WATER QUALITY MANAGEMENT IN CONNECTED CATCHMENT- SHALLOW LAKE SYSTEMS - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 35

plants provide excellent food and habitat for zooplankton, insects, fish, waterfowl and other wildlife.
They also lock up sediments, helping keep the water more clear.
Depth:
Shallow lakes (and deeper wetlands) are often less than five meters deep, although in some cases they
might be as deep as ten meters. Most lakes do have some shallow lake components to them in bays.
Shoreline zone:
Technically referred to as the littoral zone, this zone is evident by the stands of emergent aquatic
plants such as cattails, bulrush, and reeds that are present, as well as submerged plants such as coontail
water lily, potamogeton species and floating plants such as water hyacinths. Healthy shallow lakes
have plants growing throughout the entire basin, creating an extended littoral zone. Nutrient/sediment
mixing: Sediment and nutrients in shallow lakes, unlike in deeper lakes, are constantly mixing. In a
shallow lake where there is not much of a temperature difference and nutrients and sediments can
easily be stirred up by wind, wave action and undesirable fish species.
Fluctuating water levels:
Shallow lakes can often benefit from periods of low water that stimulates beneficial aquatic plant
growth. When water levels remain too high, too long, plant growth can be obstructed and water quality
deteriorates. Algae growths usually result from such conditions.
Fish:
Low water conditions can help set the stage for winterkills that can decrease or eliminate populations
of undesirable fish species such as carp and black bullhead. While shallow lakes can support
populations of game fish, low levels of dissolved oxygen and winterkills tend to limit their numbers.
Land use impacts:
Agricultural chemicals as mentioned earlier, run-off from agricultural lands, drainage water and soil
particles that flow into a shallow lake will eventually cause the lake to become seriously degraded.
Shallow lakes can be more susceptible to such run-off than their deeper water lakes.
Surface water use:
Surface water use can sometimes be as important as land use management in maintaining a healthy
shallow lake. Aquatic vegetation can suffer from too many fishing nets docks, boats and outboard
motors on a lake. It's important to note that shallow lakes, even though they share common
characteristics, are each unique in their own way. The surrounding terrain, land use practices, and lake
use are some of the considerations to be taken into account when dealing with management of shallow
lakes. Specific properties of shallow lakes and their surrounding catchments that should be defined
thoroughly are the aqautic vegetation and commercial fisheries or fish ponds . These components of
the lake physical system have direct impact on the lake water quality and trophic status.
Aquatic Vegetation
The vegetation of water and swamp habitats creates a complex area in the ecotone zone between water
and land, where the transport of allochtonic matter takes place (Joniak et al., 2007). The nearshore or
meadow vegetation may be a barrier restricting the distribution of anthropogenic contamination (e.g.,
Szpakowska, 1999). In relation to aquatic macrophytes, opinions considering the role of macrophytes
in modyfying the physical-chemical features of their environment have as yet not been defined. On
one hand the dynamics of water in shallow reservoirs or lakes is often determined by irregular
processes e.g., floods, wind mixing etc., which have a great influence on water parameters (Joniak et
al., 2000). On the other hand overgrowing macrophytes may intake nutrients from water or restore
them from sediments into the water (Grane´ li & Solander, 1988). Nowadays, particular attention is
paid to the relative role of aquatic vegetation, which influences physical, chemical and biological
parameters.
Macrophytes or water vegetation can have opposite impacts on the water body. Once a lake has lost
its submerged plants, it can be very difficult to re-establish them. This is thought to be due to
'alternative stable states', the idea that shallow lakes exist in either a state dominated by plants or a
state dominated by phytoplankton (microscopic algae). Each state has a set of feedbacks that operate
to buffer against changing to the other state. The switch from a plant-dominated lake to a
phytoplankton-dominated lake most often occurs as the lake becomes enriched by nutrients,