The quality of water in Yamuna river in Delhi has turned from bad to worse. Many projects undertaken under the aegis of state and central governments, NGOs and locals have hardly made a dent in the pollution level. A study was undertaken at the Wazirabad barrage, Delhi, to compare some simple indices of water pollution at two sites, before and after the river is contaminated by the 'Delhi pollution'. It was observed that all the six physico-chemical indices and one biological parameter used to assess water pollution were found to be many times higher than the normal. The salient results of water tests after the river's entry into Delhi were: Hardness- 40mg/ml, Alkalinity - 400 mEq/l, BOD - 53.84 mg/l, pH - 7.6, Chlorides - 283.7 ppm and Conductance at 0.954 mn siemen. The microflora status of polluted water was about 100 times worse than 'clean' upstream water. The various recommendations and steps that must be taken to prevent and control pollution are suggested.

KEY WORDS Yamuna, River, Water pollution, Delhi, BOD, Alkalinity, Conductance, Chlorides, Microflora

INTRODUCTION
(1) Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans), by various chemicals, toxins, pesticides, sewage, industrial waste or micro-flora (e.g. bacteria and parasites). It occurs when pollutants are directly or indirectly discharged into water bodies without treatment to remove harmful compounds. Water pollution affects the entire biosphere-plants and organisms living in water, damaging individual species, entire populations and natural biological