@article{BarbosaAlmeidaRabeloCoelhoetal.2018, author = {Barbosa, Luis Romero and Almeida, Cristiano das Neves and Rabelo Coelho, Victor Hugo and Freitas, Emerson da Silva and Galvao, Carlos de Oliveira and de Araujo, Jose Carlos}, title = {Sub-hourly rainfall patterns by hyetograph type under distinct climate conditions in Northeast of Brazil}, series = {RBRH Revista Brasileira de Recursos H{\´i}dricos Brazilian Journal of Water Resources}, volume = {23}, journal = {RBRH Revista Brasileira de Recursos H{\´i}dricos Brazilian Journal of Water Resources}, publisher = {Associa{\c{c}}{\~a}o Brasileira de Recursos H{\´i}dricos}, address = {Porto Alegre}, issn = {1414-381X}, doi = {10.1590/2318-0331.231820180076}, pages = {14}, year = {2018}, abstract = {The lack of process-based classification procedures may lead to unrealistic hyetograph design due to complex oscillation of rainfall depths when assimilated at high temporal resolutions. Four consecutive years of sub-hourly rainfall data were assimilated in three study areas (Guaraira, GEB, Sao Joao do Cariri, CEB, and Aiuaba, AEB) under distinct climates (very hot semi-arid and tropical wet). This study aimed to define rainfall events (for Minimum Inter-event Time, MIT, and Minimum Rainfall Depth, MRD, equal to 30 min and 1.016 mm, respectively), classify their hyetograph types (rectangular, R, unimodal with left-skewed, UL, right-skewed, UR, and centred peaks, UC, bimodal, B, and shapeless, SL), and compare their key rainfall properties (frequency, duration, depth, rate and peak). A rain pulse aggregation process allowed for reshaping SL-events for six different time spans varying from 2 to 30 min. The results revealed that the coastal area held predominantly R-events (64\% events and 49\% rainfall depth), in western semi-arid prevailed UL-events (57\% events and 63\% rainfall depth), whereas in eastern semi-arid mostly were R-events (61\% events and 30\% rainfall depth) similar to coastal area. It is concluded that each cloud formation type had important effects on hyetograph properties, differentiating them even within the same climate.}, language = {en} } @article{deFigueiredodeAraujoMedeirosetal.2016, author = {de Figueiredo, Jose Vidal and de Araujo, Jose Carlos and Medeiros, Pedro Henrique Augusto and Costa, Alexandre C.}, title = {Runoff initiation in a preserved semiarid Caatinga small watershed, Northeastern Brazil}, series = {Hydrological processes}, volume = {30}, journal = {Hydrological processes}, publisher = {Wiley}, address = {Hoboken}, issn = {0885-6087}, doi = {10.1002/hyp.10801}, pages = {2390 -- 2400}, year = {2016}, abstract = {This study analyses some hydrological driving forces and their interrelation with surface-flow initiation in a semiarid Caatinga basin (12km(2)), Northeastern Brazil. During the analysis period (2005 - 2014), 118 events with precipitation higher than 10mm were monitored, providing 45 events with runoff, 25 with negligible runoff and 49 without runoff. To verify the dominant processes, 179 on-site measurements of saturated hydraulic conductivity (Ksat) were conducted. The results showed that annual runoff coefficient lay below 0.5\% and discharge at the outlet has only occurred four days per annum on average, providing an insight to the surface-water scarcity of the Caatinga biome. The most relevant variables to explain runoff initiation were total precipitation and maximum 60-min rainfall intensity (I-60). Runoff always occurred when rainfall surpassed 31mm, but it never occurred for rainfall below 14mm or for I-60 below 12mmh(-1). The fact that the duration of the critical intensity is similar to the basin concentration time (65min) and that the infiltration threshold value approaches the river-bank saturated hydraulic conductivity support the assumption that Hortonian runoff prevails. However, none of the analysed variables (total or precedent precipitation, soil moisture content, rainfall intensities or rainfall duration) has been able to explain the runoff initiation in all monitored events: the best criteria, e.g. failed to explain 27\% of the events. It is possible that surface-flow initiation in the Caatinga biome is strongly influenced by the root-system dynamics, which changes macro-porosity status and, therefore, initial abstraction. Copyright (c) 2016 John Wiley \& Sons, Ltd.}, language = {en} } @article{BronstertdeAraujoBatallaVillanuevaetal.2014, author = {Bronstert, Axel and de Araujo, Jos{\`e} Carlos and Batalla Villanueva, Ramon J. and Costa, Alexandre Cunha and Delgado, Jos{\´e} Miguel Martins and Francke, Till and F{\"o}rster, Saskia and G{\"u}ntner, Andreas and Lopez-Tarazon, Jos{\´e} Andr{\´e}s and Mamede, George Leite and Medeiros, Pedro Henrique Augusto and Mueller, Eva and Vericat, Damia}, title = {Process-based modelling of erosion, sediment transport and reservoir siltation in mesoscale semi-arid catchments}, series = {Journal of soils and sediments : protection, risk assessment and remediation}, volume = {14}, journal = {Journal of soils and sediments : protection, risk assessment and remediation}, number = {12}, publisher = {Springer}, address = {Heidelberg}, issn = {1439-0108}, doi = {10.1007/s11368-014-0994-1}, pages = {2001 -- 2018}, year = {2014}, abstract = {To support scientifically sound water management in dryland environments