Transforming Drainage with Saturated Buffers
May 08, 2018
In 2007 my nephew, Chris Slater, did an amazing thing. He donated his left kidney to his uncle (my brother-in-law). Because of that selfless act, his donated kidney filtered waste products from the blood of another person, extending a life by 10 years.
For the past few years, Dr. Dan Jaynes, USDA-Agriculture Research Service, and Dr. Tom Isenhart, Iowa State University, have been researching ways to filter tile water. Their research culminated in development of a new water protection practice – saturated buffers. Like a kidney, saturated buffers filter nitrates out of tile water before discharge into a water body. Jaynes and Isenhart have developed a method to intercept the tile water that would otherwise flow directly into a stream or river. The intercepted water is fed through shallow tile lines (distribution pipes) installed parallel to a stream, which results in the removal of a significant portion of the nitrates.
© Dr. Dan Jaynes, USDA-ARS
Early results indicate that a well-designed saturated buffer can conservatively remove 35% of the nitrates delivered through a tile line. Using a pretty simple hydrological/biological concept, the saturated buffer intercepts the water from a tile line about 30 to 50 feet from the edge of water body. The water is then diverted into shallow, perforated tile lines (distribution pipes) that run parallel to a stream or river. To be effective, the tile lines must be installed in a buffer area, with permanent vegetation (e.g., vegetative buffer strip). As the water is redirected into the perforated tile, it flows out into the soil, raising the water table throughout the entire length of the vegetated area. The higher water table in the buffer creates saturated soil conditions and enables the natural biological uptake and denitrification processes to reduce nitrogen in the water. Effectively, this process decreases the excess nutrient load from drained croplands to surface water.
Photo by Lynn Betts. This project was supported by an Iowa NRCS funded Conservation Innovation Grant to the Soil and Water Conservation Society
Jaynes reports that a properly designed saturated buffer costs approximately $5000 and removes on average about 35% of the nitrate flowing through the tile line. To me, that nitrate reduction is significant. Perhaps even more importantly, it doesn’t require regular maintenance. It will be there year after year. Imagine how this simple practice – saturated buffers – could impact water quality goals. That is precision conservation and something we should be talking to farmers about. But there’s more.
Once a farmer is sold on a conservation practice like a saturated buffer, it’s important to move quickly before money runs out or other priorities rise to the top. Sometimes, when designs are slow to materialize, the famer’s priorities change, the money runs out, or interest dwindles. Then the practice may never get implemented.
We simply cannot afford to have a backlog of farmers waiting to install effective conservation practices. If the voluntary effort for soil and water conservation is going to work, we must reduce the design time from days, weeks, and months, to hours and minutes. With LiDAR, soils maps, environmental models, and GIS systems, we can analyze multiple layers of data and create an initial design. We need to do better. We are running out of time, just like my brother-in-law, who needed a kidney to survive. We can’t wait any longer.
Saturated buffers are a new practice that requires some new engineering skills. In the next 12 months, Agren® plans to build a design tool for saturated buffers. It is anticipated that a conservation technician will be able to do a preliminary design of a saturated buffer in a matter of minutes. We’ve done it with ponds, wetlands, grassed waterways, variable width buffers, and water & sediment control basins; we will do it for saturated buffers!