Water Management Flashcards
two main factors that set the limits on how much oxygen can be “held” by a freshwater lake
temperature and altitude.
How does temperature affect the amount of oxygen in water?
warm water holds less oxygen than cool water
as altitude increases, the
amount of oxygen in a lake
decreases
all aquatic organisms
use dissolved oxygen gas (O2
) that is constantly
entering water from two main sources:
atmosphere and from photosynthesis
Oxygen from the atmosphere continuously
enters the surface of a waterbody through a
process known as
diffusion.
In most freshwater environments, DO (Disolved Oxygen) measurements usually range somewhere between
six and ten milligrams per liter
fish and other aquatic life will
begin to experience stress when
measurements drop down to
three or four milligrams per liter
Few organisms are
able to survive in water when dissolved oxygen
levels are below
2 milligrams per liter
water described as having a dissolved
oxygen saturation of greater than 100 percent
supersaturated
Dissolved oxygen
is the amount of oxygen
measured in water, in milligrams per liter
(mg/L).
Oxygen saturation
is the potential that a
waterbody has for holding oxygen, based
primarily on water temperature and altitude.
______ is the ratio
between actual dissolved oxygen measurements and the water’s potential for holding
oxygen
Percent oxygen saturation
Using a nomogram,4
one can use both
the temperature of the water and dissolved
oxygen measurements to determine
what the
percent oxygen saturation should be at any
given time.
the main
influencing factors on water temperature
Energy from the sun and the temperature of the
air surrounding a lake or waterbody
_______determine the influence that air temperature will have on a lake
The size of a water-body and the volume of water
Other Factors Influencing Water Temperature
inflows and outflows, lake
morphometry, wind, waves and lake color
the smallest density difference for
one degree of change of water occurs at
4 degrees Celsius
as the difference in density
increases, so does the amount of
energy required
to mix the two layers of water
Lakes that mix only once a year are often
referred to as
monomictic.
lakes
that mix once a year, during the coldest part of
the year, are referred to as
cold monomictic
Shallow lakes, like many of the waterbodies
found in Florida, are considered to be
polymictic
Lakes with low productivity (i.e., the amount of algae, aquatic plants, fish and
wildlife) tend to
experience small changes in oxygen concentrations,
over a 24-hour period
Large inputs of dissolved and particulate
organic matter can
reduce oxygen concentrations
in lakes
Water temperature “drives” several important
life processes for fish including their
metabolic
rate, growth rate, and reproduction
