Biological and Environmental Engineering

Research Focus

The ecohydrology group laragely focuses on interactions between hydrological and ecological systems, including agroecosystems and urban ecosystems. However, our research projects cover a broad range of topics that often take us somewhat outside of this focus area. The ultimate goal of most of our work is to develop better strategies for protecting water quality and the "natural" environment. Some themes that we are currently building projects around are:

Our research projects tend to be fluid, with one leading naturally to another and often taking us in unexpected directions. Thus, it is difficult to keep track of all the individual efforts. Below are descriptions of a few broad research areas that capture much of our work but are by no means comprehensive.

Some Key-Collborators:
Peter Groffman (Inst. for Ecosystem Studies)
James Shapleigh (Cornell)
John Regan (Penn State Univ.)
Sujay Kaushal (Univ. of Maryland)
Drinkwater Lab (Cornell)
David D'Amore (USFS PNW LAb, Juneau, AK)

There is good evidence that parts of the landscape that are prone to saturation constitute biogeochemical “hotspots,” i.e., areas where reaction rates are disproportionately high relative to the surrounding environment. We are focusing largely hydrological controls on phosphorus, nitrogen, and greenhouse gas processes. This is an exciting area of research in part because of the variety of methods we are employing to quantify these processes at different special and temporal scales, including isotopic methods, static chambers, micrometeorology, and, more recently, microbial approaches including metagenomics.

For nitrogen we are primarily focused on denitrification at different points in the landscape. One goal is to "map" denitrification hotspots over entire watersheds and another is to develop agricultural strategies mimic natural denitrification hotspots to reduce nitrogen loads to streams and rivers.

Phosphorus mobility in soil remains largely mysterious. We have a suite of projects characterizing, quantifying, and modeling phosphorus mobility and transport. Recently we have turned to microbiological methods to locate and quantify microbial populations and species that may impose important controls on how mobile phosphorus is. One class of microbe that appears especially interesting is "phosphorus accumulating organism" or PAO, which has been widely studied in the context of waste water treatment (enhanced biological phosphorus reduction), but has only recently been identified in soils.

Somewhat more recently we have started to investigate places where human alterations induce otherwise unnatural soil moisture conditions, for example, stormwater detention basins, road ditches, and septic system leach fields. We are interested in processes within these features that may help protect water quality as well as processes that may contribute to greenhouse gas emissions or consumption.

Erin and static chamber
in a leachfield

Liza & Lauren sampling a detention basin                        
DAPI stain shows intracellularpolyphosphate in a bioflim
Selected publications

Anderson, T.R., P.M. Groffman, M.T. Walter. 2015. Using a soil topographic index to distribute denitrification fluxes across a northeastern headwater catchment. Journal of Hydrology 522: 123-134. [doi: 10.1016/j.jhydrol.2014.12.043]. URL

Anderson, T.R., C.L. Goodale, P.M. Groffman, M.T. Walter. 2014. Assessing denitrification from seasonally saturated soils in an agricultural landscape: A farm-scale mass-balance approach. Agriculture, Ecosystems & Environment 189: 60-69 [doi: 10.1016/j.agee.2014.03.026] (online Mar. 29, 2014). URL

Li J., T.R. Anderson, M.T. Walter. 2012. Landscape scale variation in nitrous oxide flux along a typical Northeastern US topographic gradient in the early summer. Water, Air & Soil Pollution 223(4): 1571-1580 [doi: 10.1007/s11270-011-0965-8]. URL

McPhillips, L.E. and M.T. Walter. 2015. Hydrologic conditions drive denitrification and greenhouse gas emissions in stormwater detention basins. Ecological Engineering 85: 67-75. [doi:10.1016/j.ecoleng.2015.10.018] (online Oct. 18, 2015). URL

Funding Sources        NYAES        


Dr. Helen Dahlke (UC Davis)
Dr. Pete Marchetto (U. Minnesota)
Dr. Dan Luo (Cornell)

There are innumerable challenges in monitoring the environment. Therefore, we are always experimenting with new ways to observe the environment from super simple approaches that could be implemented by middle school students to 21st century approaches using tools like bionanotechnology.

On the low-tech end of the spectrum our focus has been on stream monitoring, primarily with a focus on stream discharge, but also considering other parameters as well. We are doing things like using field cameras to track stream depth, floating fruit to measure flow velocity, engaging with builder spaces to develop inexpensive stream stage instruments, and experimenting with different approaches to crowdsourcing stream depth information. This is an exciting and dynamic area of investigation in our group.

