paper accepted in Water Resources Research this week.  The study suggests that dissolved organic carbon (DOC) in headwater streams may be generated from shallow to bedrock regions in the catchment, which mostly occur near the catchment divides and channel heads.  The study also suggests that hydropedological patterns are critical to understanding DOC sources to streams.

Abstract: We investigated potential source areas of dissolved organic carbon (DOC) in headwater streams by examining DOC concentrations in lysimeter, shallow well, and streamwater samples from a reference catchment at the Hubbard Brook Experimental Forest. These observations were then compared to high frequency temporal variations in fluorescent dissolved organic matter (FDOM) at the catchment outlet and the predicted spatial extent of shallow groundwater in soils throughout the catchment. While near-stream soils are generally considered a DOC source in forested catchments, DOC concentrations in near-stream groundwater were low (mean = 2.4 mg/L, standard error = 0.6 mg/L), less than hillslope groundwater farther from the channel (mean = 5.7 mg/L, standard error = 0.4 mg/L). Furthermore, water tables in near-stream soils did not rise into the carbon rich upper B or O horizons even during events. In contrast, soils below bedrock outcrops near channel heads where lateral soil formation processes dominate had much higher DOC concentrations. Soils immediately downslope of bedrock areas had thick eluvial horizons indicative of leaching of organic materials, Fe, and Al and had similarly high DOC concentrations in groundwater (mean = 14.5 mg/L, standard error = 0.8 mg/L). Flow from bedrock outcrops partially covered by organic soil horizons produced the highest groundwater DOC concentrations (mean = 20.0 mg/L, standard error = 4.6 mg/L) measured in the catchment. Correspondingly, streamwater in channel heads sourced in part by shallow soils and bedrock outcrops had the highest stream DOC concentrations measured in the catchment. Variation in FDOM concentrations at the catchment outlet followed water table fluctuations in shallow to bedrock soils near channel heads. We show that shallow hillslope soils receiving runoff from organic matter-covered bedrock outcrops may be a major source of DOC in headwater catchments in forested mountainous regions where catchments have exposed or shallow bedrock near channel heads.

Gannon, J.P., Bailey, S.W., McGuire, K.J., Shanley, J.B., 2015. Flushing of distal hillslopes as an alternative source of stream dissolved organic carbon in a headwater catchment, Water Resources Research, doi: 10.1002/2015WR016927. 

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Creating a research brand – advice from my Ph.D. advisor published today in Science

Science-2015-McDonnell-758Published in the working life section of Science, Jeff provides some good advice for early career academics – it’s “critical to find one’s focus and voice and have it heard—quickly.”  He discusses how early career scientists need to develop brand identity and reinforce this brand as much as possible.  Defining the optimal degree of focus and brand width is key.  Great advice!


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Contribution to new textbook on the critical zone

Principles and Dynamics of the Critical ZoneA new textbook called Principles and Dynamics of the Critical Zone was just published.  I co-authored a chapter of the book on Ecohydrology in the Critical Zone with Georgianne Moore, Peter Troch and Greg Barron-Gafford.  Here is the publisher’s description of the book:

Principles and Dynamics of the Critical Zone is an invaluable resource for undergraduate and graduate courses and an essential tool for researchers developing cutting-edge proposals. It provides a process-based description of the Critical Zone, a place that The National Research Council (2001) defines as the “heterogeneous, near surface environment in which complex interactions involving rock, soil, water, air, and living organisms regulate the natural habitat and determine the availability of life-sustaining resources.”

This text provides a summary of Critical Zone research and outcomes from the NSF funded Critical Zone Observatories, providing a process-based description of the Critical Zone in a wide range of environments with a specific focus on the important linkages that exist amongst the processes in each zone.

This book will be useful to all scientists and students conducting research on the Critical Zone within and outside the Critical Zone Observatory Network, as well as scientists and students in the geosciences – atmosphere, geomorphology, geology and pedology.

Moore, G.W., McGuire, K.J., Troch, P.A., Barron-Gafford, G. 2015. Chapter 8. Ecohydrology and the critical zone: processes and patterns across scales. In: Giardino, J. and Houser, C. (Eds.), Principles and Dynamics of the Critical Zone. Developments in Earth Surface Processes, Volume 19, pp. 239-266, Elsevier, Amsterdam, The Netherlands, doi: 10.1016/B978-0-444-63369-9.00008-2.

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Sprinkling on the model

Kevin, Brian, and I went to Coweeta to improve the irrigation system. They installed a pressure pump to the water line, then we placed tipping bucket rain gauges at randomized locations, and then Brian turned on the water. Water pressure was high enough! We tuned each sprinkler head so that water reached just to the other side of the soil model. Data from the rain gauges showed how much water we sprinkled. Overall, the irrigation system looked very good. I will return to fine-tune the water pressure settings and irrigation timing, then wet up the soil model so that we can install more monitoring instruments. Before we left, I opened the met station data logger and found several wiggling wasp larvae inside their nest! I relocated them and, luckily, nobody was hurt.



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