Ressembling moon craters, Brazil’s micro-dams – barraginhas in Portuguese – have become a successful solution for storing water and preventing soil erosion in rural areas. Credit: Luciano Cordoval
By Mario Osava
SETE LAGOAS, Brazil, Dec 11 2024 – They look like attempts to copy the moon’s surface, in some cases, as craters multiply in the grasslands. But they are actually micro-dams, barraginhas in Portuguese, which have spread in Brazil as a successful way to store water and prevent soil erosion in rural areas.
The creator of the project encouraging these holes is Luciano Cordoval, an agronomist who works for the state-owned Brazilian Agricultural Research Corporation (Embrapa) in Sete Lagoas, a municipality of 227,000 people in the state of Minas Gerais, central Brazil.
He recommends the barraginha should be 16 metres in diameter and deep enough to hold 1.2 metres of water. Its earthen edges rise 80 centimetres above the water level, with a spillway for the excess. In practice, these dimensions vary greatly.
The Barraginhas Project, promoted by Cordoval from Embrapa in Sete Lagoas, which is mostly dedicated to maize and sorghum research as one of the company’s 43 units, was directly involved in the construction of some 300,000 micro-dams, estimates the agronomist.
But the innovator believes that in all they reach two million throughout the country, as many institutions, companies and municipalities have adopted the innovation, recognised as a social technology, and spread it on their own initiative.
Cordoval’s intense training activity contributes to this, calling the disseminators of his barraginhas, who stand out in various regions of Brazil, his “clones”. The agronomist also promotes exchanges among municipalities, in which groups that have already built many micro-dam farms pass on their knowledge.
These micro-dams are suitable for land with a low slope. Embrapa recommends not to build them on slopes steeper than 15%.
For steeper slopes, Cordoval suggests another way of retaining water, which he called “contour lines with cochinhos”, i.e. ditches that follow the contour lines but are interrupted by a succession of water tanks in the form of troughs, which in Brazil are called cochos de agua.
Large landowners and small farmers recognise the benefits of these ways of retaining rainwater. In many cases, water shortages disappeared, springs were revived and with them small watercourses.
Antonio Alvarenga, owner of 400 hectares in Sete Lagoas, is an exemplary case of pioneering. He built his first 28 micro-dams with support from Cordoval in 1995, two years before Embrapa’s Barraginhas Project was formally launched.
He continued to build them and estimates to have added “more than 100” to the initial 28. The farm of degraded and dry land was totally modified. The recovery of the water table has allowed him to have an “artificial” 42,000 square metre lagoon and to quadruple the number of cattle on his property.
The water retained in the micro-dams feeds the water table that makes the lagoons viable and recovers the wells that are the source of drinking water for millions of rural families in Brazil. This is proven by photos that show the water level in the wells rose a little after the construction of the barraginhas.
The success of the micro-dams is especially evident on degraded land, which is estimated to exceed 90 million hectares in Brazil, mainly due to extensive cattle farming.
The aim is to restore moisture in a large part of the country, affected by deforestation, agricultural expansion and other human activities.
Climate change aggravates water scarcity in a wider territory, especially in the Semi-Arid, which covers 100 million hectares in the interior of the Northeast region, and in the Cerrado, Brazil’s savannah-like region, which extends over 200 million hectares.
In addition to micro-dams, contour ditches and other forms of rainwater harvesting reduce the erosion that impoverishes the soil and silts up rivers in Brazil.
A type of barraginhas, generally smaller in size, which also proliferate in Brazil, are built alongside roads as a way of preventing erosion.