Agricultural recycling can be managed in two basic ways: a closed loop system, where drained or tailwater is directly recirculated onto the same field, or it can be directed to a different nearby field. The actual recycling mechanism isn’t particularly important - adding water to subsurface drain tiles and raising the water table is an option where drainage tiles are already in use, while sprinkler irrigation or drip irrigation work well in other regions. Typically, closed loop systems are best employed where water will quickly be reused, since untreated water stored for extended periods is likely to suffer significant water quality problems.
Open loop systems, on the other hand, involve diverting runoff water to a separate storage or treatment area and holding it until it’s needed. Because runoff water in open loop systems is typically destined for storage longer than a few days, these systems usually incorporate elements for reducing sedimentation and excess nutrients. Wetlands, saturated buffers, and bioreactors can all be used as part of an open loop system.
Both open and closed-loop recycling systems offer important advantages to farmers as well as the environment. In a closed-loop system, nutrients that are already in the water are reapplied to crops, reducing the amount of fertilizers that need to be added. In some cases, pesticides and selective herbicides may still be effective and provide a certain amount of protection as well. Essentially, these systems change harmful nutrient-rich water into a valuable resource. Farmers must be careful, however, that closed loop systems redirect waters to fields bearing crops that are compatible with any residual chemicals in the water.
Open-loop systems include features that employ natural processes to remove and absorb pollutants, improving water quality and ultimately protecting critical aquatic ecosystems, both near and far. Excess water treated and released from an open-loop system, and ultimately into the environment, will be free of most contaminants and won’t cause the same devastating damage.
The Benefits of Recycling Farm Water
Both tailwater and tile drainage carry high levels of nutrients like nitrates and phosphorus, as well as leached pesticides, herbicides, salts, and other pollutants. These contaminants, when released directly into the environment, can cause far-reaching environmental damage. Excess nutrients can produce algae blooms in local waterways, contaminate downstream drinking water sources, and are responsible for an enormous dead zone in the Gulf of Mexico. Now an annual summer event, this dead zone triggers lethal red tides, disrupts the region’s seafood industry, and causes fish kills, human illness through shellfish poisoning, and death of marine mammals and shore birds. Any system that reduces the amount of contaminated water entering our water supplies - both surface waters and groundwater - helps protect our health, our food, and our environment.
Crop yields are significantly higher when crops receive appropriate amounts of water at appropriate times. Eliminating stress caused by too much or too little water has been shown to improve soybean yields by 50%, tomato yields by 40%, and corn yields by as much as 95%. These improvements provide more than enough return to justify converting proportionally small amounts of land to use as a reservoir when the benefits include greater drought resilience, more sustainable agricultural practices, improved food security, and better water quality.
