Correct Option
The correct option is The Luni.
Explanation
The Luni is the most significant river in the arid region of western Rajasthan. It is an ephemeral river that forms an essential part of the inland drainage system of the Thar Desert.
Detailed Analysis
- Origin and Confluence: The Luni originates from the western slopes of the Aravalli Range near Pushkar in the Ajmer district. At its source, it is formed by two primary branches: the Saraswati and the Sabarmati (often referred to locally as the Sagarmati to distinguish it from the major Sabarmati river of Gujarat). These two streams join at Govindgarh. From this confluence point onwards, the river is known as the Luni.
- Course: After the confluence at Govindgarh, the river flows in a south-westerly direction through the districts of Nagaur, Pali, Jodhpur, Barmer, and Jalore in Rajasthan.
- Termination: It does not reach the sea but disappears into the marshy lands of the Rann of Kutch in Gujarat.
- Salinity: The water of the Luni is fresh near its origin but turns saline after reaching Balotra (Barmer) due to the high salt content in the soil of the region.
Note on other options:
- The Mahi: Originates in the Vindhya Range (Madhya Pradesh) and flows into the Gulf of Khambhat.
- The Banas: Originates in the Khamnor Hills (Aravalli Range) and is a tributary of the Chambal river.
- The Ghaggar: An inland drainage river originating in the Shivalik hills, often associated with the ancient Saraswati, but not formed by the confluence mentioned in the question.
Key Takeaway: The Luni river is formed by the confluence of the Saraswati and the Sabarmati (Sagarmati) at Govindgarh and is the largest river in the Thar Desert region.