Erosion and sediment delivery from upland areas to waterbodies is a major problem impacting water quality in the United States and elsewhere. Measures to reduce these impacts are either targeted at reducing erosion on-site or at reducing delivery of sediment to waterbodies. AMEENA (Areal Modeling of Erosion for Environmental Nonpoint Applications) is a spatially distributed model that estimates erosion and deposition on a watershed scale by predicting erosion and transport over the landscape surface. Erosion is predicted based on the Revised Universal Soil Loss Equation (RUSLE), and sediment transport capacity is estimated as a function of upslope flow volume, local gradient, and land use. Gross erosion is routed to edge-of-stream with a routing algorithm that iteratively compares available sediment with transport capacity on a cell by cell basis from ridge cells to stream cells. The model is implemented completely within a raster GIS to facilitate use of the model as a tool to readily evaluate impact of land use practices on sediment delivery to streams. AMEENA was validated using field data of net erosion and sediment deposition from three field studies. AMEENA predicted the spatial distribution of net erosion and deposition better than WaTEM/SEDEM which is a distributed parameter erosion model based on a similar modeling approach. AMEENA's suitability to simulate the impact of management practices such as filter strips and critical area planting was evaluated on plot (profile) scale and catchment scale simulations. Results of plot scale simulations were intuitive and the model proved more reasonable for these scenarios than did RUSLE2 and WEPP. The catchment scale study highlighted features of AMEENA that are not available in RUSLE2 and WEPP in terms of identifying erosion “hot spots” and the ability to utilize the explicit sediment flow path identification in locating best placement of off-site sediment control measures. Since AMEENA does not account for in-stream erosion processes, it is not suitable for simulating areas dominated by channel or gully erosion. / Ph. D.

Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: A study of the state of reservoir sedimentation in South Africa based on reservoir sediment deposit data, has shown that a considerable number of reservoirs have serious sedimentation problems. The analysis of the reservoir sediment deposit data showed that almost 25% of the total number of reservoirs have lost between 10 to 30% of their original storage capacity. The average storage loss due to sedimentation in South African reservoirs is approximately 0.3% per year while the average annual storage loss for all the reservoirs in the world is 0.8%. The aim of this research was to develop sediment yield prediction methods based on analytical approaches and mathematical modelling. The sediment yield prediction methods can be used in planning and management of water resources particularly in reservoir sedimentation control. The catchment erosion and sediment yield modelling methods can be applied in temporal and spatial analysis of sediment yields which results are essential for detailed design of water resources, particularly in the identification of critical erosion areas, sediment sources and formulation of catchment management strategies. Current analytical methods for the prediction of sediment yield have been reviewed. Nine sediment yield regions have been demarcated based on the observed sediment yields and catchment characteristics. Empirical and probabilistic approaches were investigated. The probabilistic approach is based on analysis of the observed sediment yields that were calculated from reservoir sediment deposit, river suspended sediment sampling data and soil erodibility data. The empirical equations have been derived from regression analysis of the variables that were envisaged to have a significant effect on erosion and sediment yields in South Africa. Empirical equations have been developed and shown to have accurate and reliable predictive capability in six of the nine regions. The probabilistic approach has been recommended for the prediction of sediment yields in the remaining three regions where reliable regression equations could not be derived. The predictive accuracy of both the probabilistic and empirical approaches was checked and verified using the discrepancy ratio and graphs of the observed and calculated data. While the analytical methods are needed to predict the sediment yield for the whole catchment, mathematical modelling to predict sediment yields is applied for more detailed analysis of sediment yield within the catchment. An evaluation of available catchment sediment yield mathematical modelling systems was carried out. The main criteria for the choice of a numerical model to be adopted for detailed evaluation was based on the following considerations: the model’s capabilities, user requirements and its application. The SHETRAN model (Ewen et al., 2000) was therefore specifically chosen because of its ability to simulate relatively larger catchment areas (it can handle catchment scales from less than 1km2 to 2500km2), its ability to simulate erosion in channels, gullies and landslides, its applicability to a wide range of land-use types and ability to simulate land use changes. Another model, ACRU (Smithers et al., 2002) was also reviewed. The aim of the model evaluation was to provide a conceptual understanding of catchment sediment yield modelling processes comprising model set up, calibration, validation and simulation. The detailed evaluation of the SHETRAN model was done through a case study of Glenmaggie Dam in Australia. The flow was calibrated and validated using data from 1975 to 1984, and 1996 to 2006 respectively. The results for both the calibration and validation were reasonable and reliable. The sediment load was validated against turbidity derived sediment load data from 1996 to 2006. The model was used to identify sources of sediment and areas of higher sediment yield. The land use of a selected sub-catchment was altered to analyse the impact of land use and vegetative cover on the sediment yield. Based on the results, the SHETRAN model was confirmed to be a reliable model for catchment sediment yield modelling including simulation of different land uses. / AFRIKAANSE OPSOMMING: ‘n Studie van die stand van damtoeslikking in Suid-Afrika toon dat daar ernstige toeslikkingsprobleme by baie reservoirs bestaan. ’n Ontleding van die toeslikkingsyfers gegrond op damkomopmetings