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Dispersed Profile Waterway

Revisiting Waterway Design to Maximize Retention

If you’re familiar with nutrient runoff and the dangers that nitrogen can cause when it enters waterways, then you understand how essential it is that farmers and others take steps to cut back on our fertilizer footprint (if you’re not familiar with the problem then please check out our blog post on it here).

The good news: There are various ways to control the nutrient runoff from your fields, including cover crops, buffer strips and grass waterways.

Cover crops are those that are planted after cash crops have been harvested. Farmers will come through a field and plant clover or turnip, which gather up extra nitrogen from the soil and store it in a safe form. Unfortunately, while effective, this method provides several problems for the average farmer. For one, it’s expensive to spend on seed for an additional crop every year, especially when you won’t see any direct profit from it. Perhaps, more importantly, planting cover crops doesn’t sync too well with some cash crops, including corn and soybeans. These are typically harvested during September or October, which means the cover must be planted as cold and tough weather sets in. Can you guess the two biggest American crops? Yeah, corn and soy.

Waterways are a bigger investment at the onset but will ultimately pay off dramatically compared to the repetitive cost of cover crops. It’s important to note that not all waterways are created equally: If you want to prevent the maximum amount of nitrogen from entering the waterway, you need to opt for those with “dispersed profiles.”

This means that the waterway takes the shape of a very gradual “u,” somewhat like the mouth on the original “smiley” face. The other variety is a “concentrated profile,” which more closely resembles a “v” or just a “|_|”. The disadvantage of the concentrated profile is based around its sharp angles, which do less to control erosion while creating the waterway. This means more nitrogen falls into the waterway along with the soil carrying it.

So why would anyone opt for a concentrated profile? It does boost two advantages, in the eyes of many: One, it moves drainage water much quicker than its dispersed brethren. Secondly, it takes up much less space thanks to those aforementioned sharp angles. Farmers appreciate this fact, as it leaves more land open for their craft.

The latter argument relies on faulty logic, however. The speed at which the drainage moves through the channel comes at a cost, exaggerating the erosion that would otherwise be prevented by a dispersed waterway. As the years roll on and erosion continues, a chunk of land that was “saved” by building a concentrated waterway is lost, taking its nitrogen byproducts with it.

In short, concentrated waterways don’t go that far in terms of preventing the loss of land.


Still, many farmers would rather avoid using more space for their waterways. The common outlook is that adding a waterway to farmland divides a field into two, smaller fields: Plowing and harvesting now must be done on one side, and then continued on the other, rather than conveniently handled in one fell swoop.

This is also a misconception. The hidden beauty of dispersed waterways and their gradual slopes is that, when properly constructed, farm equipment can successfully travel from one side to the other without issue.

The ultimate advantage, and the point of this post, is that dispersed grass waterways ultimately provide superior nitrogen-blocking capabilities. Not only does the subtle grade of waterway’s walls prevent erosion, the grass serves almost as a net, gathering the extra nitrogen and using it for its own growth. Concentrated don’t prevent the problem; they encourage it.

If you want to construct a dispersed waterway on your property, there’s no better way to encourage the growth of the essential grass than to invest in a good erosion control blanket, which holds the ground firm until the grass can grow and stabilize the earth with its roots. Nancy’s Kritter Kind Blankets are optimal, promoting germination with HydroPam and biodegrading naturally once its job is done.

Keep nitrogen where it belongs: in your soil, boosting the growth of your crops. Don’t let it get downstream instead.

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