In 2023, each dollar invested by Embrapa in technology generated a return of US$ 2.27 to society. Farmers who adopted the technology had an average increase of 375 kg in production per year, which generated extra income of over R$ 7000 per hectare. The Brazilian Semiarid region, once originally unsuited for agriculture, has become a productive crop area due to underground dams. Economic impacts were evaluated from two aspects: increase in yield and expansion of production; both had positive results. Improvement of underground dams resulted in the project GuardeÁgua, which will generate an electronic platform. A study carried out by Embrapa Soils evaluated the economic impacts for farmers who have an underground dam on their farms in the Brazilian Semiarid Region. The study considered a period of 18 years, 2006 to 2023, in which there was an average increase per year of 375 kg in production, generating an extra income of R$ 7,361.10 for all those who adopted this social technology compared to the ones who do not have it on their farms. For years, Embrapa has carried out an assessment study of economic, social, environmental, and institutional impacts provided by underground dams, and the results are described every year in Embrapa Social Report. In 2023, the study showed that the benefit-cost ratio was 2.27, that is, for each US$ 1.00 invested by Embrapa in this social technology, society gained back US$ 2.27. The underground dam is a successful technology in the Brazilian Semiarid region, since it allows dry areas that would be unsuited for agriculture to become croplands cultivated by family farmers. Currently, there are around 3,000 underground dams in the Brazilian Northeast, and this technology targets small-scale properties. According to Veramilles Aparecida Fae, an analyst at Embrapa Soils and one of the authors of the study, the economic impacts of underground dams were evaluated from two aspects: increase in yield and expansion of production. “The yield calculated in the economic feasibility study considered a scenario of normal rainfall, and the average amount of farmer surplus of those who adopted the technology was obtained through historical data of the economic evaluation of underground dams, which is carried out annually by an Embrapa team, between the years of 2006 and 2023”, the economist explains. She adds the estimated average price of the production in kilograms was calculated based on surveys in local markets, verifying 78 items that may have been produced by the farmers. “The study showed an estimate of R$ 19.65 per kilogram, which, multiplied by the surplus annual production of 375 Kg, results in an annual average income of R$ 7,361.10 per hectare for those who have an underground dam on their farms”, Faé comments. To analyze the data, the investment to build the underground dam and the time to recover the investment were calculated using profitability parameters in two different scenarios. The first one considered that the farmer had received government or NGO subsidies and spent R$ 20,000; the second took into account that the farmer had not received any support and spent R$ 27,000. Embrapa experts found out that in all analyzed scenarios, the Internal Rate of Return (IRR) was higher than the Brazilian official inflation index, the Extended National Consumer Price Index (IPCA), which guarantees the economic return on the amount invested from the third year onwards for the farmers who counted on financial support, and from the fourth year onwards for the ones who paid all construction costs by themselves. “Regarding economic aspects and considering all available indexes, we can say that the technology is beneficial and viable, presenting positive results in all the indicators that were surveyed”, Igor Rosa Dias de Jesus affirms. He is the supervisor of Prospecting and Technology Assessment Management Sector at Embrapa Soils and responsible for the studies of underground dam impacts. He explains that the production chain in the most arid areas of the Brazilian Semiarid region is strongly anchored in agriculture and livestock farming for human and animal consumption, and the farmers sell surplus at local agroecological markets. “The great advantage of underground dams is the new suitability of areas that would not be appropriate for cultivation before their construction. The availability of new croplands throughout the year represents significant impacts in the sites where the dams are set up”, he adds. The water availability also improves the soil quality and provides rehabilitation of previously degraded lands in the Semiarid region, since it avoids nutrient loss through erosion and leaching. Additionally, the dams contribute to land appreciation, according to the study of technology impacts assessment. Production in areas with underground dams Cultivation in underground dam areas that were evaluated in the study carried out by Embrapa Soils and partners is basically for self-supply, as they produce corn, beans, cassava, sweet potatoes, carrots, yam, lettuce, chives, beets, coriander, garlic, cabbage, kale, okra, tomatoes, chicory, peppers, pumpkin, chayote, watermelon, melon, acerola, guava, mango, papaya, pineapple, passion fruit, soursop, cashew, coconut and sugar cane, as well as forage grass and cochineal cactus, stored as silage for animal feeding. Pictures above by: Fernando Gregio With the use of the technology, each family has from six to eight head of cattle, usually with two of them producing milk; around 10 to 15 head of chicken or turkey; and five to ten sheep or pigs. “During the rainy season, the number of animals tends to increase, enabling farmers to sell surplus, such as dairy and eggs. Some farmers have even owned 30 head of cattle and 50 birds; the number of animals vary according to drought intensity. During drier seasons, there is an estimated reduction of 60% to 70% in relation to rainy periods. Some farmers have apiaries and others produce and sell creole seeds of watermelon, beans and other grains for local crops”, Igor de Jesus adds. Impacts of underground dams – testimonials How underground dams work The technology called underground dam basically consists of a layer made of plastic canvas placed 3 to 5 m deep in trenches that are dug in steep agricultural areas. Thus, the water does not flow away downstream because it is intercepted