a modelling system has been developed for the quantitative assessment of water and sediment fluxes in catchments, transport in the river system, and retention in reservoirs. The spatial scale of interest is the mesoscale because this is the scale most relevant for management of water and land resources. This modelling system comprises process-oriented hydrological components tailored for dryland characteristics coupled with components comprising hillslope erosion, sediment transport and reservoir deposition processes. The spatial discretization is hierarchically designed according to a multi-scale concept to account for particular relevant process scales. The non-linear and partly intermittent run-off generation and sediment dynamics are dealt with by accounting for connectivity phenomena at the intersections of landscape compartments. The modelling system has been developed by means of data from nested research catchments in NE-Spain and in NE-Brazil. In the semi-arid NE of Brazil sediment retention along the topography is the main process for sediment retention at all scales, i.e. the sediment delivery is transport limited. This kind of deposition retains roughly 50 to 60 \% of eroded sediment, maintaining a similar deposition proportion in all spatial scales investigated. On the other hand, the sediment retained in reservoirs is clearly related to the scale, increasing with catchment area. With increasing area, there are more reservoirs, increasing the possibility of deposition. Furthermore, the area increase also promotes an increase in flow volume, favouring the construction of larger reservoirs, which generally overflow less frequently and retain higher sediment fractions. The second example comprises a highly dynamic Mediterranean catchment in NE-Spain with nested sub-catchments and reveals the full dynamics of hydrological, erosion and deposition features. The run-off modelling performed well with only some overestimation during low-flow periods due to the neglect of water losses along the river. The simulated peaks in sediment flux are reproduced well, while low-flow sediment transport is less well captured, due to the disregard of sediment remobilization in the riverbed during low flow. This combined observation and modelling study deepened the understanding of hydro-sedimentological systems characterized by flashy run-off generation and by erosion and sediment transport pulses through the different landscape compartments. The connectivity between the different landscape compartments plays a very relevant role, regarding both the total mass of water and sediment transport and the transport time through the catchment.}, language = {en} } @article{SoaresPereiraGomesCostaFoersteretal.2019, author = {Soares Pereira, Francisco Jairo and Gomes Costa, Carlos Alexandre and F{\"o}rster, Saskia and Brosinsky, Arlena and de Araujo, Jose Carlos}, title = {Estimation of suspended sediment concentration in an intermittent river using multi-temporal high-resolution satellite imagery}, series = {International journal of applied earth observation and geoinformation}, volume = {79}, journal = {International journal of applied earth observation and geoinformation}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0303-2434}, doi = {10.1016/j.jag.2019.02.009}, pages = {153 -- 161}, year = {2019}, abstract = {There is a shortage of sediment-routing monitoring worldwide, despite its relevance to environmental processes. In drylands, where water resources are more vulnerable to the sediment dynamics, this flaw is even more harmful. In the semi-arid Caatinga biome in the North-east of Brazil, rivers are almost all intermittent and hydro-sedimentological monitoring is scarce. In the biome, water supply derives from thousands of surface reservoirs, whose water availability is liable to be reduced by siltation and sediment-related pollution. The goal of this research was to evaluate the potential of multi-temporal high-resolution satellite imagery (RapidEye) to assess the suspended sediment concentration (SSC) in the medium-sized intermittent Jaguaribe River, Brazil, during a 5-year period. We validated 15 one-, two- and three-band indices for SSC estimation based on RapidEye spectral bands deduced in the context of the present investigation and nine indices proposed in the literature for other optical sensors, by comparing them with in-situ concentration data. The in-situ SSC data ranged from 67 mg.L-1 to 230 mg.L-1. We concluded that RapidEye images can assess moderate SSC of intermittent rivers, even when their discharge is low. The RapidEye indices performed better than those from literature. The spectral band that best represented SSC was the near infrared, whose performance improved when associated with the green band. This conclusion agrees with literature findings for diverse sedimentological contexts. The three-band spectral indices performed worse than those with only one or two spectral bands, showing that the use of a third band did not enhance the model ability. Besides, we show that the hydrological characteristics of semi-arid intermittent rivers generate difficulties to monitor SSC using optical satellite remote sensing, such as time-concentrated sediment yield; and its association with recent rainfall events and, therefore, with cloudy sky.