TY - JOUR
T1 - Hydrologic control of dissolved organic matter concentration and quality in a semiarid artificially drained agricultural catchment
AU - Bellmore, Rebecca A.
AU - Harrison, John A.
AU - Needoba, Joseph A.
AU - Brooks, Erin S.
AU - Kent Keller, C.
N1 - Funding Information:
This research was performed at the R.J. Cook Agronomy Farm (CAF) of the USDA/ARS Long Term Agroecosystem Research Network. Climate change scenario output for the Palouse River at Hooper was downloaded from the Columbia Basin Climate Change Scenarios Project website at http://warm.atmos.washington.edu/2860/products/sites/?site=6076. These materials were produced by the Climate Impacts Group at the University of Washington in collaboration with the WA State Department of Ecology, Bonneville Power Administration, Northwest Power and Conservation Council, Oregon Water Resources Department, and the B.C. Ministry of the Environment. Drain discharge, soil water chemistry, water table measurements, and bioassay data are included in the supporting information. Funding for this research was provided by the US Geological Survey 104B and 104G grants via the State of Washington Water Research Center (agreements G11AP2013, 99HQGR220, 02HQGR0134, and 1434-HQ96-GR02696), the US Department of Agriculture grants for Site-specific Climate-friendly Farming (SCF) (award #2011-67003-30341) and Regional Approaches to Climate Change (REACCH) (award #2011-68002-30191), and a Washington State University Vancouver mini grant. Research was also made possible with support from the National Science Foundation via Nitrogen Systems: Policy-oriented Integrated Research and Education Program (grant 0903714) and the Graduate Research Fellowship Program (grant 0806677). We would like to acknowledge researchers at Cook Agronomy Farm who helped with sampling and data analysis for this project (C. J. Kelley, B. Donaldson, T. Anderson, and J. Smith), J. Goldman and K. Cawley for help with fluorescence analysis, and C. J. Kelley, C. H. Orr, D. Huggins, J. Smith, D. Brown, and R. Boylan for helpful discussions, and suggestions from two anonymous reviewers that greatly improved the manuscript.
Publisher Copyright:
© 2015. American Geophysical Union. All Rights Reserved.
PY - 2015/10
Y1 - 2015/10
N2 - Agricultural practices have altered watershed-scale dissolved organic matter (DOM) dynamics, including in-stream concentration, biodegradability, and total catchment export. However, mechanisms responsible for these changes are not clear, and field-scale processes are rarely directly linked to the magnitude and quality of DOM that is transported to surface water. In a small (12 ha) agricultural catchment in eastern Washington State, we tested the hypothesis that hydrologic connectivity in a catchment is the dominant control over the concentration and quality of DOM exported to surface water via artificial subsurface drainage. Concentrations of dissolved organic carbon (DOC) and humic-like components of DOM decreased while the Fluorescence Index and Freshness Index increased with depth through the soil profile. In drain discharge, these characteristics were significantly correlated with drain flow across seasons and years, with drain DOM resembling deep sources during low-flow and shallow sources during high flow, suggesting that DOM from shallow sources bypasses removal processes when hydrologic connectivity in the catchment is greatest. Assuming changes in streamflow projected for the Palouse River (which contains the study catchment) under the A1B climate scenario (rapid growth, dependence on fossil fuel, and renewable energy sources) apply to the study catchment, we project greater interannual variability in annual DOC export in the future, with significant increases in the driest years. This study highlights the variability in DOM inputs from agricultural soil to surface water on daily to interannual time scales, pointing to the need for a more nuanced understanding of agricultural impacts on DOM dynamics in surface water.
AB - Agricultural practices have altered watershed-scale dissolved organic matter (DOM) dynamics, including in-stream concentration, biodegradability, and total catchment export. However, mechanisms responsible for these changes are not clear, and field-scale processes are rarely directly linked to the magnitude and quality of DOM that is transported to surface water. In a small (12 ha) agricultural catchment in eastern Washington State, we tested the hypothesis that hydrologic connectivity in a catchment is the dominant control over the concentration and quality of DOM exported to surface water via artificial subsurface drainage. Concentrations of dissolved organic carbon (DOC) and humic-like components of DOM decreased while the Fluorescence Index and Freshness Index increased with depth through the soil profile. In drain discharge, these characteristics were significantly correlated with drain flow across seasons and years, with drain DOM resembling deep sources during low-flow and shallow sources during high flow, suggesting that DOM from shallow sources bypasses removal processes when hydrologic connectivity in the catchment is greatest. Assuming changes in streamflow projected for the Palouse River (which contains the study catchment) under the A1B climate scenario (rapid growth, dependence on fossil fuel, and renewable energy sources) apply to the study catchment, we project greater interannual variability in annual DOC export in the future, with significant increases in the driest years. This study highlights the variability in DOM inputs from agricultural soil to surface water on daily to interannual time scales, pointing to the need for a more nuanced understanding of agricultural impacts on DOM dynamics in surface water.
KW - agriculture
KW - artificial drainage
KW - dissolved organic carbon
KW - dissolved organic matter
KW - fluorescence
KW - hydrology
UR - http://www.scopus.com/inward/record.url?scp=84956712638&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84956712638&partnerID=8YFLogxK
U2 - 10.1002/2015WR016884
DO - 10.1002/2015WR016884
M3 - Article
AN - SCOPUS:84956712638
VL - 51
SP - 8146
EP - 8164
JO - Water Resources Research
JF - Water Resources Research
SN - 0043-1397
IS - 10
ER -