618 LIMNOLOGY
Ducks and geese may also graze on the shoreline and affect
lake water quality via the nutrients and fecal coliform bac-
teria in their wastes. Native plantings along lake shorelines
and streambanks of creeks that are tributary to lakes serve
multiple functions: improving wildlife habitat; acting as a
physical barrier to intrusion by ducks and geese; increas-
ing shoreline soil stability thereby preventing erosion; and
moderating impacts of surface water runoff by filtering out
suspended solids, nutrients, and toxic chemicals.
Alternatives to standard lawn maintenance and landscap-
ing practices include minimal use of fertilizers, reduction in
lawn size, regular thatching and aeration, incorporation of
native plants in new landscaping, soil enhancement through
mulching and composting rather than chemical fertilizers,
and integrated pest management techniques rather than
chemical pesticides.
Household hazardous wastes should be properly disposed
of at collection sites and never in storm drains. Homeowners
should be educated about non-toxic alternatives to common
household cleaning products.
When cars are washed near storm drains, wash water car-
ries oils, greases, nutrients, heavy metals, suspended solids,
and soaps to local water bodies including lakes and their
tributaries. Residents of a lake watershed should be encour-
aged to wash their cars at commercial car wash facilities,
which discharge wash water to the sanitary sewer system.
People who do wash their cars at home should be informed
about draining wash water to vegetated areas such as lawns,
using a high pressure nozzle with trigger to minimize water
usage, and using commercial products that clean vehicles
without water.
The feeding of waterfowl by lakeside residents should
be discouraged. Pet and domestic animal waste should be
properly disposed of away from a lake and surface water
pathways that reach a lake.
Business owners should be educated about BMPs, such
as proper storage of toxic chemicals and proper mainte-
nance and repair of oil-water separators in order to prevent
the discharge of petroleum hydrocarbons, metals, and other
toxics to lakes and their tributaries. Many local and state
agencies provide technical assistance to businesses in pre-
venting or reducing the discharge of pollutants to lakes and
streams.
State and local agencies such as conservation districts
should also educate agricultural landowners about agricul-
tural BMPs to improve pastures, maintain healthy livestock,
dispose of or recycle livestock water, restrict livestock access
to lakes and their tributaries (e.g., building fences around
streams which are inlets to lakes), and prevent discharge of
pollutants from livestock waste and farm operations to lakes
and tributaries. Cost-sharing incentives and technical assis-
tance increase the success rate of these measures.
Maintaining on-site wastewater treatment systems (septic
systems) in good working order is another way to reduce phos-
phorus loading to a lake. Lakeside and watershed residents and
business owners should know about septic system operation
and maintenance practices, such as using no- or low-phos-
phate detergents, composting organic wastes rather than usinggarbage disposals, selecting and maintaining optimal veg-
etative cover over drainfields, and inspecting and cleaning the
system on a regular basis to ensure proper system functioning.
This can be accomplished through articles in lake association
newsletters, through brochures, and through workshops con-
ducted by local and state agencies.In-Lake Restoration Techniques In-lake restoration tech-
niques that can be used to control internal phosphorus
loading are phosphorus inactivation and precipitation (e.g.,
aluminum sulfate treatment), removing sediments from the
lake bottom (dredging), hypolimnetic aeration, hypolimnetic
withdrawal, dilution, and artificial circulation. Following is
a discussion of the principles, advantages and disadvantages
of each technique.
Adding aluminum sulfate (alum) to a lake reduces the
lake’s phosphorus content by precipitating phosphorus and
retarding its release from the sediments (Cooke et al. , 1993a).
When alum is added to the water column, a polymer forms
that binds phosphorus and organic matter. The aluminum
phosphate-hydroxide compound (commonly called alum
floc) is insoluble and settles to the lake bottom. Dramatic
increases in water clarity typically occur immediately fol-
lowing an alum treatment, as suspended and colloidal par-
ticles are removed from the water column by the floc.
Alum has been used extensively in the United States, with
general success in controlling phosphorus release from lake
sediments for several years (Cooke et al. , 1993a; Garrison
and Knauer, 1984). If external sources of phosphorus are
not controlled, the effectiveness of alum will decrease with
time as the alum layer on the sediments becomes covered by
nutrient-rich silt and organic material. The lake may there-
fore need to be treated again. Regular long-term monitoring
is required in an alum-treated lake to evaluate the effective-
ness of the treatment.
The alum dose should be based on the pH and alkalin-
ity of the lake, and the potential toxicity of aluminum to the
lake (Cooke et al. , 1986, 1993a; Kennedy and Cooke, 1982).
As alum is added to a lake, pH and alkalinity decrease and
dissolved aluminum concentrations increase; alkaline lakes
can tolerate higher alum doses than can softwater lakes.
Adding alum to a lake with low to moder ate alkalinity
requires careful planning to ensure that pH and alkalinity
are not lowered to levels that would stress aquatic biota.
The use of sodium aluminate as a buffer permits a greater
alum dose to be used. Such buffering agents have been
applied with alum in several northeastern lakes and high
success in maintaining normal lake pH and alkalinity levels
(Cobbossee Watershed District, 1988; Dominie, 1978). The
use of sodium carbonate in the alum treatment of Long Lake
in western Washington was also highly successful in main-
taining safe pH and alkalinity levels, as well as in improving
lake water quality (KCM, 1994).
Alum is a promising technique for reducing algae through
physical settling and removal during the application and
through the long-term control of internal nutrient loading. The
treatment does not kill the algae instantaneously in the water
column, but settles them on the lake bottom, where they dieC012_002_r03.indd 618C012_002_r03.indd 618 11/18/2005 10:36:48 AM11/18/2005 10:36:48 AM