Reviving the traditional tank irrigation systems of Andhra Pradesh

The tank irrigation systems of South India

Tank irrigation systems have been used since times immemorial to cultivate crops in India, primarily paddy, and are found in high numbers in the South Indian states of Andhra Pradesh, Karnataka, Tamil Nadu and Telangana accounting for 20–30 percent of the total net irrigated area in several districts. Tanks provide livelihood protection to rural populations and the irrigable capacity (command area) of each tank is between 50 and 250 ha. Despite the benefits they provide, India’s total irrigated area from tank sources has declined by around 59 percent from 4.56 million hectares (m ha) in 1960–61 to 1.89 m ha in 2013–14. 

However, tank irrigation is still prevalent in the states of Andhra Pradesh, Karnataka and Tamil Nadu. The net tank-irrigated area accounts for 13.30 percent in Andhra Pradesh, 16.57 percent in Tamil Nadu and 6.16 percent in Karnataka of the total net irrigated area of 28.79, 26.72 and 40.32 m ha respectively according to 2019-2020 figures.

Marginal and small farmers still face difficulty growing crops due to the loss in tank-irrigated land since they cannot afford to use groundwater. A persistent decline in tank performance may cause water shortage and the total disappearance of eco-friendly water sources, notably affecting marginal and small farmers. 

This study titled 'Tank performance and its impact on rural livelihoods of tank commands in Andhra Pradesh, India: a spatial analysis approach' from Current Science looks at two different tank irrigation systems, viz. non-system tank in Chittoor district and system tank in Srikakulam district, Andhra Pradesh and aims at:
•    Evaluating the general characteristics of the non-system and system tanks in the area
•    Understanding factors influencing performance of system and non system tanks

What are system and non system tanks

Tanks are hydraulically interconnected systems that are organised into a cascade or chain pattern, with the surplus from the upstream tank feeding tanks downstream. When they are supplied by a channel diverting water from a river, they are called 'system tanks' (ST). Tanks that are filled only by rain, runoff and/or surplus water are called 'non-system tanks' (NST). Water in the tanks is treated as a collective resource, to be shared by all farmers in the villages, which calls for cooperation and set rules within and between village. 

The study

The study evaluated the performance of system and non system tanks from Srikakulam district of the North Coastal Andhra region and Chittoor district of the Rayalaseema region.

Non-system tank

The command area of the tank from Srikulam was 168.22 ha, spread across 540 farm households. Therefore, a single farmer would have only 0.31 ha of land to produce and support his/ her family. The tank had only one filling and 40 percent of siltation and 20 percent of encroachment in the foreshore region reduced water availability during the crop season to just 60 days (with good rainfall).

Reliance of the command area on rice agriculture and a small area devoted to groundnut production (dryland) resulted in perilous conditions due to inadequate maintenance, lack of inputs and decreased water availability. The tank received water storage with the start of good rainfall, which lasted just 3–4 months and farmers thus had to rely on groundwater irrigation by digging additional wells to overcome the water scarcity.  The number of wells in the command area increased from 100 to 200 in the last 30 years with each well meeting the water needs of 2–3 farmers.

System tank

The command area of the system tank from Chittor was 208.77 ha shared by 485 farmers. During a crop season, the tank water supply was more, and water was accessible for 120 days (4 months), which was significantly more than that available in the non-system tank, but lesser availability of water for irrigation as compared to 10 years back.  Encroachment (40 percent) on the shoreline and siltation (25 percent) of the water spread area affected the overall amount of water available.

While encroachment was a problem, siltation was lesser than in a non-system tank and farmers had to use  micro-irrigation to overcome irrigation water shortages to reduce crop failures and yield losses due to the lack of water. 

System tanks performed better as compared to non system tanks

Encroachment and siltation were lower in the system tank due to proper maintenance and operation in the tank bed and foreshore area. Farmers felt that there was an increased siltation problem in the non-system tank as a result of social forestry.

The existence of formal or informal water user groups (WUAs) and the availability of financial resources facilitated the repair and maintenance of tank beds and enhanced the water spread area, hence reducing encroachment and siltation levels. Also, multiple cropping patterns and farming methods help farmers diversify their income and use the water in their tanks more efficiently.

The study makes the following recommendations:

• Optimisation of tank water resources between the non system and system tanks with effective measures of desiltation and encroachment to improve tank performance and the livelihoods of tank command area farmers. 
• Sustainability in water use by carefully using tank water supplemented with subsidised microirrigation sources. 
• Inclusion of major areas under less water-intensive crops (coarse cereals under the non-system tank and pulses and millets under the system tank) to help mitigate water scarcity in the command areas of the tanks.
• Check on social forestry, which was found to be another factor that posed a heavy siltation challenge with the reduction of water storage capacity in the non system tanks. 
• Effective desiltation measures with participatory water management to improve water storage capacity and filling pattern, while proper maintenance of supply channels for equitable distribution of tank water across the tank command area farms under both tank systems. 
• Human-induced factors like encroachment in the foreshore area and tank bed to be mitigated by imposing serious penalties and pricing under the surveillance of the Irrigation Department officials of the concerned tanks. 
• Strengthening Water Users Associations (WUAs) will benefit the command area farms to avoid demand–supply gaps, encroachment problems, improving the number of water availability days and particularly improvement in the socio-economic structure of tail-end farms under both tank systems.