toon dat omtrent 25% van die totale getal reservoirs tussen 10 en 30% van hulle oorspronklike opgaarvermoë verloor het. Die gemiddelde tempo van damtoeslikking in Suid-Afrika is 0.3%/jaar, wat laer is as die wêreld gemiddeld van 0.8%/jaar. Die oogmerk met hierdie navorsing was om sedimentlewering voorspellingsmetodes te ontwikkel deur gebruik te maak van analitiese metodes en wiskundige modellering. Die sedimentlewering voorspellingsmetodes kan gebruik word vir die beplanning en bestuur van waterbronne en veral vir damtoeslikking beheer. Die opvangsgebied erosie en die sedimentlewering modelleringsmetodes kan toegepas word in tydveranderlike en ruimtelike ontleding van sedimentlewering. Hierdie inligting word benodig vir die detail ontwerp van waterhulpbronne en veral vir die identifisering van kritiese erosiegebiede, bronne van sediment en die formulering van opvangsgebied-bestuur strategië. ‘n Literatuuroorsig oor die huidige metodes vir die voorspelling van erosie en sedimentlewering is gedoen. Nege sedimentasie streke is afgebaken in Suid-Afrika, gegrond op waargenome damtoeslikkingsdata en opvangsgebied-eienskappe. Proefondervindelike en waarskynlikheidsbenaderinge is ondersoek. Die waarskynlikheidsbenadering is gegrond op die ontleding van waargenome damtoeslikking wat bereken is uit reservoir opmeting data en rivier gesuspendeerde sediment data, asook data oor gronderosie. Die proefondervindelike metode se vergelykings is afgelei vanuit regressie ontleding van die veranderlikes wat ‘n belangrike invloed het op die erosie en sedimentlewering in Suid-Afrika. Daar is bevestig dat die ontwikkelde proefondervindelike (empiriese) vergelykings ‘n akkurate en betroubare voorspellingsvermoë in ses van die nege streke het. Die waarskynlikheidsbenadering is aanbeveel vir die voorspelling van sedimentlewering in die ander drie streke, waar betroubare regressie vergelykings nie afgelei kon word nie. Die voorspellingsakkuraatheid van albei metodes is nagegaan en bevestig deur gebruik te maak van die teenstrydigheidsverhouding en grafieke van die waargenome en berekende data. Analitiese metodes van sedimentleweringsvoorspelling is nodig vir ‘n volle opvangsgebied, terwyl wiskundige modellering om sedimentlewerings te voorspel gebruik kan word om ‘n meer in diepte ontleding van die sedimentlewering binne ‘n opvanggebied te doen. ‘n Evaluasie van beskikbare wiskundige modelle wat opvangsgebied sedimentlewering kan voorspel, is gedoen. Die hoofkriteria vir die keuse van ‘n model vir gebruik by gedetailleerde ontleding is gegrond op die volgende: die vermoëns van die model, wat verbruikers benodig en die aanwending van die model. Die SHETRAN model (Ewen et al., 2000) is spesifiek gekies weens sy vermoë om relatief groter opvangsgebiede te simuleer (dit kan opvangsgebiede van 1km2 tot 2500km2 wees) asook om erosie in kanale, dongas en grondverskuiwing simuleer. Dit kan toegepas word op ‘n wye reeks grondtipes en kan ook die gevolge simuleer as die gebruik van die grond verander. ‘n Ander model, ACRU (Smithers et al., 2002) is ook ondersoek. Die doel van die modelevaluering was om ‘n konseptuele begrip te kry van sedimentlewering modelleringsprosesse wat die opstelling, kalibrasie, toetsing en simulasies insluit. Die volledige evaluasie van SHETRAN is gedoen deur middel van ‘n gevalle-studie van die Glenmaggiedam in Australia. Die riviervloei is gekalibreer en getoets deur gebruik te maak van data wat strek van 1975 tot 1984, en van 1996 tot 2006 onderskeidelik. Die resultate van beide die kalibrasie en die toetswas redelik en betroubaar. Die sedimentlading is gekalibreer teen velddata van 1996 tot 2006. Die model is gebruik om bronne van sediment te identifiseer, asook gebiede met ‘n hoër sedimentlewering. Die gebruik van die grond op ‘n gekose sub-opvangsgebied is verander om die impak van grondgebruik en plantbedekking op sedimentlewering te ontleed. Die resultate bewys dat die SHETRAN model ‘n betroubare model is vir groot opvangsgebied sedimentlewering modellering, asook vir die simulasie van verskillende grondgebruike.

Είναι ευρέως γνωστό ότι οι διαδικασίες της διάβρωσης του εδάφους επηρεάζονται από ένα πλήθος βιοφυσικών και ανθρώπινων παραγόντων και εμφανίζονται με διαφορετικές εντάσεις σε διαφορετικά περιβάλλοντα. Εντούτοις, οι χωρικές και χρονικές κλίμακες των διαδικασιών είναι ακόμα ανεπαρκώς κατανοητές. Ως εκ τούτου, ο έλεγχος και ο υπολογισμός της διάβρωσης και της απόθεσης αποτελεί ένα σύνθετο και δύσκολο στόχο. Επομένως, είναι ανάγκη να βελτιωθεί η κατανόηση των διαδικασιών λαμβάνοντας υπόψη την ποσοτική τους έκφραση, ώστε να είναι σε θέση ειδικοί επιστήμονες να αναλύσουν το αντίκτυπο του φαινομένου αυτού. Αντικείμενο της παρούσας μεταπτυχιακής διατριβής είναι η εκτίμηση μοντέλου διάβρωσης και στερεοπαροχής στον ταμιευτήρα του ομώνυμου φράγματος του ποταμού Πηνειού, στην περιοχή του Νομού Ηλείας. Απώτερος στόχος αυτής της μελέτης είναι ο υπολογισμός και η εκτίμηση του όγκου των φερτών υλών που έχουν αποτεθεί στον ταμιευτήρα του φράγματος, με αποτέλεσμα την πολυετή δυσλειτουργία του, με σκοπό την εφαρμογή πρακτικών που θα δώσουν παράταση στην οικονομική ζωή του έργου. Προς την κατεύθυνση αυτή αναπτύχθηκε μια μέθοδος η οποία συνδυάζει την Παγκόσμια Εξίσωση Εδαφικής Απώλειας (Universal Soil Loss Equation - USLE) με τα Γεωγραφικά Συστήματα Πληροφορίας (GIS), συγκεκριμένα το λογισμικό ArcGIS 10. Η USLE υπολογίζει την μακροπρόθεσμη μέση ετήσια απώλεια εδάφους πολλαπλασιάζοντας πέντε συγκεκριμένους παράγοντες που περιγράφουν τα χαρακτηριστικά λεκανών, όπως η διαβρωτικότητα της βροχόπτωσης, η διαβρωσιμότητα του εδάφους, η μορφολογία του εδάφους, η φυτοκάλυψη του εδάφους και η διαχείριση των εδαφών κατά της διάβρωσης. Το GIS χρησιμοποιείται για την αποθήκευση των συντελεστών της USLE ως μεμονωμένα ψηφιακά επίπεδα τα οποία πολλαπλασιάζονται μεταξύ τους για να δημιουργήσουν έναν δυναμικό χάρτη εδαφικής διάβρωσης. Αυτός ο συνδυασμός παρέχει έναν τρόπο εκτίμησης της πιθανής διάβρωσης του εδάφους σε μια περιοχή με τις υπάρχουσες πηγές δεδομένων. Ο εντοπισμός των περιοχών που παρουσιάζουν μεγαλύτερο κίνδυνο διάβρωσης και η χαρτογράφησή τους, συμβάλουν στην πρόληψη της περαιτέρω υποβάθμισης του εδάφους με χρήση των απαραίτητων αντιδιαβρωτικών μέτρων. Για τον υπολογισμό του συντελεστή διαβρωτικότητας της βροχόπτωσης (R) και για την εξαγωγή του χάρτη κατανομής της χρησιμοποιήθηκαν οι μηνιαίες και ετήσιες μετρήσεις βροχόπτωσης από πέντε μετεωρολογικούς σταθμούς που εντοπίζονται στην λεκάνη απορροής ανάντη του φράγματος. Ο συντελεστής διαβρωσιμότητας του εδάφους (Κ) απαιτεί