How many members here know about this?
After the depopulation at the end of Indus Valley Civilization around ~1500bce, the Lower Indus Plains (Sindh and the parts of Punjab south of the Salt Range) remained sparsely populated and predominantly pastoral till the late 1800s to early 1900s when the British Canal Colonies brought back cultivation after 3000 years.
The above maps of population density of British India from the late 1800s testify to this
Source for Colonies : https://en.wikipedia.org/wiki/Punjab_Canal_Colonies
Additional Evidence to support this-
Pre-Islamic empires in what is today Pakistan tended to concentrate their centers of power towards the northern, wetter fringe - Gandhara, Potohar, Northern fringe of Punjab between Sialkot and Lahore.
There are no Ashokan edicts between Yamuna and Gandhara, and then suddenly you find a high density of archeological remains in Gandhara.
Material remains of Indo-Greeks, Sakas, Kushans, Indo-Parthians, and Huns are all concentrated in either Gandhara or the northern fringe of Punjab centered at Sakala, before directly moving to the banks of Yamuna.
East Asian Buddhist Pilgrims like Xuanzang etc don't have much to say about the lower Indus basin while they had tons to say about Gandhara, and then directly moved towards Yamuna .This is despite the fact that the "Rai dynasty" of Sindh was Buddhist.
While Multan was an important urban center after the coming of Islam, the lands around it continued to be predominated by semi-nomadic or nomadic pastoralists.
According to Mughal Revenue records, Lahore Subah produced much higher revenues than Multan + Sindh.
https://www.reddit.com/r/MapPorn/comments/1gh9ta9/land_revenue_of_provinces_under_the_mughal/
Punjabi folktales like Heer-Ranjha describe a predominantly pastoralist society for a reason.