Field Day: Held June 14, 2006

NoTill Field Day. Click here for more information.
Field Day 2006

Earth Day 2006 Report. Click here for more information.
 
Earth Day 2006

Field Day: Held April 27, 2005

NoTill Field Day. Click here for more information.

NRCS Signs Highlight Conservation Practices Click here for more information.

 
Field Day 2005

Field Day: Held September 8, 2004

Speakers: Dick Schultz Iowa State University
Department of Natural Resource Ecology and Management

Kathy Koskovich Iowa Department of Natural Resources
Private Lands Wildlife Biologist

Angie Christian Farm Service Agency
Program Technician

Attendance: 20 participants

Conservation Buffer Field Day

Dick Schultz from the Department of Natural Resource Ecology and Management at Iowa State University was the presenter at a conservation field day in the Storm Lake Watershed. The field day featured Steve Turnquist’s riparian buffer along Powell Creek. Both riparian and grass buffers are important conservation practices because they filter sediment and chemical run-off from adjacent fields before it reaches the creek. Installing filter strips along Powell Creek, protects Storm Lake from potential sediment run-off and build up. Another benefit of Riparian and Native Grass buffers is they attract wildlife. Pheasants can be found in a well maintained buffer making them excellent sites for hunting. Song birds and small mammals are also attracted to these areas (Commonly Asked Questions About Riparian Management Systems, Agroecology Issue Team pamphlet). Buffers are also an important practice to slow water movement during rain fall and snow melt. When stream channels are straightened through routine farming practices, it allows water to flow downstream at an increased volume and speed, taking nutrients and sediment with it. These then deposit downstream, eventually reaching Storm Lake. Buffers are also used to keep soil in the field where it is needed and used. During a rain event, top soil moves across the surface. When there is no grass buffer, the soil continues moving into the neighbor’s field, Powell Creek, and even Storm Lake. Dick Schultz also talked about Boulder Weirs, by comparing them to beaver dams. The function of a boulder weir is not to back up water, but to slow movement to prevent down cutting in the channel. Grade control structures in the form of a series of boulder weirs can be used both to help stabilize the channel from further down-cutting and to act as a diversion for water entering wetlands placed along the channel. The weirs eliminate down-cutting of the channel by providing continuous pools and riffles and slowing the velocity of the baseflow. They also reduce bank erosion by raising the baseflow several feet thus reducing bank height below the critical level of collapse.

The boulder weirs will be only 2-3 ft high and will be placed so that water is not backed into field drain tiles. These structures reintroduce riffles and pools into the channel which not only control the energy of the water but also provide habitat for fish and the invertebrates they feed on. These are also supported by the Iowa DNR Fisheries Bureau for use in improving in-stream habitat. They are better than low-head dams because they allow fish to travel across them in all but the lowest flows. Weirs will be placed at the natural frequency of pools and riffles, that being about 5-7 times the channel width.

The weirs consist of a series of crest stones that extend across the channel and are tied several feet into each bank. These crest stones provide a slight V to concentrate low flow at the center of the channel. The height at the V is between 2-2.5 ft. On the up-stream side of the weir an approach apron has a slope of 4:1 and on the down-stream side of the crest stones the apron has a 20:1. This gentle long slope on the down side of the crest dissipates energy from water moving over the crest and armors the bed against any scouring. The weirs are placed at a typical pool-riffle sequence of 5-7 times the channel width. Each down-stream weir will back water onto the apron of the adjacent up-stream weir.
Completed Weirs