by the plastic canvas, so the soil upstream remains wet for many months, and becomes suitable for cultivation. A spillway is also built so that, when there are flows above expected, the extra water is stored in wells built upstream the underground dam. The idea is to store the little water from rainfall that occurs during the year in areas of water scarcity, such as the Brazilian Semiarid region, allowing the cultivation of the soil from 3 to 5 months after the rainy season, depending on how much rainfall there was during the year. “Some underground dams, built in appropriate environments, produce all year long, including periods of rainfall scarcity”, Albani Vieira da Rocha affirms. He is the executive coordinator of Centro de Desenvolvimento Comunitário de Maravilha (Cdecma), which is a reference entity to support, inform and strengthen family farmers living in the Médio Sertão de Alagoas territory. The technology, which is in the public domain, has been developed since the 1980s. At first, Embrapa Semiarid was responsible for the project, including its current model and some modifications, such as using plastic canvas instead of stones and cement. From 2007 onwards, Embrapa Soils, by its Recife Research and Development Execution Unit (UEP Recife), started developing R&D actions using the underground dams to contribute to mitigate and cope with climate changes in the region. Photo by: Fernando Gregio GuardeÁgua project The impact assessment study, which has been developed for the last decades, shows that family farmers have redesigned their agroecosystems using underground dams and being part of diverse projects linked to the technology. However, the study report emphasizes that this social technology requires the expert teams to constantly help the farmers who adopt it. In that sense, the GuardeÁgua project was elaborated in July 2023, in Alagoas state, based on local farmers’ demand, by Embrapa Soils and partners – such as Articulação Semiárido Brasileiro (ASA Alagoas), represented by the Centro de Apoio Comunitário de Tapera em União a Senador (Cactus), Centro de Desenvolvimento Comunitário de Maravilha (Cdecma), Associação de Agricultores Alternativos (Aagra) and Instituto Terra Viva (ITViva); Federação da Agricultura e Pecuária do Estado de Alagoas (Faeal) and Serviço Nacional de Aprendizagem Rural (Senar-AL). The objective is to codevelop and improve management systems of water, soil, and planting to increase the sustainability of agroecosystems with underground dams in the state of Alagoas, strengthening social, economic, and ecological reproduction of family farmers living in the Semiarid region of the state, allowing them to be less dependent on compensatory policies. Since 2007, UEP Recife has been developing research in the Semiarid region of Alagoas state with experimental farmers, a network of partners from civil society, government, and the third sector, aiming to prevent hunger and end poverty through the social technology of underground dams, which promotes better water usage and access. GuardeÁguais due to be concluded by May 2026, and it is being developed in diffuse communities in territories of low, medium and high Semiarid region of Alagoas, for and with farmers who are reference and leaders recognized by the communities. They should be seen as the radiating multipliers of the technological innovations developed “We count on the consolidation and active participation of a sociotechnical network that expects to train local farmers, planning and implementing strategies to strengthen solidary spaces with self-management and protagonism of the families. This institution network predicts methodologic, technologic, and practical strategies that will enable socioproductive inclusion of both families and community”, Maria Sonia Lopes da Silva, a researcher at UEP Recife and the leader of the project, details. The researcher emphasizes that, besides the investment from Embrapa Management System, the project is searching for funds from federal government, Alagoas state government and city halls, through social programs and public policies, as well as parliamentary amendments and sources of funding for research and development projects and partnerships with the third sector. Farmers demanded the project The Semiarid region of Alagoas state is composed of 38 municipalities, being characterized by frequent absences, scarcity, and high spatial and temporal variability of rainfall, with an annual average between 400 and 800 mm, and average evapotranspiration values between 1,400 and 1,500 mm. Researchers and technicians of the project say that the implantation of social technology of capitation and storage of rainwater for multiple usages has been increasing in the last years, through government programs and individual initiatives by farmers, seeking socioproductive inclusion to generate income, value, autonomy, and dignity of local farming families. “Underground dam is a social hydric technology that is already validated by the communities of Semiarid region of Alagoas, but we still need to face some challenges, especially regarding the appropriate place to implement the technology and use and management of water, soil, and crops”, Maria da Paz Souza Pimentel, the institutional coordinator at Cactus, affirms. Maria Sonia da Silva explains that Embrapa has already solved the problem on appropriate places for underground dams in the project ZonBarragem Alagoas in 2019. Embrapa designed and handed in to the state government eight maps of potential areas appropriate for underground dams. “At the beginning of 2020, Embrapa Soils was required by local farmers, represented by Cactus, to codevelop research to define ecological-based agricultural practices, as well as cocreation of digital tools to help defining potential areas to build the dams. This idea came up with the GuardeÁgua project”, Flávio Adriano Marques, a technical coordinator at UEP Recife, comments. According to Antônio Gomes Barbosa, the coordinator of Program P1+2 at ASA, the high risk of climate variations in the Caatinga biome is another challenge that justifies studies on storage practices of water in the soil and on appropriate crops, contributing to the productive inclusion of farming families to cope with the Semiarid environment. Photos by: Fernando Gregio Read more about the GuardeÁgua project here.