CONTENTS-
Abstract
Introduction
Lakes
Sampling
Results
Acknowledgement
Appendix

Lake ecosystems are an integral part of the Bangalore city. Lakes in Bangalore were mainly created to serve the need for drinking and agriculture. But unplanned urbanisation and industrialisation has lead to the contamination of these water bodies. Varthur lake, situated in south Bangalore has a water-spread area of 2.5 sq. km. The lake water is mainly used for agriculture and supports a wide diversity of flora and fauna. The inflow of sewage and agricultural runoff in addition to the inflow of contaminated water from Bellandur lake has led to the rapid deterioration of the lake. As the contaminated lake water is used for irrigation purposes, it is essential to assess the soil quality in and around lake. Various physico-chemical soil parameters were analysed using standard methods and the results are discussed in the paper.

Bangalore's topology is full of valleys and ridges and lot of lakes. There are no rivers flowing through it. People from all walks of life following different culture,   speaking different languages and from equally different strata of economy blend into the community here. Whoever visits Bangalore once will always long to settle down here, because the weather conditions, the greenery and the hospitality of the Kannadigas attract them.

Bangalore city is the capital of Karnataka with a population of 42 lakh people. It   was founded by Magadi Kempe-Gowda in 1550's. It has the distinction of being called “THE GARDEN CITY”. Now it has been christened as “SILICON CITY”.

  An adequate water supply is   a matter of life or death, not only for human beings but also for every form of animal and plant life from the lowest   Amoeba to the tallest Redwood tree. A man would soon die if he lost as little as 15 percent of his body's water, and almost every organism is heavily dependent on water, as more than 50 percent of its body weight is made up of water.

The need for water increases almost daily as population grows. But it is increased economic development that places the greatest demand on the water supply. Water is often unavailable in either sufficient quantity or quality in many areas of the world.

Lakes are integral part of the hydrologic cycle, short-lived features of the terrain, which begin to die the moment they are created. Many lakes die of an excess of sediments and and gravel settled in the bottom, slowly turning the lake into a mud flat or swamp and finally filling the lake entirely.

From Bangalore city, about 18 kms towards south is a lush green serene typical countryside village called “VARTHUR” with a population of about 15,000 people. The village attracts many a passer by because of its large lake called the “Varthur Lake” spread over an approximate area of 2.5 sq.kms. The road from HAL Airport, which leads to Varthur winds over a tank bund on this magnificent lake, the drive is such an exhilarating experience that you forget that you are in Bangalore.

But the burgeoning human population, the concentration of people in cities, unscientific and unplanned urbanization, growing complexity of farming and manufacturing process often burden lakes and rivers beyond their self cleansing capacities. The lake is polluted by   the phosphorus and nitrogen compounds used in laundry, detergents,   fertilizers and other activities in the catchment area.

In the catchment area of the Varthur lake, intense agricultural activity is seen. Paddy, vegetables, flowers and coconuts are some of the crops grown here. As the contaminated lake water is used for irrigation purposes, it is essential to assess the soil quality in and around lake. Various physico-chemical soil parameters were analysed using standard methods and the results are discussed in the present paper.

About 1 kg of representative soil samples was collected from six different places around the catchment area of the lake. For convenience, the samples were labelled A,B,C,D,E   and F. All the samples were air-dried for two days. The same was taken to the lab for testing. Different physico-chemical parameters were analysed according to standard methods. The result obtained is presented in the Appendix.

The analysis shows that the pH of all six samples are between 7.1 to 7.8. The pH of soil is normal and is considered optimum for paddy crops.   Conductivity shows that the soil contains more of soluble salts. Because of the presence of more salts the major nutrients get converted into the un-available form. Over a period of time, due to enormous accumulation of salts, the soil properties   will change.   For example, drainage capacity of the soil (porosity) will get reduced and the water holding capacity will increase.

Water holding capacity of all samples is very high. It indicates that the soil is less porous, because of which it retains water. Analysis of chlorides shows that the presence of chlorides ranges from 0.35mg/g of soil to 0.88 mg/g. This indicates the presence of chlorides in excess, which may ultimately lead to chlorine injury in plants.

The Varthur lake is highly polluted by sewage water. The sewage water contains nitrogen in the form of urea, uric acid.   Upon using this contaminated water over a period of time the level of nitrogen in soil increases to the abnormal level. It may cause ammonia injury as well as   the Paddy crops may become susceptible to endemic pest diseases.

In Varthur, the farmers use lake water for irrigation. The water is highly enriched with nitrates and phosphates. If the same water is used for cultivation because of the high concentration of the nitrates, plants do grow well but the yield will be very less. So our sincere request to government of Karnataka as well as to environmentalists, farmers and Varthur people   to conserve the lake.

We are thankful to Dr.T.V.Ramachandra and Miss Ahalya   from IISc.,   Mr.M.A.Khan,   Mr. M.K.Khan, Mrs. Alli Rani, Mrs.Noor Fathima, and   Mr. Masood Ahmed     from Varthur High School and Mr. M.Z.Khan,    Lecturer Environmental Science,     Government PU College, KGF for helping and guiding us to complete this project successfully.

Parameters analysed for soil samples from the paddy fields near Varthur lake.

water holding capacity   %

A      11.67%

B      38.6%

C     31.46%

D    21.27%

E    19.76%

F    14.4%

Moisture content %

A      32.13%

B     23.22%

C     30.2%

D    33.03%

E   28.24%

F    29.70%

Chlorides(mg/g)

A 0.35 mg/g

B 0.43 mg/g

C 0.58 mg/g

D 0.71 mg/g

E 0.53 mg/g

F 0.88 mg/g

K.K English High School Varthur,
Bangalore – 560 087,
Karnataka. India.
Phone: (080) – 8538051