Marcus Aurélio Soares Cruz

Chuvas intensas para o estado de Sergipe com base em dados desagregados de chuva diária

Floods have frequently been observed worldwide, particularly in urban and rural areas of Brazil as a consequence of antropic impacts and climate change. To cope with the problem hydraulic structures are designed based on the observed maximum flood, or statistically predicted through the rainfall-duration relationship established with recorded data, which are generally scarce. Due to the lack of such data, disaggregation of daily rainfall is generally utilized. In the State of Sergipe-Brazil, the rainfall-duration relationships were established utilizing disaggregated daily rainfalls, observed in 48 stations, and the probability distributions of Weibull and Gumbel. The best results were obtained with the Weibull distribution. The spatial distributions of the parameters of the rainfall-duration relationships demonstrated the high rainfall variability in the region.

ANÁLISE DE SENSIBILIDADE DOS PARÂMETROS DO MODELO SWAT E SIMULAÇÃO DOS PROCESSOS HIDROSSEDIMENTOLÓGICOS EM UMA BACIA NO AGRESTE NORDESTINO

Erosion has been recognized as the main cause of soil degradation and is accelerated by human intervention in watersheds, causing losses to the agricultural sector and damaging the environment. To estimate the impacts caused by land use or climate changes on hydrosedimentological processes, physically-based distributed models have been shown to be quite effective. In this study, the SWAT model was calibrated and validated for two subwatersheds of the Japaratuba Mirim river watershed, one located upstream of the Fazenda Pao de Acucar - PA (137.3 km2), and another located upstream of Fazenda Cajueiro - CJ (277.8 km2) in the state of Sergipe, to simulate runoff and soil erosion. To test the sensitivity of the calibrated parameters, the runoff was also simulated by a cross application of the 12 most sensitive parameters in the two watersheds, from 1985 to 2000. The results showed that the model was able to simulate the runoff and forecast, in a consistent way, the sediment yield. However, while the cross application of the parameters from the bigger (CJ) to the smaller watershed (PA) resulted in satisfactory Nash-Sutcliffe efficiency (NSE) and percent bias (PBIAS), the opposite was not true.

Groundwater quality for irrigation purposes in Piauí River Basin in the State of Sergipe, Brazil

Groundwater use for agricultural purposes has been intensified in the State of Sergipe, mainly in the regions with more serious water shortage from surface sources. However, irrigation is still restricted to small areas like home gardens. In part, this problem is due to lack of studies on characterization of water resources, including availability and quality of groundwaters, detecting the spatial distribution of viable sources of groundwater for different uses. The potential hazards related to soil salinity and sodicity, toxicity of specific ions for crops, and clogging of components of microirrigation systems were evaluated. Physicochemical data of water from 278 deep wells located in Piaui River Basin, in the State of Sergipe, Brazil, were used considering the FAO restriction criteria for irrigation purposes. Maps of spatial distribution of groundwater quality indicators in the watershed were prepared by ordinary kriging procedures. Groundwaters showed good quality for irrigation use, mainly in the center-downstream portion of the river basin. There was a trend in increasing the salt concentration in water from the coast to inland in the Piaui River Basin area.

Applicability of TRMM Precipitation for Hydrologic Modeling in a Basin in the Northeast Brazilian Agreste

Determining precipitation using remote sensing is gaining space in hydrologic studies, helping make up for the lack of data in many regions of Brazil. The products from satellite TRMM (Tropical Rainfall Measuring Mission) are widely applied in studies in Brazil, but there are still few results about their applicability for hydrologic modeling in the Northeast Region, which is characterized by an irregular precipitation regime. The objective of this study is to evaluate the feasibility of using the TRMM 3B42 V7 data for hydrologic modeling in the Japaratuba river basin in Sergipe at three timescales: daily, every ten days, and monthly. The comparative analysis between the rainfall data from rain gauges and TRMM did not indicate satisfactory adequacy at these studied scales, since the TRMM data underestimated the total rainfall for all stations used in the study. However, for the hydrologic modeling, acceptable values were obtained for the efficiency coefficients evaluated only for the ten-day and monthly scales.