Which of the following is the longest lake in India in terms of length along its north–south axis?

Introduction / Context:
India has many important lakes, including fresh water, brackish and high altitude lakes. Some exam questions focus on which lake is the largest by area, which is the longest, or which is the highest. This question asks you to identify the longest lake in India in terms of its linear extent, especially along its north–south length, a fact often highlighted for coastal Kerala.

Given Data / Assumptions:

• The options include Vembanad, Pulicat, Kolleru, Pangong and Chilika lakes. • We are concerned with length, especially the north–south stretch, rather than just surface area or volume. • All lakes mentioned are significant water bodies but differ in shape, size and location.

Concept / Approach:
Vembanad Lake, located in Kerala, is recognised as the longest lake in India, running parallel to the Arabian Sea coast and forming an important part of the state backwater system. While Chilika and Pulicat are large brackish lagoons on the east coast, and Pangong is a long high altitude lake partly in India and partly in another country, standard Indian geography references identify Vembanad as the country longest lake. Kolleru is a large fresh water lake but more compact in shape. Therefore, the correct answer is Vembanad Lake.

Step-by-Step Solution:
Step 1: Recall that Vembanad Lake lies along the Kerala coast and stretches for a considerable distance north to south, connecting several districts. Step 2: Remember that this elongated shape makes Vembanad the longest lake in India, even though other lakes may have comparable or larger areas in some classifications. Step 3: Compare with Chilika Lake in Odisha, which is the largest brackish water lagoon in India but does not surpass Vembanad in linear north–south length. Step 4: Consider Pulicat Lake between Andhra Pradesh and Tamil Nadu, which is also a lagoon but smaller in length than Vembanad. Step 5: Note that Kolleru Lake is more circular in shape and Pangong Lake extends across an international border, with only part of it in India; standard school level fact lists still highlight Vembanad as the longest lake in India. Therefore, select Vembanad Lake as the correct answer.

Verification / Alternative check:
Most Indian geography textbooks and exam preparation guides mention Vembanad Lake as the longest lake in India. They also distinguish it from Chilika Lake, which is emphasised as the largest brackish water lagoon. When you look at a map, Vembanad appears as a long, narrow water body parallel to the Kerala coast, confirming its considerable length. The other lakes, although important, do not match this long, continuous stretch within India boundaries.

Why Other Options Are Wrong:
Pulicat Lake: A coastal lagoon on the east coast, but smaller in length than Vembanad and not commonly cited as the country longest lake. Kolleru Lake: A large fresh water lake in Andhra Pradesh, more compact in shape and not the longest. Pangong Lake: A long high altitude lake in the Himalayas, but only a portion lies in India and it is not usually listed as the longest lake of India in standard exam references. Chilika Lake: The largest brackish water lagoon in India by area, but still not the longest lake when measured by linear extent compared to Vembanad.

Common Pitfalls:
Students often confuse the terms largest and longest, or forget whether the emphasis is on area or length. Because Chilika frequently appears in questions about large lakes, some learners mistakenly pick it as the longest as well. Another source of confusion is Pangong, which seems long on a map but extends beyond India borders, and standard Indian exam facts focus on lakes fully within India territory. To avoid these errors, remember the specific identity: Vembanad Lake is highlighted as the longest lake in India, while Chilika is known for being the largest brackish lagoon.

Final Answer:
The longest lake in India is Vembanad Lake.