The Luni is the largest river in the Thar Desert of northwest India. It originates in the Pushkar valley of the Aravalli Range, near Ajmer, passes through the southeastern portion of the Thar Desert, and ends in the marshy lands of Rann of Kutch in Gujarat, after travelling a distance of 495 km (308 mi). It is first known as Sagarmati, then after passing Govindgarh, it meets its tributary Sarasvati, which originates from Pushkar Lake and from then on it is called Luni.
Course of River Luni or Lavanaravi river, south of the estimated route of the ancient Sarasvati river
The Thar Desert, also known as the Great Indian Desert, is an arid region in the north-western part of the Indian subcontinent that covers an area of 200,000 km2 (77,000 sq mi) in India and Pakistan. It is the world's 18th-largest desert, and the world's 9th-largest hot subtropical desert.
Thar Desert in Rajasthan, India
Vedic and present-day Gagghar-Hakra river-course, with Aryavarta/Kuru Kingdom, and (pre-)Harappan Hakkra/Sutlej-Yamuna paleochannels as proposed by Clift et al. (2012) and Khonde et al. (2017). See also this satellite image. 1 = ancient river 2 = today's river 3 = today's Thar desert 4 = ancient shore 5 = today's shore 6 = today's town 7 = dried-up Harappan Hakkra course, and pre-Harappan Sutlej paleochannels (Clift et al. (2012)).
A NASA satellite image of the Thar Desert, with the India–Pakistan border
View of the Thar Desert