Question

What are the two main seasons when lake water overturn occurs?

1. Spring and Autumn (Fall)
2. Summer and Winter
3. Late Winter and Early Spring
4. Late Summer and Early Winter

• A. 3 only
• B. 2 only
• C. 1 only
• D. All

Answer 1

Answer:

C. 1 only

Spring overturn

• In spring and early summer season the increased solar radiation melts the ice cover, which, as it attains a temperature of 4 degree Celcius, becomes dense and heavy and sinks to the bottom, displacing the lower water which moves up.

• This circulation of water is further helped by the prevailing summer winds and is called spring overturn

Autumn (fall) overturn

• In autumn or early winter the air temperature falls, resulting in the cooling of the surface waters.

• When the surface water cools to 4°C it becomes dense and heavy and sinks to the hot-tom displacing the bottom warm water which rises to the surface.

• This mixing of the surface and bottom layers is further facilitated by strong winter winds and is called 'fall overturn'