What you see just to the southwest is not some mosquito-infested
swamp, it is an engineered wetland working for you and me to keep
our lakes and streams clean!
A variety of engineered (man-made) wetlands are found around
Lincoln, NE. These systems are designed to control erosion and
treat/remove pollutants in storm water runoff from the local
neighborhood before it enters the streams that lead to nearby
Holmes Lake. This storm water runoff wetland was developed through
a coordination of the City of Lincoln, the Lower Platte NRD, Olsson
Associates, and the Colonial Hills Neighborhood Association.
In 1962 the U.S. Army Corps of Engineers completed a 123-acre
reservoir in southeast Lincoln, Nebraska. This reservoir, known as
Holmes Lake, was created primarily for flood control on the
Antelope Creek as well as to serve recreational needs for the
citizens of Lincoln. Since this time, the Lincoln Parks and
Recreation Department has been responsible for the management of
the lake and surrounding public facilities.
In recent years, due to urban development throughout the area,
the lake has experienced excessive amount of sediment and nutrient
loadings creating cloudy waters and an overall degraded condition.
In fact, since 1962, the bottom of the lake has risen eight feet.
In 1992 the Lower Platte South NRD and the City of Lincoln
initiated watershed improvement efforts. These early efforts
included information/education programs and the installation of
pollution control measures, including this wetland.
The lake's watershed covers a 5.2 square-mile area, which, in
1995, was estimated to be 40% developed for residential and
commercial use. Since that time, development has increased
considerably and is now estimated to cover 80-90% of the watershed
area. This means that a good portion of the stream network is now
curbs and gutters, storm sewers and low-flow liners. In 2002
(before dredging and improvement), EPA estimated that more than
10,000 tons of sediment and 8000 lbs of phosphorous were flowing
into Holmes Lake each year. They established a target loading of
5000 tons sediment and 160 lbs of phosphorous per year--that's a
50% and 97% reduction!
Watershed improvement and lake restoration cost $5.5 million
dollars. Dredging Holmes lake increased its depth from an average
3-9 feet to a maximum of 14 feet. Nearly 321,000 cubic yards of
sediment were removed from the lake bottom. About 2.4 miles of
shoreline were stabilized with rock and native plants, and 10 acres
of wetlands were created. Six new rock jetties were installed to
provide fishing access and protect shorelines. The project extended
the recreational life span of the lake by more than 100 years. This
in turn enhanced fishing and brought back the lake's clarity, which
has been missing.
At the coordinates, you will find a sign that describes this
particular wetland project in my neighborhood. To get credit for
this cache, you need to provide in an email to me the following
information:
1. What two nutrients are treated in this wetland? What do you
think are the sources of these nutrients?
2. What two components in the wetland help to control erosion?
Holmes Lake watershed