At the other end of the spectrum we are applying the power of nanoscale technology to answer landscape-scale questions, an exciting new frontier in science and engineering. We are able to simultaneously identify and characterize multiple flowpaths at field and watershed scales by labeling or coding tracers with unique DNA-based nanobarcodes. By using DNA, our barcodes are essentially unique combinations of base-pairs, of which there are essentially limitless combinations. We are currently using these tracers to map-out the “plumbing” in glaciers and karst groundwater systems. We are also using them to trace potential waste water transport in septic-system dominated watersheds. One goal of this research is eliminating "nonpoint" problem associated with nonpoint source (NPS) pollution, i.e., the problem of locating from where in the landscape water pollution originates.

One page summary of our DNA tracers
Short slide show prepared for the NSF
Watch a USDA CSREES Video about some of our environmental nanotechnology research

Research Highlight in International Innovation Journal Website Selected publications (*indicates undergraduate co-authors)

Dahlke, H., A.G. Williams, C.B. Georgakakos*, S.K.W. Leung*, A.N. Sharma, S.W. Lyon, M.T. Walter. 2015. Using concurrent DNA tracer injections to infer glacial flow pathways. Hydrological Processes 29(25): 5257-5274. [doi: 10.1002/hyp.10679] (online Oct. 6, 2015).URL

Sharma, A.N., D. Luo, M.T. Walter. 2012. Hydrological tracers using nano-biotechnology: Proof of concept. Environmental Science & Technology 46 (16): 8928–8936 [doi: DOI: 10.1021/es301561q] (available on-line July. 25, 2012). URL

Smith, J., B. Gao, H. Funabashi, T.N. Tran, D. Luo, B.A. Ahner, T.S. Steenhuis, A.G. Hay, M.T. Walter. 2008. Pore-scale quantification of colloid transport in saturated porous media. Environmental Science & Technology 42(2):517-523 [doi: 10.1021/es070736x]. URL

Chelsea wonders if a stick or apple will win
crowdsourcing stream stage
Christine & Selene release tracers into a local creek
On a Swedish glacier
Funding Sources       


Some Key-Collborators:
Dr. Yves Parlange

Dr. Rebecca Schneider
Dr. Zeyuan Qui (NJIT)
Dr. Richard Stedman (Natural Resources)
Upstate Freshwater Institute
Finger Lakes Institute
Owasco Watershed Lake Assoc. (OWLA)
Cornell Cooperative Extension
Many Soil and Water Conservation Districts

Nonpoint source (NPS) pollution is considered the dominant threat to water quality, and has been for many decades. Thus, this topic has been a major theme in our lab for a long time; it also a large topic that requires us to combine laboratory experiments, field monitoring, and modeling to address it. Our goal is to understand the fundamental processes facilitating transport of NPS pollutants from the landscape to surface- and ground-water so that we can devise better strategies and tools for mitigating this problem.

Some of our research is very basic, e.g., the physics of how raindrop impacts on soil or impervious surfaces move sediment, solutes, and pathogens into overland flows. We also have very applied research, e.g., assessing the effectiveness of agricultural best management practices (BMPs) or stormwater detention basins. One dominant area of research has been improving our understanding of storm runoff processes, especially variable source areas (VSAs), i.e., areas in the landscape that are prone to getting wet-enough to generate storm runoff. The Soil and Water Lab has a legacy of VSA runoff research including the famous Dunne and Black (1970) papers in Water Resources Research (Dick Black was a former member of the Soil and Water Lab). We have developed a wide range of watershed hydrology models for predicting where, when, and how much runoff is generated and we have coupled these with different methods for predicting loads. One new project area is considering the roles of ditches and other human modifications to the landscape's natural drainage system on pollutant transport.

Ultimately, we try to translate our basic research into usable tools or guidelines (e.g., phosphorus indices). One new direction we are taking this work is to forecast runoff and nonpoint source pollution generation and provide this information in ways that allow, for example, visualization on mobile devices so that decision makers can use these predictions in real-time. We have a prototype online that generates maps of forecasted VSAs (click here. We are also developing cost-effective field monitoring networks to track landscape moisture conditions to make real-time and forecast predictions of where storm runoff will likely occur.

dairy cows
MacGyvered wier for stormwater detention basin discharge
Forecasted runoff generating areas (red) on a mobile device

Selected publications

Buchanan, B.P., K. Falbo, R.L. Schneider, Z.M. Easton, M.T. Walter. 2012. Hydrologic impact of roadside ditch networks in an agricultural watershed in Central New York: Implications for non-point source pollution. Hydrological Processes [doi: 10.1002/hyp.9305 ] (online May 2012) (in press). URL

Gao, B., M.T. Walter, T.S. Steenhuis, W.L. Hogarth, J.-Y. Parlange. 2004. Rainfall induced chemical transport from soil to runoff: Theory and experiments. Journal of Hydrology 295(1-4): 291-304. pdf

