Effect of subsurface drainage on streamflow in an agricultural headwater watershed

Authors: King, Kevin; Fausey, Norman; Williams, Mark

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2014
Publication Date: 7/30/2014
Publication URL: http://handle.nal.usda.gov/10113/61408
Citation: King, K.W., Fausey, N.R., Williams, M.R. 2014. Effect of subsurface drainage on streamflow in an agricultural headwater watershed. Journal of Hydrology. 519:438-445.

Interpretive Summary: Tile drainage is critical to crop production agriculture in the humid, poorly drained regions of the world. Studies of tile drainage hydrology from individual tile exist, however tile drainage hydrology in the context of watershed hydrology is not well understood. Long-term tile and watershed scale hydrology measurements from a watershed in Ohio indicate that tile drainage accounts for approximately half of the water that exits the watershed and the largest contribution occurs in the winter. Additionally, tile drainage discharge can be predicted from a combination of precipitation and antecedent moisture characteristics. The findings have major implications for improving hydrologic prediction technologies and selecting best management practices to address tile drainage discharge concerns.

Technical Abstract: Artificial drainage, also known as subsurface or tile drainage is paramount to sustaining crop production agriculture in the poorly-drained, humid regions of the world. Hydrologic assessments of individual plots and fields with tile drainage are becoming common; however, a major void exists in our understanding of the contribution of systematic tile drainage to watershed hydrology. A headwater watershed (4 km2) in central Ohio, USA and all functioning tile were monitored from 2005-2010 in order to characterize the magnitude and frequency of flows, quantify the role and seasonal contributions of tile drainage to watershed hydrology, and relate tile drainage to precipitation and antecedent conditions. Results indicated that tile drainage contributions to watershed hydrology were significant. Specifically, 21% of precipitation (206 mm) was recovered through tile drainage annually. Tile drainage also accounted for 47% of watershed discharge and was seasonally variable. Median monthly tile discharges in winter (23.4 mm), spring (10.2 mm), and fall (15.6 mm) were significantly greater (P < 0.05) than the median monthly summer discharge (0.9 mm). Collectively, tile discharge was found to be a function of precipitation amount, maximum intensity, duration, and previous 7-day precipitation amount. However, seasonal tile discharge was a function of only a subset of these variables, which suggests that tile drainage can either be rainfall or antecedent controlled and/or intensity or duration driven. Results from this study will help enhance hydrology and water quality prediction technologies as well as the design and implementation of best management practices that address water quality concerns.