Avaliação da aplicação de modelos de desprendimento em bacia experimental do semiárido brasileiro

Granulometria é um dos principais fatores que afetam a dinâmica de sedimentos em bacias hidrográficas, desde seu desprendimento do solo matriz até o transporte ou deposição pela rede e reservatório. Objetivou-se com esse trabalho analisar o comportamento granulométrico dos sedimentos em uma bacia do semiárido brasileiro, no bioma Caatinga e analisar a eficiência da aplicação de modelos de estimativa do padrão granulométrico do sedimentos desprendido das encostas. O estudo foi realizado na bacia hidrográfica do Pentecoste, situada no semiárido do Ceará. A parte experimental da pesquisa foi realizada na Bacia Experimental do Vale do Curú (BEVC) com coleta de dados pluviométricos e hidrossedimentológicos, amostras de solo da bacia de captação, precipitação diária e de escoamentos superficiais, durante a quadra chuvosa entre os anos de 2015 e 2017. Modelos de desprendimento de sedimentos divulgados na literatura foram testados e aplicados para a área de estudo. Os resultados mostraram que o modelo de desprendimento de sedimento da encosta proposto por Foster et al. (1981) apresentou os melhores resultados quando comparado aos demais, com coeficiente de Nash e Sutcliff (NS) de 0,99, em ambiente de cobertura vegetal mista. Evaluation of the application of detachment models in the experimental basin of the Brazilian semi-arid region A B S T R A C TSize grain is one of the main factors that affect sediment dynamics in watersheds, from its detachment from the soil to the transport or deposition through the drainage network and reservoir. The objective of this research was to analyze the granulometric behavior of the sediments in a Brazilian semi-arid basin in the Caatinga biome and to analyze the efficiency of the application of models for the estimation of the granulometric pattern of sediments detached on slopes. The study was carried out in the Pentecost basin, located in the semi-arid region of Ceará. The experimental part of the research was conducted in the Curú Valley Experimental Basin (BEVC) with rainfall and hydrosedimentological data collection, soil samples from the catchment basin, daily precipitation and surface runoff during the rainy season between 2015 and 2017. Models of sediment release disclosed in the literature were tested and applied to the study area. The results showed that the slope sediment detachment model proposed by Foster et al. (1981) presented the best results when compared to the others, with Nash and Sutcliff coefficient (NS) of 0.99, under mixed vegetation cover.Keywords: size grain, Foster model, Experimental Basin of the Curú Valley, Caatinga biome.

Use of proximal sensor for soil classes separation applying Principal Component Analysis (PCA)

The spectrally active components of the soil allow the realization of integrative analyzes of soil aspects such as their classification. The purpose of this study was to evaluate the separation of soil classes from spectral reflectance data using principal components analysis (PCA). The study was carried out in the Aiuaba Experimental Basin located in the municipality of Aiuaba, Ceará, Brazil. Soil samples were collected in Ustalfs, Ustults and Ustorthents profiles. The samples were submitted to spectral analysis by a spectroradiometer and, subsequently, to PCA. Principal components were used to identify which of them contribute more significantly to the separation of the soil classes analyzed, based on their relationship with the soil attributes using a two-dimensional graphical analysis. From the examination of spectral behavior data of the different soil classes, the use of PCA allowed the separation of the classes Ustorthents, Ustalfs and Ustults from each other.

Abacus to Predict Groundwater Recharge at Non-Instrumented Hydrographic Basins

One of the first steps to implement a policy for groundwater resources management is knowing the groundwater recharge. However, the unavailability of data and resources to execute field studies increase the uncertainty associated with the estimation of groundwater recharge. To fill this gap, the present work aimed to propose a method to predict groundwater recharge at non-instrumented hydrographic basins. The approach proposed is based on using an abacus to execute the transposition and/or regionalization of results generated in an experimental basin. The methodology comprised the estimation and mapping of recharge rates in the experimental basin using three distinct approaches—numerical modelling of the saturated zone, distributed hydrological modelling of the vadose zone, and the method of fluctuation of the water table elevation—and the following generation of the abacus, with average recharge values for combinations of soil class, land use/cover and slope using geographic information systems. The results indicate that the abacus is consistent for some Ferrasol areas, that the reliability of average regionalized values depends on the complexity of the physical environment—soil class, land use/cover, and slope—and that new studies, focusing on the hydro-physical characterization of soils, might produce more reliable estimations.

