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SEDIMENT BUDGETS 1 & 2

A pair of edited proceedings were produced for an IAHS ICCE symposium co-sponsored by UNESCO, held in April 2005 at Foz do Iguaçu, Brazil, a contribution to the International Sedimentation Initiative (ISI) of the UNESCO International Hydrological Programme (IHP VI). The contents of both are listed overleaf; the preface and abstracts of the papers in each can be seen at www.iahs.info.

A sediment budget provides an integrated view of the sediment sources, transfers, sinks and outputs of a drainage basin, and in so doing draws together the many different aspects of erosion, and sediment mobilization, transport, storage, and yield. Several key developments have influenced recent sediment budget investigations:

– increasing awareness of the environmental implications of increased sediment loads in rivers and of the need for effective sediment management and control strategies.

– advances in the techniques and models available for establishing and predicting catchment sediment budgets including use of 137Cs, 210Pb and 7Be as sediment tracers; continuous recording of suspended sediment flux; application of distributed modelling, remote sensing, and GIS

– recognition of the need to quantify sediment-associated chemical fluxes.

The papers reviewed and edited for these volumes exemplify these developments internationally.

Sediment Budgets 1 Edited by Des E. Walling & Arthur J. HorowitzPubl. 291 (2005)ISBN 1-901502-87-2; + 372 + xii pp. Price £63.00

Volume 1 focuses on the main components of the sediment budget:

– Sediment mobilization and sources – Sediment transport and transfer – Sediment storage – Sediment yields

Sediment Budgets 2 Edited by Arthur J. Horowitz & Des E. Walling Publ. 292 (2005) ISBN 1-901502-92-9; + 358 + xii pp. Price £63.00

Volume 2 emphasizes the value of sediment budgets in providing an integrating framework, for both scientific in-vestigations and environmental management:

– Sediment budgets – Modelling sediment budgets and their components – Human impact on sediment budgets – Sediment problems and sediment management strategies

Contents

Preface by Arthur J. Horowitz & Des E. Walling

1 Sediment Budgets

Using soil redistribution to understand soil organic carbon redistribution and budgets Jerry C. Ritchie, Gregory W. McCarty, Erik R. Venteris & Thomas C. Kaspar

3

The role of organic matter in sediment budgets in forested terrain Mary Ann Madej

9

Evaluating sediment sources and delivery in a tropical volcanic watershed Anton Rijsdijk

16

Key controls and scale effects on sediment budgets: recent findings in agricul-tural upland Java, Indonesia Albert I. J. M. Van Dijk & L. A. Sampurno Bruijnzeel

24

Major components of a sediment budget for four river catchments in Poland Kazimierz Banasik, Mariusz Barszcz & Jan Brański

32

The sediment budget of an alpine catchment in a scaling context Helmut M. Habersack & Stephan Schober

37

The sediment budgets of arctic drainage basins Bent Hasholt 48

Erosion and dam siltation in a Rif catchment (Morocco) Ali Faleh, Ana Navas & Abdelhamid Sadiki

58

Targeting erosion control using spatially distributed sediment budgets Scott N. Wilkinson, Jon M. Olley, Arthur M. Read & Ron C. DeRose

65

2 Modelling Sediment Budgets and their Components

Predicting sediment rating curves with a cellular landscape model Dirk H. De Boer

75

Evaluation of a physically-based model to simulate the runoff and erosion pro-cesses in a semiarid region of Brazil Ricardo De Aragão, Vajapeyam S. Srinivasan, Koichi Suzuki, Akihiro Kadota, Manabu Oguro & Yojiro Sakata

85

Determination of sediment yields in the Vacacaí-Mirim River basin using MUSLE Leandro Casagrande & João Batista Dias De Paiva

94

Evaluation of optimized parameter values of a distributed runoff–erosion model applied in two different basins Celso Augusto G. Santos, Vajapeyam S. Srinivasan & Richarde Marques Da Silva

101

Relationship between simulated sediment yield and scale in a semiarid region of Brazil Eduardo E. De Figueiredo & James C. Bathurst

110

Digital elevation model error and its effect on modelling soil erosion and catch-ment geomorphology G. R. Hancock

119

Sediment transport in a small agricultural watershed—evaluation of WEPP simu-lations with measured data Andreas Klik, Werner Jester & Christian Rauter

127

Sources of uncertainty in estimating suspended sediment load Celina Smith & Barry Croke

136

Using remote sensing to investigate erosion rate variability in a semiarid water-shed, due to changes in vegetation cover Jaime Garatuza-Payán, Raquel Sánchez-Andrés, Salvador Sánchez-Carrillo & Jose M. Navarro

144

Testing the SEDD model in Sicilian basins Costanza Di Stefano, Vito Ferro & Mario Minacapilli

152

Modelling sediment yield in burned areas Maria Cristina Rulli, Matteo Spada, Silvia Bozzi, Daniele Bocchiola & Renzo Rosso

162

Dynamic and modelling of sediment associated nutrients in a low mountain en-vironment Gregor Ollesch, Irina Kistner, Yuri Sukhanovski & Michael Rode

171

Some experience on the prediction of suspended sediment concentrations and fluxes in Croatia Josip Petras, Neven Kuspilic & Duska Kunstek

179

Prediction of erosion and deposition in a mountainous basin Kwang Ik Son & Jae Joon Lee

185

Simulation and scenario analysis of soil erosion in the Miyun reservoir watershed Baolin Su, Haifeng Jia, Jianping Wang, Yuan’an Hu & Shengtong Cheng

194

3 Human Impact on Sediment Budgets

Land degradation and sediment dynamics in the South African Karoo Ian D. L. Foster, John Boardman, James Keay-Bright & Michael E. Meadows

207

The impact of hydropower development on the sediment budget of the River Bei-arelva, Norway Jim Bogen & Truls E. Bønsnes

214

Using tracer based sediment budgets to assess redistribution of soil and organic material after severe bush fires Peter Wallbrink, William Blake, Stefan Doerr, Rick Shakesby, Geoff Humphreys & Pauline English

223

Can reservoir bottom sediments be used in the estimation of long-term catchment sediment budgets? Ingrid F. Small, John S. Rowan, Robert W. Duck, Tom D. Dyer, Stewart W. Franks & Adam Wyatt

231

Impact on sediment yield due to intensification of tobacco production in a catch-ment in southern Brazil Gustavo Henrique Merten & Jean Paolo Gomes Minella

239

Distribution and sediment yield in the upper basin of the Paraguay River and in the Pantanal Matogrossense, Brazil Newton De Oliveira Carvalho, Carlos Nobuyoshi Ide, Luiz Augusto Araújo Do Val, Manoel Afonso Costa Rondon, Armando Garcia Arnal Barbedo & Luiz Fernando De Abreu Cybis

245

Impact of ground-based timber harvesting on suspended sediment yield in the Sungai Weng Experimental Watersheds, Kedah, Peninsular Malaysia F. S. Lai, I. Akkharath & K. S. Low

253

Sediment budget as evidence of land-use changes in mountainous areas: two stages of evolution Luc Descroix, Emmanuèle Gautier, Anne Laure Besnier, Okechukwu Amogu, David Viramontes & Jose Luis Gonzalez Barrios

262

Climate change and changes in sediment transport capacity in the Colorado Plat-eau, USA Robert T. Milhous

271

Regulation du Fleuve Senegal et flux de matieres particulaire vers l’estuaire depuis la construction du Barrage de Diama Alioune Kane