Heilig, A., D. DeBruyn*, M.T. Walter, C.W. Rose, J.-Y. Parlange, T.S. Steenhuis, G.C. Sander, P.B. Hairsine, W.L. Hogarth, L.P. Walker. 2001. Testing a mechanistic soil erosion model with a simple experiment. Journal of Hydrology 244: 9-16. pdf

Truhlar, A.M., A.E. Salvucci,M.T. Walter, L.D. Warnick, A.G. Hay, T.S. Steenhuis. 2015. Effects of manure-application practices on curli production by Escherichia coli transported through soil. Environmental Science & Technology 49(4): 2099–2104. URL

Shaw, S.B., J.R. Stedinger, M.T. Walter. 2010. Evaluating urban pollutant build-up/wash-off models using a Madison, Wisconsin catchment. ASCE Journal of Environmental Engineering 136: 194-203. URL Walter, M.T., M.F. Walter, E.S. Brooks, T.S. Steenhuis, J. Boll, K.R. Weiler. 2000. Hydrologically sensitive areas: Variable source area hydrology implications for water quality risk assessment. Journal of Soil and Water Conservation 55(3): 277-284. pdf, URL

Funding Sources        NYAES    


Some Key-Collborators:
Alex Flecker (Cornell)

Art DeGaetano (Cornell)
Andrew Myer (WRI, Hudson River Estuary Program)
Cliff Kraft (Cornell)
Greg Poe (Cornell)
Elizabeth Anderson (Florida International)
Sharon Anderson (Tompkins Co. CCE)

Many human activities have profound impacts on stream behavior and aquatic habitat. One indirect linkage is human induced climate change, the impacts of which on stream discharge are still not well understood. Understanding these impacts and finding ways to mitigate associated environmental problems is a growing part of our research portfolio.

People re-plumb the landscape in ways that alter the natural linkages between a watershed and its streams. We have been particularly interested in road ditches, subsurface drainage, and culverts (stream crossings). We are currently working with a wide variety of organizations to gather data on road culverts across New York State to assess whether they are potential barriers to aquatic connectivity and whether their hydraulic capacity is sufficient to pass large storm flows. So far we see that a large percentage of culverts are severely undersized and this problem is likely to be exacerbated by climate change.

Another on-going project is evaluating the potential impacts of hydropower development in the Amazonian Andes. Literally hundreds of hydroelectric dams are proposed in this region and it is not obvious what the magnitude of impact will be on the hydrologic regime and associated ecosystem services. This project faces numerous challenges including a dearth of data and very dynamic, powerful streams and rivers.

We have similar on-going efforts in the Marcellus Shale region of the Eastern US, where water withdrawals and gas well development has a significant potential to negatively impact the regions streams. We are beginning a similar effort in the Western, US (Montana, Wyoming, Dakotas), where oil, gas, and coal development may be impacting that region’s streams.

Although this area of research is often focused on highlighting problems or tensions between human activities and streams, we are also developing and evaluating attempts to improve this relationship. For example, we are assessing the impacts of New York State’s “Trees for Tribs” program on stream water quality and aquatic health. Initially limited to the Hudson River valley, the Trees for Tribs (as in tributaries) program has been involved in facilitating the replanting of degraded riparian areas since 2007, and in 2015 the NYS Dept. of Environmental Conservation took the program state-wide. Hopefully our analyses will help identify where the program is having positive impacts and where we need additional efforts.

Selected publications

Auerback, D.A., B.P. Buchanan, A.V. Alexiades, E.P. Anderson, A.C. Encalada, E.I. Larson, R.A. McManamay, G.L. Poe, M.T. Walter, A.S. Flecker. 2016. Towards catchment classification in data-scarce regions. Ecohydrology (accepted).

Buchannan, B., D.A. Auerbach, R.A. McManamay, J. Taylor, A.S. Flecker, J.A. Archibald, D.R. Fuka, M.T. Walter. 2016. Assessing environmental flow needs in the context of unconventional natural gas development in the Marcellus Shale. Ecological Applications (accepted).

Knighton, J.O. and M.T. Walter. 2016. Critical rainfall statistics for predicting watershed flood responses: Rethinking the design storm concept. Hydrological Processes (accepted).

Marjerison, R.D., A.M. Meyer, A.T. DeGaetano, M.T. Walter. Road culvert suitability in the Hudson River Valley. ASCE Journal of Hydrologic Engineering (submitted).

Wilson, N., M.T. Walter, J. Waterhouse. 2015. Indigenous knowledge of hydrologic change in the Yukon River Basin. Arctic 68(1): 93-106.pdf URL

monitoring a road ditch

wild western US river       culvert to nowhere (M. Thomas)
students in creek

challenges in Ecuador
Funding Sources    Appalachian LCC


Dr. J.-Yves Parlange, Dr. Tammo S. Steenhuis, & the Rain Machine...
Friends, mentors, and colleagues to whom I'm forever indebted.