Ludhiana is the largest city in Punjab and one of the most industrialised in northern India, and it is almost entirely unplanned.
Its industry grew in the residential fabric: workshops in courtyards, dyeing units next to houses, and industrial estates that filled and overflowed. That pattern is why the Buddha Nullah carries what it carries.
Its workforce is heavily migrant and lives in dense settlements with poor services. Its air quality is among the worst in Punjab.
It is also the state's economic engine and the reason Punjab has any manufacturing base at all.
The city's expansion has taken agricultural land continuously and its water supply comes from a falling aquifer.
Every problem in Punjab's urban planning is visible in Ludhiana at full scale, and the city works anyway, which is both the argument for it and against doing anything about it.
The knitwear trade works as a chain of tiny units: one man with two machines, another who dyes, another who prints, another who packs. The finished garment leaves Ludhiana for the whole of India and for export.
The Buddha Nullah carries dyeing effluent and untreated sewage into the Sutlej above the Harike headworks, which is the intake for canals supplying Rajasthan and southern Punjab.
The migrant workforce, from Bihar and Uttar Pradesh mostly, is what the industry runs on. It is counted by nobody and housed by nobody.