279

Impact des modifications climatiques et anthropiques sur les flux de matières de quelques bassins fluviaux du Cameroun L. Sigha-Nkamdjou, D. Sighomnou, G. Lienou, J. R. Ndam, M. Bello, R. Kamgang, G.E. Ekodeck, M. R. Ouafo, G. Mahe, J. E. Paturel & E. Servat

291

4 Sediment Problems and Sediment Management Strategies

Influence of reservoir sedimentation on water yield in the semiarid region of Brazil José Carlos De Araújo, Axel Bronstert & Andreas Güntner

301

Reassessment of Porto Primavera Reservoir sedimentation in view of updated sediment measurements Aloísio Celeri, Carlos F. Castro Alves & Newton De Oliveira Carvalho

308

Estimation of soil erosion and sedimentation in Ramganga Reservoir (India) using remote sensing and GIS Sanjay K. Jain, Sharad K. Jain & K. D. Sharma

315

Sediment delivery and budgets in reservoir watersheds Su-Chin Chen & Yi-Cheng Lai

324

Impact des lâchers du barrage El-Moustakbal sur l’envasement d’un barrage de prise d’irrigation, Blida, Algérie Benina Touaibia, Mohamed Touaibia, Bachir Benlaoukli, Abdelaziz Bessalem & Mohamed Fewzi Sidi Moussa

333

Key word index 341

List of the contents of Sediment Budgets 1 (IAHS Publ. 291)

Preface

Since the early 1980s, the International Commission on Continental Erosion (ICCE) of the International Association of Hydrological Sciences (IAHS) has organized a large number of highly successful symposia and workshops dealing with various aspects of erosion and sedimentation. These have included: The Symposium on Erosion and Sediment Transport Measurement, Florence, Italy, 1981

(IAHS Publ. 133);The Symposium on Recent Developments in the Explanation and Prediction of Erosion

and Sediment Yield, Exeter, UK, 1982 (IAHS Publ. 137);The Symposium on Dissolved Loads of Rivers and Water Quantity/Quality Relationships,

Hamburg, Germany, 1983 (IAHS Publ. 141);The Symposium on Drainage Basin Sediment Delivery, Albuquerque, New Mexico, USA,

1986 (IAHS Publ. 159);The Workshop on Erosion, Transport and Deposition Processes, Jerusalem, Israel, 1987

(IAHS Publ. 189); The Symposium on Sediment Budgets, Porto Alegre, Brazil, 1988 (IAHS Publ. 174); The Symposium on Sediment and the Environment, Baltimore, USA, 1989 (IAHS

Publ. 184); The Symposium on Erosion, Debris Flows and Environment in Mountain Regions,

Chengdu, China, 1992 (IAHS Publ. 209); The Symposium on Erosion and Sediment Transport Monitoring Programmes in River

Basins, Olso, Norway, 1992 (IAHS Publ. 210);The Symposium on Sediment Problems: Strategies for Monitoring Prediction and Control,

Yokohama, Japan, 1993 (IAHS Publ. 217); The Symposium on Variability in Stream Erosion and Sediment Transport, Canberra,

Australia, 1994 (IAHS Publ. 224); The Symposium on the Effects of Scale on the Interpretation and Management of Sediment

and Water Quality, Boulder, USA, 1995 (IAHS Publ. 226);The Symposium on Erosion and Sediment Yield: Global and Regional Perspectives,

Exeter, UK, 1996 (IAHS Publ. 236); The Symposium on Human Impact on Erosion and Sedimentation, Rabat, Morocco, 1997

(IAHS Publ. 245); The Symposium on Modelling Soil Erosion, Sediment Transport and Closely Related

Hydrological Processes, Vienna, Austria, 1998 (IAHS Publ. 249); The Symposium on the Role of Erosion and Sediment Transfer in Nutrient and

Contaminant Transfer, Waterloo, Canada, 2000 (IAHS Publ. 263); The Workshop on Erosion and Sediment Transport Measurement in Rivers: Technological

and Methodological Advances, Oslo, Norway, 2002 (IAHS Publ. 263); The Symposium on the Structure, Function and Management Implications of Fluvial

Sedimentary Systems, Alice Springs, Australia, 2002 (IAHS Publ. 276);The Symposium on Erosion Prediction in Ungauged Basins: Integrating Methods and

Techniques, Sapporo, Japan, 2003 (IAHS Publ. 279);The Symposium on Sediment Transport through the Fluvial System, Moscow, Russia, 2004

(IAHS Publ. 288)

The Foz do Iguaçu symposium on Sediment Budgets builds on this legacy and focuses on the important topic of sediment budgets. In so doing, it returns to a theme that was first considered almost 17 years ago, also in Brazil, at the Porto Alegre Symposium on Sediment Budgets (IAHS Publ. 174). It is highly appropriate that Brazil should again be the venue of this second symposium on sediment budgets, both

because of the success of the first meeting and because of the many sediment-related problems that are faced by this vast country, with its many large rivers and its wide range of physiographic conditions. Also, with nearly 17 years having elapsed since the original symposium, it is timely to revisit this important topic, which draws together the many different aspects of erosion and sediment mobilization, sediment transport, sediment storage, and sediment yield, by providing an integrated view of the sediment sources, transfers, sinks and outputs of drainage basins, at many different scales. The symposium has been co-sponsored by UNESCO and represents a contribution to the International Sedimentation Initiative (ISI) of the UNESCO International Hydrological Programme (IHP VI).

There have been several key developments in the general area of sediment budget investigations during the years since the Porto Alegre symposium. First, there has been an increasing awareness of the wide-ranging environmental implications of increased sediment loads in rivers and of the need for an improved understanding of catchment sediment budgets as an essential prerequisite for the development of effective sediment management and control strategies. Second, there have been major developments and advances in the techniques and models available for establishing and predicting catchment sediment budgets. The use of environmental radionuclides, such as 137Cs, 210Pb and 7Be, as sediment tracers has, for example, opened up many new opportunities for investigating catchment sediment budgets, particularly in relation to identifying sediment sources, quantifying rates of sediment mobilization, and establishing the importance of sediment sinks. In addition, the continuous recording of surrogate measures of suspended sediment flux (e.g. turbidity) in lieu of manual sampling, with all its attendant problems, has provided an improved understanding of the short-term temporal variability of suspended sediment concentrations and has resulted in more reliable estimates of suspended sediment fluxes. Equally, developments in distributed modelling and the use of remote sensing have been exploited in sediment budget investigations to provide an improved capacity to represent the marked spatial variability in the components of the sediment budgets encountered in many catchments and river basins. Further, the advent of readily available GIS software for desktop computers and associated databases has provided a much more accurate basis for spatial analysis and for providing details on the type of land-use variations that can exercise significant impacts on erosion and sediment yield. Finally, there appears to be a growing recognition of the significance of fine sediment as a carrier of a wide variety of chemical constituents, including trace elements, persistent organic pollutants, and nutrients, and the need to quantify sediment-associated chemical fluxes. Many of these developments are usefully exemplified in the papers of the Foz do Iguaçu Symposium.

The response to the call for papers for the Foz do Iguaçu symposium far exceeded expectations (more than 150 abstracts), and should be viewed as an indication of how significant sediment-related issues are to the environmental and scientific communities. As a result, the symposium was extended over the full duration of the Scientific Assembly (five days). More than 80 papers were selected for oral presentation and inclusion in the pre-published proceedings, and a substantial number of the remaining papers will be presented as posters. It is hoped to publish the poster papers as a CD. For the first time for an ICCE symposium, it has proved necessary to produce two volumes of proceedings (IAHS Publications 291 and 292); these contain 81 papers.