μετρήσεις πεδίου για την εκτίμηση των ιδιοτήτων του εδάφους. Στην παρούσα μελέτη, λόγω αδυναμίας συγκέντρωσης δειγμάτων, οι ιδιότητες του εδάφους εκτιμήθηκαν με γεωλογικά κριτήρια και εν συνεχεία με τη χρήση του GIS δημιουργήθηκε χάρτης κατανομής διαβρωσιμότητας του εδάφους. Με βάση το Ψηφιακό Μοντέλο Αναγλύφου της περιοχής μελέτης υπολογίστηκε ο τοπογραφικός συντελεστής (LS), ενώ βάσει του CORINE και σύμφωνα με τη βιβλιογραφία υπολογίστηκε ο παράγοντας κάλυψης και διαχείρισης γης (C). Τέλος, ο συντελεστής διαχείρισης των εδαφών κατά της διάβρωσης (P) ορίστηκε ίσος με τη μονάδα (1) καθώς δεν έχει παρθεί κανένα μέτρο για την προστασία των εδαφών κατά της διάβρωσης σε όλη την λεκάνη απορροής. Βάσει των παραπάνω υπολογισμών προέκυψε η μέση ετήσια απώλεια εδάφους ανά μονάδα επιφάνειας της λεκάνης απορροής ανάντη του φράγματος, η οποία ανέρχεται στους ----- t/ha ή SE=---- t/km2. Κατόπιν υπολογισμού της μέσης ετήσιας εδαφικής διάβρωσης, βάσει εμπειρικής μεθόδου υπολογίστηκε ο συντελεστής (%) στερεοαπορροής και κατ' επέκταση η μέση ετήσια στερεοαπορροή της λεκάνης ανάντη του φράγματος Πηνειού, η οποία ανέρχεται σε ----- t/ha ή ----- t/km2. Για την συγκεκριμένη λεκάνη απορροής το ----- των παραγόμενων φερτών υλών είναι αυτό που τελικά μεταφέρεται και αποτίθεται κάθε χρόνο στον ταμιευτήρα του φράγματος, τα οποία ανέρχονται σε ------ t. / It’s widely known that the procedures of soil erosion are affected by a number of biophysical and human factors and appeared with different intensities in different places. However, the spatial and temporal scales of the procedures are still poorly understood. Therefore, the control and the calculation of soil erosion and deposition are a complex and difficult task. So, it’s necessary to improve the understanding of the procedures, taking into account their quantitative expression, in order to scientists be able to analyze the impacts of this phenomenon. The main purpose of this thesis is the estimation of the erosion and sediment model in the reservoir of the homonymous dam of river Peneus, in the prefecture of Ilia. The ultimate goal of this study is to calculate and estimate the volume of sediment that have been deposited in the reservoir of the dam, resulting in perennial dysfunction , in order to implement practices that will give extension in the economic life of the project. For this propose a method has been developed that combines the Universal Soil Loss Equation- USLE with Geographic Information Systems- GIS. This method is the software ArcGIS 10. The USLE equation calculates the long-term average annual soil loss by multiplying five specific factors that describe the characteristics of the basins, such as the rainfall erosivity, the soil erodibility, the topography, the vegetation cover of the soil and the management of soil erosion. The GIS system is used to store the USLE’s factors as individual digital levels that are multiplied together to create a dynamic map of soil erosion. This combination provides a way of estimating of the possible erosion of the soil in an area with the existing data sources. The identification of the areas of greatest risk of erosion and their cartography, helped to prevent further soil degradation by using the necessary corrosion measures. For calculating the rainfall erosivity factor (R) and for the extraction of the distribution map of erosion are used monthly and annual rainfall measurements from five meteorological stations located in the watershed upstream of the dam. The soil erodibility factor (K) requires field measurements to estimate the properties of the soil. In this study, due to our inability to obtain samples, soil properties were evaluated with geological criteria and subsequently using the GIS created map distribution of soil erodibility. Based on the digital elevation model of the study area, was calculated the topographic factor (LS), while under CORINE and the literature was calculated the capper and land administration (C). Finally, the factor of soil management against erosion (P) was set equal to one (1) as there has not been taken any step to protect soils against erosion throughout the basin. Based on the above calculation showed average annual soil loss per unit area of the watershed upstream of the dam, which amounts to ---- t/ha or SE=---- t/km2. After calculation the average annual soil erosion, based on the empirical method has calculated the sediment delivery ratio and thus the average annual sediment yield of the watershed upstream of the dam Peneus, which is -----t/ha or ----- t/km2. For this specific watershed the ----% of the produced sediment is what ultimately transported and deposited annually in the reservoir of the dam, which amount to ---- t.

Lake Tana Basin is of significant importance to Ethiopia concerning water resources aspects and the ecological balance of the area. The growing high demands in utilizing the high potentials of water resource of the Lake to its maximal limit, pictures a disturbing future for the Lake. The objective of this study was to assess the influence of topography, soil, land use and climatic varia-bility on the hydrological and hydrodynamic processes of the Lake Tana Basin. The physically based SWAT model was successfully calibrated and validated for flow and sediment yield. Se-quential uncertainty fitting (SUFI-2), parameter solution (ParaSol) and generalized likelihood un-certainty estimation (GLUE) calibration and uncertainty analysis methods were compared and used for the set-up of the SWAT model. There is a good agreement between the measured and simulated flows and sediment yields. SWAT and GIS based decision support system that uses multi-criteria evaluation (MCE) was used to identify the most vulnerable areas to soil erosion in the basin. The results indicated that 12 to 30.5% of the watershed is high erosion potential. Pro-jected changes in precipitation and temperature in the basin for two seasons were analyzed using outputs from fifteen global climate models (GCMs). A historical-modification procedure was used to downscale large scale outputs from GCM models to watershed-scale climate data. The results showed significant changes in streamflow and other hydrological parameters in the period between 2045-2100. SWAT was combined with a three dimensional hydrodynamic model, GEMSS to investigate the flow structure, stratification, the flushing time, lake water balance and finally the Lake‘s water level response to planned water removal. We have found an alarming and dramatic fall of the water levels in Lake Tana as response to the planned water withdrawal. The combination of the two models can be used as a decision support tools to better understand and manage land and water resources in watersheds and waterbodies. The study showed that the Lake Tana Basin may experience a negative change in water balance in the forthcoming decades due to climate change as well as over abstraction of water resources. / QC 20100720

