Estimativa da disponibilidade e qualidade das águas da bacia do igarapé Carrapato, em Boa Vista, Roraima

Abstract

The State’s economic development has occurred by the expansion of the primary sector due to the increased domestic demand, the proximity of markets such as Manaus and the Caribbean, and the encouragement of production through projects from public-private partnerships. This has generated an increasing pressure of the use of natural resources, which might cause negative impacts such as: lost of soil and fertility, abolition of biodiversity and degradation of the quality and quantity of water offered by watersheds used at the region. Therefore, this study aimed to investigate the main morphometry, the flow, the water quality and the soil use of the river basin of the igarapé Carrapato, located in Boa Vista, RR. For the morphometry of the basin’s igarapé Carrapato maps were used in mapping and surveying field with the use of GPS and altimeter. For the flow, measures have been taken with the monthly use of a reel, over a year. For the water quality, in four points of the stretch of main water, water was collected to evaluate the turbidity, the levels of potassium and iron, pH, electrical conductivity, levels of sodium, calcium and magnesium. The climatological water balance (BHC) of the basin was done using the data collected from the basin and the precipitation and evapotranspiration estimated by Penman- Monteith FAO. The results of the BHC revealed a period of seven months of water deficit (October to April) and another of five months of excess water (May to September).The total deficit was recorded 405,3 mm, while the surplus was 1119,1 mm. The basin had a drainage area of 84,71 km², a perimeter of 58,3 kilometers and form factor of 0,311, indicating an elongated shape, therefore unlikely to floods. The results showed that the flow of igarapé was 0,293 m³.s-1 at the most critical month (April). The demand for water has shown to be increasing, indicating the urgent need for planning in the use of water resources. Regarding the water quality, the parameters of total iron, calcium, magnesium, sodium, potassium, pH, electrical conductivity and turbidity, have always been below those set out by the guidelines for the use of water for irrigation and consistent with its natural condition of water surface, revealing a good water quality.