Lake Winnipeg - Eutrophication

Question 1

what are the 3 primary inflows to lake winnipeg. and the one outflow

Answer 1

the Winnipeg
River (majority of flow~
49%), the Saskatchewan
River (~ 25%) and the Red
R. (~ 16%)
-the nelson river is the only outlet

Question 2

where does most of the P come from

Answer 2

Most P comes to lake from RR ~ 66-68%, even though the Red
River only accounts for about 16% of inflowing water

Question 3

what are some issues with the lake

Answer 3

• Sometimes large and toxic algal blooms;
• Lack of understanding of effects of zebra mussels;
• There are occasionally toxic blooms in the lake, where one toxin – microcystin-LR is elevated, especially in nearshore areas, it is not currently known if any toxins are accumulating in fish
  within the lake.
• Best to stay away from algal blooms.

Question 4

causes of lake winnipeg eutrophication

Answer 4

Lately, increased levels of inflows (flashier rain events, wet years), especially from the Red River, have resulted in an increase in P. red river accounts for 68% of the P and half of that originates from feilds and cities south of the border.
The City of Winnipeg treatment plants account for about 3-4% of the inputs

Question 5

when does the P loading take place

Answer 5

98% of P loading to the system occurs
in the spring, and fields with intensive agriculture, animal feedlots
and those draining larger communities are contributing a much
larger proportion of nutrients than other surrounding areas

Question 6

netley Libau marsh

Answer 6

When marshes function
well, they “clean” the water before it gets to the lake. It’s health has been
declining since the early 1900s due to a variety of reasons. The greatest, likely being the Netley Cut (next).
Common carp were also introduced into the marsh in the 1940s. and reduced drawdown from hydro

Question 7

Summary of Eutrophication

Answer 7

Increased nutrient levels lead to an increase in algal primary productivity.
Over time, this can result in a shift in species diversity – from a more diverse algal community to a less diverse algal community,
made up primarily of nitrogen-fixing blue-green algae.
Most of these algae are not as palatable to aquatic organisms and
many can also produce toxins.
In many systems, this overgrowth can lead to oxygen depletion in
the water when the algae die, sink to the bottom and decompose.

Question 8

Summary of Causes of Lake Winnipeg Eutrophication

Answer 8

There are many reasons why algae (and nutrients) are increasing
in Lake Winnipeg including:
* Increased runoff from city surfaces and inputs directly from
sewage treatment plants without proper tertiary treatment to
effectively reduce nutrient levels;
* Draining of the majority of wetlands in the Red River Valley;
* Use of fertilizers and spreading of manure on fields, especially
in the late fall;
* Increased runoff from fields and possibly also through tile
drainage systems;
* Poor health of Netley-Libau marsh;
* Internal cycling of nutrients within the lake; and
* Climate Change.

Question 9

steps to improve lake winnipeg

Answer 9

check slides