As características climáticas e socioeconômicas do semi-árido brasileiro requerem tecnologias específicas de utilização e conservação dos recursos hídricos. É preciso analisar as alternativas de obtenção de água para usos diversos. Em contraposição às formas tradicionais de acumular água em pequenos reservatórios de superfície (açudes) e perfuração de poços no cristalino, têm-se buscado alternativas como poços de grande profundidade nas áreas sedimentares, metodologias para redução da evaporação e controle da salinização, destinação e uso de efluentes. Por fim, obras de integração de bacias hidrográficas e transporte de água a grande distância começam a ser construídas na região. A abordagem dessas diferentes políticas hídricas para o semi-árido é o objetivo deste trabalho.

Remote estimation of chlorophyll-a in turbid and productive estuaries is difficult due to the optical complexity of Case 2 waters. Although recent advances have been obtained with the use of empirical approaches for estimating chlorophyll-a in these environments, the understanding of the relationship between spectral reflectance and chlorophyll-a is based mainly on temperate and subtropical estuarine systems. The potential to apply standard NIR-Red models to productive tropical estuaries remains underexplored. Therefore, the purpose of this study is to evaluate the performance of several approaches based on multispectral data to estimate chlorophyll-a in a productive tropical estuarine-lagoon system, using in situ measurements of remote sensing reflectance, R_rs. The possibility of applying algorithms using simulated satellite bands of modern and recent launched sensors was also evaluated. More accurate retrievals of chlorophyll-a (r² > 0.80) based on field datasets were found using NIR-Red three-band models. In addition, enhanced chlorophyll-a retrievals were found using the two-band algorithm based on bands of recently launched satellites such as Sentinel-2/MSI and Sentinel-3/OLCI, indicating a promising application of these sensors to remotely estimate chlorophyll-a for coming decades in turbid inland waters. Our findings suggest that empirical models based on optical properties involving water constituents have strong potential to estimate chlorophyll-a using multispectral data from satellite, airborne or handheld sensors in productive tropical estuaries.

Water availability for a range of human uses will increasingly be affected by climate change, especially in the arid and semiarid tropics. The main objective of this study is to evaluate the infrastructure sufficiency in meeting water demand under climate-induced socio-hydrological transition in the Capibaribe River basin (CRB). The basin has experienced spatial and sectoral (agriculture-to-urban) reconfiguration of water demands. Human settlements that were once dispersed, relying on intermittent sources of surface water, are now larger and more spatially concentrated, which increases water-scarcity effects. Based on the application of linked hydrologic and water-resources models using precipitation and temperature projections of the IPCC SRES (Special Report: Emissions Scenarios) A1B scenario, a reduction in rainfall of 26.0% translated to streamflow reduction of 60.0%. We used simulations from four members of the HadCM3 (UK Met Office Hadley Centre) perturbed physics ensemble, in which a single model structure is used and perturbations are introduced to the physical parameterization schemes in the model (Chou et al., 2012). We considered that the change of the water availability in the basin in the future scenarios must drive the water management and the development of adaptation strategies that will manage the water demand. Several adaptive responses are considered, including water-loss reductions, wastewater collection and reuse, and rainwater collection cisterns, which together have potential to reduce future water demand by 23.0%. This study demonstrates the vulnerabilities of the infrastructure system during socio-hydrological transition in response to hydroclimatic and demand variabilities in the CRB and also indicates the differential spatial impacts and vulnerability of multiple uses of water to changes over time. The simulations showed that the measures proposed and the water from interbasin transfer project of the São Francisco River had a positive impact over the water supply in the basin, mainly for human use. Industry and irrigation will suffer impact unless other measures are implemented for demand control.

Despite the advances undertaken in recent years, modeling watershed’s hydrological responses remains a complex task, especially in data-scarce areas. In order to overcome this, new models with distinct representations of hydrological processes continue to be developed, incorporating spatial data and geoprocessing tools. In this article, the CAWM IV (Campus Agreste Watershed Model Version IV) model is presented. It is a conceptual model developed with the purpose of contributing mainly to the hydrological modeling of basins inserted in semi-arid regions. The article provides the layout of the mathematical model structure and a set of results obtained from the application of the model to basins with different characteristics. The main features of the model are the reduced number of parameters to calibrate and the incorporation of the basin physical characteristics in the calculation of several attributes, in order to facilitate the process of regionalization for other similar basins, particularly due to the absence of flow data. The CAWM IV model was applied to four basins located in the state of Pernambuco, in the Northeast region of Brazil. The model presented adequate behavior for 55 to 92% of the simulated events, depending on the criteria of performance indicators used in the analysis.

This paper develops a discharge allocation model for public water supply for a set of communities, considering available and planned reservoirs and interbasin transfer projects. Reservoir operation rules were defined for maximum water withdrawals in function of the storage volume over a period of 45 years, and then the discharges to be transported from the different sources to 18 locations were defined, minimizing the costs. Generalized Reduced Gradient and Particle Swarm Optimization algorithms were used in the optimization processes. The model was applied in the Agreste region of the state of Pernambuco, Brazilian semiarid. This region has the worst water balance in the entire country and three interbasin water transfer systems are under construction. Due to the interconnection among the systems, it will be possible to supply the communities from one or another source. The results showed that the optimized operation of the reservoirs can minimize water transfer and costs.