Remote sensing offers an increasingly wide array of imagery with a broad variety of spectral and spatial resolution, but there are relatively few comparisons of how different sources of data impact the accuracy, cost, and utility of analyses. We evaluated the impact of satellite image spatial resolution (1 m from Digital Globe; 30 m from Landsat) on land use classification via ArcGIS Feature Analyst, and on total suspended solids (TSS) load estimates from the Soil and Water Assessment Tool (SWAT) for the Cambori u watershed in Southeastern Brazil. We independently calibrated SWAT models, using both land use map resolutions and short-term daily streamflow (discharge) and TSS load data from local gauge stations. We then compared the predicted TSS loads with monitoring data outside the model training period. We also estimated the cost difference for land use classification and SWAT model construction and calibration at these two resolutions. Finally, we assessed the value of information (VOI) of the higher-resolution imagery in estimating the cost-effectiveness of watershed conservation in reducing TSS at the municipal water supply intake. Land use classification accuracy was 82.3% for 1 m data and 75.1% for 30 m data. We found that models using 1 m data better predicted both annual and peak TSS loads in the full study area, though the 30 m model did better in a subwatershed. However, the 1 m data incurred considerably higher costs relative to the 30 m data ($7000 for imagery, plus additional analyst time). Importantly, the choice of spatial resolution affected the estimated return on investment (ROI) in watershed conservation for the municipal water company that finances much of this conservation, although it is unlikely that this would have affected the company's decision to invest in the program. We conclude by identifying key criteria to assist in choosing an appropriate spatial resolution for different contexts.
Changes in the Earth's landscape have been the focus of much environmental research. In this context, hydrological models stand out as tools for several assessments. This study aimed to use the Soil and Water Assessment Tool (SWAT) hydrological model to simulate the impact of changes in land use in the Camboriú River Watershed in the years 1957, 1978, and 2012. The results indicated that the SWAT model was efficient in simulating water flow and sediment transport processes. Thus, it was possible to evaluate the impact of different land use scenarios on water and sediment yield in the catchment. The changes in land use caused significant changes in the hydro-sedimentological dynamic. Regarding flow, the effects of land use changes were more pronounced at both ends of the curve representing duration of flow. The worst scenario was identified for the year 2012, which saw the highest peak discharges during flood events and lowest flows during the dry season. Concerning soil erosion, the highest values were identified for sub-basins that were predominantly covered by rice paddies and pastures; this was attributed mainly to surface runoff and changes in land use (represented by C-USLE). Overall, the Camboriú River Basin did not experience severe soil erosion issues; however, it was found that changes in land use related to soil and climate characteristics may increase soil degradation, especially in years with high precipitation levels.Keywords: Land use; Basin; Hydrologic scenarios. RESUMOAs mudanças de paisagem têm sido foco de pesquisas na área ambiental. Nesse contexto, os modelos hidrológicos se destacam como ferramentas para diferentes análises. Nesse trabalho, o objetivo foi utilizar o modelo hidrológico SWAT para simular os impactos das alterações no uso e ocupação das terras da bacia hidrográfica do Rio Camboriú (BHRC) entre os anos de 1957, 1978 e 2012. Os resultados indicaram que SWAT foi eficiente para simulação da vazão e da perda de solo possibilitando a quantificação dos impactos a partir da simulação de cenários. As mudanças na cobertura do solo acarretaram alterações significativas no regime hidrossedimentológico. Para a vazão, os impactos foram maiores nos extremos da curva de permanência. O cenário 2012 se destacou negativamente por apresentar as maiores vazões de pico e as menores vazões em período de estiagem. Para a perda de solo, os maiores valores foram identificados nas sub-bacias com uso predominante para rizicultura e pastagens, o que foi atribuído, fundamentalmente, a alterações da taxa de escoamento superficial e aos fatores relacionados ao uso, manejo do solo e práticas conservacionistas. De maneira geral, a BHRC não apresentou problemas severos de perda de solo, entretanto, as mudanças na paisagem associadas as características edafoclimáticas podem favorecer a degradação do solo, principalmente em anos com elevados volumes de precipitação.Palavras-chave: Uso e ocupação das terras; Bacia hidrográfica; Cenários hidrológicos.RBRH, Porto Alegre, v. 22, e33, 2017Simulation of land use...
RESUMOOs estudos hidrológicos em bacias experimentais têm sido realizados devido à necessidade de compreensão dos processos que controlam o movimento da água e sedimentos e seus impactos na disponibilidade e qualidade das águas. Os modelos hidrológicos são ferramentas com alto potencial para a simulação de cenários hipotéticos em diferentes escalas. Assim, o objetivo desse trabalho foi avaliar a eficácia do modelo SWAT para representação do fluxo hidrossedimentológico em uma bacia hidrográfica catarinense a partir dos procedimentos usuais de calibração e validação. O estudo foi realizado na bacia do rio Camboriú com uma área de 195 km². Na análise do desempenho do modelo comparou-se os dados de vazão e sólidos transportados medidos e simulados na seção de controle. Os resultados obtidos atestaram a capacidade do SWAT para as simulações hidrossedimentológicas nessa bacia. Entretanto, foi preciso realizar a sua calibração para que as simulações atendessem os critérios de qualidade estabelecidos. Após a calibração, observou-se uma tendência de subestimativa das variáveis simuladas, porém, dentro de limites aceitáveis. Além disso, foi possível comprovar a eficiência do modelo para simulação das curvas de permanência das variáveis estudadas, caracterizando o SWAT como uma ferramenta importante na gestão de bacias hidrográficas como a do rio Camboriú.Palavras-chave: gestão, transporte de sedimentos, vazão.Calibration and validation of the SWAT model for hydrologic simulation in a river basin located in the north coast of Santa Catarina ABSTRACT Hydrological studies in experimental basins have been widely carried out in order to understand the processes that control the movement of water and sediment and their impact on the availability and quality of water. For this purpose, the hydrological models are used to simulate hypothetical scenarios at different spatial and temporal scales. The goal of this study was to evaluate the efficiency of the SWAT model to represent the hydrosedimentological flow
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