- Does drought make blue-green algae worse?
There are two aspects of drought, heat and lack of moisture. Blue-green algae need nutrients,
and cell growth and division increases as the water temperature increases. Nutrients come from
runoff or from internal cycling from bottom sediments under certain conditions. Biological activity, such as cell growth and division,
also increases exponentially with an increase in water temperature (biological activity increases 2 to 10 times with every degree of temperature).
In shallow bodies of water, sediments tend to be a ready source of nutrients – especially when the lake, pond or
reservoir alternates between a stratified and un-stratified state. If the shallow lake or flowage is filled with rooted vascular plants (lake weeds), the water body typically
responds by becoming more weedy, which may result in the water remaining clear and not as prone to algae blooms.
If rooted lake plants are not present, planktonic algae growth explodes (blooms) until it is limited by either lack
of water clarity (often self-shading) or the amount of nutrients available (less likely because of internal recycling).
In deeper waters (lakes that remain
stratified throughout the summer), nutrients in the bottom sediments tend to be isolated from the
surface waters where blue-green algae grow. However, deep, stratified lakes are not necessarily immune
from blue-green algae issues. Warm water temperatures, lots of sunlight and stratification can lead
to blooms, especially by nitrogen-fixing species. However, these blooms are less due to drought than to heat,
sunlight and calm weather.
With less water flowing into flowages and reservoirs, the residence time of water in the pool increases. Slower moving water,
along with increased temperatures, gives algae more opportunity to grow (algae typically need about 10 days
of residence time).
- Does the drought make Cladophora worse?
Cladophora, which grows in Lake Michigan, is a little bit different than blue-green algae.
Since it grows on the lake bed, it needs clear water, but growth (cell division) is still a function of water temperature.
High water temperatures increase biological activity and potentially (and likely) increase the growth rate of Cladophora. And while greater growth of Cladaophora doesn't mean more toxins,
what it does mean is that more ends up on the beach, causing much higher bacterial counts which is a problem.
- Why are water levels on my lake lower?
Low water levels are occurring in many places throughout the state and the reasons
why vary according to the type of lake and circumstances. Lakes where water levels are
controlled by a dam or other structure may not experience as drastic a drop as natural
glacial kettle lakes common to northern Wisconsin and the central sands area. These
lakes typically have water levels that are controlled by the elevation of the groundwater
table, which in turn reflects the amount of rain water and snow melt that soaks into the
ground and eventually reaches an aquifer -- minus the amount of groundwater discharging
from the aquifer to lakes, rivers and wetlands and public and private water wells. Lower water tables occur if less water enters the aquifer or more is taken out, or both. A drought, changes in land use that allow less water to soak into ground, increases in pumping -- all can affect groundwater table levels, and in turn, lake levels. Often, it's a combination of all three: lean water years due to natural conditions like a drought are exacerbated by human actions; people withdraw more water, or pave over more land and destroy wetlands, decreasing the water reaching aquifers. Groundwater monitoring well records in some areas indicate that water levels today are nearing the low levels seen in the late 1950s to mid-1960, and which contrast to the high peaks seen in the early 1990s. Learn more about low lake levels by reading this article (Exit DNR for a pdf 719kb).
- What causes water levels to go up and down?
Lake water levels can fluctuate naturally due to rain and snowfall,
which varies widely from season to season and year to year. While
some lakes with streams running into them show the effect of
rainfall almost immediately, others, such as seepage lakes, may
not show the effect for months. Seepage lakes are landlocked
water bodies that do not have a stream coming into or out of them
but get most of their water from precipitation or runoff,
supplemented by groundwater. Seepage lakes are the most common
type of lakes in Wisconsin and many of them in northern Wisconsin
are now experiencing lower water levels. Although changes in water
levels may be perceived as a problem for property owners, it is
natural for lakes to go up and down in cycles that are decades long.
- Are low water levels bad for lakes?
The short answer is no. In fact, periodic low water conditions
can be beneficial for lake ecosystems. It consolidates sediments,
allows new plants to colonize the lake bed and it provides
habitat for rare plants and shorebirds. In fact, one of our
rarest shoreline plants, Fassett's Locoweed, is dependent upon
periodic fluctuations of water levels to grow. This plant is
only found in a handful of lakes on the planet (all in Wisconsin)
and all of these lakes are subject to wide fluctuation in water
levels. When water levels return, this expansion of plants becomes
habitat for fish and wildlife, removes nutrients from water, and
can increase water clarity. However, human actions that cause
water levels to drop farther than this natural variation, or
prevent the lake from returning to normal conditions, may harm
the lake and its inhabitants over the long-term.
- Is it OK to "clean-up" my beach or remove vegetation on the
exposed lake bed during low water periods?
In general, it is best to avoid disturbing the exposed lake bed.
Shorelines and shallow areas of lakes play a vital role in
providing habitat for fish and wildlife and for protecting
water quality. A diverse native plant community provides the
best habitat and defends against invasive species getting
established. Until water levels return to normal, it is
important for shoreline owners to avoid inadvertently harming
exposed lakeshore areas.
There are some activities which may be necessary to maintain
access, control invasive species, and reduce nuisance
accumulations of biological material. The following fact
sheet on Beach Maintenance may help you do these activities
in a way that minimizes harm to exposed lakeshore areas. =>
Most activities conducted on the exposed lake bed including
beach grooming and cutting or chemically treating
plants are regulated by the DNR, but there are a few
activities that don't require a permit. For example,
some minor vegetation management (except for wild rice) and
other activities done by hand do not require permits from
the DNR. Please be careful to avoid cutting any legally protected threatened
or endangered plant species, which are located on the lakebed, which is public
The following activities require a permit: cutting an area
larger than 30 feet wide, driving a motor vehicle on the lakebed,
tilling, and chemically treating vegetation if the area is wet.
The permits are designed to assure that the activity does not
damage the lake or the sensitive exposed habitat. Visit the
following website for more information about permits.
- Can anything be done to restore water levels (or remove excess water)?
On lakes with connecting streams or dams or other water level
control structures, modifications may be considered to
temporarily raise or lower the water level due to extreme
conditions. However, permanent changes in water levels
have huge implications for downstream property owners and
users and are often very controversial. Establishing or
changing levels on a lake with a water control structure
will require DNR approval. The following website has more
Lakes without natural outlets are even more difficult to address.
Pumping water into a seepage lake can be expensive and results in
very little change in the water level, as most of the water is
basically recycled back to the local groundwater system.
- What about high water levels?
High water levels can boost the amount of nutrients from runoff
and flooded lakeshore soils, as well as create health problems with flooded septic
systems and private wells. Fluctuating water levels can also increase shoreline
Getting rid of excess water is complex and may not be feasible, especially if
the surrounding landscape and waterways are also flooded, or at high levels.
Generally, permits are required to pump or divert water either from the lake
itself or from the outlet stream if the purpose is for bringing back or maintaining
the normal level of your lake. Contact your local water management specialist
for more information.
Again, changing levels on a lake with a water control structure (e.g. dam)
will require DNR approval
Wednesday, July 24, 2013