The papers published in the two proceedings volumes cover a wide range of topics, and draw together information and findings from many different areas of the world, including North and South America, Australia, Europe, Africa and Asia. The

inclusion of a significant number of papers with a South American focus represents an important achievement, since this area of the world has been poorly represented in most previous symposia, with the notable exception of the Porto Alegre Symposium held in 1988. The papers have been grouped into eight themes that cover the key components of catchment sediment budgets as well as a number of integrating themes.

Volume 1 of the proceedings focuses on the main components of the sediment budget and includes sections dealing with, firstly, Sediment mobilization and sources, secondly Sediment transport and transfer, thirdly Sediment storage, and, finally, Sediment yields. The papers highlight important advances in our understanding of soil and sediment redistribution in small catchments, the major developments in sediment source tracing that have occurred since 1988, key improvements in monitoring techniques, greatly improved understanding of the role and behaviour of sediment sinks, particularly river flood plains, and the increasing availability of reliable data on sediment yields from different areas of the world and particularly for many of the large rivers of Brazil.

Volume 2 includes four sections containing papers that emphasize the value of sediment budgets in providing an integrating framework, or perspective, for both scientific investigations and for environmental management. The section on Sediment budgets reports the results of studies for catchments in a wide range of environments and emphasizes the increasing availability of information on the nature of such budgets. The next section on Modelling sediment budgets and their components highlights both the wide range of modelling approaches, and the potential for applying existing models within a sediment budget framework. The section on Human impact on sediment budgets emphasizes the potential importance of human activity, especially land-use activities, in modifying both the individual components of the sediment budget and the overall budget, and contains a number of papers dealing with the impact of dams. Finally, the section on Sediment problems and sediment management strategies, whilst containing only a limited number of papers, demonstrates how the sediment budget concept can be integrated into environmental management strategies.

The editors would like to express their gratitude to UNESCO and IAHS for their financial and logistical support for the Symposium and to their Brazilian co-convenors Newton Carvalho and Edmilson Teixera for their valuable help in publicizing and promoting the symposium, screening abstracts, and organizing the symposium programme. The task of reviewing, editing and compiling the two proceedings volumes, containing more than 80 papers, within the space of four months, has proved a major challenge and thanks are extended to all the contributing authors who helped by providing manuscripts in a timely manner and by responding promptly to reviewers’ and editors’ comments and queries, and to the Geography Department of the University of Exeter and the US Geological Survey for their invaluable support. Thanks also are extended to Michel Meybeck (University of Paris VI) for his generous help in editing several of the manuscripts written in French. Equally, special thanks are due to Cate Gardner and Penny Farnell who took the numerous and diverse electronic files containing the papers and their figures and tables, and converted, standardized and formatted them to produce the final printed volumes, in record time. They also provided valuable guidance and gentle reminders of deadlines and outstanding tasks, which ensured that the editors completed their work by the final deadline.

Art Horowitz

US Geological Survey, Peachtree Business Center 3036 Amwiler Road, Atlanta, Georgia 30360, USA

Des WallingDepartment of Geography, University of Exeter

Amory Building, Rennes Drive, Exeter EX4 4RJ, UK

Sediment Budgets 2 (Proceedings of symposium S1 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 292, 2005 3-8.

Using soil redistribution to understand soil organic carbon redistribution and budgets

JERRY C. RITCHIE1, GREGORY W. McCARTY2, ERIK R. VENTERIS3 & THOMAS C. KASPAR4

1 USDA-ARS Hydrology and Remote Sensing Laboratory, Beltsville, Maryland 20705, [email protected]

2 USDA-ARS Environmental Quality Laboratory, Beltsville, Maryland 20705, USA3 Ohio Division of Geological Survey, Columbus, Ohio 43224, USA4 USDA-ARS National Soil Tilth Laboratory, Ames, Iowa 50011, USA

Abstract Patterns of soil organic carbon (SOC) vary across the landscape leading to uncertainties in SOC budgets, especially for agricultural areas where water, wind, and tillage erosion redistribute soil and SOC. This study determined SOC patterns related to soil redistribution in small agricultural fields. Soil redistribution patterns were determined using the fallout caesium-137 technique in agricultural fields in Maryland and Iowa, USA. In two Iowa fields, SOC ranged from 0.5 to 5% whereas in the Maryland field the SOC ranged from 0.4 to 2.9%. Soil organic carbon was statistically significantly correlated with soil 137Cs inventories and soil erosion/deposition rates. Sites of soil erosion in Iowa and Maryland had significantly lower average concentrations of SOC (2.4% and 1.3%, respectively) than sites of soil deposition (3.4% and 1.6%, respectively). These studies show the impact of soil redistribution patterns, within a field or catchment, and aid in understanding SOC patterns and budgets.Key words caesium-137; carbon; carbon sequestration; deposition; erosion; soil redistribution; soil organic carbon

Sediment Budgets 2 (Proceedings of symposium S1 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 292, 2005, 9-15

The role of organic matter in sediment budgets in forested terrain

MARY ANN MADEJUS Geological Survey Western Ecological Research Center, 1655 Heindon Road, Arcata, California 95521, [email protected]

Abstract The production and transport of suspended particulate matter usually are major components of a sediment budget, but the organic and inorganic fractions of this material are not commonly differentiated. In four forested streams in the northwestern United States, the organic content of suspended sediment samples ranged from 10 to 80 weight percent for individual flood events. For a given stream, as a percentage of suspended sediment, organic content was highest during base flows and the early rising and late falling limbs of hydrographs, but on an annual cumulative basis, most organic flux occurred during a few days of high flow. By weight, the

inorganic component of suspended sediment dominated the annual sediment flux in three of the catchments, but organics represented more than half the suspended sediment load in an old growth redwood stream. Although commonly minor by weight, organic suspended sediment can have important effects on aquatic biological communities, turbidity measurements, and eutrophication in estuaries. Key words California; carbon; export; particulate organic matter; redwood; sediment flux; seston; turbidity

Sediment Budgets 2 (Proceedings of symposium S1 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 292, 2005., 16-23

Evaluating sediment sources and delivery in a tropical volcanic watershed

ANTON RIJSDIJKJ.v.d Borchstr. 24b, NL-3515 XE Utrecht, The [email protected] with DHV Consulting Engineers, Amersfoort, The Netherlands

Abstract This paper presents the results of a two-year integrated study that considered the relationship between erosion and river sediment yield in a volcanic upland river catchment in Indonesia. Sediment yield was measured in three subcatchments, as well as in the main catchment. In addition, all possible sources of sediment were quantified and compared with the river sediment yield. Rainfed agricultural land contributed nearly half of the soil erosion, on average, while hillside trails, settlements and roads, and non-surface erosion contributed the rest. The high sediment delivery ratios (>100%) suggest an efficient sediment transport mechanism, even in the lower parts of the main catchment and subcatchments. Often, sediment budget evaluations compare only measured (suspended) sediment yields with estimated erosion values for agricultural land. However, the results of this study make it clear that all components of the balance should be included. Key words humid tropics; sediment delivery ratio; sediment yield; soil erosion

Sediment Budgets 2 (Proceedings of symposium S1 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 292, 2005, 24-31.