}, language = {en} } @article{PereiraMedeirosFranckeetal.2019, author = {Pereira, Bruno and Medeiros, Pedro Henrique Augusto and Francke, Till and Ramalho, Geraldo and F{\"o}rster, Saskia and De Araujo, Jose Carlos}, title = {Assessment of the geometry and volumes of small surface water reservoirs by remote sensing in a semi-arid region with high reservoir density}, series = {Hydrological sciences journal = Journal des sciences hydrologiques}, volume = {64}, journal = {Hydrological sciences journal = Journal des sciences hydrologiques}, number = {1}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0262-6667}, doi = {10.1080/02626667.2019.1566727}, pages = {66 -- 79}, year = {2019}, abstract = {Water fluxes in highly impounded regions are heavily dependent on reservoir properties. However, for large and remote areas, this information is often unavailable. In this study, the geometry and volume of small surface reservoirs in the semi-arid region of Brazil were estimated using terrain and shape attributes extracted by remote sensing. Regression models and data classification were used to predict the volumes, at different water stages, of 312 reservoirs for which topographic information is available. The power function used to describe the reservoir shapes tends to overestimate the volumes; therefore, a modified shape equation was proposed. Among the methods tested, four were recommended based on performance and simplicity, for which the mean absolute percentage errors varied from 24 to 39\%, in contrast to the 94\% error achieved with the traditional method. Despite the challenge of precisely deriving the flooded areas of reservoirs, water management in highly reservoir-dense environments should benefit from volume prediction based on remote sensing.}, language = {en} } @article{DeAraujoGuentnerBronstert2006, author = {De Araujo, Jos{\`e} Carlos and G{\"u}ntner, Andreas and Bronstert, Axel}, title = {Loss of reservoir volume by sediment deposition and its impact on water availability in semiarid Brazil}, issn = {0262-6667}, doi = {10.1623/hysj.51.1.157}, year = {2006}, abstract = {A methodology is presented to assess the impact of reservoir silting oil water availability for semiarid environments, applied to seven representative watersheds in the state of Ceara, Brazil. Water yield is computed using stochastic modelling for several reliability levels and water yield reduction is quantified for the focus areas. The yield-volume elasticity concept, which indicates the relative yield reduction in terms of relative storage capacity of the reservoirs, is presented and applied. Results chow that storage capacity was reduced by 0.2\% year(-1) due to silting, that the risk of water shortage almost doubled in less than 50 years for the most critical reservoir, and that reduction of storage capacity had three times more impact oil yield reduction than the increase in evaporation. Average 90\% reliable yield-volume elasticity was 0.8, which means that the global water yield (Q(90)) in Ceara is expected to diminish yearly by 388 L s(-1) due to reservoir silting}, language = {en} } @article{CostaBronstertdeAraujo2012, author = {Costa, A. C. and Bronstert, Axel and de Araujo, Jose Carlos}, title = {A channel transmission losses model for different dryland rivers}, series = {Hydrology and earth system sciences : HESS}, volume = {16}, journal = {Hydrology and earth system sciences : HESS}, number = {4}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-16-1111-2012}, pages = {1111 -- 1135}, year = {2012}, abstract = {Channel transmission losses in drylands take place normally in extensive alluvial channels or streambeds underlain by fractured rocks. They can play an important role in streamflow rates, groundwater recharge, freshwater supply and channel-associated ecosystems. We aim to develop a process-oriented, semi-distributed channel transmission losses model, using process formulations which are suitable for data-scarce dryland environments and applicable to both hydraulically disconnected losing streams and hydraulically connected losing(/gaining) streams. This approach should be able to cover a large variation in climate and hydro-geologic controls, which are typically found in dryland regions of the Earth. Our model was first evaluated for a losing/gaining, hydraulically connected 30 km reach of the Middle Jaguaribe River (MJR), Ceara, Brazil, which drains a catchment area of 20 000 km(2). Secondly, we applied it to a small losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch Experimental Watershed (WGEW), Arizona, USA. The model was able to predict reliably the streamflow volume and peak for both case studies without using any parameter calibration procedure. We have shown that the evaluation of the hypotheses on the dominant hydrological processes was fundamental for reducing structural model uncertainties and improving the streamflow prediction. For instance, in the case of the large river reach (MJR), it was shown that both lateral stream-aquifer water fluxes and groundwater flow in the underlying alluvium parallel to the river course are necessary to predict streamflow volume and channel transmission losses, the former process being more relevant than the latter. Regarding model uncertainty, it was shown that the approaches, which were