UPSC Prelims 2025Question 23Geography

Consider the following water bodies:
I. Lake Tanganyika
II. Lake Tonlé Sap
III. Patos Lagoon
Through how many of them does the equator pass?

Options

Correct answer: a

Decision rule

Fix each water body's latitude before counting: only bodies within a degree or two of zero qualify; tropical is not equatorial.

(a) Only one

Let’s examine the latitudinal position of each of the listed water bodies relative to the Equator (0° latitude):

Lake Tanganyika – Yes, it lies on and around the Equator.
- Located in East-Central Africa, bordered by Tanzania, Democratic Republic of Congo, Burundi, and Zambia.
- The Equator passes through the northern part of the lake.
Lake Tonlé Sap – No, it lies north of the Equator.
- Located in Cambodia, southeast Asia.
- Latitude: ~13° North
Patos Lagoon (Lagoa dos Patos) – No, it lies south of the Equator.
- Located in southern Brazil (state of Rio Grande do Sul).
- Latitude: ~30° South

(b) Only two – Incorrect, as only Lake Tanganyika lies on the Equator.
(c) All the three – Incorrect, as two are clearly away from the Equator (north and south).
(d) None – Incorrect, one lake (Tanganyika) is crossed by the Equator.

Lake	Country / Region	Latitude	Crossed by Equator?
Lake Tanganyika	Tanzania, DRC, Burundi, Zambia	~3° S to 4° S	Yes (northern tip)
Lake Tonlé Sap	Cambodia	~13° N	No
Patos Lagoon	Brazil (Rio Grande do Sul)	~30° S	No

Equatorial Lakes: Water bodies like Lake Victoria, Lake Albert, and Lake Tanganyika are located near or on the Equator.
Climatic Relevance: Equatorial lakes have tropical rainforest climates, high biodiversity, and limited seasonal variation in temperature.
Hydrological Importance: Lakes like Tanganyika are important for regional fisheries, transport, and climate regulation.

Lake	Location (Countries/Regions)	Latitude Range	Crosses Equator?	Geographical Significance
Lake Tanganyika	Tanzania, Democratic Republic of Congo, Burundi, Zambia	~3°S to ~8°S	Yes	One of the largest and deepest freshwater lakes in the world; part of the East African Rift System; supports rich biodiversity and major fisheries.
Lake Tonlé Sap	Cambodia	~13°N	No	Largest freshwater lake in Southeast Asia; known for its seasonal expansion and importance to agriculture and fisheries in the Mekong Basin.
Patos Lagoon	Brazil (State of Rio Grande do Sul)	~30°S	No	One of the largest lagoons in South America; separates the Atlantic Ocean from coastal wetlands; important for navigation and ecological diversity.

Concept	Explanation
Equator (0° Latitude)	Imaginary line dividing the Earth into Northern and Southern Hemispheres; influences tropical climate zones
Equatorial Lakes	Lakes located on or near the Equator (e.g., Lake Victoria, Lake Tanganyika); characterized by high rainfall
Latitude and Climate	Latitude affects sunlight intensity and seasonality; equatorial lakes have warm, stable climates year-round
Lagoons vs. Lakes	Lagoons are typically shallow coastal water bodies separated from the sea; lakes are inland and deeper