Key controls and scale effects on sediment budgets: recent findings in agricultural upland Java, Indonesia

ALBERT I. J. M. VAN DIJK1,2 & L. A. SAMPURNO BRUIJNZEEL2

1 CSIRO Land and Water, PO Box 1666, Canberra, ACT 2601, [email protected]

2 Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 HV Amsterdam, The Netherlands

Abstract This study presents recent field research in a small agricultural catchment in upland West Java, and identifies the key controls, and scale effects, on sediment yields. Vegetative cover

proved the dominant control on surface runoff and sediment generation, with additional variation attributed to slope and soil surface structure. Vegetation also provided the link between the water, sediment, and carbon cycles. Use of a process model to replicate and upscale field measurement to hillslope scale, highlighted the lack of a predictive theory linking vegetative cover to rainfall infiltration, as well as problems associated with the unaccounted covariance of terrain attributes that promoted sediment generation. At the hillslope to catchment scale, changes in slope gradient, and the presence of less erodible substrates became additional constraints on sediment yield. A conceptual framework to describe the changing importance of different sediment transport and deposition processes with increasing spatial scale was developed.Key words carbon cycling; catchment sediment budget; ecohydrology; erosion processes; scale effects; sediment delivery


Major components of a sediment budget for four river catchments in Poland

KAZIMIERZ BANASIK1, MARIUSZ BARSZCZ1 &JAN BRAŃSKI2

1 Department of Water Engineering and Environmental Recultivation, Warsaw Agricultural University, ul. Nowoursynowska 166, PL-02 787 Warsaw, Poland [email protected]

2 Research and Design Office HYDROS, ul. Smoleńska 16 Bm. 58, PL-01 698 Warsaw, Poland

Abstract Two major components of catchment sediment budgets, upland erosion and sediment yield, have been estimated and compared for four river systems located in the southern mountainous part of Poland. The river catchments have areas ranging from 297 to 957 km 2, and are characterized as having relatively high intensity denudation processes in Poland. Upland erosion has been estimated with the use of the universal soil loss equation (USLE), for which erosive factors had been computed for local climatic conditions (using a 29-year rainfall record). Sediment yields have been estimated on the basis of long-term measurements. Specific sediment yields in the catchments vary from 35 to 110 t km-2 year-1, whereas sediment delivery ratios vary from 3 to 34%. Key words delivery ratio; sediment budget; sediment yield; USLE


The sediment budget of an alpine catchment in a scaling context

HELMUT M. HABERSACK & STEPHAN SCHOBERDepartment of Water, Atmosphere, Environment, Institute of Water Management, Hydrology and Hydraulic Engineering, BOKU–University of Natural Resources and Applied Life Sciences, Vienna, Muthgasse 18, A-1190 Vienna, Austria

[email protected]

Abstract This paper discusses the sediment budget of an alpine catchment in a scaling context. Over a three-year period, the spatio-temporal development of the sediment budget of the alpine Sölk-basin in Austria was analysed by means of monitoring and modelling. Sedimentation problems in a reservoir at the outlet of the basin required improved sediment management. From a scaling perspective, the boundary conditions and major processes operating within a catchment, such as the geomorphological setting, are controlled by its long-term development. Within this long-term development, short-term unsteady sediment supply, erosion, transfer, deposition, and remobilization processes control reservoir sedimentation and determine the appropriate management strategy. The results show that overall sediment budget management (beyond managing the reservoir itself) must address catchment analysis (down- and upscaling, the River Scaling Concept) and that a scale-oriented approach leads to sustainable development of the sediment regime.Key words reservoir sedimentation; scaling; sediment budget


The sediment budgets of arctic drainage basins

BENT HASHOLTInstitute of Geography, University of Copenhagen, Øster Voldgade 10, DK 1350 Copenhagen K, [email protected]

Abstract The characteristics of arctic drainage basins are discussed in relation to sediment transport processes. Methods used for quantification of the processes are described, together with the technical problems encountered in their application in this environment. A preliminary budget for the glacierized Mittivakkat drainage basin, situated in Greenland, is presented. The dominant processes are glacial erosion and the fluvial transport of the eroded material.Key words arctic; Greenland; sediment budget


Erosion and dam siltation in a Rif catchment (Morocco)

ALI FALEH1, ANA NAVAS2 & ABDELHAMID SADIKI3

1 Département de Géographie, Faculté des Lettres Saiss, Fès, [email protected]

2 Departamento de Edafología, Estación Experimental de Aula Dei, CSIC Zaragoza, Spain3 Département de Géologie, Faculté des Sciences, Dhar Mahraz, Fès, Morocco

Abstract In the Rif region (northern Morocco), various check dams were constructed in the 1990s, but high siltation rates led to their total infilling in a few years. The objective of this work

mailto:[email protected]

was to assess the processes generating soil particles, and their accumulation, in the Abdelali check dam. A bathymetric survey was carried out to quantify the volume of sediments and the total erosion rate. Further, fallout 137Cs was determined to estimate soil loss in selected areas, and to identify the main sources of sediment. The radiotracer led to the identification of different sediment sources; erosion rates appear to be a function of vegetative cover, topography, and/or land use. Based on the two methods, it was possible to assess the contribution of rill and bank erosion; it appeared to represent about one third of the total accumulated sediments. The combination of these techniques proved to be a suitable approach for establishing catchment sediment budgets with a view toward promoting strategies for better soil and water management.Key words Abdelali; bathymetry; caesium-137; check dam; erosion; Morocco; Rif; sedimentation; siltation


Targeting erosion control using spatially distributed sediment budgets

SCOTT N. WILKINSON, JON M. OLLEY, ARTHUR M. READ & RON C. DEROSECSIRO Land and Water, PO Box 1666, ACT 2601, Australia [email protected]

Abstract There is a growing interest in restoring rivers; however, the restoration work required often exceeds the resources available. Consequently, management actions need to be targeted to achieve the greatest benefit. A thorough knowledge of local sediment budgets could represent a substantial management technique in this regard. The SedNet model has been used extensively to construct local sediment budgets throughout river networks. In the model, sediment is supplied to each link of the network from hillslope erosion, gully erosion, and channel bank erosion, and then routed through the network, with deposition occurring in river channels, on flood plains, and in reservoirs. The model enables the determination of the contribution from each erosion source, at each point in the river network. The SedNet model is applied to the Murrumbidgee River, and shows how spatially distributed sediment budgets can be used to target erosion control activities. Key words riverbank erosion; sediment budget; sediment tracing; SedNet; targeting


Predicting sediment rating curves with a cellular landscape model

DIRK H. DE BOERDepartment of Geography, University of Saskatchewan, 9 Campus Drive, Saskatoon, Saskatchewan S7N 5A5, [email protected]

Abstract Sediment rating curves are used frequently to estimate suspended sediment concentration for the subsequent calculation of sediment fluxes and to establish sediment budgets. This paper discusses a cellular model (Cascade 6) of erosion and sediment transport in a drainage basin that is used to derive sediment rating curves. In Cascade 6, water and sediment are routed


from each cell to its lowest neighbour, and ultimately, to the drainage basin outlet. The sediment flux from one cell to the next is a nonlinear function of discharge and slope. The Cascade 6 model was applied to the 45-ha Catsop basin, a loess-covered agricultural basin with a gently to moderately sloping topography located in South-Limburg, The Netherlands. The Cascade 6 (a partly empirical model) results compare favourably with those generated by LISEM (a fully physically-based model). However, Cascade 6 is far less demanding in terms of input data, which gives it a distinct advantage as the interpretation of the modelling results is much more straightforward.Key words Cascade 6; erosion; erosion model; LISEM; sediment rating curve; sediment transport


