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In The Arid Region of Alagoas, Where The Average Annual Rainfall Barely Exceeds 400 Millimeters, Farmers Are Managing To Produce Food All Year Round Thanks To Subterranean Dams, Simple And Effective Structures That Store Millions Of Liters Of Water Beneath The Ground And Transform The Dry Soil Into Fertile And Productive Areas.
The semi-arid region of Alagoas experienced an atypical rainfall period between late 2022 and early 2023, driven by the La Niña phenomenon. Still, local farmers like Dona Valdilene know that this scenario is temporary. To cope with long periods of drought, the alternative has been to invest in climate-compatible solutions, such as building subterranean dams.
These structures function like an “invisible water tank: they are dug into the ground and lined with high-strength plastic sheeting, which prevents rainwater from evaporating quickly. Moisture remains in the soil for up to five months, supplying crops of sweet potatoes, beans, passion fruit, spring onions, cilantro, among others.
The farmer’s farm, which was previously unproductive, now maintains a fertile area of 1.5 hectares with constant production. Even a 10-year-old cashew tree, which had never borne fruit, began to produce with the presence of stored water.
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Dam Changes Routine in The Field and Reduces Migration
Another success story is that of farmer Lenildo do Nascimento, who abandoned seasonal work in other states and settled permanently on the land where he was born. With the support of Senar, he built his own subterranean dam and became less dependent on rain to feed his animals and support his family.
Milk production also gained strength with the cultivation of silage irrigated by water from the well generated by the dam. Lenildo reports that in good years, he sells up to ten goats per year, a number that drops to three when the drought is severe. The dam ensures enough food for the goats to come into heat and maintain production.
The construction of the dam takes about four days and considers technical criteria such as soil type, relief, and drainage network. The zoning done by Embrapa in 2019 mapped the entire state of Alagoas, identifying areas with high, medium, and low potential for implementation.
An Ancient Technology Adapted To The Brazilian Sertão
Subterranean dams are not new. There are records of their use dating back to before the Empire in Brazil, and also in countries like India, Argentina, and regions of Africa. The modern version with plastic sheeting was developed in the 1980s by Embrapa, becoming an efficient, functional, and low-cost solution.
Each dam can cost around R$ 30,000 and has the capacity to store up to 25 million liters of water — as in the case of Seu Dedé, another farmer in the region, who built two structures on his property, totaling about 100 million liters accumulated.
The presence of water transformed Seu Dedé’s property into a national reference. Farmers, researchers, and visitors from all over Brazil and even from 22 countries have already signed the farm’s visitor book.
Technical And Social Support Expands The Initiative’s Impacts
The Senar is one of the main responsible for spreading the technique in the state, with more than 200 dams already built. In addition to donating the structure, the institution provides beneficiaries with guidance on management, maintenance, and sustainable water use.
According to agronomist engineer Fernando Vieira, the secret to efficiency lies in soil with low slope, presence of clay, and suitable geology. The infiltrated water remains in the subsoil, prevented from evaporating, and can be accessed by wells or pipes installed at the base of the dam.
This information was disclosed in a report by the Globo Rural program, with additional data from Embrapa specialists and Senar technicians who monitor the projects in the field.
Have you ever imagined that a hole in the ground can store millions of liters of water and ensure abundance in the sertão even without rain? How is this technology currently functioning in rural communities?
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