Buffer strips may actually increase watershed pollution
GRAND FORKS, N.D. – Have we been heading down the wrong path in terms of reducing pollution from streams and rivers?
In his presentation, he looked at water pollution from two different sources – the first being the sediment that is deposited into our streams, rivers and eventually into the lakes; and secondly, the nutrients, especially phosphorus, that are being washed into these waters and ending up in Lake Winnipeg.
“When I was a student, I was always told that gully erosion and streambank erosion was around 15 percent of the sediment load of most watersheds,” Lobb said.
Most of the phosphorus that ends up in the lake is actually coming from the runoff (dissolved phosphorus), and not the sediment, he said.
“This extends beyond vegetation in the field, and this point is important particularly to people in Minnesota, to the riparian areas, because vegetation in riparian areas can actually be a source of phosphorus, not a sink.
“The vast majority of our water and nutrients leave our landscape when the land and vegetation are frozen and riparian areas cannot work in that situation.
Those areas may have some function in lowering phosphorus in runoff when there is vegetation growing during runoff, but even then runoff concentrates into narrow paths and largely passes through riparian areas.
“By encouraging riparian areas that are unmanaged and poorly designed, you risk creating more of a problem and we have been stating this for the last two or three years.” During the question and answer session that followed, Lobb said Minnesota State officials are aware of this situation, that at least in the northern half of Minnesota, riparian buffer strips may not actually decrease the phosphorus runoff problem.
The suggested solution – Lowering the phosphorus runoff into lakes such as Lake Winnipeg, will require managing the runoff more so than soil erosion.
“If you are going to manage the runoff, you have to think about how you are going to get that water into the soil, store it in the soil and use it where it lands.