RODRIGUES, Joseilson Oliveira. O uso da terra e a resposta hidrológica de pequenas bacias em regiões semiáridas. 2009. 128 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Curso de Mestrado em Engenharia Agrícola, Fortaleza-CE, 2009. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-07-07T14:22:18Z No. of bitstreams: 1 2009_dis_jorodrigues.pdf: 16309402 bytes, checksum: b2ab17d81f17cb85baf29eae39b670db (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-07-07T14:23:26Z (GMT) No. of bitstreams: 1 2009_dis_jorodrigues.pdf: 16309402 bytes, checksum: b2ab17d81f17cb85baf29eae39b670db (MD5) / Made available in DSpace on 2016-07-07T14:23:26Z (GMT). No. of bitstreams: 1 2009_dis_jorodrigues.pdf: 16309402 bytes, checksum: b2ab17d81f17cb85baf29eae39b670db (MD5) Previous issue date: 2009 / This work was carried out to evaluate and to compare the hydrologic and sedimentologic behaviour of small rural catchments in the semiarid Northeast of Brazil, as well as to asses the influence of the anthropogenic action over soil and water resources. The study of theses processes is very important for the definition of strategies to a better management of small watersheds and the definition of sustainability plans. The study area is located in the Alto Jaguaribe basin, in the Iguatu County, State of Ceará, Brazil. Four small catchments B1, B2, B3 and B4, neibor to each other, were delimited and equipped with Parshall flumes, water level sensors, rain-gauges and automatic sediment samplers, aiming hydrossedimentologic studies under natural rainfall conditions. In this research, the areas of studied catchments areas are smaller than three ha. In the B1 part of cover vegetation was cut, making it possible to assess the influence of changes in the vegetation cover over runoff, peak discharge and sediment yield. In the others catchments (B2, B3 and B4), cover vegetation was keeping in undisturbed condition, representing the natural condition in the semiarid region of northeast Brazil. The data analysed comprises the hydrologic year of 2009 on the four experimental unities and some events on the months of January, February and March of 2008 on the small catchment B2. Despite the proximity of the monitored unities, the results show high spatial and temporal variability of the hydrossedimentologic answer, and the antecedent soil moisture as the main variable responsible for such modifications. It was observed that lowering the density of the Caatinga vegetation influenced runoff and sediment yield, with greater effects over the first events. Accumulated sediment yield reached values of 1.45, 1.39 and 0.12 ton.ha-1 for the micro-catchments B1, B2 e B4, respectively, at the end of the year 2009. Among all investigated catchments, B3 presented the highest values of runoff and peak discharges, with runoff coefficient average around 28%. The B4 experimental unit had a hydrossedimentologic behaviour very different from the other catchments, showing the lowest values of peak discharge, runoff and sediment yield, and this behaviour can be explained to the soil characteristics. The results presented in this study contribute with important information for the hydrossedimentologic study of semiarid regions, and can be used to guide further research in small catchments with ephemeral regime. / O objetivo central desse trabalho foi avaliar e comparar o comportamento hidrológico e sedimentológico em pequenas bacias rurais no semiárido nordestino, verificando a influência da ação antrópica sobre os recursos solo e água. O estudo desses processos é de suma importância na definição de estratégias para o melhor gerenciamento de pequenas bacias hidrográficas e na definição de planos de sustentabilidade. A área de investigação localiza-se na bacia do Alto Jaguaribe, mais precisamente no município de Iguatu, na região conhecida como Centro Sul do estado do Ceará. A área experimental é composta por quatro microbacias com denominação de B1, B2, B3 e B4 localizadas próximas entre si, foram delimitadas e equipadas com calhas Parshall, sensores de nível de água, pluviógrafos e coletores automáticos de sedimentos visando estudos hidrossedimentológicos em condições de chuva natural. Nessa pesquisa as áreas das bacias em avaliação não excederam 3 hectares, sendo na microbacia B1 aplicado um tratamento (raleamento), que permitiu avaliar a influência da alteração na cobertura vegetal da Caatinga sobre o escoamento superficial, descarga máxima e produção de sedimentos. As demais microbacias experimentais B2, B3 e B4 foram mantidas inalteradas, sem intervenção antrópica, representando condições naturais de pequenas bacias rurais do semiárido do nordeste. Os dados analisados abrangem toda a estação chuvosa de 2009 nas quatro unidades experimentais e alguns eventos nos meses de janeiro, fevereiro e março de 2008 na microbacia B2. Apesar da proximidade entre as unidades de monitoramento, os resultados revelaram grande variabilidade espaço-temporal das respostas hidrossedimentológicas, sendo a umidade anterior do solo a variável de destaque na modificação destas. Os resultados mostraram que a prática de raleamento da Caatinga teve influência na alteração do escoamento superficial e produção de sedimentos, sendo os efeitos maiores sobre os primeiros eventos. A produção acumulada de sedimentos atingiu ao final de 2009 valores de 1,45; 1,39 e 0,12 ton ha-1 para as microbacias B1, B2 e B4, respectivamente. De todas as microbacias investigadas, B3 apresentou os maiores valores de escoamento superficial, e descargas máximas, com coeficiente de escoamento médio em torno de 86%. A unidade experimental B4 mostrou-se com comportamento hidrossedimentológico bastante diferenciado das demais microbacias, sendo nesta encontrado as menores magnitudes de descarga máxima, escoamento superficial e produção de sedimentos, comportamento este associado principalmente às características físicas do solo da microbacia. Os resultados encontrados fornecem elementos importantes no campo hidrossedimentológico em regiões semiáridas, podendo ser empregados para nortear pesquisas futuras em microbacias com escoamento efêmero.