Evaluation of a physically-based model to simulate the runoff and erosion processes in a semiarid region of Brazil

RICARDO DE ARAGÃO1, VAJAPEYAM S. SRINIVASAN1, KOICHI SUZUKI2, AKIHIRO KADOTA2, MANABU OGURO2 & YOJIRO SAKATA2

1 Department of Civil Engineering, Federal University of Campina Grande, Av. Aprígio Veloso, 882, Bodocongó, Campina Grande, Paraíba 58109-970, [email protected]

2 Department of Civil and Environmental Engineering, Ehime University, Japan 3 Bunkyo-cho, Matsuyama-shi, Ehime-ken 790-8577, Japan

Abstract: A physically-based distributed model called Catchment Hydrology Distributed Model—CHDM, developed by Lopes (1995), was tested in an experimental basin, located in a representative semiarid region in northeastern Brazil. This model is a refinement of an earlier model, WESP, which has been found to simulate infiltration, runoff, and erosion processes well, in one dimension, within small-sized basins. Different from WESP, which is based on a simple mass balance that does not take into account the limiting transport capacity of flow, CHDM has a built in choice of six different transport capacity relationships. The model was evaluated utilizing the runoff and erosion data collected for natural rainfall events in the Sumé Experimental Basin, where erosion plots of 100 m2 and micro-basins of about 0.5 ha were installed. The model proved to be consistent and useful for runoff and erosion prediction in the semiarid region of Brazil.Key words physically-based models; runoff, semiarid region; soil erosion


Determination of sediment yields in the Vacacaí-Mirim River basin using MUSLE

LEANDRO CASAGRANDE1 & JOÃO BATISTA DIAS DE PAIVA2

1 University of Cruz Alta – UNICRUZ – Cruz Alta /RS, Parada Benito, 98025-810–Postal 15029 Porto Alegre, RS 91501-977, Brazil [email protected]

2 Hydraulic and Sanitation Department, Technology Center, Federal University of Santa Maria, Faixa de Camobi, Km


9, Campus Universitário – Santa Maria, RS 97105-900, Brazil

Abstract The objective of this study was to determine sediment yields in the Vacacaí-Mirim watershed which has an area of some 1150 km2, and which lies between 29°3655–29°3950S and 53°4630–53°4929W. Estimates were made using the Modified Universal Soil Loss Equation (MUSLE) in conjunction with the Williams & Berndt sediment routing model. The catchment was divided into 93 sub-basins, with drainage areas ranging from 0.7 to 115 km2. The MUSLE parameters were determined in the 93 sub-basins; three sub-basins, representative of the three physiographic provinces in the catchment, were selected for the determination of William’s routing coefficient. Requisite data were obtained from a combination of sources (e.g. satellite imagery; national army maps) and entered into a GIS database. The Soil Conservation Service curve number methodology and the Santa Maria rainfall equations developed by Belinazo & Paiva were used to generate hydrographs for the study area. Based on a 50-year return flow, maximum discharge ranged from 7.69 to 567.14 m3 s-1 and flow volumes ranged from 23 193.75 to 11 983 872 m3. Estimated sediment yields ranged from 0.02 to 0.84 t ha-1. Key words Brazil; sediment yield, small watersheds; Vacacaí-Mirim River basin


Evaluation of optimized parameter values of a distributed runoff–erosion model applied in two different basins

CELSO AUGUSTO G. SANTOS1, VAJAPEYAM S. SRINIVASAN2 & RICHARDE MARQUES DA SILVA1

1 Department of Civil Engineering, Federal University of Paraíba, 58059-900, João Pessoa (PB), Brazil [email protected]

2 Department of Civil Engineering, Federal University of Campina Grande, 58109-970, Campina Grande (PB), Brazil

Abstract A distributed, physically-based, and event oriented runoff–erosion model called WESP (Watershed Erosion Simulation Program) has been used to model the runoff and erosion processes in the micro-basins of the Sumé Experimental Basin by calibrating the parameters of the model with local data. In order to obtain regional estimates of these parameters, the model was applied to the data from an erosion plot in another experimental basin within the same region. Optimum values for the model parameters were obtained utilizing a genetic algorithm named SCE-UA (Shuffled Complex Evolution–University of Arizona). The study shows that the parameter values are close to each other, and regional estimates of the parameters could make the model an efficient predictive tool for ungauged basins in the region.Key words optimization of parameters; runoff–erosion simulation; WESP model


Relationship between simulated sediment yield and scale in a semiarid region of Brazil

EDUARDO E. DE FIGUEIREDO1 & JAMES C. BATHURST2

1 Water Resources Research Engineering Area, Department of Civil Engineering, Federal University of Campina Grande, PO Box 505, 58109-970 Campina Grande (PB), [email protected]

2 Water Resource Systems Research Laboratory, Department of Civil Engineering, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK

Abstract The runoff and sediment yield processes in a representative basin located in the semiarid region of Northeast Brazil (SeNeB) were modelled with the physically based and spatially distributed model SHETRAN. Field data were used to parameterize, test, validate, and simulate the runoff and sediment yields. The model parameters were tested at plot area scales (100 m2) and then used to simulate larger catchments (0.5 ha–140 km2) with different grid resolutions. The results achieved at every basin scale and grid size showed that observed runoff and sediment yields were simulated with physically meaningful results. Similar results were produced with different grid size resolutions applied to the larger catchments, but peak discharges, annual volumes, and sediment yields varied with the land use, rainfall regime, and basin area. Simulated sediment yields decreased as basin area increased, and relationships were established for different conditions of land use and rainfall.Key words scale effect; sediment yield; semiarid; uncertainty


Digital elevation model error and its effect on modelling soil erosion and catchment geomorphology

G. R. HANCOCKSchool of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales, 2308, [email protected]

Abstract In many cases it is useful and appropriate to assess potential erosion risk both in the undisturbed environment and in catchments heavily disturbed by humans. One method for assessing risk, when modelling environmental processes, is to quantify the error(s) associated with model input parameters and include this in the modelling process. This study examines the impact of digital elevation model (DEM) error on the estimation of soil loss and geomorphological changes in a Northern Territory, Australia catchment. Multiple realizations (or versions) of the same catchment were created by including positional error in the DEM. The SIBERIA erosion model was run for a simulated 1000-year period, using these multiple catchment realizations as this is the expected minimum design life for rehabilitated uranium mines in the area. Examination of the area–slope relationship, hypsometric curve, and cumulative area distribution after 1000 years of simulated erosion demonstrates little geomorphological difference. Statistically significant differences occur when comparing channel network statistics. A probabilistic assessment allows an estimation of the statistical ranges of incision and average erosion. Key words geomorphology; hydrology; risk assessment; SIBERIA; soil erosion modelling



Sediment transport in a small agricultural watershed—evaluation of WEPP simulations with measured data

ANDREAS KLIK, WERNER JESTER & CHRISTIAN RAUTERDepartment of Water, Atmosphere and Environment, Institute of Hydraulics and Rural Water Management, BOKU-University of Natural Resources and Applied Life Sciences, A-1190 Vienna, [email protected]

