The region of Espirito Santo
Espirito Santo covers an area of 46,180 km2. The topography of the state is categorized by 40% lowland coastal landscape and 60% “Serra” highlands. The watersheds aredivided into twelve sub-basins. Its largest river, the Rio Doce, extends 853 km, originating at the confluence of the Piranga and Carmo near the foothills of the Mantiqueira and Espinhaco mountain ranges in the neighboring state of Minas Gerais. A significant amount of the region’s agricultural (coffee and sugar cane in particular), industrial, and mining production occurs within the Rio Doce basin, which contains a population of roughly 3.1 million people. The region holds two main climatic types: tropical rainy and humid mesothermal. The first one dominates the lowlands and is characterized by high temperatures throughout the year and average temperature above 22°C. The humid mesothermal climate is found in mountainous areas in the south of the region and is characterized by low temperatures in the winter and an average temperature below 18°C.
The Rio Santa Maria da Vitoria (SMV) and the Rio Jucu are the main river basins that supply water to Vitoria, the capital of Espírito Santo. The Greater Vitoria Metropolitan Area (GVMA) is the 14th largest city in Brazil, with a population of roughly 1.6 million people. The region receives most of its rain during the October through January time period and receives an average rainfall of roughly 918mm annually. The SMV watershed covers a region of 1,660 km2, with a river length of 122 km. The upper region of the SMV basin is characterized by mountainous landscapes and is composed of roughly 40% natural forested landcover. The central SMV basin meanwhile, is primarily influenced by rural development, pasture land, and agricultural uses such as banana, coffee, eucalyptus, and sugar cane. There is little to no treatment of wastewater in the upper and central regions of the basin. The SMV passes through five municipalities of varying size: Santa Maria de Jetiba, Santa Leopoldina, Cariacica, Serra, and Vitoria. The SMV river mouth empties into the Bay of Vitoria, an important commercial port for the region, and forms the island of Vitoria, the capital city of Espirito Santo. The SMV provides water for roughly 30% of the greater Vitoria population. There are two dams on the SMV upstream of Vitoria, the Rio Bonito and Suico dams, which produce ten and thirty megawatts of electric energy per year, respectively. These dams significantly alter the sediment transport and storage dynamics of the basin, storing large amounts of sediments in their reservoirs. A significant amount of sediments from the riparian zone and tributaries enters the river downstream of these dams.
The municipalities in the upper watershed (Domingos Martins, Marechal Floriano, Santa Maria, and Santa Leopoldina Jetibá) have predominantly been used by traditional small family farmers, with an average farm size of 20 to 30 ha and an average of about two families for property. The main agricultural activities are the cultivation of maize, beans, root crops, coffee, bananas, horticulture, orchards, plantations, livestock, and poultry. Other economic activities found in the area include mining, eucalyptus plantations, and small hydropower plants. These traditional agricultural practices in the headwater regions of these watersheds has resulted the reduction and fragmentation of forest cover. In turn, this reduction, coupled with the rugged local relief, has resulted in soil erosion, which has harmed water quality, leading to higher treatment costs and reducing the storage capacity of reservoirs.