Improving the Design of Saturated Riparian Buffers for Nitrate Removal
Saturated buffers (SBs) are a relatively new edge-of-field conservation practice that reduce nitrate export from agricultural lands by redistributing tile drainage as shallow groundwater, allowing for denitrification and plant uptake of nitrate. In order to maximize nitrate load removal, it’s important to consider the trade-off in choosing the SB width. A larger width allows for a longer residence time, increasing the opportunity for removal of the nitrate that enters the buffer, while a smaller width allows a greater percentage of the total tile flow to enter the buffer, therefore treating more of the nitrate. Based on this trade-off, an equation for the optimal width was developed by maximizing the nitrate removal effectiveness of the SB. All six study sites have an optimal width that is smaller than the current width, two of which have optimal widths below the USDA Code 604 minimum buffer width. The effectiveness of these SBs would have been 6% to 128% greater if they were designed using the optimal width. Altering current design standards and incorporating the equation for the optimal width into the design process would result in improved water quality.