FARIAS, Teresa Raquel Lima. Estradas rurais não pavimentadas como fonte de sedimentos em bacia hidrográfica do semiárido. 2016. 97 f. : Tese (doutorado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Programa de Pós-Graduação em Engenharia Agrícola, Fortaleza-CE, 2016. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-08-05T17:12:33Z No. of bitstreams: 1 2016_tese_trlfarias.pdf: 2470558 bytes, checksum: 30335a2cc35e4a28efe3e35816823a1e (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-08-05T17:15:47Z (GMT) No. of bitstreams: 1 2016_tese_trlfarias.pdf: 2470558 bytes, checksum: 30335a2cc35e4a28efe3e35816823a1e (MD5) / Made available in DSpace on 2016-08-05T17:15:47Z (GMT). No. of bitstreams: 1 2016_tese_trlfarias.pdf: 2470558 bytes, checksum: 30335a2cc35e4a28efe3e35816823a1e (MD5) Previous issue date: 2016 / Approximately 80% of the road network in Brazil is unpaved. Studies have reported high erosion rates and runoff produced by the road infrastructure in various parts of the world and report that unpaved roads are significant sources of sediment in river basins. For two years (2013-2014), monitoring in the field under natural rainfall conditions was conducted to characterize runoff and sediment yield of unpaved rural road segments and the respective slopes in semiarid area of the Caatinga biome of northeastern Brazil, vulnerable to desertification. It was assessed the application of modelling in the yield of sediments from road surface. The sediment yield values measured in the years 2013-2014 ranged from 0.30 Mg.ha-1.year-1 to 0.92 Mg.ha-1.year-1, higher than those recorded in the preserved area, but generally lower than those reported in the literature for unpaved roads. However, it is a semiarid area with low rainfall and characterized by low runoff coefficients, which limits the sediment yield and the hydrological connectivity in the area, additionally the two monitoring years coincided with drought in the region. In the monitored road slope segments, sediment yield from the non-vegetated slope was about ten times that of the slope with vegetation. On the road surfaces, the annual sediment yield (normalized by the slope) in a segment with traffic was three times higher than that without traffic, in addition, events occurring after maintenance activities generated sediment concentration peaks as high as 5,000 mg.L-1 in these areas. In the road segment scale, among the models tested for the predicting of sediment yield, the USLE associated with the Maner equation, proved to be a suitable approach, the best results being obtained for the road without traffic due to no interference from external factors, such as traffic and maintenance activities, which are not explained by the model. In the scale of the Benguê catchment (933 km²), where the roads occupy only 0.7% of the surface, the modelling indicated that these areas contributed with approximately 7% of the total soil loss. The results of this study suggest that the sediment yield from roads and slopes with bare surface is at least one order of magnitude higher than those recorded in the preserved areas of the basin. Maintenance activities on roads and traffic of vehicles contribute to the increased availability of sediments and impacting the sediment concentrations, but produce lower impact on the sediment loads, which depend on runoff and the its occurrence after reprofiling of roads. It was also found that the natural vegetation of the semiarid region has potential in capturing sediments in road slopes, with an important role in breaking down connectivity between sediment flows from unpaved roads and the natural drainage system of the catchment. / Aproximadamente 80% da malha viária no Brasil não possui pavimentação. Estudos têm registrado elevadas taxas de erosão e escoamento superficial produzidas pela infraestrutura viária em várias partes do mundo e reportam que estradas não pavimentadas são fontes significativas de sedimentos em bacias hidrográficas. Durante dois anos (2013-2014) foi conduzido monitoramento em campo sob condições de chuva natural para caracterizar escoamento e produção de sedimentos de segmentos de superfície de estradas rurais não pavimentadas e talude viário, em área semiárida do bioma Caatinga do nordeste do Brasil, vulnerável à desertificação. Também avaliou-se a aplicação de modelagem na predição da produção de sedimentos de superfície de estradas. Os valores de produção de sedimentos medidos nos anos de 2013-2014, variaram de 0,30 Mg.ha-1.ano-1 a 0,92 Mg.ha-1.ano-1, superiores aos registrados na área em condição preservada, porém em geral inferiores aos reportados na literatura para estradas não pavimentadas. Entretanto, trata-se de uma área semiárida com baixa pluviometria e caracterizada por baixos valores de coeficiente de escoamento superficial, o que limita a produção de sedimentos e a conectividade hidrológica da área, além de os dois anos de monitoramento terem coincidido com período de seca na região. Nos segmentos de talude rodoviário monitorados, a produção de sedimentos do talude sem vegetação foi cerca de dez vezes superior à do segmento com vegetação. Na superfície de estradas, a produção de sedimentos anual (normalizada pela declividade) em um segmento com trânsito foi três vezes mais elevada que da estrada sem trânsito, além disso, eventos que ocorreram após atividades de manutenção das vias geraram picos de concentração de sedimentos superiores a 5.000 mg.L-1 nessas superfícies. Na escala de segmento de estrada, entre os modelos avaliados para predição da produção de sedimentos, a USLE associada a equação de Maner, mostrou-se uma abordagem adequada, em que os melhores resultados foram obtidos para a estrada sem trânsito, devido a não interferência neste segmento, de fatores externos como trânsito e atividades de manutenção, não explicados pelo modelo. Já na escala da Bacia do Benguê (933 km²), onde as estradas ocupam apenas 0,7% da superfície, a aplicação de modelagem mostrou que estas contribuíram com aproximadamente 7% do total de perdas de solo na área. Os resultados deste estudo sugerem que a produção de sedimentos em estradas e taludes com superfície desnuda é pelo menos uma ordem de magnitude superior àquelas registrada nas áreas preservadas da bacia. Atividades de manutenção nas estradas e o trânsito de veículos contribuem para o aumento da disponibilidade de sedimentos com impacto nos valores de concentração de sedimentos, mas impactando menos as cargas de sedimentos que dependem do escoamento superficial e da ocorrência de eventos após manutenção das vias. Constatou-se que a vegetação natural do semiárido tem potencial na captura de sedimentos em taludes rodoviários, com papel importante na quebra de conectividade entre fluxos de sedimentos provenientes de estradas não pavimentadas e o sistema de drenagem natural da bacia.

