Nagabhushan Charantimath
Abstract
Lotic and lentic water ecosystems play vital role in balancing the natural environment. The boundaries of lentic water body are subjected to change seasonally. Manipulation of reservoirs by anthropocentric causes such as setting up hydro-thermal plants, various types of industries, discharge of sludge and other commercio-domestic intervention disturbs the natural habitats. Tungabhadra reservoir is located at coordinates 76° 21' 10" E and 15° 15' 19" N irrigates the neighbouring agricultural land and generates 72 MW capacity hydro-electric power from the erected plant. At the full level of 497.7 m above Mean Sea Level, the reservoir extends over 37,814 ha. The hydrological parameters were assessed within the period between (2011-12 and 2019-20). The mean values of air temperature, water temperature, turbidity, TDS, TSS, Electric Conductivity, Total alkalinity, COD, BOD, Dissolved Oxygen, Sulphates, Nitrates, Phosphates, Calcium, Magnesium, Iron, Fluoride, Free carbon dioxide, pH, Chloride and total hardness were compared with the same parameters approximately a decade ago. The results showed wide range of fluctuation in EC (38 to 342.50), increased BOD from 2.25 to 3.25 mg/l, high DO of 5.93 mg/l, sulphates 37 to 65 mg/l, less concentration of Nitrates from 2.05-2.55 mg/l, Calcium. 27.25-33.75 mg/l, Magnesium 7.13-11.28 mg/l, relatively high levels of Iron (1.63-3.25 mg/l), high levels of Fluoride (0.4-0.68 mg/l), wide range of Carbon dioxide (1.4- 1.6 mg/l), sub-alkaline pH from 8.08-8.48 and total hardness from 75-98 mg/l. Four phytoplankton groups; Desmidaceae, Bacillariophyceae, Chlorophyceae and Cyanophyceae and five zooplankton groups; Protozoa, Rotifera, Cladocera, Ostracoda and Copepoda were enumerated at genus level. The immense water spread area of the reservoir and diluting nature of the lentic water ecosystem has retained all the hydrological parameters within the permissible limits of CPCB and BIS. The promising potentiality of Tungabhadra reservoir still attracts many fishermen for both capture and culture fishery.