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Session 4Limnology of Lakes, Reservoirs and Wetlands

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Chairman: Dr. Chakrapani B. K.

Rapporteur: Sudira H. S

Environmental Aspects of Lake Water and its Quality Management

Sukumaran K.

Address

Water is a renewable resource, which is naturally recycled in the hydrological cycle. Surface water has a short residence time compared to groundwater and the storage of surface water is contained in water bodies like reservoirs, lakes and ponds. Pollutants discharged by human activities pollute water bodies, which has severely degraded the water quality. The quality of water is affected by natural factors such as minerals in the water, geometry of terrain and the climate of the region. It is essential to restore and maintain the physical, chemical and biological integrity of water bodies to achieve the required water quality, which ensure protection and propagation of fish, wildlife, plants and also envisage recreation in and on water. The ranges of pollutants discharged into surface water bodies are domestic sewage, industrial wastewater, agricultural runoff, stormwater etc. 

More oxygen demanding wastes are prominent pollutants of lakes. Presence of phosphorus in toxic chemicals discharged by industries dominates pollution of lakes. Knowledge of lake system is essential to know the role of phosphorus in polluting lakes. Lake water in the temperature zones become stratified during summer and overturn in the winter due to changes in water temperature. Lakes contain several distinct zones of biological activity, euphotic, littoral and benthic. In euphotic zone, plants produce more oxygen by photosynthesis. In littoral zone, with shallow water, rooted water plants grow. Lake bottom zones with sediments becomes fertile. All algae require macronutrients such as carbon, nitrogen, phosphorous and micronutrients such as trace elements. 

Among the other available nutrients only phosphorous is not readily available from atmosphere or natural water supply. The amount of phosphorous controls the quantity of algal growth and productivity of lakes. The phosphorous concentration should be below 0.010 to 0.015 mg/L to limit algal blooms. Phosphorous is contributed from municipal and industrial wastewater and agricultural runoff, as it is plant nutrient and ingredient of fertilisers. Acidification of lakes due to carbon dioxide to form carbonic acid, which makes the lake water acidic and harm fish. Control of acidification of lake water is related to control of atmospheric emissions of sulphur and nitrogen oxides. India being an agriculturally oriented country, the importance of lake water contribution as potential of minor irrigation is substantial. The surface water potential of India is high; but its utilization is one of the poorest as its share is only 20% of the available resources. The evaporation loss of surface water in India is 57.1%, which is significant in terms of economy and natural resources of surface water. Annual evaporation losses from reservoirs in India vary between 150 200 cm except in states of extremes i.e., Rajasthan and Jammu and Kashmir whose figures are 300 and 50 cm respectively. The irrigated area in India as per 1996 data was only 33.59% of the total arable land and land under permanent crops in the country. The estimated mean annual rainfall in the country is 1194 mm. The paper highlights the need for proper watershed management and also for water supply and irrigation. Discussion and conclusions are drawn in emphasizing the significance of surface water preservation from pollution and its optimal use and safe utilization.

Address: Department of Civil Engineering, 
Adhiyamaan College of Engineering Hosur, Tamil Nadu, India
Phone: (04344) 560575

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