Ooty is one of the most important hill stations in Tamil Nadu. It has a beautiful lake located 2.6km from Vannarpet called as Ooty lake.   This lake is more than a century and a half old. It was formed by blocking a maintain stream. It has a shoreline of 5km long and has a maximum depth of 15m.

The Ooty lake receives its water from the surface runoff in the following areas; past larks Hill, St. Mary's Hill, Missionary Hill, Fern Hill and Elk Hill. Besides the above runoff a perennial stream from upper Koddappamund Hills joins the lake. At Ooty the stream joins the Ooty channel which in turn joins the Ooty lake at the south end of the lake. About 2.6 km length of the channel receives almost all the polluting material, which are passed on to the lake. The major pollutants which are receiving from the untreated dairy waste products, unsewered waste water, oil and grease form workshops and sullage from railway colony and near by area joins the channel in large quantities a few metres before its tail end.   Due to the discharge of sullage water in to the lake, the excessive water hyacinth and algal growth in the water body leads to eutrophication. At present the lake water is green in colour and has an algal odour.   Due to the wastewater from the workshops, the south end of the lake water is highly polluted than the other ports of the lake. So we have to adopt source restoration methods to safe guard our existing natural lakes.

The Ooty Lake is more than one and a half centuries old. It was formed by blocking a mountain stream. The lake has a shoreline of 5 km long. It has maximum depth of 15m, but in the innermost parts of the lake the depth is about 6 to 7m. The lake is a huge and renowned tourist attraction. On a lean day it draws about 500 visitors and in peak season the number of daily visitors exceeds 2000. Forty five oar boats and 10 motor boats are at the disposal of the tourists from 9.00 am to 5.00 pm on all days of the year.

The lake receives its water from the surface runoff in the following areas             

•  Part of Larks Hill

•  St. Mary's Hill

•  Missionary Hill

•  Fern Hill

•  Elk Hill.

                Besides the above runoff a perennial stream from upper Koddappamund Hills joins the lake. Until it reaches the Ooty municipal limits at Vannarpet, the stream water is clear and free from pollution. It is even used for domestic purpose in these areas.

                 At Ooty the stream joins the channel, which in turn joins the Ooty Lake at the south end of the lake. The Ooty channel is totally 2.6 km long from Vannarpet to the point where it joins the lake. It is over this 2.6 km length that the channel receives almost all the polluting material, which is passed on to the lake.

•  The Nilgiri District Co-Operative Milk Producers Union Dairy (which handles 35,000 lit of milk / day and also makes by products like butter, ice-cream, cheese, etc ) discharges its wastes in to the channel.

•  CTC workshops discharge oil and grease into the channel.

•  CTC canteen discharges its wastes into the channel.

•  Sullage from Railway Colony, Nazareth Convent etc., joins the channel in large quantities a few meters before its tail end.

•  A broken sewer discharges profusely into the channel opposite to Alankar theatre.

•  There are many unsewered establishments along the bank of channel, which discharge their wastewater into the channel.

•  The Chairing Cross wastewater from a public conveyance joins the channel.

•  As it passes through the bazaar the channel receives pollutants like washings from garages, street washings, garbage, etc.

•  Chlorella

•  Chrysococcus

•  Scenedesmus

•  Phaecus

•  Navicula

•  Synedra

•  Coleps

•  Daphnia

•  Vorticella

•  Coelastrum

•  Melosira

•  Anacystis           

•  Biological Control

•  Physical Control

•  Chemical Control.

5.1 Biological Control

A wide variety of biological methods to control algae have been investigated. These include

•  The use of pathogens (viruses, bacteria , fungi)

•  Control through the feeding activities of grazers

•  Control by the manipulation of inter – relationships among plants, animals and their environment

Biological Methods offer an attractive means of controlling excessive algae. To be successful in biological control, organisms (pathogens and grazers) must have a high rate of survival under    various conditions, i.e.,   able to reduce the population of the problem species and   coexist with other native aquatic fauna.

5.2 Physical Control

Physical Methods of algal control include the mechanical removal of algae (harvesting), application of dyes (light exclusion or limitation), the removal of bottom sediments (dredging) and the use of explosive charges of ultrasonic radiation.      

5.3 Chemical Control

•  The application of algaecides is the most widely used algal control technique.

•  The most popular chemicals are copper compounds especially copper sulphate. Potassium permanganate has been used with success in a few instances.

