The CAG report which studied the pollution levels in Lucknow and Varanasi from 2011 to 2015 has revealed that the Gomti river is more polluted than the Ganga.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/gomti-river-lucknow-more-polluted-ganga-varanasi-cag-report
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/daily-news-analysis-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/uttar-pradesh
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/gomti
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/lucknow-t
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/river-pollution
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/ganga
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/varanasi-t
[9] http://admin.indiaenvironmentportal.org.in/thesaurus/comptroller-and-auditor-general-india-cag
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/state-pollution-control-board-spcb-0