River Yamuna is the largest tributary of the Ganga River in North India. Its total length is around 1370 kilometers. Yamuna originates from the Yamunotri Glacier of Uttar Kashi in Uttar Pradesh. River Tons and Giri are the important tributaries of Yamuna and principle source of water in mountainous ranges. Yamuna flows through the states of Delhi, Haryana and Uttar Pradesh, before merging with the Ganges at Allahabad. World famous cities like Delhi, Mathura and Agra lie on its banks. On the basis of hydrological and ecological conditions Yamuna has been classified into five segments that are Himalayan Segment, Upper Segment, Delhi Segment, Eutriphicated Segment and Diluted Segment [1]. Table 1 and Figure 1 show the area covered under these segments, while Table 2 shows the state wise land use pattern of the catchment area of river Yamuna. After origin Yamuna river flows through several valleys for about 200 km in lower Himalayas and emerges into Indo-Gangetic Plains. In the Himalayan Segment (from Yamunotri Glacier to Tajewala Barrage) the river water quality is good and it meets all the standards also. Within this segment in Hathnikund/Tajewala in Yamuna Nagar district of Haryana state, river water is diverted into Eastern Ya-muna Canal (EYC) and Western Yamuna Canal (WYC). Generally no water is allowed to flow in the down-stream of the Taje-wala Barrage especially during summers and winters to fulfill the water demand of the surrounding districts. Due to this the river remains dry in many areas between Tajewala and Delhi. Whatever water flows between Tajewala Barrage and Delhi of the river is the untreated or partially treated domestic and industrial effluents discharge by several drains. After crossing a route of 224 km of upper segment Yamuna enters Delhi. The Yamuna water is again trapped by Wazirabad barrage for the domestic supply of water to Delhi. Usually no water or extremely little water is allowed to flow downstream of this barrage during lean seasons. There is another barrage Okhla barrage 22 km downstream of Wazirabad barrage this segment is called Delhi segment and it receives water from seventeen sewage drains of Delhi, Najafgarh drain. It is considered as the most polluted segment of Yamuna River. From this segment Yamuna water is diverted into Agra canal for irrigation. River water is not allowed to flow downstream during summers; beyond the Okhla barrage whatever water flow in Yamuna River is the domestic and industrial wastewater generated from east Delhi, Noida and Sahibabad and joins the river through Shahdara drain. At the upstream of Mathura Gokul barrage is also decreasing the flow and thereby polluting the river. Yamuna river after receiving water through other important tributaries joins the river Ganga and the underground Saraswati at Prayag (Allahabad) after traversing about 950 km [1].

Yamuna River passing through 22 km in Delhi was once described as the lifeline of the city, but today it has become one of the dirtiest rivers in the country. According to the Central Pollution Control Board (CPCB) the water quality of Yamuna River falls under the category "E" which makes it fit only for recreation and industrial cooling, completely ruling out the possibility for underwater life [2]. The pollution of the Yamuna River from domestic discharges from Delhi, Ghaziabad, Noida, Faridabad, Mathura and Agra has rendered the river unfit for any use. Yamuna's water quality in the Himalayan segment and in the segment after confluence with the Chambal river is relatively good [3-5]. In Delhi around 3296 MLD (million litres per day) of sewage by virtue of drains out falling in Yamuna and approximately 3.5 lakh people live in the 62000 Jhuggis that have come up on the Yamuna river bed and its embankment [6]. Because of the low flow (due to different barrages) and huge quantity of waste it receives the Yamuna river within the limits of the city have been given the dubious distinction of being one of the worst polluted rivers of the country by the Central Pollution Control Board (CPCB). According to the latest status of water quality in India (2007) released by CPCB the Yamuna water quality at Okhla and Nizamudin bridges has been described as the worst affected. As per data on water quality of water bodies and groundwater locations; it was placed seventh on the list of rivers with highest Biochemical Oxygen Demand (BOD), one of the most important indicators of pollution. The total biochemical oxygen demand content in the Yamuna was 93 mg/L, while the permissible level is 3 mg/L. The CPCB report says that the level of Dissolved Oxygen throughout the year in Yamuna was less than 4 mg/L and it was 0.0 mg/L at few locations down-stream of urban settlements due to discharge of untreated and partially treated wastewater. The water quality of Yamuna has deteriorated at Paonta Sahib, Kalanaur, Sonepat, Palla, Nizammudin, Okhla, Mazawali, Mathura, Agra, Bateshwar, Etawah, Juhika and Allahabad the western Yamuna canal downstream of Yamuna Nagar at Damla is " grossly polluted due to municipal and industrial waste water disposal".

The Yamuna is widely worshipped by devotees in India. A few centuries ago it prompted the Mughals to build one of their most magnificent monuments; the Taj Mahal on its bank; but today it has been reduced to a pale and stinking drain. About 57 million people depend on Yamuna River water. With an annual flow of about 10,000 cubic metres (cum) and usage of 4,400 cum (of which irrigation constitutes 96 percent), the river accounts for more than 70 percent of Delhi's water supplies. Available water treatment facilities are not capable of removing the pesticide traces. Waterworks laboratories cannot even detect them. Worse, Yamuna leaves Delhi as a sewer, laden with the city's biological and chemical wastes. Downstream, at Mathura and Agra, this becomes the main municipal drinking water source. Here, too, existing treatment facilities are not capable of detecting pollutants contained by river water. Thus, consumers in Mathura and Agra ingest unknown amounts of toxic pesticide residues each time they drink water. In Agra and Matura districts, the domestic and industrial users produce large quantities of waste products and the waterways provide a cheap and effective way of disposing them. Apart from that, water is discharged in Yamuna from Gokul barrage and Keetham Lake, 28 km upstream from Agra. Mathura refinery lifts raw water directly from Mathura canal, which acts as a feeder source for Keetham Lake. The water, which is released from the refinery, also seems to pollute Yamuna. During dry weather, the flow of Yamuna River consists almost entirely of effluents. The degree of pollution of Yamuna can be assed from an incident recounted below.