Today we know the need to preserve environmental resources, which include soils and hydrology. Estimates of water loss and soil erosion are held in different countries, using empirical or conceptual models such as SWAT (Soil and Water Assessment Tool), used to predict the impact of changes in the use and soil management, among others on soil loss and the flow of the watercourse. This model, through their routines, is able to simulate and quantify in a watershed as the dynamics of water flow and sediment occurs, the supply of information on the maps and tabular data format is required. This thesis set up two goals: first to identify the most appropriate spatial resolution for simulations, comparing the measured field data with simulated data flow and sediment yield. To this end, we analyzed how the product image affected the performance of the SWAT simulation application without being calibrated by changing their spatial resolutions of 10, 30, 50, 100 and 200 meters. After there were three analysis processes to determine which resolution gave better results of simulation, called analysis of percentage, and statistical regression, concluding that the image with 200 meter resolution showed the best results of simulation of liquid flow in the channel and without sediment transport model calibration. The second objective is to perform a simulation for basin Guapore validate and calibrate the model for liquid flow, analyzing the results for the sediment delivery with a period of 10 years of data. Performed the simulation is performed sensitivity analysis indicated that seven parameters as the most sensitive. Then ensued for calibration, effecting to change these parameters manually for flow and later to sediment production. Was used to analyze the efficiency calibration, the coefficient of efficiency. According to bibliography, this should keep values above 0.50 to be considered calibrated. For flow data were obtained for a range of average six years analyzed 0, 578 After calibration values, executed to validate the model using a seven-year period, reaching up to data an average flow of 0.68 COE. The model presented below one year with values determined by the bibliography, being satisfactory calibration and validation. As for the transport of sediment was not possible to calibrate and validate the model because the coefficient of efficiency showed high values, inferring that the main causes have been simplifying the soil loss equation uses the simulator to make some calculations, especially related to the length and steepness of slope, and basin size. Furthermore, by deducting the measured sediment data showed high variability within months of the years, making it difficult adjusting the parameters. It was concluded that the simulation process is valid for analysis and establishment of public conservation measures and preventive use of environmental resources, especially those related to the cultivation of land, and that the most appropriate spatial resolution of 200 meters for large basins. This resolution is not, perhaps, the reality for small basins, further studies should be performed. / Sabe-se da necessidade de preservar os recursos ambientais, onde incluem-se os solos e a hidrologia. Estimativas da perda de água e solo por erosão são realizadas em diversos países, utilizando-se modelos empíricos ou conceituais, como o SWAT (Soil and Water Assessment Tool), utilizado para predizer o impacto das alterações no uso e no manejo do solo, entre outros, sobre a perda de solo e a vazão de curso de água. Este modelo, através de suas rotinas, tem condições de simular e quantificar em uma bacia hidrográfica como ocorre a dinâmica de fluxo de água e sedimentos, sendo necessário o abastecimento de informações no formato de mapas e dados tabulados. Nesta tese estabeleceram-se dois objetivos: o primeiro identificar qual a resolução espacial mais adequada para simulações, comparando-se dados medidos a campo com dados simulados de vazão e produção de sedimentos. Para tanto, analisou-se como o produto imagem afetou o desempenho de simulação do aplicativo SWAT sem estar calibrado, alterando-se as respectivas resoluções espaciais das imagens em 10, 30, 50, 100 e 200 metros. Após realizaram-se três processos de análise para determinar qual resolução gerou melhores resultados de simulação, denominadas de análise de percentagem, estatística e regressão, concluindo-se que a imagem com 200 metros de resolução apresentou os melhores resultados de simulação de vazão liquida no canal e transporte de sedimentos sem a calibração do modelo. O segundo objetivo é realizar uma simulação para a bacia de Guaporé validar e calibrar o modelo para vazão líquida, analisando-se os resultados para o aporte de sedimentos com um período de 10 anos de dados. Realizada a simulação, executou-se análise de sensibilidade que indicou sete parâmetros como os mais sensíveis. Seguiu-se, então, para calibração, efetivando-se a mudança destes parâmetros de forma manual para vazão e posteriormente para produção de sedimentos. Utilizou-se, para analisar a eficiência da calibração, o coeficiente de eficiência. Conforme a bibliografia, este deverá manter valores acima de 0,50 para ser considerado como calibrado. Para os dados de vazão obtiveram-se valores médios para um intervalo de seis anos, analisados de 0, 578. Após a calibração, executou-se a validação do modelo utilizando-se um período de sete anos, alcançando-se para os dados de vazão um valor médio de COE de 0,68. O modelo apresentou um ano com valores abaixo do determinado pela bibliografia, sendo satisfatória a calibração e validação. Já para o transporte de sedimentos não foi possível calibrar o modelo e validar, pois o coeficiente de eficiência apresentou valores elevados, inferindo-se que as principais causas foram a simplificação da equação de perdas de solo que o simulador utiliza para fazer alguns cálculos, principalmente relacionados ao comprimento de rampa e declividade, e o tamanho da bacia. Além disso, deduzindo-se que os dados de sedimentos medidos apresentaram uma alta variabilidade dentro dos meses nos anos, o que dificultou o ajuste dos parâmetros. Concluiu-se que o processo de simulação é valido para análises e estabelecimento de medidas públicas de conservação e uso preventivo dos recursos ambientais, principalmente aqueles relacionados ao cultivo de solos, e que a resolução espacial mais adequada é de 200 metros para grandes bacias. Esta resolução não é, talvez, a realidade para pequenas bacias, devendo ser realizado estudos complementares.

Made available in DSpace on 2016-12-08T15:50:04Z (GMT). No. of bitstreams: 1 PGMS14DA021.pdf: 1596222 bytes, checksum: 429152a00872f6dbd34d929c38428e3c (MD5) Previous issue date: 2014-03-27 / By 1947, Ellison, defined soil erosion as a process of breakdown and sediment transport by erosive agents, and factors involved in the process should be studied separately. From there, a series of models and mathematical equations were developed to predict soil erosion. At one extreme, empirical models, similar to Equation Universal Soil Loss Models - USLE, considering annual average soil loss, are relatively simple and require little computational effort. However, present difficulties when it comes to scaling for different scenarios of those tested, and are not indicated for individual events. At the other extreme, the mathematical models with a high degree of complexity, require great effort in the generation of the input data, and computational work in their processing. Although a purely physical model is desirable, the amount of required information makes it virtually impossible, suggesting the adoption of an intermediate model between purely physical and empirical. A simplified model proposed by Hartley (1987) to estimate runoff, sediment yield and soil loss can be an alternative in this universe. This model, despite a physical basis, requires a set of data similar to the USLE. The research aims to examine the Hartley model, build and adapt new routines to be incorporated in the original model and validate it in some real situations. The first steps of this work consisted in searching and organizing data on losses of soil and water by rainfall erosion, originating database for soil conservation and water available on CAV/UDESC. The simulations were performed with the data obtained in experiments conducted in two soils, clayey loam structured soil (Hapludox) and Inceptisol. The model performance was evaluated according to the confidence index, which summarizes the results of the indices of concordance and correlation. The model proved capable of predicting water losses, with correlation coefficients between 0.75 and 0.91, similar to levels of concordance from 0.73 to 0.91. The performance of the model ranged from tolerable to very good. For soil loss, the