The climate change experienced in recent years has not only changed the rainfall pattern but also accentuated water scarcity across India. In many parts of Tamil Nadu, for instance, people meet their daily needs by paying ₹10 for a bucket of water. The data released by the Ministry of Water Resources indicate that the demand for water will exceed supply by 2050 due to increased requirement for industry and agriculture. As the un-utilised water resources is shrinking at a faster pace, there is a need to renovate and rebuild existing small water bodies (tanks, etc), especially in Tamil Nadu where water scarcity is rampant already.

Benefits of tanks

Unlike in the northern States, tanks have been the main water source of Tamil Nadu for centuries. The State has a total of 41,127 tanks with a total storage capacity of 347 tmc (thousand million cubic feet). This is more than the total water storage capacity of all the dams in Tamil Nadu. Therefore, the State’s water scarcity cannot be solved without tanks. Although tanks are small in size, the benefits they provide are huge.

Due to the presence of tanks in all parts of Tamil Nadu, water is provided at a low cost for all purposes — drinking, domestic needs, animal husbandry, and irrigation. Unlike large dams, tanks are easy to manage due to their small size. The maintenance cost of tanks is also very low as compared to canal irrigation.

Unlike canal irrigation, conflicts between tail-end and head-reach farmers are negligible under tank irrigation. Since tanks are the main source of irrigation for resource-poor small and marginal farmers, they help improve their livelihood. Increased storage of water in tanks helps in recharge of wells, reducing the over-exploitation of groundwater. The tanks located in every village prevent women from having to walk long distances to fetch drinking water.

Present status

The tanks which have been meeting the water needs for a long time are now rapidly disappearing. Analysis carried out using time-series data suggests that changes in rainfall patterns cannot be the main reason for defunct tanks. Due to continuous encroachment in the catchment areas including the water-flow channels that carry rainwater to the tanks, their water storage capacity has declined, resulting in a sharp decline in the area irrigated by tanks.

India’s tank irrigated area in 1960-61 was 46.30 lakh hectares (lha), which declined to 22.05 lha in 2021-22. During the same period, the tank irrigated area in Tamil Nadu decreased from 9.36 lha to 3.99 lha (see Chart 1). Most of the farmers who are cultivating crops using tank irrigation have left agriculture. Surprisingly, the tank-irrigated area in Tamil Nadu has not increased even in years with above-average rainfall.

One of the main reasons for vanishing tanks is rapid urbanisation that has led to encroachment of water-spread area for construction of buildings. The Central Government’s Standing Committee on Water Resources, in its 16th Report on ‘Repair, Renovation and Restoration of Water Bodies’, has stated that municipal and panchayat bodies have mostly encroached upon tanks for construction and other purposes.

India’s Fifth Minor Irrigation Census (2013-14) reports that of a total of 5.92 lakh tanks and small water bodies in India, 72,853 are defunct due to poor maintenance. Similarly, the First Census of Water Bodies published by the Ministry of Water Resources in 2023 states that 38,496 water bodies (mostly small ones) have been encroached upon in India. As many as 7,828 water bodies have been encroached in Tamil Nadu alone. As a result, the share of tank-irrigated area to net-irrigated area has consistently declined from 38 per cent in 1960-61 to 14 per cent in 2022-23 in Tamil Nadu (see Chart 2). The unprecedented water scarcity experienced now in Tamil Nadu is partly due to the neglect of tanks.

Pointers for the future

To face the challenges posed by climate change, immediate steps are to be taken to repair, renovate and restore the tanks to increase their storage capacity. Encroachments on catchment areas and water-flow channels should be removed, facilitating rainwater to flow unhindered to the tanks. Respecting the judgment by the Madurai Bench of the Madras High Court on September 6, 2014, the government should ban all construction activities in places where tanks are located.

Due to poor storage of water in tanks, groundwater continues to be over-exploited for agriculture and drinking water needs. The data from the Central Groundwater Board (March 2020) show that of the 1,166 blocks in Tamil Nadu, 723 are classified as over-exploited. Therefore, it is necessary to increase water availability from tanks to reduce the exploitation of groundwater.

In the past, under the ‘Kudimaramathu’ scheme of the Tamil Nadu government to renovate tanks, emphasis was given to increasing the water storage capacity by removing silt from the tanks’ basin. Emphasis must, therefore, be given to repairing the water-flow channels blocked by encroachments.

To increase water retention, tanks also need to be renovated regularly by allocating adequate funds. Some corporates are involved in renovating tanks under the corporate social responsibility scheme. If the government joins hands with them in modernising tanks, the overall performance of the tanks can be improved.

Due to climate change, India received below-average rainfall in 17 of the 32 years from 1990 to 2021. Some have warned that rainfall may decrease due to climate change, further exacerbating water scarcity in States like Tamil Nadu, which has now the lowest per capita annual water availability (750 cubic meters) among the major States (1,544 cubic meters). Therefore, measures are needed to repair and restore all the tanks to increase their storage capacity and reduce water scarcity emanating from climate change.

The writer is former full-time Member (Official), CACP, New Delhi. Views are personal