•  An algaecide should be species-specific, and species selective, non-toxic to other organisms in the food chain, be harmless to humans and aquatic organisms, have no adverse effect on water quality, not accumulate in lake sediments and be inexpensive and easy to apply.

In order to assess the degree of pollution quantitatively the parameters were measured.

•  BOD 5 @ 20 o C

•  COD

•  Permanganate value

•  Dissolved Oxygen

•  Turbidity

•  Total Solids

•  Nitrogen and Phosphorus

•  Oil   and Grease

•  pH

•    Iron   and Manganese

•  Chloride

•  Hardness  

•  Sulphate & Sulphide

•  Bacteriological examination for Water Sample

•  The microscopic   examination of lake water to identify the types of algae present.

•  Total Elimination of External Loading

•  Intervention in the lake ecosystem (aeration, removal of the upper layer of sediment, etc)

7.1 Total elimination of external loading

•  It is imperative that the influent channel feeding the lake is totally free from any sewage, sullage, dairy waste etc.,

• All unsewered establishments should be properly sewered and connected to the existing sewer system.

7.2 Intervention in the Lake ecosystem

  This can be done by the following methods

•  Aeration of water

•  Diversity of hypolimnic water

•  Precipitation   of phosphorus in the lake

•  Aeration of sediment

•  Removal of sediment

•  Covering of sediment

•  Direct reduction of biomass concentration in the lake.

7.2.1 Aeration of Lake water

   Oxygen Depletion occurs in the hypolimnion due to the decomposition of organic matter.

Some aeration methods are

•  Destratification, where the cold hypolimnic water is pumped to the surface and mixed with the warm epilimnic water.

•  Pumping of hypolimnic water to the surface, where it is aerated by contact with the atmosphere and transported back to the hypolimnion.

•  Aeration directly into the hypolimnion.

7.2.2 Diversion of Hypolimnic Water

Hypolimnic water is rich in nutrients and poor in oxygen. By replacing the epilimnic water with hypolominc water, the nutrient and oxygen balance should improve.

7.2.3 Precipitation of Phosphorous in the lake

Phosphates in the lake can be precipitated by the use of aluminum sulphate

7.2.4 Direct reduction of the bio mass concentration in the lake

In hyper eutrophic lakes the primary production of the bio mass is significantly higher than grazing which means that the major flow of organic matter is through respiration and the cycle “primary production detritus mineralisation” dominates food chain recycling.

7.2.5 Aeration of Sediments

The principle of sediment aeration is the same as described under aeration of hypolimnic water

7.2.6 Removal of Sediment

The storage of exchangeable phosphorous in the sediment may considerably delay the   restoration phase, especially for shallow lakes with a long water retention time

7.2.7 Covering of Sediments

Covering of Sediment will prevent the release of nutrients to the water body.

The hill stations in India are a legacy of British rule. We have not added to the list of hill stations after independence, but the worst part is that we have allowed the existing hill stations to deteriorate. Ooty is no exception to this.

The present condition of the lake is a mute testimony to the deterioration of the quality of the environment in this hill station. In view of improving the environmental state of the lake and the hill station, the following considerations should be adopted

•  The quality of the lake water should be monitored fortnightly for important parameters like DO, BOD, COD, oil and grease, turbidity etc.

•  Any sudden deterioration in quality should be viewed seriously and measures must be taken to locate the source of pollution and prevent it.

•  The restoration methods suggested should be implemented.

•  Educating the   public on the need to maintain a clean environment is important.

•  The traffic condition (operation of boats) of the lake should be improved.

•  Entry of the materials containing nitrogen and phosphorous should be prevented. Unless eutrophication is arrested immediately, the lake may end up as a marsh.

A concerned effort to make the channel and the environment clean is indeed the need of the hour.

•  Raman.K.Raman (1985), Controlling Algae in W/S Impoundments, Jour. AWWA,

•  R.A.Ferrera and M.A.Dimino (1985), A case study Analysis for Seasonal Nitrification: Economic Efficiency and Water Quality Preservation, Jour. WPCF.

•  David.A.Belta (1970), D.O.Variations in Stratified Lakes, Jour. ACCE, Env. Engg. Division, October 1970

Govt. College of Technology,
Coimbatore – 641 013.
Tamil Nadu, India.
E-mail: basanthi_coim@yahoo.co.in