February 3, 2015
The big push across much of Indiana, especially southern Indiana, over the past 30 years was to install water and sediment control basins, called wascobs for short, in rolling fields to help prevent soil from being lost. The theory was that when soil was lost, nutrients attached to the soil would be lost too.
The theory is still true. However, Jane Hardisty, state conservationist in Indiana for the Natural Resources Conservation Service, says that new information is leading to new technology.
Where's the pipe? In the past a water and sediment control basin might have been constructed here to help slow down soil erosion. Now soil conservationists are suggesting a new practice, a blind inlet, because it has less chance of allowing water carrying nutrients like phosphorus to gain direct entry into streams and creeks.
Wascobs are basically small earthen dams with a riser pipe that leads to an underground tile line. Most have been designed so that farmers could still drive and farm over them. Occasionally there was a need for a larger wascob which would have grass on the back side and which farmers would plant around.
The wascobs do a good job of collecting sediment. Instead of washing off the field, the flow of water is stopped, breaking its flow down the slope, and some soil may accumulate in the dry dam, as they're also known.
"The emphasis is on water quality today," Hardisty says. "We've learned that a form of phosphorus can dissolve in the water instead of attaching to soil particles. It's a small percentage of the amount applied but it's enough to get into lakes and streams."
When it ends up in big bodies of water, like Lake Erie, it causes algae blooms, which in turn can produce toxins. That's a problem if a large city is drawing its drinking water from the Lake. It happened in Toledo, Ohio, last summer. The weekend shutdown of the city water system made waves which are still reverberating.
Wascobs which are in place will be left alone, Hardisty notes. But in the future a different practice, known as a blind inlet, may be used. Basically it has more cover instead of letting water run directly into the riser that is a direct source into the tile and the creek or stream.
"We've realized that the riser that connected directly to the tile line could allow water with nutrients like phosphorus in it to enter the tile and then travel into the creek or stream through the tile outlet. Newer practices are being designed to help address that issue, she notes.
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