Limnological studies on parambikulam Aliyar-project-I Aliyar Reservoir (Madras State), India

Summary

The limnology of a softwater impoundment has been studied. The deep reservoir did not exhibit stable thermal stratification though biochemical stratification was quite usual. Oxygen supersaturations were rare but mostly the surface water was over 50% saturated. Oxygen deficits were noticed but they were not severe. Anoxic bottom condition was noted only once. Low alkalinity, low hardness, low chloride, calcium, silicate were characteristic of this water. nitrate was not detected, but on some days phosphates were recorded. Oxygen absorbed from permanganate was fairly high. Though chemical parameters indicate its oligotrophic nature, plankton composition gives the contrary impression. Blue-greens especiallyMicrocystis aeruginosa occurred almost round the year. Diatoms also occurred throughout the year with two exceptions. Primary production values varied but were high during diatom abundance and restricted by low nutrient levels, low carbondioxide and lower plankton numbers. Vertical and diurnal changes in alkalinity, dissolved oxygen and pH values point to a moderately eutrophic tendency.