Abstract During the 2002 growing season spatially and temporally distributed data on surface runoff, soil erosion, soil water content and crop development were collected from a 16-ha watershed in lower Austria, for which there was no information on water and sediment output. The watershed version of the Water Erosion Prediction Project (WEPP) model was applied without calibration to calculate the spatial distribution of erosion processes within the watershed. The field measured data were used to validate the simulation results. A good agreement between observed and simulated values was obtained for surface runoff, soil water storage and crop yields, whereas soil erosion was underestimated. Overall, WEPP is a useful and appropriate tool for estimating sediment transport in small agricultural used watersheds. However, calibration of the model input parameters is needed to improve sediment loss predictions.Key words Austria; simulation models; soil erosion; surface runoff; WEPP


Sources of uncertainty in estimating suspended sediment load

CELINA SMITH1 & BARRY CROKE1,2

1 Centre for Resource and Environmental Studies, Building 48A, Linnaeus Way, The Australian National University, Canberra, ACT 0200, [email protected]

2 Integrated Catchment Assessment and Management Centre, School of Resources, Environment and Society Building 48A, Linnaeus Way, The Australian National University, Canberra, ACT 0200, Australia

Abstract An important task in the assessment of suspended sediment load estimates is to qualify and (where appropriate) quantify the uncertainty associated with that estimate. A sediment rating curve is a relationship between suspended sediment concentration and flow used in the calculation of a load estimate. However, this method assumes particular characteristics in the input data. It was found that historical data for the Murrumbidgee River catchment, Australia, did not possess all these assumed characteristics because of variations in suspended sediment sampling methods, a lack of metadata, and a lack of a sufficient number of samples covering the range of flow conditions. These factors inhibited the use of sediment rating curves for developing an appropriate suspended sediment load estimate and its associated uncertainty.Key words Murrumbidgee River catchment, Australia; suspended sediment; uncertainty



Using remote sensing to investigate erosion rate variability in a semiarid watershed, due to changes in vegetation cover

JAIME GARATUZA-PAYÁN, RAQUEL SÁNCHEZ-ANDRÉS, SALVADOR SÁNCHEZ-CARRILLO & JOSE M. NAVARRODepartment of Water and Environmental Sciences, Instituto Tecnológico de Sonora, 5 de Febrero 818 Sur, Ciudad Obregón, Sonora CP-85000, [email protected]

Abstract The vegetation cover status of a watershed is a key control of erosion intensity. Any management plan must therefore take into account temporal changes in surface condition within a watershed. The type and condition of the vegetation cover are the most important watershed characteristics affected by seasonal and inter-annual changes. In order to explore these effects further, a study was undertaken in the 74 532 km2 Yaqui River basin. Ten Landsat scenes covering the three seasons in 1976, 1983 and 1992 were used to assess inter-annual changes in surface cover over the Yaqui catchment, while monthly composites of NOAA-AVHRR NDVI images were employed to evaluate intra-annual or seasonal changes in the vegetation cover. Maps of vegetation type and density, based on satellite images, were used to derive distributed estimates of the vegetation cover factor in the Universal Soil Loss Equation. The results show that vegetation cover is closely related to seasonal precipitation variability and to the inter-annual variability associated with global scale phenomena such as ENSO. The study demonstrates the usefulness of distributed estimates of erosion potential for improving understanding of the relationships between vegetation cover and erosion in semiarid watersheds and as a tool for improved catchment management. Key words erosion; Mexico; remote sensing; semiarid areas; vegetation cover


Testing the SEDD model in Sicilian basins

COSTANZA DI STEFANO, VITO FERRO & MARIO MINACAPILLIDipartimento di Ingegneria e Tecnologie Agro-Forestali, Facoltà di Agraria, Università di Palermo, Viale delle Scienze,I- 90128 Palermo, [email protected]

Abstract The Sediment Delivery Distributed (SEDD) model combines the universal soil loss equation (USLE) or the revised universal soil loss equation (RUSLE) with a sediment delivery ratio to predict basin sediment yield. The model was applied to seven Sicilian basins, ranging in size from 20 to 213 km2. Each basin has a reservoir located at its outlet. The model was applied to each basin using a raster scheme, and a subroutine of ArcInfo software to identify the hydraulic path linking each hillslope cell to the nearest stream cell, and to calculate both the travel time and the sediment delivery ratio of each cell. A procedure for estimating the coefficient, which appears in the expression for determining the sediment delivery ratio of each cell, was developed. As the sedimentation volume for each of the seven reservoirs was known, it was possible to compare measured values with those calculated by the SEDD model. The agreement between measured sediment yield values and calculated ones confirmed the reliability of the proposed



estimation procedure and indicates that it should be possible to apply the SEDD model to ungauged basins.Key words distributed models; GIS; SEDD; sediment yield measurements; soil erosion; USLE


Modelling sediment yield in burned areas

MARIA CRISTINA RULLI, MATTEO SPADA, SILVIA BOZZI, DANIELE BOCCHIOLA & RENZO ROSSODepartment of Hydraulic, Environmental, Road and Surveying Engineering, Hydraulics, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano MI, [email protected]

Abstract The effects of forest fires on runoff and soil erosion were investigated by means of field experiments and model simulations. A set of rainfall simulation experiments were carried out on two plots with different fire histories in a typical Mediterranean area. A distributed soil erosion and sedimentation model, calibrated based on plot experiments, was used to investigate hillslope and channel erosion in a 1.5-ha drainage basin. The comparison between simulated runs, and observed data, indicate that the model is capable of accurately estimating sediment yields for the basin. The current approach provided good results in driving the transition from the plot scale, at which field rainfall simulator experiments are usually carried out, to the larger watershed scale, where hydrological models are more suitable for developing appropriate post-fire catchment rehabilitation plans. Key words erosion; fire; hydrological models; rainfall simulator


Dynamic and modelling of sediment associated nutrients in a low mountain environment

GREGOR OLLESCH1, IRINA KISTNER2, YURI SUKHANOVSKI3 & MICHAEL RODE2

1 Department of Soil Science, UFZ–Centre for Environmental Research, Brueckstrasse 3A, D-39114 Magdeburg, [email protected]

2 Department of Hydrological Modelling, UFZ–Centre for Environmental Research, Brueckstrasse 3A, D-39114 Magdeburg, Germany

3 All Russian Research Institute of Agronomy and Soil Erosion Control, Karl Marx Str. 70B, RU-305021 Kursk, Russia

Abstract The characterization of the temporal variability and the spatial heterogeneity of particulate phosphorus transport is important for mitigating nonpoint sources of pollution. Investigations were



conducted in the 1.44 km2 Schaefertal catchment, which is located in the lower Harz Mountains, Germany. Continuous measurement of discharge and event-based automatic sampling were carried out for sediments and phosphorus (P) at the catchment discharge gauge station. The modelling tool WASIM/AGNPS/SMEM/ANIMO was used to analyse the spatial heterogeneity of runoff and to identify phosphorus source areas, especially in the winter. The complex catchment response to runoff generation and sediment and P transport is shown in hysteresis curves that are both clockwise and anti-clockwise. There is also evidence for the depletion of sediment availability during some events. An event specific sediment/P relationship can be identified as a result of source area characteristics and the characteristics of runoff connectivity to the channel. The sediment/P ratio is significantly higher in the case of long transport distances in the catchment compared to short transport distances, with source areas near the gauge station. Phosphorus export coefficients, or similar empirical tools, do not seem applicable in the Schaefertal catchment since the hydrological characteristics lead to event-based differentiated P enrichment in suspended sediment. The proposed modelling approach is mainly process-oriented, and can be used to identify management options in small-sized catchments.Key words AGNPS; erosion; Germany; modelling; phosphorus; WASIM; winter condition


