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Congress: 2008
Author(s): Ferdnando Cavalcanti da Silva, Walter Collischonn
Ferdnando Cavalcanti da Silva is Master in Water Resources and Environmental Sanitary by IPH/UFRGS (Institute of Hydraulics Research) and Civil Engineer by UFPB. Address: QNM 22, Conjunto H, lote 33 Ceilândia Norte – DF, Brazil CEP: 7

Keyword(s): water use permit, surface water and groundwater management, Brazil
AbstractWater use permit is one of Brazilian water resources policy instrument established in law no. 9.433/97, which is known as the National Water Policy. According to that law, the whole hydrologic cycle should be taken in consideration when defining water rights, so surface water and groundwater must be manage as a single resource. However, in Brazilian water use allocation practice, surface water and groundwater interaction is not considered due to the lack of hydrogeological information on watersheds and to the water agencies focus on surface water management. Furthermore, scientific knowledge on this subject is still scarce especially on water integrated use in the large- scale. According to Brazilian Constitution, surface water can own either to states, in the case of water bodies sited exclusively in a state territory, or to federal government, in the case of water bodies sited in federal territories, the ones that run through more than one state and transboundary rivers. Almost all Brazilian water agencies have already defined water use permit criteria for surface water bodies. These criteria are based on stream-flow thresholds like percentages of 7Q10, Q90 or Q95. On the other hand, groundwater management procedures are not clearly defined yet. A first difficulty is due to legislation. Although groundwater and mineral water can be exploited from same aquifers, to Brazilian Constitution groundwater is a state property hence must be managed by states’ agencies and mineral water is considered a mineral resource and so it is a federal property that must be managed by federal government. The National Water Policy neither assigns legally attributions nor water use permit criteria to groundwater management. Consequently, there are no criteria for aquifer exploitation and in practice groundwater management is only based on well construction standards and pumping tests with no consideration of its connection with surface water. This study aims to propose a water use permit criterion that could consider surface water and groundwater integrated use in the watershed scale by simulating different withdrawal scenarios in the MGB-IPH (Large Basin Model-IPH), a rainfall-runoff distributed hydrological model. The simulated scenarios combine percentages of surface water abstractions based on reference stream-flows with percentages of groundwater exploitation based on aquifer recharge estimated by Q90/Q50 index from FDC that represents the proportion of groundwater contribution to river flows. Then, curves relating surface water and groundwater integrated use and its impacts on river minimum flows were obtained. These curves may support surface water and groundwater withdrawal threshold definition in the macro-scale. A case study was applied in the Upper Paranaíba river basin, a tributary of Paraná River in Brazil. Results showed that maximum groundwater withdrawal in the basin should be less than estimated aquifer recharge. And to put in practice the consideration of surface water and groundwater integrated allocations, like prescribed in law no. 9.433/97, it is suggested that the total water use permits in a basin be considered equivalent, for example, a 0.5 m³/s groundwater withdrawal would imply in a lack of 0.5 m³/s of surface water available in the basin.
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