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Ponds
are living entities, which evolve and age. If left alone
lakes gradually fill in and become swamps and then meadows.
This is natural. This process can take thousands of years
or just a few depending largely on the geomorphology of
the lake and activities around the lake. People may think
that they want a "natural" pond, but what they really want
is to maintain the pond in a relatively young condition
rather than letting it age and transform into a swamp. This
is not different than what people try to achieve around
their homes. Considerable time and money are spent maintaining
gardens in a particular age or state rather than letting
them evolve naturally to weeds and shrubs. Lakes also require
knowledge and maintenance to assure their health and continued
beauty.
Healthy
ponds contain balanced communities of microorganisms,
invertebrates, fishes and plants. If the populations of
the communities become unbalanced the health and longevity
of the lake can be detrimentally affected. For instance,
algae and other aquatic plants produce cell mass from carbon
dioxide by the process of photosynthesis. The death of these
plants results in increasing deposits of carbon or sludge
within the lake. Excessive plant growth usually results
in rapid accumulation of sludge, filling in and aging of
the lake and even in production of noxious odours and bad
flavour in the fishes.
The
well being of the biological communities are directly
affected by the physico-chemical conditions within the lake.
The oxygen and phosphorous levels, the depth and shape of
the lake and the bottom substrate among other factors, which
interact with the biological communities to influence overall
lake health. This is what aquatic ecology is all about.
There
are no miracle solutions, but there are many tools,
which can be used by ecological engineers to restore and
maintain lakes. Among these are aeration*,
bioaugmentation (the seeding of water purifying organisms
from bacteria to fishes, and invertebrates to plants), biofilters,
chemicals which bind phosphorous or reduce algae or oxidize
sludge or colour water, plant harvesting and dredging etc.
Pond management requires monitoring of the physico-chemical
and biological processes to decide which tools are appropriate
and when they should be used.
*Aeration
Pond aeration is the best method to control water quality
and algae. It is very important not to overlook aeration
in small basins and in ponds which have a large organic
load and that are typically mucky at the bottom. We strongly
promote air diffusion at the bottom of the pond as the
best form of aeration. Fountains and cascades are aesthetically
pleasing and offer some surface aeration but we recommend
bottom air diffusion as the most efficient way to improve
and maintain good water quality.
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There are five principal steps to a successful pond health
care maintenance or restoration program:
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1. Definition
of the treatment goals, what exactly is desired and what is possible
— e.g., clearer water, control of algae and/or rooted aquatic
plants, a sport fishery, odour control, a refuge for water fowl,
boating, water skiing, swimming, supply of irrigation water. Some
of these goals may conflict with others. It is important for users
of the pond to understand clearly what is possible and realistic
and what is not.
2. Definition
of physico-chemical and biological realities — Parameters
such as shape and depth of the pond, water and chemical inputs
and losses, physico-chemical composition of the water and biological
populations, within the pond , are critical factors to be integrated
in a management plan. The health of the pond cannot be assured
without considering the surrounding drainage basin with respect
to run off, choice of fertilizers and fertilizing practices etc.
Considerable data may already exist. If not, this data will have
to be collected so that an intelligent management program can
be planned to achieve the targeted goals.
3. Development
of the management program for the lake — This is based upon
integration of the treatment goals (Step 1), knowledge of the
lake (Step 2) and legal realities.
4. Implementation
of the management program — This includes a treatment plan
as well as regular health monitoring. It is not possible to prescribe
a single treatment protocol for all eventualities for a living
community for all time. A sound pond health care maintenance program
must be able to be adjusted with seasons, age or accidents. This
approach is no different than what we do when we go to a doctor
or a dentist. Examinations are obviously required to optimize
treatments.
5. Feedback
and interaction between the lake health care team and users association
— In the case of management of lakes it is essential to maintain
regular communication with the users associations for feed back
on the program as well as possible changes in the treatment goals
(Step 1).
©1999
Karl F. Ehrlich, Ph.D & Marie-Claude Cantin Ph.D
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