Saturated Buffers for Removing Nitrate from Artificial Subsurface Drainage.

Saturated buffers are one of the newest tools available for reducing nitrate losses to surface waters from artificial subsurface (tile) drainage.  Saturated buffers reconnects tile drainage with shallow groundwater flow in riparian buffers in tile –drained landscapes by a simple modification of the tile drain outlet and installing new perforated pipe along the top of the buffer to induce shallow subsurface flow within the buffer.  However, there is still little information available for the effectiveness of this practice over a range of soil and landscapes, and little information on potential site limitations for installing the practice.  This paper will present results from over 10 field-years of observations of the nitrate removal performance of saturated buffers.  Total nitrate removed, nitrate removal as a fraction of nitrate delivered to the tile outlet, the cost of nitrate removal per kg of nitrate-N removed, and the fraction of tile flow intercepted by the tile over time will be presented for multiple sites.  The paper will also look at site characteristics that are known to have limited the performance of installed saturated buffers and estimate the potential water quality improvements possible at a watershed scale.  More information on this practice can be found at the Transforming Drainage website https://www.transformingdrainage.org/