Controls on coastal overwash morphology in natural and built environments

<p>Overwash is a key mechanism controlling the flux of sediment from the front of a barrier island to the top and back of an island during a storm event. The process is essential for barrier environments to maintain their height and width relative to sea level. Barrier topography and vegetation – and also road networks and buildings – can direct overwash flow, and thus the shape and size of sedimentary deposits that overwash leaves behind. Controls on overwash deposition have been examined more closely in natural settings than in developed zones. But overwash poses a major hazard to coastal infrastructure, and accurate prediction of storm impacts requires quantitative insight into the dynamics of overwash morphology in built settings. Here, we compare barrier floodplain controls across a range of spatial "fabrics", both natural and built (e.g., sparse to dense vegetation coverage; sparse to dense configurations of roads and buildings), to explore how these fabrics affect scaling relationships for overwash morphology. Integrating empirical measurements from post-storm imagery, trials of an analogue model in a small experimental basin, and results from a numerical toy model, we identify thresholds at which floodplain fabrics cause scaling relationships to change, or "break". Our findings illustrate a continuum in overwash pattern formation between endogenous self-organisation and exogenous forcing templates, and set up further inquiry into the dynamics of flood deposition in built environments.</p>

TIME OF CONCENTRATION IN AN EXPERIMENTAL BASIN: METHODS FOR ANALYSIS, BACKWATER EFFECTS AND VEGETATION REMOVAL

There are several empirical and theoretical formulas used for the estimation of the time of concentration (Tc). However, it has been shown that the Tc estimation may vary in several orders of magnitude depending on the method. In this study we compare 10 different methods for the estimation of the Tc using sub-basins and backwater effects to analyze those results. We also analyzed if the vegetation removal changes the Tc in the basin. The study area is the basin of the Federal University of Santa Catarina (UFSC) campus in Joinville with a significant part in a wetland and there is backwater effect caused by the Piraí river. Applying the empirical and theoretical equations found a significant variation of Tc estimates, the standard deviation in relation to the general average was around 65%. The influence of vegetation removal and drainage of a canal had an effect of reducing the Tc by 50%.

Hydrological modeling of an experimental basin in the semiarid region of the Brazilian State of Pernambuco

Hydrological simulation models have proven to be an important tool for managing and planning water resources, enabling the assessment of the impacts of rainfall on surface runoff and soil moisture. This work therefore aimed to apply the SWAT model for the analysis of hydrological processes in the Experimental Basin of the Jatobá Stream, in the semiarid region of the State of Pernambuco, Brazil, considering the calibration and validation of the model from streamflow and soil moisture data. Moreover, the study investigated hydrological effectiveness in a recovery scenario in areas of higher topographic elevation of the arborescent Caatinga and the behavior of the hydrological components under an agricultural expansion scenario. Events which occured between 2009 and 2010 were used to calibrate and validate streamflow and soil moisture data. The calibration and validation of streamflow exhibited efficiency coefficients (NSE) of 0.58 and 0.42, respectively, and 0.53 and 0.46 for soil moisture. The adjustment of the parameters was considered adequate for representing streamflow recession periods. It was also verified that the alternative process of calibration and validation with soil moisture reduced uncertainty. Regeneration of the vegetative cover over 21% of the hilltop areas of arborescent Caatinga led to a significant increase in percolation (42%) and a decrease of 34% in soil moisture (due to water consumption by plants), thus contributing to the recovery of headwaters, increasing resilience to water scarcity. On the other hand, the 38% expansion of agriculture caused an increase of 11% in surface runoff and, consequently, an increase of 10% in soil moisture.

Status and perspectives of hydrological research in small basins in Europe

There is an uncontradicted consensus that experimental basin research plays an important role for the understanding of hydrological processes. Based on this, deepened knowledge concepts and hydrological models have been developed, which enable and support water management planning and decision making in all facets of hydrologically driven aspects like floods, climate change impact and environmental research. The following paper starts with a brief introduction to the history of hydrological monitoring and the initiation of hydrological research based on experimental watersheds. It highlights the international activities promoting and disseminating these kind of field research. Due to the personal involvement of the author, a special focus is given to the activities of the Euro-Mediterranean Network of Experimental and Representative Basins ERB and on the recent experimental basins inventory in Austria. As collection and provision of data form an important prerequisite for any further hydrological assessment, it is proposed that data sets and their providers in charge have to be cited and acknowledged in the research papers. These citations should gain the equivalent evaluation and ranking of paper citations and could stimulate the willingness for data provision. As a conclusion it can be stated that experimental basin research is carried out worldwide, but there is a lack of international communication among the stakeholders. A future development should therefore strengthen the communication platforms and foster extended data exchange.