Some experience on the prediction of suspended sediment concentrations and fluxes in Croatia

JOSIP PETRAS, NEVEN KUSPILIC & DUSKA KUNSTEKFaculty of Civil Engineering, University of Zagreb, Kaciceva 26, 10000 Zagreb, [email protected]

Abstract Botonega Reservoir was constructed as a multi-purpose facility for flood control and for the storage of surface runoff for drinking water and irrigation. Because of the underlying flysch deposits and hilly terrain, soil erosion in the region is extensive. In order to assess the impact of erosion and sediment transport into the reservoir, soil erosion intensity, as well as sediment yields and transport, were estimated for the catchment. The initial evaluation was carried out according to Gavrilovic’s parametric method, which is traditionally used in Croatia. During an 11-year period, hydrological surveys were conducted in the catchment. The calculated values generated using Gavrilovic's method are approximately 11 times higher than the measured quantities, and hence, appear unreliable. However, upon combining Gavrilovic’s method with GIS technology, estimations of sediment production and transport for the 11-year measurement period only exceeded the measured values by 37%. This leads to the conclusion that Gavrilovic’s method, when used in conjunction with GIS technology, can produce reasonably accurate estimations.Key words catchment area; erosion processes; Gavrilovic’s parametric method; GIS; suspended sediment


Prediction of erosion and deposition in a mountainous basin


KWANG IK SON1 & JAE JOON LEE2 1 Department of Civil Engineering, Yeungnam University, Gyungbuk 712-749 South Korea

[email protected] Departnebt of Civil Engineering, Kumoh National Institute of Technology, Gyungbuk, South Korea

Abstract A model for identifying areas of erosion and deposition over a mountainous basin was developed based on the mass balance principle. The program consists of three steps: (a) estimation of soil erosion; (b) determination of flow amount and direction; and (c) estimation of mass balance. Soil erosion was estimated with the USLE. A single-direction flow and a multi-direction flow algorithm were applied to estimate slope length (L). The Maximum Downhill Slope Method (MDS) and the Neighborhood Method (NBH) were used to estimate the slope degree (S). Sediment transport resulting from eroded soil was estimated using Ferro’s (1998) and Swift’s (2000) sediment delivery ratio (SDR). The flow direction was determined using a geographic information system (GIS) program. The model was validated by comparing the predicted sediment yields for three basins with measured data. Ferro's SDR Method combined with the MDS Method produced the best results for mountainous basins in Korea. Key words sediment delivery ratio; sediment deposition; sediment erosion


Simulation and scenario analysis of soil erosion in the Miyun Reservoir watershed

BAOLIN SU, HAIFENG JIA, JIANPING WANG, YUAN’AN HU & SHENGTONG CHENGDepartment of Environmental Science and Engineering, Tsinghua University, Beijing 100084, [email protected]

Abstract The Soil and Water Assessment Tool (SWAT) was applied to the Miyun Reservoir watershed to simulate soil erosion. Two tributaries within this watershed, the Chao and Bai rivers, were simulated separately and hydrological and soil erosion processes were calibrated and validated using observed data from downstream gauging stations. Data analyses and simulation results indicate that soil erosion in both sub-watersheds predominantly occurs during flood seasons, and soil erosion is closely correlated with the spatial distribution of rainfall. Although the Bai sub-watershed has a larger drainage area than the Chao sub-watershed, the former contributes less sediment to the Miyun Reservoir than the latter because two upstream reservoirs (Yunzhou and Baihepu) intercept upstream sediment. Several rainfall scenarios were set up to simulate the influence of changing rainfall patterns; as a result, key areas of soil erosion were identified.Key words Miyun Reservoir; scenario analysis; soil erosion; SWAT model


Land degradation and sediment dynamics in the South African Karoo


IAN D. L. FOSTER1, JOHN BOARDMAN2, JAMES KEAY-BRIGHT2 & MICHAEL E. MEADOWS3

1 Centre for Environmental Research and Consultancy, SE (Geography), Coventry University, Priory Street, Coventry CV1 5FB, [email protected]

2 Environmental Change Institute, University of Oxford, 5 South Parks Road, Oxford OX1 3UB, UK3 Department of Environmental & Geographical Science, University of Cape Town, Private Bag, Rondebosch 7701,

South Africa

Abstract Land degradation has led to sedimentation in farm dams in the headwaters of the Seekoei River. Two small catchments (<10 km2) with farm dams were selected for investigation, but detailed results are only presented for one of them. Caesium-137 and unsupported 210Pb are present in the dam sediments; event-driven layers are apparent from fine gravels contained within layers deposited over the last ~50 years. The 137Cs reference inventories are low by northern hemispheric standards (~53 mBq cm-2). Activities in dam sediments frequently exceed 4 mBq g-1, and the total inventory for the dam master core exceeds 470 mBq cm-2. While extensive gully systems exist in both catchments, the high 137Cs activities in the sediments suggest that sediment delivered to the dam over the last five decades is dominated by topsoil erosion. This conclusion is generally supported by the mineral magnetic data.Key words caesium-137; environmental magnetism; Karoo; land degradation; radionuclides; South Africa


The impact of hydropower development on the sediment budget of the River Beiarelva, Norway

JIM BOGEN & TRULS E. BØNSNESNorwegian Water Resources and Energy Directorate, PO Box 5091, Maj., N-0301 Oslo, Norway [email protected]

Abstract Since 1994, as a result of hydropower development, the River Beiarelva has been affected by a water diversion. From 1989 to 1993, before the diversion, annual suspended sediment loads varied from 7900 to 23 500 t year-1, and suspended sediment concentrations (SSC) remained below 200 mg l-1. Once the diversion was implemented, initial loads declined (<4000 t year-1); however, in the following years they increased (i.e. 40 000 and 67 000 t year-1 in 2002 and 2003, respectively). Maximum SSC also increased and exceeded 4000 mg l-1. These changes appear due to alterations in both sediment delivery and storage. Glacial sediment yields vary both between glaciers, and from year to year (i.e. between 16 and 2100 t km-2). Unglacierized areas supply less sediment; however, higher rates may occur during floods. After the hydropower plant became operational, the Beiarelva’s discharge and sediment transport capacity declined and sediment storage increased. About 50% of glacially-derived sediment is diverted, but overflow at the intakes during floods can cause extensive erosion in the regulated tributary reaches. Since the onset of regulation, sediment storage occurs during low-flow years, whereas channel flushing occurs during floods. Further, SSC changed from being supply- to discharge-limited. Key words diversion; hydropower; reduced transport capacity; sediment budget; sediment flushing; temporal sediment storage




Using tracer based sediment budgets to assess redistribution of soil and organic material after severe bush fires

PETER WALLBRINK1, WILLIAM BLAKE2, STEFAN DOERR3, RICK SHAKESBY3, GEOFF HUMPHREYS4 & PAULINE ENGLISH1

1 CSIRO Land & Water, PO Box 1666, ACT 2601, [email protected]

2 School of Geography, University of Plymouth, Plymouth PL4 8AA, UK 3 Department of Geography, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, UK4 Department of Physical Geography, Macquarie University, North Ryde, Sydney,

