Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2014
Publication Date: 1/1/2015
Citation: Williams, M.R., King, K.W., Fausey, N.R. 2015. Drainage water management effects on tile dicharge and water quality. Agricultural Water Management. 148:43-51.
Interpretive Summary: Elevated nutrient concentrations in drainage waters are common and can lead to negative impacts on water quality in receiving surface waters. This study monitored two tile drain outlets over a 7 year period to examine the use of drainage water management as a best management practice to decrease nutrient losses. Drainage water management was found to decrease both tile flow and nutrient loss compared to a conventional, free-draining tile system. Based on the results of this study, drainage water management has the potential to be a viable best management practice for improving water quality in Ohio’s tile drained landscapes.
Technical Abstract: Drainage water management (DWM) has received considerable attention as a potential best management practice for improving water quality in tile drained landscapes. However, only a limited number of studies have documented the effectiveness of DWM in mitigating nitrogen (N) and phosphorus (P) loads. The objective of this study was to evaluate the effects of DWM on hydrology and nutrient loads in subsurface drainage water. Tile discharge and nutrient concentrations in two adjacent tile drains in a central Ohio, USA headwater watershed were monitored from 2006 through 2012. A control structure was installed at one site in 2009 to manage the depth of the potential water table. The impact of DWM was assessed using a before-after control-impact study design. Results showed that DWM significantly influenced both the volume of tile discharge and nutrient loads. From 2009 through 2012, DWM significantly decreased annual tile discharge between 5 and 71 mm (p < 0.02), which was equivalent to a 6.6 to 27.1% reduction in tile flow. DWM also significantly decreased annual nitrate-N (NO3-N) loads (-9.3 to 46.8%) (p < 0.01). Mean annual loads of dissolved P, although not significant (p > 0.05), were decreased by 69.7% following implementation of DWM. Nutrient concentrations were not significantly affected by DWM (p > 0.05). This suggests that decreases in nutrient loads were primarily due to reductions in tile flow rather than changes in concentration resulting from reduced soil conditions often associated with DWM. While the effectiveness of DWM in mitigating nutrient loads in this study was less than the effectiveness of DWM reported in similar studies, greater than 20% reductions in mean annual loads of NO3-N and greater than 60% reductions in mean annual loads of dissolved P indicate that DWM has the potential to be a viable best management practice in Ohio’s tile drained landscapes.