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The water crisis experienced in recent years in the State of Minas Gerais, Brazil, has corroborated the need of conscientious use of water, based on use-efficient technologies, capable of inducing reuse. Considering worldwide experiences, this study had the objective of analyzing the potential use of domestic sewage treated in irrigated agriculture in the Paracatu river basin, a region recognized as a water conflict area by the State Government. The methodology consisted of evaluating current uses and comparing the volume of raw water demand for irrigation to the volume generated in the sewage treatment plants in the Paracatu river basin; estimating the cost of effluent trucking down to the treatment plants; and comparing the established values paid for the use of raw water and the estimated cost of treated effluent transportation. Water demand for irrigation is approximately 182 x 106 m3/year and the volume produced by the sewage treatment plants is 8,36 x 106 m3/year, approximately 4,6% of the irrigation demand. The comparison between the established values paid for the use of raw water and the estimated cost of treated effluent transportation indicates a relationship between 12 e 2%. Em Minas Gerais, a crise hídrica dos últimos anos corroborou a necessidade de adoção de tecnologias eficientes para a diminuição dos desperdícios e o reuso de água. Vistas as experiências de reuso em vários países, o objetivo deste estudo é analisar o uso potencial de esgoto doméstico tratado na agricultura irrigada na bacia hidrográfica do rio Paracatu, região com Declarações de Área de Conflito – DAC formalizadas. A metodologia consistiu em: avaliar os usos e comparar o volume de água bruta demandado para irrigação com o volume gerado no tratamento de efluentes na bacia do rio Paracatu; estimar o custo do transporte do efluente para reuso, por caminhão pipa; e comparar o valor de cobrança pelo uso dos recursos hídricos com o custo estimado do transporte de água de reuso. A demanda de água bruta para a irrigação é de aproximadamente 182 x 106 m3/ano e o volume de água de esgotos tratados é de 8,36 x 106 m3/ano, cerca de 4,6% da demanda para fins de irrigação. A comparação entre o valor de cobrança da água bruta outorgada e o custo estimado do transporte de água, aponta para uma relação entre 12 e 2%.

Non-point source pollution (NPSP) is perhaps the leading cause of water quality problems and one of the most challenging environmental issues given the difficulty of modeling and controlling it. In this article, we applied the Manning equation, a hydraulic concept, to improve models of non-point source pollution and determine its influence as a function of slope - land cover roughness for runoff to reach the stream. In our study the equation is somewhat taken out of its usual context to be applies to the flow of an entire watershed. Here a digital elevation model (DEM) from the SRTM satellite was used to compute the slope and data from the RapidEye satellite constellation was used to produce a land cover map later transformed into a roughness surface. The methodology is applied to a 1433 km 2 watershed in Southeast Brazil mostly covered by forest, pasture, urban and wetlands. The model was used to create slope buffer of varying width in which the proportions of land cover and roughness coefficient were obtained. Next we correlated these data, through regression, with four water quality parameters measured in situ: nitrate, phosphorous, faecal coliform and turbidity. We compare our results with the ones obtained by fixed buffer. It was found that slope buffer outperformed fixed buffer with higher coefficients of determination up to 15%.

In this article, a methodology for evaluating the effect of land use/land cover on the quality of nearby stream water in a semiarid environment is described and tested on a large watershed in Southeastern Brazil. The approach aims at identifying the width of the riparian area having the strongest effect on different water quality parameters. The land use/land cover data were generated from remotely sensed data while water quality point data were supplied by a government agency. Testing was conducted for both the rainy and dry seasons in an effort to understand the direct effect of surface runoff. The approach combines cartographic modelling using a geographical information system (GIS) and statistics to establish the strength of the relationship between water quality, land use and the distance from the stream. Results suggest a strong relationship between land use/land cover and turbidity, nitrogen and fecal coliforms. They also suggest that each of these parameters has a unique behavior when distance from the stream is considered. Finally, although it was expected that the models would apply better during the wet season, some parameters had the opposite behavior and displayed a better fit during the dry season.