In the high Himalayas, the melting waters of the Siachen Glacier are the main source of which of the following rivers?

Introduction / Context:
The Siachen Glacier, located in the eastern Karakoram range in the northern part of the Indian subcontinent, is one of the longest glaciers in the non polar regions of the world. It is also strategically significant. From a physical geography perspective, knowing which river systems receive meltwater from this glacier helps in understanding the headwaters of the Indus river basin and the hydrology of high altitude regions.

Given Data / Assumptions:

• The question is about the main river fed by the melting waters of the Siachen Glacier.
• Options given: Beas, Sutlej, Shyok, and Nubra.
• All listed rivers belong to the broad Indus basin region but arise from different specific headwaters.
• We assume the standard hydrological description used in Indian geography texts.

Concept / Approach:
The Siachen Glacier lies near the watershed between the Indus river system and other river basins. Its meltwater forms a stream that initially flows into the Nubra river. The Nubra then flows into the Shyok, and the Shyok ultimately joins the Indus. Therefore, while all these rivers are connected via the larger drainage network, the immediate and direct recipient of Siachen meltwater is the Nubra river. Identifying the primary channel rather than downstream rivers is the key.

Step-by-Step Solution:
Step 1: Recall the geographic location of the Siachen Glacier in the eastern Karakoram, close to the Nubra valley region. Step 2: Understand that meltwater from the glacier flows southward into the upper reaches of the Nubra river. Step 3: Recognise that the Nubra river then joins the Shyok river further downstream. Step 4: The Shyok river itself later merges with the Indus river, so Beas and Sutlej are part of the wider Indus basin but far away geographically. Step 5: Since the question asks for the main river whose headwaters receive the glacier melt directly, the answer must be the Nubra.

Verification / Alternative check:
A quick map based check would show the Siachen Glacier lying to the north of the Nubra valley, with the glacier snout feeding streams that become tributaries of the Nubra river. In contrast, the Beas and Sutlej originate in the Himachal region and have no direct connection to the Siachen area. The Shyok is a larger tributary of the Indus that receives the Nubra, but it is still a step downstream from the actual glacier melt inflow, confirming Nubra as the primary receiving river.

Why Other Options Are Wrong:
Beas originates in the central Himalayas near Rohtang Pass in Himachal Pradesh and is unrelated to the Siachen Glacier. Sutlej rises near Lake Rakshastal in Tibet and flows through Himachal Pradesh and Punjab, again distant from Siachen. The Shyok does ultimately carry water that once flowed from Siachen, but only after it has passed through the Nubra river; it is therefore not the immediate main source channel. Hence, these options do not satisfy the precise wording of the question.

Common Pitfalls:
Students sometimes focus on prominent names like Shyok or Sutlej because they are better known, or they think mainly about the Indus river itself rather than intermediate tributaries. Another issue is treating the entire upper Indus basin as a single unit without paying attention to how specific glaciers feed particular valleys. To avoid errors, always trace the direct path from the glacier snout to the nearest named river in the hierarchy.

Final Answer:
The melting waters of the Siachen Glacier are the main source of the Nubra river in the Nubra valley.