Every year, India faces water scarcity due to delayed monsoons and inadequate rainfall in certain places. This has resulted in deaths due to water scarcity and water-borne diseases.

Historically, tanks and lakes were an important source fulfilling water demands of the population. Kautilya’s Arthashastra (1) (4th century BC) gives copious information regarding the construction of dams, canals, management of canal water, including exemption from tax. Rules for the location of tanks were also outlined. According to the Smriti’s (2), persons who breached tanks were given the death penalty by drowning in the tank water.

Earth dams as  well as mansonry dams were constructed in very large numbers, in tens of thousands, from the 2nd century to the 17th century. The dams were constructed across the same river, one below the other, as well as across its tributaries. One such series of tanks in Mysore had no fewer than 1,200 inter-dependent tanks. The total numbers of tanks in Mysore was 37,000, the largest of which had a surface of 40 sq.kms.(3)

There were 43,000 tanks in Madras which were functioning in the 19th century; 10,000 tanks were in disrepair.(4) The area irrigated from these tanks exceeded 14,15,000 hectares. In Madhya Pradesh, there were 50,000 small private tanks which irrigated 2,62,600 hectares(5). About 3,25,000 hectares of land were irrigated before the British occupation of India.

After the British came to India, between 1836 to 1866, irrigation works at the deltas of the Godavari, Cauvery, Krishna and Ganges were implemented. Canal systems were built in Bengal and Bombay regions.(6) By 1900 AD, the total area irrigated (from all sources) was 13.4 million hectares, of which 4.5 million hectares was from productive and protective (irrigation) works and 3 million hectares was from minor works like tanks. Canals irrigated about 45% of the area, wells irrigated 35% and tanks irrigated 15%  and others 5% of the area.(7)

These figures clearly show tanks, lakes and wells being important source of water supply. But in recent times, they have been dissapearing one by one. According to the Survey and Settlement Records of the Government prepared in the early 1930s, there were 937 lakes, tanks and waterbodies in Bangalore. The area of the tank-bed of these waterbodies was 26,468 acres. But today the area lost in the tank beds is 2,500 acres, according to a preliminary survey by the Survey and Settlement and the Revenue Department.

According to a report in The Times of India (5 July 2009), there were 264 lakes in 1970; now they are 84. In January 2000, the Bangalore Development Authority breached a 32-acre lake, Arakere Tank bund, to make a road.The Chikkamaranahalli tank, Malady tank, Miller tank all dried out. After the tanks dried out, their land was used for different constructions and other purposes.

Mr. Umesh, Assistant Executive Engineer, Lake Development Authority, Bangalore, in a radio programme on “Lake Restoration”(8), said, “There were 182 tanks in Bangalore. Only 81 of them have survived. As the city grows, the tanks disappear. A sports complex has replaced the Koramangala tank. What was once known as Chalaghatta Kere (tank) is now a golf course. The present day Kempegowda Bus Stand in Subhashnagar has replaced a huge tank. Whenever we attempt to build something, our eyes first fall on tank space. People don’t prevent it because it is done for their convenience. Such demands and developments make tanks disappear.”
                         

Udaipur city, Rajasthan, is surrounded by the Aravalli hills and five lakes - Pichola,  Fatehsagar, Rangsagar, Swaroopsagar and Dudh Talai. Of these, it has been estimated that the capacity of Pichola is reducing every year by 0.93 percent, and that of Fatehsagar by 1.16 percent. The Dal Lake (Srinagar) has shrunk more than 15 km over the last 60 years.

Drying up of lakes and tanks is a major problem, as it affects the hydrological cycle. Small ponds are formed when rainfall gets collected in small pockets. These not only provide water directly, but seep into the soil and increase the level of the ground water table. Due to this, water can be extracted using wells. But nowadays, as grounds are being levelled due to urbanization, water is flowing as “run-off” instead of seeping into the soil. This reduces the ground water table, inturn resulting in drying up of tanks.

Further, tanks are being polluted by letting sewage and industrial effluents into it. Solid domestic waste amounting to 20-25 tonnes per day is also dumped close to the lakes in Udaipur. According to a report by Pradeep Shrivastav, Reader, Department of Liminology, Barkatullah University, Bhopal, the bacterial load in the lakes (of Bhopal) has shot up 20 times between 1985 and 1993, pointing towards the degradation of water quality due to organic waste.

Some of the major causes for disappearing tanks are: 

- Unchecked extraction and blocking of inlet ducts

- ‘Eutrophication’ due to industrial effluents and agricultural wastes

- ‘Siltation’ of tank bed

- Drying of tanks for construction purposes

- Encroachment of dried tank lands

- Deforestation resulting in loosening of soil

- Dumping garbage and sewage into the tanks

- Growing of weeds in the tank making it useless. 

All this has led to flooding of cities during heavy rains, scarcity for drinking water, water borne diseases, damage to aquatic life.

Saving the tanks and lakes must be utmost priority. Dying and contaminated tanks must be restored. Some restoration methods(9) that could be employed are:

1] Total elimination of external loading: this means that the channel feeding the lake is totally free from any sewage, sullage and dairy waste etc. All unsewered systems should be properly sewered.

2] Aeration of lake water: Pumping of hypolimnic water to the surface, where it is aerated by contact with the atmosphere and transported back to the hypolimnion. This is required for reducing oxygen depletion in the hypolimnion due to decomposition of organic matter.

3] The quality of lake water should be monitored by measuring at fornightly intervals important parameters like DO, BOD, COD, oil and grease, turbidity etc. 

4] Entry of materials containing nitrogen and phosphorus should be prevented. Unless eutrophication is arrested immediately the lake may end up as a marsh.

Besides, weeds and silt deposits in tanks should be removed, planned constructions should be implemented, and rain-water harvesting should be practiced. Educating the public on the need to maintain a clean environment is imperative.

Singapore can serve as an example. The Singapore government(10) has invested more than 5.0 billion Singapore dollars (3.45 billion US) to build water-related infrastructure over the past seven years, including four plants that recycle sewage water for homes and industries.
A 7,000-kilometre (4,340-mile) drainage network directs rainwater to 15 reservoirs. A 48-kilometre (29.76-mile) underground tunnel system will feed sewage water into the facility, capable of treating 800,000 cubic metres (176 million gallons) daily.

Ravi Narayan, advisor to Argyam, opines: “Singapore once had problems with the Singapore River, which got mixed up with sewage. But they restored it. Much of it through governance, unlike policies here that change from one budget period to another.”(11)

It is high time that people and government realize the gravity of the situation and address the issue of dying tanks. Otherwise, future generations will have to face large scale water scarcity.

References

1] Kautilya Arthashastra, edited by R.P.Kangle, (2.1.20-23)(3.9.33-34)
2] Manusmriti(9.274), Yagnavalkyasmriti(2.20.233), Vishnusmriti(5.15)
3] Sankey, R.(1896), Discussion on paper by Pennycuick, J. "Diversion of Periyar".
4] Smith, R.B.(1856), "Irrigation in Southern India".
5] Buckley, R.B.(1905), "Irrigation works of India".
6] Ibid.
7] Report of Indian Irrigation Commision (1972)
8] Environmental Information System (ENVIS), Government of India
9] Meenambhal.T (2002), "Pollution of Ooty Lake and Restoration", Lake 2002 (Symposium On Conservation, Restoration and Management of Aquatic Ecosystem)
10] "Singapore Becomes a Model for Water Technology and Reuse"(July 8, 2009), Agence France Presse.
11] Times of India (5 July 2009)

The author is a student of civil engineering, Mysore