Extension News

Protect Ponds and Stream Banks with Research-based Practices


By Jesse Randall, Forestry Specialist
Rich Clayton, Fisheries Specialist
Iowa State University Extension

Iowans can implement low-cost yet high-yield solutions to improve stream and pond quality and aesthetics on their properties. Some estimates place the number of farm and acreage ponds in Iowa in excess of 90,000. Many acreage owners find a pond or stream on their property is a source of pride, enjoyment and can add to the property’s value. This interface between water and soil can also be a source of long-term problems if not managed properly.

Acreage owners use ponds for a variety of reasons including swimming, fishing and ice skating.. Properly managed ponds will yield years of enjoyment. The largest single problem that an Iowa pond owner faces is balancing nutrient inputs. With proper vegetation management these nutrients can be partially captured on land, which can greatly reduce midsummer pond vegetation problems. In Iowa, phosphorous and nitrogen additions are the primary nutrients that affect pond health. These additions are not solely due to agricultural runoff. Some is “urban” runoff from lawn fertilization, grub and weed control, as well as the vegetation cut by mowers.

Five inexpensive options can control or limit sources of unwanted nutrients
• Leave a grass “filter” strip that is mowed annually (to control woody growth) rather than weekly. Infrequent mowings will help slow overland water flow which carries phosphorous and nitrogen as well as silt directly into the pond.

• Canada geese are a major source of nutrients in ponds and can be the direct cause for midsummer algae blooms. Limit local geese populations by leaving a tall grass strip along the edge of your pond. Canada geese prefer areas that allow them to see approaching predators. A tall grass strip near the water’s edge will not be attractive to them.

• If mowing is desired, begin mowing close to the pond after the major spring weather has passed. Then limit the number of mowings and set the mower at a higher setting. Blow grass clippings onto the land rather than into the water. As grass clippings decay, they are a source of nutrients acting as a fertilizer.

• Use the small contour differences around the pond to reduce inputs particularly if you can identify where overland water enters the pond. These areas are “hotspots” where grass should be left unmowed or mowing is limited as described above. The width of the filter strip can vary depending on the topography and the watershed extent. Our recommendation is to make it as wide as you can without compromising other activities.

• If all mowing is discontinued, woody vegetation encroachment will occur over time. Landowners can control the type and density of woody vegetation by strategically planting beneficial trees and shrubs. Woody vegetation can shade areas of the pond to help control temperature and sunlight (influencing pond vegetation), provide habitat cover for wildlife and songbirds, increase pond bank stabilization and provide the homeowner added privacy.

Recent research has begun to focus on in-stream flow and the impacts of active stream bank erosion. Acreage owners often do not own enough of the stream length to realize large downstream changes in water quality. However, they can take steps to limit siltation and nutrient inputs. When multiple adjacent acreage owners combine efforts, improvements can help the overall stream health.

One of the first improvements is livestock control. In Iowa, livestock are often in pasture areas adjacent to streams. Restricting livestock from the stream area will allow grasses and woody vegetation to establish and begin to hold the stream bank. In severe cases, where stream banks have begun to erode creating steep bank situations, a more direct conservation approach is needed.

Stream revetments are one simple method landowners can create by themselves with tools and materials common on most acreages. Stream revetments are structures that slow the water, which reduces the stream’s power and causes the stream to add silt in strategic areas that can then be planted with fast growing vegetation such as willows, buttonbush and various sedges. A revetment can also modify the stream bank slope so it can handle the energy from large water flow events.

Students in an Iowa State University course began a stream bank revetment project by anchoring seven to 10-foot tall red cedar trees (top of the tree pointing downstream) with several wraps of wire to old T-posts that were driven into the stream bed where the bank meets the water. They overlapped trees to create a continuous row.

During floods, sediment was deposited behind the cedar trees, which added to the bank. Willow and buttonbush shrubs were planted in these silted areas. Grasses and forbs began to grow and helped stabilize the bank. (See photos showing the progress.)

Once established, revetments need only minor maintenance -- cutting back the willows in the first few years to stimulate root growth and expansion of the trees. These 12-16 inch cuttings, if clipped in early spring before bud break, can be driven directly into the soil bank (leaving 1-2 inches above the soil surface) where they will root and grow into new seedlings.

In time, these revetments will grow and expand to create wildlife corridors, help moderate stream temperatures, and improve the stream’s capacity for aquatic life. For more information, see Iowa State’s natural resource ecology and management extension site at www.nrem.iastate.edu/extension/.

This article is from the July 2009 issue of Acreage Living,  Another article in this month’s issue—
Septic Systems: Out of Sight -- Out of Mind -- and Out of Pocket


Contacts :

Jesse Randall , Natural Resources Ecology & Management, (515) 294-1168, randallj@iastate.edu

Richard Clayton , Natural Resources Ecology & Management, (515) 294-8616, rclayton@iastate.edu

Lynette Spicer , Extension Communications, (515) 294-1327, lspicer@iastate.edu