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Working With Waterways

Grassy waterways are a great conservation practice to keep vital soil and nutrients from leaving your place.

By Oscar H. Will III | Photos By Charlie Rahm, Courtesy of USDA NRCS

DOWNLOAD: USDA Conservation Reserve Program Grassed Waterway Guidelines (PDF) >>

Grassy waterways and swales can direct water flow while preventing, or at least minimizing, soil erosion on your property. With proper design, seeding and maintenance, waterways slow and spread the flow of water so that soil particles will settle out on your land instead of in some distant river delta.

Here’s how to plant and maintain a new waterway on earthworks that direct rainwater into a pond or wetland and/or carry cropland runoff into a natural drainage area. Once you have engineers design waterways for your place and the heavy equipment has left, you can plant and maintain those earth structures yourself with a little know-how and a few tools. 

These instructions assume a small, grassy waterway. As scale increases, so too must the size of the equipment in order to be efficient. To establish and maintain a small waterway, you will need the following equipment:

  • Compact or larger tractor
  • Rear-blade attachment
  • Broadcast spreader
  • Rotary tiller or disc
  • Solid-stand seeder
  • Rotary cutter or hay mower
  • No-till drill for interseeding

Planting

1.  After your earthmoving company has finished grading—to the USDA’s specifications if for a grassed waterway on land in the Conservation Reserve Program (CRP)—you can do a final smoothing of the waterway, using your tractor and rear blade to blend any accidental ridges or dips in the soil surface left by the larger equipment.

2.  Ask your county Extension or other local expert for advice on what perennial seed mix makes the most sense to plant on your new waterway. Include a fast-germinating nurse crop, if recommended. If your waterway project is part of an official USDA program, its guidelines will likely make many of the decisions for you. 

3.  Pull a few soil samples from various locations in the waterway, and have them tested through your county Extension office. Your test results should include a recommendation on needed amendments to ensure that the seed mix you plant can thrive. 

4.  Apply the amendments using a rented broadcast-spreader buggy from your local elevator; or if your area is small enough, you can use a 3-point mounted broadcast spreader on your tractor. If amendment incorporation is recommended, a light disking or very shallow rotary tilling should suffice. 

5.  Rent or borrow a solid-stand seeder sized appropriately for your tractor. Make sure it has the needed seedboxes for legumes and native grasses, should they be included in your seed mix. Apply the seed to the waterway. With well-timed rains, your seed should sprout rapidly and begin to form a protective cover for the soil. 

6.  In the first year, control weeds by mowing when they begin to flower. Set the mower to the highest level to cut weeds while staying above the planted vegetation. (Note: Once the grass is fully established, mowing and other maintenance is not allowed on CRP grassed waterways in the United States between April 1 and Aug. 1 to protect ground-nesting wildlife.)

7.  If your new waterway receives significant runoff and some small areas of erosion occur, repair them by regrading and replanting. You can spread straw or even place straw bales in the areas of highest flow to slow it down during the establishment year. 

Maintenance

1.  Control weeds and trees in your waterway with mowing or judicious spraying. Remember that chemicals in runoff may cause damage to downstream waterways. If you hay your waterway, take a single cutting (if allowed by your USDA contract), and focus on maintaining a good stand of soil-holding plants first and foremost.

2.  Repair bare or thin areas using a no-till drill designed for interseeding into established pastures and meadows, and treat those areas as you would a newly established waterway.  

3.  If your waterway is not just part of an erosion repair practice in a perennial pasture or hay meadow, pay close attention to the interface between cropland and the waterway. Even with minimal tillage in the field, over time, a ridge can form where the cropland and the waterway meet. This ridge will divert runoff from the cropland along the interface with the waterway, defeating its purpose. Likewise, if your waterway includes stoloniferous grasses (having horizontal, above-ground, creeping stems with roots and shoots), it will tend to creep into the cropland, thus shrinking tillable acreage. Maintain the cropland/waterway interface with careful tillage and grading using your tractor’s tiller or disc and the rear blade. 

4.  Even with the best waterways, rare rain events can cause some of the vegetation to wash out, leaving eroded passages in the waterway. Those washouts are best repaired quickly by moving soil back into place or obtaining new soil to fill them. Then replant and protect the seeding with straw bales to give the new fill time to settle and the new plants time to get established.