The Origin of Sutlej River and Rakshastal Lake
The Sutlej River is one of the major rivers in the Indian subcontinent, flowing through the regions of Tibet, Himachal Pradesh, Punjab, and finally merging with the Indus River in Pakistan. It originates from the Rakshastal Lake, which is located near the holy Mount Kailash in Tibet. Rakshastal Lake is a freshwater lake, and it is believed to be connected underground to the Mansarovar Lake.

Salinity of Rakshastal Lake
Rakshastal Lake is often referred to as a saline lake due to its high mineral content, including salts and other dissolved substances. The salinity of a lake depends on various factors such as the inflow and outflow of water, evaporation rates, geological characteristics of the surrounding area, and human activities. In the case of Rakshastal Lake, it is believed that the high mineral content is due to the surrounding volcanic activity and the presence of alkaline soil.

Factors Affecting Salinity of Rivers
The salinity of a river is determined by numerous factors, including the characteristics of its source, the inflow of water from tributaries, and the geological composition of the surrounding area. The Sutlej River, despite originating from Rakshastal Lake, does not have a saline nature. This can be attributed to the following factors:

1. Dilution: The Sutlej River receives water from various tributaries, including glacial meltwater and other freshwater sources. The inflow of freshwater dilutes the salinity of the river and reduces its mineral content.

2. Geological Composition: Unlike Rakshastal Lake, the geological composition of the surrounding area through which the Sutlej River flows might not contain high amounts of salts or other minerals. This results in a lower salinity of the river water.

3. Erosion and Filtration: The river water undergoes natural processes of erosion and filtration as it flows through different terrains. These processes help in removing impurities and reducing the salinity of the water.

4. Human Intervention: Human activities such as agriculture, irrigation, and industrial usage can further dilute the salinity of river water. The Sutlej River, being a vital water resource for agriculture and other human needs, might have undergone significant dilution due to human intervention.

Conclusion
The Sutlej River, despite originating from Rakshastal Lake, does not have a saline nature due to various factors such as dilution from freshwater sources, the geological composition of the surrounding area, natural processes of erosion and filtration, and human activities. These factors collectively contribute to the reduction of salinity in the river water, making it suitable for various purposes like irrigation, drinking water, and industrial usage.