Coweeta experimental hillslope soil models shown in photographs in 1961 (Lloyd Swift, left, and Alden Hibbert, right) and 2015 (Kevin McGuire, left, and Raymond Lee, right), simulation of irrigation using HYDRUS-2D, and conceptual drawing.
PROJECT TITLE: Clean Water from Complex Natural Systems: Soil and Hydrological Controls
SPONSOR: Institute for Critical Technology and Applied Science
PROJECT DURATION: 1 May 2014 to 30 April 2016
PRINCIPAL INVESTIGATORS: Brian Strahm, Kevin McGuire, Jennifer Knoepp (USFS), Stephen Schoenholtz
GRADUATE STUDENTS: Raymond Lee, Ph.D. student
PROJECT SUMMARY: Excess reactive nitrogen (N) in the environment is a major component of global change. Nitrogen loading is a critical problem impacting surface waters at scales ranging from headwaters to coastal waterways, with nitrate being of particular concern. Reactivity within, and rates of transport through the soil system control nitrate export to surface waters. When and where reactive processes versus transport control overall export is unclear and limits our ability to predict nitrate loading under future climate and land use scenarios. Current research has not successfully differentiated these two drivers effectively because different disciplines typically focus on one perspective or the other. An interdisciplinary approach that simultaneously quantifies soil and hydrologic controls of nitrate export is required to solve this problem. A field- scale physical model offers an opportunity to constrain major sources of variability and evaluate processes controlling nitrate export. Use of a one-of-a-kind, field-scale physical model on a hillslope at the USDA Forest Service Coweeta Hydrologic Laboratory and NSF Long-term Ecological Research site will enable high-resolution characterization of N reactivity, while simultaneously supporting accurate quantification of nitrate transport. This holistic understanding of fate and transport of nitrate in the environment is broadly applicable wherever issues of global change and land-use raise concerns about the ability of complex natural systems to provide clean water to sustain ecosystem services and communities.
PUBLICATIONS:
Lee, R. M., K. J. McGuire, B. D. Strahm, J. D. Knoepp, C. R. Jackson, and R. D. Stewart. (2020) Revisiting the Hewlett and Hibbert (1963) hillslope drainage experiment and modeling effects of decadal pedogenic processes and leaky soil boundary conditions. Water Resources Research 56: e2019WR025090, doi: 10.1029/2019WR025090. [link][pdf]
Lee, R. M., B. D. Strahm, K. J. McGuire, and J. D. Knoepp. Impacts of coupled nitrification-denitrification on a 15NO3 tracer moving through a hillslope catena out to a stream. In prep. Lee, R. M., B. D. Strahm, K. J. McGuire, and J. D. Knoepp. Lagged export of a 15NO3 tracer relative to a conservative tracer on an experimental hillslope. In prep.LINKS: