The studies on the ecology of Indian freshwaters have been very few . Some valuable work has however been done in recent years on smaller freshwater bodies by IYENGAR (1940), GONZALVES & JOSHI (1946), GANAPATHI , PHILIPOSE (1960), ZAFAR (1959 ' 67), SINGH (1960), GEORGE (1962 '66), SITHARAMAIAH (1965) and KHAN & QUAJJAM (1966) . These reveal the diversity and complexity of the ecological phenomena and made one feel the necessity of much more data, particularly on ionic composition and the behaviour of basic elements, to give a clear understanding . It was with this in mind that the present study, which spread over a period of two years, was undertaken . Three ponds subjected to diverse causes of pollution lying in the vicinity of Hyderabad (540 m above mean sealevel) were selected for this purpose .
Factory Pond
It had an area of 0.0148 km 2 and a maximum depth of 2 .0 meters . The water level rose by about a meter in the monsoon season. An artificial bund formed the northern margin of the pond and a good number of rice fields, lying at its northern side, extended up to a distance of three km. It supported a thick growth of Eichhornia crassipes (MART .) SOLMS, which covered its entire surface during winter and early part of the summer season . The pond, locally known as Nagmaiahkunta or Nallakunta, was designated as Factory pond since it was surrounded by many factories which dumped *Part of the thesis approved for the Ph .D. Degree of the Osmania University 1969 .