The Yamuna, another sacred river of the Hindus, is an important tributary of the Ganga. The river rises from the Yamunotri glacier (6,387m above msl) at the Banderpoonch peak in the Uttarkashi district of Uttaranchal. The river flows 1,367 km from its source to its confluence with the Ganga at Allahabad.
The annual flow of the river is about 10,000 cum. The annual usage is 4,400 cum of which 96 per cent is for irrigation. The Hindon, Chambal, Sindh, Betwa and Ken join the river in its 1,200 km- long journey through the plains.
At the Tajewala barrage, 172 km from its source, the Western and the Eastern Yamuna Canals divert the entire river water into Haryana and Uttar Pradesh for irrigation and other uses. Precipitation in the catchment area of the river is restricted to three monsoon months of July, August and September. Consequently, the river flow is not uniform throughout the year and the level of pollution increases during dry period.
For the study of pollution the total course of Yamuna, may be divided into five segments- Himalayan (172 km). Upper (224 km), Delhi (22 km), Eutrophicated (490 km), and Diluted (468 km) -of which the last three are much polluted. The Himalayan segment from its source to Tajewala barrage is almost free from pollution. The Upper segment between Tajewala and Wazirabad has become the victim of the rich agriculture of Haryana.
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The withdrawal of water to canals (west and east Yamuna canals) further aggravates the situation. Wastes from the industrial areas of Kurukshetra, Yamuna Nagar, Karnal. Panipat and Sonepat are discharged into the river and the irrigation canal (Table 31 .IV) and greatly reduce the water quality of the river. The capital city of Delhi is the largest polluter of Yamuna. The city is the largest consumer of water, with a production of 2,728 mid of treated water. Though the length and basin area of the river in Delhi is barely 2 percent, it contributes 71 percent of the waste water and 55 per cent of the total BOD load discharged into the river every day. About 9322,800 mid of untreated sewage find its way to the river through 19 major drains.
The toxic effluents include 200 tons of BOD and 160 tons of suspended solids being discharged into the river every day. The river has been reduced to the ‘open sewer of Delhi’. ‘Before the Yamuna enters Delhi, 100 milliliters of its water contain about 7,500 disease causing bacteria but after receiving city sewage the number of bacteria increases to 24 million.’
The segment downstream of Delhi becomes more polluted by the city waste from Agra and Mathura. Consequently the BHC load increases from 218.83 nanogram per liter (Delhi) to 1,733.23 nanogram per litre (Agra). Similarly, the DDT load of203 mg/1 of water at Delhi is increased to 1,802.58 mg/1 at Agra. The segment is so highly polluted that the colour of the water turns to green owing to the presence of algae and phytoplankton’s (eutrophication), hence called eutrophicated. Downstream from the Yamuna-Chambal confluence the quality of water improves after the meeting of the Hindon, Sindh, Betwa and Ken rivers.