model showed higher rates, with values of 0.96 and 0.95 for the correlation and concordance, respectively. The performance of the model for soil loss, had great values / Por volta de 1947, ELLISON, definiu a erosão do solo como um processo de desagregação e transporte de sedimentos por agentes erosivos, e que fatores envolvidos no processo deveriam ser estudados separadamente. A partir daí, uma série de modelos e equações matemáticas foram desenvolvidas para predizer a erosão do solo. Num extremo, os modelos empíricos, semelhantes à Equação Universal de Perda de Solo USLE, por considerar valores médios anuais de perdas de solo, são relativamente simples e requerem pouco esforço computacional. No entanto, apresentam algumas dificuldades quando se trata de extrapolação para cenários diferentes daqueles testados, além de não serem indicados para eventos individuais. Noutro extremo, os modelos matemáticos, com alto grau de complexidade, exigem grande esforço na geração dos dados de entrada e muito trabalho computacional no seu processamento. Embora seja desejável um modelo puramente físico, a quantidade de informações requeridas torna-o praticamente inviável, o que indica a adoção de um modelo intermediário entre puramente físico e empírico. Um modelo simplificado, proposto por Hartley (1987) para estimar o escoamento superficial, a produção de sedimentos e a perda de solo, pode ser uma alternativa neste universo. Este modelo, apesar de ter uma base física, requer um conjunto de dados similar àquele da USLE. A pesquisa tem como objetivo proceder à análise do modelo de Hartley, construir e adequar novas rotinas a serem incorporadas no modelo original e validá-lo em algumas situações reais. Os primeiros passos deste trabalho consistiram em buscar e organizar dados de perdas de solo e água por erosão hídrica pluvial, oriundos da base de dados de conservação do solo e água disponíveis no CAV/UDESC. As simulações do modelo foram realizadas com os dados obtidos em experimentos conduzidos em dois solos, um Nitossolo Háplico Alumínico e um Cambissolo Húmico Alumínico Léptico. O desempenho do modelo foi avaliado segundo o índice de confiança, o qual sintetiza os resultados dos índices de concordância e de correlação. O modelo mostrou-se capaz de predizer as perdas de água, com índices de correlação entre 0,75 e 0,91, semelhantes aos índices de concordância de 0,73 a 0,91. O desempenho do modelo variou de sofrível a muito bom. Para as perdas de solo, o modelo apresentou índices superiores, com valores de 0,96 e 0,95 para a correlação e a concordância, respectivamente. O desempenho do modelo, para as perdas de solo, foi considerado ótimo

Made available in DSpace on 2014-12-17T15:03:25Z (GMT). No. of bitstreams: 1 RodrigoOS_DISSERT_1-90.pdf: 2869540 bytes, checksum: 998755351b8f82fb75792f6508f6fd61 (MD5) Previous issue date: 2010-12-06 / Anthropic disturbances in watersheds, such as inappropriate building development, disorderly land occupation and unplanned land use, may strengthen the sediment yield and the inflow into the estuary, leading to siltation, changes in the reach channel conformation, and ecosystem/water quality problems. Faced with such context, this study aims to assess the applicability of SWAT model to estimate, even in a preliminary way, the sediment yield distribution along the Potengi River watershed, as well as its contribution to the estuary. Furthermore, an assessment of its erosion susceptibility was used for comparison. The susceptibility map was developed by overlaying rainfall erosivity, soil erodibility, the slope of the terrain and land cover. In order to overlap these maps, a multi-criteria analysis through AHP method was applied. The SWAT was run using a five year period (1997-2001), considering three different scenarios based on different sorts of human interference: a) agriculture; b) pasture; and c) no interference (background). Results were analyzed in terms of surface runoff, sediment yield and their propagation along each river section, so that it was possible to find that the regions in the extreme west of the watershed and in the downstream portions returned higher values of sediment yield, reaching respectively 2.8 e 5.1 ton/ha.year, whereas central areas, which were less susceptible, returned the lowest values, never more than 0.7 ton/ha.ano. It was also noticed that in the west sub-watersheds, where one can observe the headwaters, sediment yield was naturally forced by high declivity and weak soils. In another hand, results suggest that the eastern part would not contribute to the sediment inflow into the estuary in a significant way, and the larger part of the sediment yield in that place is due to anthropic activities. For the central region, the analysis of sediment propagation indicates deposition predominance in opposition to transport. Thus, it s not expected that isolated rain storms occurring in the upstream river portions would significantly provide the estuary with sediment. Because the model calibration process hasn t been done yet, it becomes essential to emphasize that values presented here as results should not be applied for pratical aims. Even so, this work warns about the risks of a growth in the alteration of natural land cover, mainly in areas closer to the headwaters and in the downstream Potengi River / Interfer?ncias antr?picas, a exemplo do desenvolvimento de obras inadequadas, da ocupa??o desordenada do solo e de seu uso indiscriminado para atividades agropecu?rias, podem intensificar o aporte de sedimentos para os estu?rios, implicando em altera??es na conforma??o de seu canal, assoreamento, altera??o da qualidade das ?guas e dos ecossistemas. Diante disso, este trabalho pretende avaliar a aplicabilidade do modelo SWAT (Soil and Water Assessment Tool) para estimar, mesmo que de forma preliminar, a distribui??o da produ??o de sedimentos ao longo da bacia hidrogr?fica do rio Potengi (BHRP) e a sua contribui??o para o estu?rio, fazendo tamb?m um paralelo com sua suscetibilidade ? eros?o h?drica, de maneira que a aplica??o dessa ferramenta possa ser cogitada para fins de planejamento e gest?o da bacia. O mapa de suscetibilidade ? eros?o h?drica foi constru?do a partir da sobreposi??o da erosividade das chuvas, da erodibilidade dos solos, da declividade do terreno e da cobertura do solo. Para a sobreposi??o desses crit?rios foi realizada uma an?lise multicriterial pelo m?todo AHP (Analytical Hierarchy Process). O SWAT foi executado para a um per?odo de cinco anos (1997 - 2001), considerando tr?s cen?rios com composi??es de cobertura do solo diferentes, com base nas formas de interfer?ncia humana: agricultura, pastagem e nenhuma interfer?ncia (background). Os resultados foram analisados em termos de escoamento superficial, de produ??o de sedimentos e de propaga??o dos sedimentos ao longo dos trechos de rio. Com os resultados das simula??es, comparados ao mapa de suscetibilidade ? eros?o, foi poss?vel constatar que as por??es de cabeceira oeste da bacia e do baixo rio Potengi retornaram os maiores valores de produ??o de sedimentos, alcan?ando 2,8 e 5,1 t/ha.ano, respectivamente, enquanto que a regi?o central foi considerada a menos suscet?vel ? eros?o e a que gera menor carga de sedimentos, n?o superando 0,7 t/ha.ano. Percebeu-se ainda que nas sub-bacias mais a oeste da bacia, onde se revelam as nascentes da rede h?drica, a produ??o de sedimentos ? impulsionada, naturalmente, pelas grandes declividades aliadas aos solos fr?geis. J? para a regi?o leste da bacia os resultados sugerem que, por for?a de sua pr?pria natureza, essa regi?o n?o contribuiria significativamente com aporte de sedimentos para o rio Potengi, de forma que a maior parte dos sedimentos produzidos ? conseq??ncia das atividades antr?picas. Para a por??o central da bacia, a an?lise da propaga??o de sedimentos aponta para um predom?nio da deposi??o em detrimento do transporte, a partir do que se conclui que muito dificilmente um evento de chuva que ocorra no alto rio Potengi contribuir? significativamente com aporte de sedimentos para o estu?rio do rio. Tendo em vista que os processos de calibra??o do modelo ainda n?o foram desempenhados, torna-se imprescind?vel salientar que os valores apresentados nos resultados deste trabalho n?o devem ser utilizados para fins pr?ticos. De todo modo, este estudo alerta para os riscos do avan?o de um processo inadequado de altera??o da cobertura natural do solo, sobretudo nas proximidades das nascentes do rio Potengi e na por??o do baixo rio Potengi. Espera-se que este trabalho contribua para motivar futuras pesquisas na ?rea e incitar as discuss?es voltadas para o manejo da BHRP, incluindo o planejamento das formas de ocupa??o e das atividades exercidas em seu territ?rio

