is Lake Access?
Access is an initiative begun in 1999 to deliver real-time water quality
information on Minneapolis metropolitan lakes to the public using
advanced sensor technology and the Internet. Beginning in 2001 the
project was expanded to include a study of the effects of lawn fertilizer
phosphorus on the phosphorus budget of nearby Medicine Lake that suffers
from eutrophication due to excessive phosphorus inputs.
is this important?
are becoming increasingly involved in land management decisions that
affect their quality of life. Access to information for making informed
decisions, however, has been a limiting factor, both in terms of availability
and understanding. Our goal is to provide relevant information to
citizens on a timely basis.
is that big yellow thing floating out in the lakes?
is a Remote Underwater Sampling Station, or RUSS unit. The RUSS is
a sensor system collects water quality information and transmits it
back to our web site. RUSS consists of a mobile underwater sensor
package connected to floating platform that contains an on-board computer,
solar panels and telemetry equipment. We use a cell phone to call
the RUSS unit and download data each morning - the units collect data
4 to 6 times per day. You can learn more about RUSS technology here.
are the RUSS units located?
RUSS units EMPACT01 and EMPACT02 were initially located in West Upper
Lake and Halsteds Bay, respectively. Another unit that was acquired
for our Water on the Web study was located in nearby Lake Independence.
Halsteds Bay, located on the far west end of Lake Minnetonka, receives
runoff water from a large watershed of mixed agricultural and urban
residential land use. As a result of the nutrient loading from runoff
water, the quality of the bay is very poor. The mean summer phosphorus
concentration is near 100 ug/L, making the bay highly eutrophic (green)
as evidenced by poor water clarity (Secchi depth < 1 m) due to excessive
algal growth. West Upper Lake, by comparison, has much better water
quality, with a mean phosphorus concentration of ~25 ug/L during the
growing season and Secchi depths averaging > 2 m. West Upper Lake
receives direct runoff only from the area immediately adjacent to
the shoreline and is much deeper than Halsteds Bay. The Lake Independence
unit, WOW02, was located in the southern part of the lake and sampled
to a depth of 30 ft. In 2001, we moved the unit from the West Upper
Lake site to Medicine Lake to provide an intensive set of lake data
fro the fertilizer experiment. We also discontinued data collection
on Lake Independence and moved the unit to Shagawa Lake in Ely, MN.
did we put the RUSS units where we did?
As good limnologists, we knew that significant algal blooms in eutrophic
Halsteds Bay were occasionally triggered by wind mixing of nutrients
from below the thermocline during big storms. We wanted to show how
this differed from the less productive West Upper Lake basin. This
fact becomes important in developing management strategies for improving
the water quality of the lake and setting accurate expectations for
the results of controlling the runoff of nutrients from the watershed.
It would also be necessary to control this in-lake source of nutrients
to get short-term (years) results. Medicine Lake was also a good candidate
for RUSS technology because previous studies indicated that, as for
Halsteds Bay, summer storms could inject large amounts of phosphorus
from bottom waters into the upper sunlit zone to fuel obnoxious algal
blooms. Beginning in 2002 we will also have a fluorometer on this
unit which is a sensor that can detect the chlorophyll in algae and
give us a near-continuous record of algal growth.
A2 - We also had to keep the units out of the way of major
water skiing routes so they are a bit closer to shore than we might
have liked. They all had have permits from the County Sheriff.
this is pretty interesting, is there anything else I should visit
on the site?
in fact, yes! The Lake Ecology section is a concise guide to the basic
physical and chemical factors that control lakes, along with detailed
information on lake biology. We also have sections for users of the
lake: boaters, swimmers, anglers, as well as a section on current
issues and a Take Action section to make it easy for you to
get involved or just obtain good information on issues and decisions
that being made about your lakes. There's lots of historical data
including "grades" for lakes in the area and also a description
of the new (2001-2003) lawn fertilizer phosphorus study in the Medicine
really impressed now, who is doing all this?
