why is the yamuna polluted

The River Yamuna, the largest tributary  of River Ganga has been one of the most
prominent & important rivers of India. Unfortunately, certain stretches of River Yamuna
are very polluted. Various urban centers e.g. Delhi, Mathura, Agra etc., which are
located on the banks of Yamuna river, draw fresh river water for various activities. In
return, almost the entire wastewater generated by these centers is disposed off into the
river. This is the prime reason for deterioration of Yamuna River water quality from
urban agglomeration of Delhi up to Chambal River Confluence.