Underground dam that stores rainwater below ground through the use of a barrier that holds water in the soil, allowing the production of food even in the driest period.
The Underground Dam, as well as other experiences already implemented in the Brazilian semiarid region, is the result of the knowledge and accumulated experience of family farmers. It is one of the social technologies that keeps water for food production in the driest periods. In it, water is stored underground, and is usually built in areas of shallows and streams, which are formed during the rainy seasons, taking advantage of the water that normally passes through the site. Social technologies, such as the Underground Dam, enable populations in semiarid areas to guarantee sovereignty and food security, in addition to financial autonomy with the marketing of their products, and the strengthening of agro-ecological practices.
HOW DOES IT WORK?
“In the Underground Dam, water is stored below ground, and is usually built in shallows or stream areas.”
In the Underground Dam, the water that is stored underground is held by a barrier formed by the construction of a ditch, which is opened up to the impermeable layer of the soil, covered by a plastic tarp and then closed. This is how the area is soaked and ready for planting. The dam also has a masonry slab, where excess water can go through and wells built that store water and can be used for light irrigation.
The Underground Dam is built in areas where water accumulates in the rainy season, such as shallows and streams;
Materials such as bricks and cement are used in the construction of the dam and wells, in addition to canvas to cover the ditch;
The water level in the water table is higher with the dam;
Soil humidity increases, contributing to crops;
Underground Dams protect water from evaporation and increase its supply, enabling diversification of production;
Once implanted, the area of the dam can be used for planting food, such as vegetables, and the water from the wells can be used to irrigate other areas, feed animals, and do household chores.
HOW DOES LIFE CHANGE?
“With the water from the Underground Dam it is possible to have food for consumption and commercialization even in the driest period”.
Access to water and food close to homes makes it possible for people, especially women and young people, who are sometimes responsible for the search for water, to participate more in the life of their communities and in the political organization of their localities. The Underground Dam contributes to ensuring the family’s food security is guaranteed, for the feeding of animals, and water for domestic activities in non-rainy periods. It means water storage, the promotion of planting without pesticides, and a contribution to income generation.
- Water from the Underground Dam contributes to the diversification of food production;
- The breeding of small animals is strengthened and guaranteed even in the dry season, as the dam stores water for the driest period;
- The water stored in the dam helps to ensure food and nutritional security with the production of agro-ecological crops;
- It contributes to financial autonomy with the commercialization of the items produced;
- In the rainy season, the Underground Dam still allows the planting of crops that need more water, such as rice and some types of grass;
- The dam water can be used for domestic chores such as for washing clothes and cleaning the house.
“Water here was very complicated. I had two artesian wells, one of which tasted bad and smelled different and I did not like to use it for animals, and the other had salty water. We even got to the point of getting water 10 km away with an ox cart, in this difficult situation. Today this is reality is over.”
Jaimilsol Rodrigues – Morro do Giral – Bahia, Brasil.
“The technician saw my yard and said that the underground dam was the one that worked best, since I wanted to plant grass. I had no faith in the dam under the ground, but my wife really wanted it and so they made the underground dam. We followed all the work, after the dam was ready we planted the grass and this time it worked. We have been supporting our animals with this grass for two years, thanks to this dam.”
Francisco Epifânio de Castro – Queimada Velha, São Lourenço – Piauí , Brasil
“The rain we had in 2004 and early 2005 was so good that water was kept in the dam until the following year, so much so that we produced two more bags of rice in 2006. And that way, we never lack couscous, pamonha and corn to eat.”
Odair Araújo dos Santos – Ipupiara – Bahia , Brasil
HOW TO DO IT?
For the construction of the Underground Dam, a suitable location must be found. It is necessary to identify an environment in which, during the rainy season, a watercourse, a stream, or a water passage goes through. This water can then be blocked by the construction of the technology, storing it even after periods of drought. There are different ways to build an underground dam, alternating models, needs, and local conditions. The following step-by-step guide to the construction process will be presented in detail, with tips and recommendations for good practices.
HOW TO LOOK AFTER IT?
The productive use of the Underground Dam must follow the principles of agroecology, that is, it must be shared by all the people that make up the family, avoiding the use of poisons and pesticides, and thus eliminating the risk of contamination of water, food, and people. This and other structural care guarantee the smooth functioning of the technology, as well as the production of healthy food.
Care for the maintenance of the structure
- The productive area of the Underground Dam must always be kept under a vegetation cover, thus avoiding the exposure of the soil to the sun;
- Organic fertilization should be done to improve soil conditions;
- Poison or pesticides should not be used in any way in food production;
- It is important to use the area of the dam with the greatest diversity of plants possible;
- Annually, the dam wall must undergo maintenance, preventing it from being destroyed by the force of the water during rainy seasons;
Care in water management
- The water quality must be monitored each year, to measure the degree of variation in salinization;
- Animals must be avoided in the area of the dam so that there is no compaction of the soil and water contamination;
- Irrigation planting must be done after the dam wall, ensuring the renewal of the area and avoiding salinization;
- If there is a large volume of water stored in the well, it is very important to use it so that the water is renewed, avoiding the risk of salinization;
- It is important that the fertilization of crops is organic, avoiding water contamination.