Access is a partnership among Hennepin Parks, the Natural Resources
Research Institute, Minnesota Sea Grant, the University of Minnesota-Duluth
Department of Education, the Minnehaha Creek Watershed District, the
Minnesota Science Museum and Apprise Technologies, Inc. We are funded
through a grant from the Environmental Protection Agency's EMPACT
program. Also check out our sister project Water
on the Web.
is my water quality?
that's one of those tough questions. But we have a place where you
can begin to look. Try the Lake
Data page to see if your lake is there. If so
you'll find all sorts of information about historical and current
conditions in your lake and, if we did our job, you should have enough
information to determine for yourself if your lake is in good shape
or not. If your lake is a Twin Cities metro lake but not listed on
the Lake Data page check back. We're making our way through all of
the data available and hope to have most metro lakes up soon.
following questions and answers were adapted from the New
Hampshire Department of Environmental
Services and from the forthcoming Minnesota Shoreline Management Guide
some foam blowing up onto my beach, where's it coming from?
foam observed in lakes and streams is a product of nature; foam is
not necessarily an indicator of pollution. Foam is created when the
surface tension of water (attraction of surface molecules for each
other) is reduced and air is mixed in, forming bubbles. Surface tension
can be reduced by both natural organic compounds and by man-made soaps
and detergents. Natural organic compounds are released by decomposing
aquatic organisms (such as algae or fish) or leached from the soil.
In a lake, wind, currents, and boats mix air with the organic compounds
present to produce foam. The foam will frequently form parallel streaks
in the open water, caused by wind-induced surface currents. It will
also collect in large quantities on windward shores, coves, or in
eddies. Natural foam has a somewhat earthy fishy aroma. Detergent
foam in contrast will have a noticeable perfumey smell.
causes surface scum on a lake?
Scum, an oily film, or yellow-green dust on the surface of a lake
make it looks contaminated but, in most cases, nothing is wrong. In
fact, something natural is probably occurring. An oily film in midsummer
is most likely caused by insect cases that were concentrated along
the shore by wind after a hatch. Insects can hatch any time from ice-out
into September. As the cases decompose, they sometimes give off an
oily film. Yellow-green dust floating on the surface in late spring
and early summer is pollen from nearby pine trees. In contrast, an
algal bloom is green to blue-green, might look soupy, and can form
thick surface scum.
does the water quality of our lake seem to get worse throughout the
Many factors, including human activity in the watershed, affect the
water quality of a lake. Just as fertilizing a lawn promotes growth,
nutrients seeping into a lake cause aquatic plants to grow. Agriculture
and communities in the watershed may be inadvertently adding nutrients
to the lake. Although lawns and agriculture are not innately harmful,
excess fertilizer causes algae to "bloom" which, in turn, decreases
light for other plants and animals. Water quality may worsen at the
peak of the growing season when sunlight and nutrients are plentiful.
Also, erosion and sediments washing in from disturbed shorelines or
construction sites bring additional nutrients and muddy the water.
Development on a lake shore usually means changes in the shoreline
plant community (i.e., cultivated grass replaces bulrush). Nutrients
and sediments wash into the water more readily without the natural
can a lake become green and stinky?
green lakes are blooming with algae. Algae are unicellular or small
aquatic plants. An algal bloom is a dense concentration of these plants.
If a lake has high concentrations of nutrients (especially nitrogen
and phosphorus), a few types of algae may be out-competing the many
other types of algae, becoming so abundant that the water appears
murky. Two common bloom-forming groups of algae are diatoms and blue-green
algae. Diatom blooms usually occur in the late spring or early summer,
turning the water brown, but not creating surface scums or odors.
Blue-green algae blooms create greater problems for lake users. The
most obnoxious forms are buoyant during the day and can form thick
surface scums, especially on a calm sunny afternoon. This scum may
be blown into shallow water making the shoreline appear slick with
blue-green paint. Sometimes surface algae are literally shocked by
sunlight and die. As they decompose, the odor can be unpleasant and
the oxygen in the water is depleted. If enough algae die and the oxygen
in the water is consumed faster than the atmosphere can recharge it,
hydrogen sulfide, which smells like rotten eggs and is very toxic
to fish, builds up in the bottom water. Unionized ammonia can also
build up to concentrations toxic to fish and other aquatic organisms.