As Indian farmers grapple with weakening and erratic monsoons over the recent years, combined with the menace of groundwater depletion, conserving and sustainably managing water resources has become all the more important.
Researchers from three Hyderabad-based institutions have extensively reviewed past studies and experiences on community-based traditional water harvesting systems, known as tanks, and conclude that the benefits of rehabilitating tank water irrigation outweigh the costs in most cases, particularly by increasing groundwater recharge. Other benefits include providing a source drinking water and fish.
They urge upscaling of tank restoration and long-term maintenance with support from the central and state governments while taking into account regional requirements. They also claim that tanks need to be included in an integrated water management policy.
The decline of tank irrigation
Tanks, usually constructed and managed by villagers, are water bodies that can hold enough water to irrigate over 100 hectares of cropland. In this ancient method of water harvesting, tanks collect and store monsoonal rainwater, which is used for drinking and protective irrigation during dry periods. The “irrigation water is supplied to crops through canal distribution systems,” explained V. Ratna Reddy, lead author of the paper and director of Livelihoods and Natural Resource Management Institute in Hyderabad.
Over the past decades, however, their use in irrigation has declined substantially. In 1950-51, tanks were used for irrigating approximately 3.6 million hectares (17 percent) of the total irrigated area in India, but in 2014-15, the share dropped to a mere 1.7 million hectares (2.5 percent). Traditionally, the southern and eastern regions have placed greater importance to tank irrigation followed by the west and the north. In fact, the south had the highest proportion of tanks in use in the country standing at 35 percent in 2000-01 compared with other regions. Regionally, the south and the north both experienced a steady drop in the area under tank irrigation from 1972 to 2008, although there was a slight uptick in the south from 2003 to 2008.
A multitude of reasons were to blame for the drastic decline in tank irrigation over the past decades from policy changes and institutional neglect to a rise in population and the shift towards groundwater.
Before India’s Independence, there were institutional arrangements to protect tanks such as Dasabandam and Kudimaramat of the south and Johads and Pals of Rajasthan and these were supported by local rulers, explain the researchers. However, the British policies viewed irrigation as a source of revenue as opposed to a protective source, which eroded these institutions. In drought-prone regions, neglect coupled with environmental degradation led to silting of the tanks as well as reduced capacities.
At the same time, populations were rising, but the tanks, which were designed only to cater to a small population, “were not able to meet the needs of an increased population,” said Reddy.
Then came the shift to groundwater, fuelled by green revolution technologies and subsidised power, said Reddy. “This has led to private management of water and public policy has conveniently ignored the maintenance of tanks.” As well-irrigation rapidly gained momentum—becoming the single largest source of irrigation—the tanks fell further into disrepair.
With overexploitation, wells started to dry up and recently there has been a revival recognising the value of these ancient systems. But efforts need to be stepped up because less than 10 percent of defunct tanks have been restored over the past two decades, according to Reddy and his co-authors, M. Srinivasa Reddy, assistant professor at the Centre for Economic and Social Studies and K. Palanisami, an emeritus agricultural economist at the International Water Management Institute.
Tanks and groundwater recharge
One of the most pressing reasons for increasing the capacity of tanks is the positive effect they have on groundwater replenishment, particularly in drought-prone regions that are dependent on well-irrigation such as Rajasthan, for example. Although most tanks have the ability to recharge groundwater, percolation tanks which are smaller, enable water to percolate into the underground aquifers during the dry periods.
Indeed, a recent 2018 study from West Bengal has unveiled a strong link between surface tank water and groundwater. The team found that in districts with a high density of tanks, the depth at which groundwater becomes available reduces (when measured from the surface), implying the positive effect of tanks in recharging groundwater levels. Because they are inextricably linked, both Koushik Chowdhury, Ph.D. student and lead author of the study, along with Reddy’s team stress that tank and well irrigation must be viewed as complementary to each other as opposed to substitutes to maintain a hydrological balance. Conjunctive use of both irrigation methods needs to be promoted, assert Reddy and colleagues, stating that they must be managed at the scale of the watershed or river basin.
Tank irrigation does not only benefit those with bore wells such as land-owning farmers. With a larger area under irrigation and more crops produced, “farm activities continue for a longer period in a year requiring more people to work on and hence more employment for the landless labour households,” explained Reddy. And, “in the long run even the small and marginal farmers benefit as they invest in wells as well,” he added.
A percolation tank restored under MGNREGA and Mission Kakatiya of Government of Telangana. Photo from Mission Kakatiya.
Tank water has been a crucial source for drinking water among the poor in the east of India. Since many people and livestock drink water from wells, percolation tanks ensure the availability of well water over a longer period of time. In arid states like Rajasthan, livestock plays a large role in rural livelihoods and the tanks help keep soil erosion in check by reducing runoff. Some farmers in the state even use the emptied tank beds for cultivation and the silt serves as fertiliser for the eroded soils.
In the region of Bundelkhand and in eastern India, tanks have been used for fishing, particularly among poor households, noted Reddy’s team. As their uses vary regionally, they emphasise that tank restoration needs to be aligned with the different stakeholders in order to be equitable and prevent any conflict of interests.
The way forward
The long-term sustainability of the tanks and the resulting benefits boils down to proper maintenance underscore Reddy and colleagues. But despite the host of benefits they provide, “there is no systematic policy to address the problems of tank systems, though some state level or even central policies exist,” said Reddy. Most of these are programme-based activities and are funded by external donors such as the World Bank, he pointed out. “There are no regular and sufficient budget allocations for maintaining the systems.”
Chowdhury concurs, stating that there are no policies to manage tank water harvesting. “Previously, these tanks were treated as wetlands in wetland policy 2012, but in 2017-policy the wetland tags were removed from tanks. This means there will be no control over the encroachment on traditional water harvesting structure.”
Apart from ramping up allocations towards rehabilitation, Reddy’s team proposes that the financing of the tanks should be treated as asset-based planning as opposed to a one-time approach. They suggest that adopting a life-cycle cost approach may help where asset management is included in the cost of the project. “Life-cycle based budgeting is not adopted in India though it is very appropriate for natural resource management programmes (irrigation, watersheds, tank irrigation, etc),” he added.
Also, tank management committees “need to be linked with the constitutionally recognised institutions such as Panchayati Raj institutions at the village level with funds, functions and functionaries,” said Reddy. “This would sustain these institutions and the tank systems in the long run.”
Under the backdrop of climate change, a comprehensive water policy that includes tank irrigation, as well as groundwater and canal irrigation, is needed that considers the varying levels of rainfall forecast in the different regions, concluded the team. This will facilitate the linking of tanks to cope with extreme precipitation events and connecting of tanks with canals to prepare for dry spells. For regions that will experience short bursts of extreme rainfall, the capacity and number of tanks need to be increased, advised Reddy.