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A erosÃo, o transporte e a deposiÃÃo de sedimentos sÃo questÃes ambientais que afetam a sociedade, principalmente devido ao decrÃscimo da produtividade agrÃcola, à diminuiÃÃo da capacidade de armazenamento dos reservatÃrios, à intensificaÃÃo dos processos de desertificaÃÃo, à ocorrÃncia de inundaÃÃes e à reduÃÃo da disponibilidade hÃdrica. A tendÃncia atual dos estudos hidrosedimentolÃgicos à abordar grandes escalas, a fim de gerar resultados com implicaÃÃes para o planejamento das bacias hidrogrÃficas. PorÃm, o monitoramento e a anÃlise hidrosedimentolÃgica de sub-bacias sÃo de grande importÃncia para o entendimento dos processos locais. AlÃm disso, esses estudos, quando consistentes, se tornam parte do banco de dados das investigaÃÃes que englobam os grandes sistemas, em algumas situaÃÃes, a escala global. Objetiva-se com esta pesquisa estudar a produÃÃo especÃfica de sedimentos na Bacia do Rio Jaguaribe (BRJ), com a proposta de analisar as relaÃÃes entre esta variÃvel e a Ãrea de drenagem, a fim de identificar se os dados possuem alometria com a escala espacial. Os dados de produÃÃo de sedimentos foram obtidos de fontes primÃrias e secundÃrias, contemplando diferentes mÃtodos de mediÃÃo e larga faixa de Ãreas (6,8 x 10-5 km a 4,8 x 104 kmÂ). Os dados primÃrios advieram do monitoramento de uma seÃÃo hidrosedimentolÃgica automatizada, monitoramento de uma encosta por pinos de erosÃo e batimetrias de reservatÃrios. Os dados secundÃrios foram originados de investigaÃÃes anteriores conduzidas em diversas escalas de sub-bacias do Rio Jaguaribe, tambÃm contemplando diferentes mÃtodos de mediÃÃo. Os resultados encontrados por esta pesquisa mostram que: (i) a calibraÃÃo do turbidÃmetro por meio da resuspensÃo de sedimentos se mostrou uma alternativa plausÃvel para as condiÃÃes semiÃridas. A melhoria da escala temporal no monitoramento sedimentolÃgico atravÃs das medidas de turbidez permitiu uma anÃlise mais representativa da dinÃmica da concentraÃÃo de sedimentos suspensos da seÃÃo estudada; (ii) a produÃÃo de sedimentos mÃdia da BRJ foi de 347 t km-2 ano-1, mÃnimo de 1,1 t km-2 ano-1 e mÃximo de 1.340 t km-2 ano-1; (iii) os atributos erosividade, geologia e cobertura vegetal, quando analisados separadamente, nÃo induziram a nenhuma relaÃÃo clara entre a produÃÃo especÃfica de sedimentos e a Ãrea de drenagem. PorÃm, as bacias com cobertura vegetal acima de 80% tiveram uma mÃdia de produÃÃo de sedimentos de 139 t km-2 ano-1, enquanto aquelas com cobertura inferior a 40% obtiveram mÃdia de 545 t km-2 ano-1, evidenciando a importÃncia da vegetaÃÃo na reduÃÃo da desagregaÃÃo do solo e transporte de sedimentos; (iv) o presente estudo indicou que a relaÃÃo entre produÃÃo de sedimentos e Ãrea de drenagem do Rio Jaguaribe, com alometria positiva para Ãreas de atà 400 kmÂ, nÃo seguiu o padrÃo regular estabelecido pelos dados de muitos rios do mundo. Salvo melhor juÃzo, a alometria positiva encontrada por este trabalho à inÃdita para regiÃes nÃo glaciais; (v) a alometria positiva encontrada por esta pesquisa pode ser um indicativo de que a DepressÃo Sertaneja, unidade geomorfolÃgica principal da BRJ, ainda està em fase de ajustamento, ou seja, os processos de erosÃo responsÃveis pelo aplainamento da superfÃcie estariam contribuindo para o aumento da produÃÃo de sedimento atà uma determinada faixa de escala. A partir da Ãrea (400 kmÂ) na qual se inicia o decaimento da produÃÃo de sedimento, os processos de deposiÃÃo dos sedimentos passam a ser dominantes sobre os processos de produÃÃo e transporte. / Erosion, transport and sediment deposition are environmental issues that affect society, mainly due to the decrease in agricultural production, decreased storage capacity of reservoirs, the intensification of desertification processes, the occurrence of floods and reduction of water availability. The current trend of the hydrosedimentological studies is addressing large scale in order to generate results with implications to planning of basins. Therefore, the monitoring and hydrosedimentological analysis of the sub-basins are of great importance for the understanding of local processes, in addition, these studies when consistently, become part of the database of investigations that cover large systems, in some situations, the global scale. The objective of this research is to study the specific sediment yield in the Jaguaribe River Basin (JRB), with the proposal to examine the relationship between this variable and the drainage area in order to identify if the data have an allometry trend with the spatial scale. The specific sediment yield data were obtained from primary and secondary sources, covering different measurement methods and a wide range of areas (6.8 x 10-5 km to 4.8 x 104 kmÂ). The primary data were originated from an automated hydrosedimentological section, monitoring of hillslope by erosion pins and reservoirs bathymetric surveys. Secondary data were originated from previous investigations conducted in several sub-basins of the Jaguaribe River, also contemplating different measurement methods and scales. The results of this research show that: (i) the calibration of the turbidimeter by sediment re-suspension method was shown to be as a reasonable alternative to semiarid conditions. Improvement at timescale of the sedimentological measures by turbidity allowed a more representative analysis of the suspended sediment concentration dynamics at studied control section; (ii) average specific sediment yield of the JRB was 347 t km-2 yr-1, the least was 1.1 t km-2 year-1 and the maximum was 1,340 t km-2 year-1; (iii) the attributes erosivity, geology and vegetation cover, when analyzed separately, didnât induce any clear relationship between specific sediment yield and drainage area. However, the watersheds with vegetation cover over 80% had an average sediment yield of 139 t km-2 year-1, while those with vegetation cover less than 40% achieved an average of 545 t km-2 year-1, showing the importance of vegetation in reducing soil detachment and sediment transport; (iv) the present study indicated that the relationship between sediment yield and drainage area of the Jaguaribe River, with positive allometry to areas up to 400 kmÂ, did not follow the regular pattern established by the data of many rivers in the world. Saved better judgment, the positive allometry found in this study is novel to with not-glacial behavior regions; (v) the positive allometry found in this research may be interpreted that the DepressÃo Sertaneja, the main geomorphological unit in the JRB, is still in adjustment phase, where the erosion processes responsible for the leveling of the surface are contributing to increase sediment yield up to certain scale. Above the area (400 kmÂ) at which specific sediment yield begins decreased, the process of sediment deposition becomes dominant upon production and transport processes.