applied for the unsaturated zone processes (highly nonlinear with elaborate numerical solutions), are much more sensitive to parameter variability than those approaches which were used for the saturated zone (mathematically simple water budgeting in aquifer columns, including backwater effects). In case of the MJR-application, we have seen that structural uncertainties due to the limited knowledge of the subsurface saturated system interactions (i.e. groundwater coupling with channel water; possible groundwater flow parallel to the river) were more relevant than those related to the subsurface parameter variability. In case of the WEGW application we have seen that the non-linearity involved in the unsaturated flow processes in disconnected dryland river systems (controlled by the unsaturated zone) generally contain far more model uncertainties than do connected systems controlled by the saturated flow. Therefore, the degree of aridity of a dryland river may be an indicator of potential model uncertainty and subsequent attainable predictability of the system.}, language = {en} } @article{MedeirosdeAraujoBronstert2009, author = {Medeiros, Pedro Henrique Augusto and de Araujo, Jose Carlos and Bronstert, Axel}, title = {Interception measurements and assessment of Gash model performance for a tropical semi-arid region}, issn = {0045-6888}, year = {2009}, abstract = {Semi-arid environments usually face water scarcity and conflicts for its use; therefore a complete understanding of the water balance in these regions is desired. To evaluate interception, measurements of precipitation, throughfall and stemflow were carried out in a Brazilian tropical semi-arid experimental watershed with well preserved Caatinga vegetation. Data analysis indicates that interception losses correspond to 13\% of total rainfall, representing an important process in the watershed's water balance, where runoff is only 6\% of total precipitation. Gash interception model was applied in the region with good results for long term simulation. Nevertheless, the model produced significant but not systematic errors on a daily basis. This was attributed to its incapability of representing the temporal variation of precipitation during the event, which is a major factor affecting interception. Rainfall intensity was shown to be a good parameter to determine an applicability threshold for Gash model in the study area.}, language = {en} } @article{CostaFoersterdeAraujoetal.2013, author = {Costa, Alexandre Cunha and F{\"o}rster, Saskia and de Araujo, Jose Carlos and Bronstert, Axel}, title = {Analysis of channel transmission losses in a dryland river reach in north-eastern Brazil using streamflow series, groundwater level series and multi-temporal satellite data}, series = {Hydrological processes}, volume = {27}, journal = {Hydrological processes}, number = {7}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1099-1085}, doi = {10.1002/hyp.9243}, pages = {1046 -- 1060}, year = {2013}, abstract = {Scarcity of hydrological data, especially streamflow discharge and groundwater level series, restricts the understanding of channel transmission losses (TL) in drylands. Furthermore, the lack of information on spatial river dynamics encompasses high uncertainty on TL analysis in large rivers. The objective of this study was to combine the information from streamflow and groundwater level series with multi-temporal satellite data to derive a hydrological concept of TL for a reach of the Middle Jaguaribe River (MJR) in semi-arid north-eastern Brazil. Based on this analysis, we proposed strategies for its modelling and simulation. TL take place in an alluvium, where river and groundwater can be considered to be hydraulically connected. Most losses certainly infiltrated only through streambed and levees and not through the flood plains, as could be shown by satellite image analysis. TL events whose input river flows were smaller than a threshold did not reach the outlet of the MJR. TL events whose input flows were higher than this threshold reached the outlet losing on average 30\% of their input. During the dry seasons (DS) and at the beginning of rainy seasons (DS/BRS), no river flow is expected for pre-events, and events have vertical infiltration into the alluvium. At the middle and the end of the rainy seasons (MRS/ERS), river flow sustained by base flow occurs before/after events, and lateral infiltration into the alluvium plays a major role. Thus, the MJR shifts from being a losing river at DS/BRS to become a losing/gaining (mostly losing) river at MRS/ERS. A model of this system has to include the coupling of river and groundwater flow processes linked by a leakage approach.}, language = {en} } @unpublished{deAraujoBatallaVillanuevaBronstert2014, author = {de Araujo, Jose Carlos and Batalla Villanueva, Ramon J. and Bronstert, Axel}, title = {Special issue: analysis and modelling of sediment transfer in Mediterranean river basins}, series = {Journal of soils and sediments : protection, risk assessment and remediation}, volume = {14}, journal = {Journal of soils and sediments : protection, risk assessment and remediation}, number = {12}, publisher = {Springer}, address = {Heidelberg}, issn = {1439-0108}, doi = {10.1007/s11368-014-1000-7}, pages = {1905 -- 1908}, year = {2014}, language = {en} }