Apportioning Sources of Fine Sediment in an Agricultural Watershed using Colour Fingerprinting
Louise R.M. Barthod a, Kui Liua, David A. Lobb a,*, Philip N. Owens b, Núria Martínez-Carreras c, Alexander J. Koiter d, Ellen L. Petticrew e, Gregory K. McCullough f, Cenwei Liua, Leticia Gasparb
a Department of Soil Science and Watershed Systems Research Program, University of Manitoba, 13 Freedman Crescent, Winnipeg, Manitoba R3T 2N2, Canada
b Environmental Science Program and Quesnel River Research Centre, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia, V2N 4Z9, Canada
c Centre de Recherche Publique – Gabriel Lippmann, Department of Environment and Agro-Biotechnologies, 41 rue du Brill, L-4422 Belvaux, Luxembourg
d Natural Resources and Environmental Studies Program, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia, V2N 4Z9, Canada
e Geography Program and Quesnel River Research Centre, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia, V2N 4Z9, Canada
f Centre for Earth Observation Science, Department of Environment and Geography, 482 Wallace Building, University of Manitoba, Winnipeg, Canada R3T 2N2
Corresponding author e-mail address: (David Lobb)
Abbreviations: STCW, South Tobacco Creek Watershed; CDA, canonical discriminant analysis; DFA, discriminant function analysis; IQR, inter-quartile range
Abstract
The use of sediment color as a fingerprint property to determine sediment sources is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. The present study aims to test the ability of color parameters to distinguish between potential sources of sediment and apportion their contributions within the South Tobacco Creek Watershed, MB, Canada (74 km2). The results are compared with the findings from a conventional fingerprinting approach undertaken in the same watershed (i.e., geochemical and radionuclide fingerprints). Suspended sediment and potential source samples were collected at sixsites along the main stem of the creek. Canonical discriminant analysis was used to determine the number of source groups. Sample color of sediments and source materials was quantified from diffuse reflectance spectrometry measurements andsixteen color coefficients were derived from several color space models (CIE XYZ, CIE xyY, CIE Lab, CIE Luv, CIE Lch, Landsat RGB, Redness Index). Experiments were undertaken to test the linearly-additive nature of the color coefficients and this was used to further refine the number of coefficients that were suitable for source apportionment. The discrimination power of the color coefficients was assessed using discriminant function analysis.The selected fingerprints were included in a Bayesian mixing model using Monte-Carlo simulation to apportion the contribution of the different sources to the sediment collected at each site. Consistent with the conventional fingerprinting approach, a switch in the dominant sediment source between the headwaters and the outlet of the watershed was observed. As the stream crosses and down-cuts through the Manitoba Escarpment, sediment is enriched with shale bedrock and stream bank materials from within and below the escarpment and depleted of topsoil and/or stream bank materials from above the escarpment.