New South Wales 2109, Australia

Abstract In the summer of 2001, a combination of severe wildfires and moderate intensity rainfall events swept through the catchment of Lake Burragorang, NSW, Australia. Beryllium-7 and 210Pbex budgets were used to assess the redistribution of soil and organic debris that occurred on hillslopes in this catchment after the wildfire. In the ~90-ha study site, the budgets showed substantial losses of 7Be from the upper plateau (10 2%) and side slopes (26 5%), and deposition on the lower footslopes and alluvial fans (2 4%). Overall, it was possible to account for ~65% of the initial amount of 7Be expected to be present with the balance, 35 6%, presumably being exported offsite. Construction of a 210Pbex

budget showed a similar pattern of internal redistribution; some 28 6 % of the total amount was exported from the site. Analysis of litter, soil and sediment samples shows that both 7Be and 210Pbex were: (a) preferentially retained near the soil surface (due to their constant deposition in rainfall), and (b) exhibited an affinity with organic material. It appears that 210Pb and 7Be budgets can reveal much about the redistribution of soil, organic (and nutrient) material after fires in these systems.Key words bushfires; downstream impacts; fallout radionuclides; organic matter; sediment budgets; soil redistribution


Can reservoir bottom sediments be used in the estimation of long-term catchment sediment budgets?

INGRID F. SMALL1, JOHN S. ROWAN1, ROBERT W. DUCK1, TOM D. DYER2, STEWART W. FRANKS3 & ADAM WYATT3

1 Environmental Systems Research Group, Department of Geography, University of Dundee, DD1 4HN, [email protected]

2 Division of Civil Engineering, University of Dundee, Dundee DD1 4HN, UK3 School of Engineering, University of Newcastle, Newcastle, Callaghan, New South Wales 2308, Australia


Abstract In the last 30 years, major progress has been made in the development of methods for establishing catchment sediment budgets. Reservoir bottom sediments are important because they provide valuable medium- to long-term archives of catchment sediment yield. Dating techniques, such as 137Cs and 210Pb further provide the opportunity to subdivide this stratigraphic record into shorter time periods. Recently, sediment-fingerprinting approaches have been applied to dated sediment cores to gain insight into changing patterns of sediment supply. In this study, a land-use-based sediment fingerprinting study was undertaken in the 4.9 km2 Crombie Reservoir catchment in northeast Scotland to infer historical changes in sediment supply over the past 135 years. The unmixing model employed, features a novel enrichment-inclusive subroutine. Fingerprinting results show a rise in agricultural sediment production from effectively zero in 1890 to >80% in 1980, with patterns broadly correlating to known land-use changes with a climatic overprint.Key words Crombie Reservoir, Scotland; enrichment; land-use reconstruction; sediment budget; sediment fingerprinting

Sediment Budgets 2 (Proceedings of symposium S1 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 292, 2005.


Impact on sediment yield due to intensification of tobacco production in a catchment in southern Brazil

GUSTAVO HENRIQUE MERTEN & JEAN PAOLO GOMES MINELLAInstitute of Hydraulic Research (IPH), Federal University of Rio Grande do Sul (UFRGS), PO Box 15029, 91501-970 Porto Alegre, RS, Brazil [email protected]

Abstract Tobacco production in southern Brazil has caused a profound impact on the environment, resulting in heavy sediment yields and diminished water quality. Public programmes have attempted to address these problems by encouraging the implementation of erosion control practices. To evaluate the impact of these programmes, a small rural catchment (1.33 km2) in Arvorezinha, in the state of Rio Grande do Sul, has been monitored since 2001. Instruments to automatically monitor flow rate and precipitation were installed in the catchment and sediment has been measured manually using a DH-48 sampler. Despite lower rainfall in 2003, there was a significant increase in the frequency of low and average flow rates, and sediment yield increased by 25% in 2003 (91 Mg km-2 year-1), compared with 2002 (73 Mg km-2 year-1). These results can be explained by a 37.7% increase in the area dedicated to tobacco cultivation in 2003, due to a rise in tobacco prices. Key words Brazil; sediment yield; small catchment monitoring; tobacco



Distribution and sediment yield in the upper basin of the Paraguay River and in the Pantanal Matogrossense, Brazil

NEWTON DE OLIVEIRA CARVALHO1, CARLOS NOBUYOSHI IDE2

LUIZ AUGUSTO ARAÚJO DO VAL2

MANOEL AFONSO COSTA RONDON2 ARMANDO GARCIA ARNAL BARBEDO2 & LUIZ FERNANDO DE ABREU CYBIS3

1 Rua Conde de Baependi, 112 ap. 904, Rio de Janeiro, RJ, Brazil [email protected]

2 Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil3 Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil

Abstract The upper basin of the Paraguay River begins on a plateau, then undergoes an abrupt fall to a plain named Pantanal in Brazil, and Chaco in Bolivia and Paraguay. This study details the sediment budget for the Brazilian Pantanal (362 376 km2) based on data collected from the main rivers of the basin between 1977 and 2002. This period coincides with a marked increase in agricultural exploitation in the region; this has triggered increased erosion on the plateau, and increased deposition on the plains. Some 58% of the sediment derived from the plateau was deposited on/in the Pantanal. This can be represented as the deposition of a uniform layer of between 0.062 and 0.33 mm year-1. It may have reached a maximum rate of 8.26 mm year-1 in some places. Although some of the increases in erosion may be the result of climate change, it is more likely the result of anthropogenic activities associated with land-use changes.Key words Brazil; degradation; deposition; sediment discharge; sediment transport


Impact of ground-based timber harvesting on suspended sediment yield in the Sungai Weng Experimental Watersheds, Kedah, Peninsular Malaysia

F. S. LAI1, I. AKKHARATH1 & K. S. LOW2

1 Department of Forest Management, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor DE, [email protected]

2 Hydrology Division, Drainage and Irrigation Department, Km 7, Jalan Ampang, 68000 Ampang, Kuala Lumpur, Malaysia

Abstract This paper reports on changes in suspended sediment production in the Sungai Weng Experimental Watersheds, in particular, watersheds W2 and W3, due to ground-based timber harvesting from 1997 to 2002. W3 was logged under normal practice using the crawler tractor-winch-lorry system, whereas W2 was logged using reduced impact logging guides such as a wider 30-m stream buffer strip and 40° slope limit, among others. Logging operations in W3 ran from February 1998 until the end of 2000 and in W2 from June 2000 to March 2003. Suspended


sediment concentrations varied within the period of study, increasing dramatically during logging. For instance, the maximum concentration levels sampled in W3 increased from 1980 mg l-1 in 1997 to a peak of 92 500 mg l-1 in 1999. After logging ceased, concentration levels fell to 30 200 mg l-1 in 2001 and to a much lower 19 500 mg l-1 the following year. Peak suspended sediment concentrations were lower in W2, however, suggesting that the extra measures taken to lower the logging impact had some influence on sediment yield in the affected basin. Based on pre-harvesting conditions, data from the Sungai Weng experimental watersheds suggest that conventional logging can increase the suspended sediment yield some 42 times during peak periods, but declines as the watershed recovers. Key words conventional logging; experimental watersheds; ground-based harvesting; Malaysia; reduced impact logging; suspended sediment


Sediment budget as evidence of land-use changes in mountainous areas: two stages of evolution

LUC DESCROIX1, EMMANUELE GAUTIER2, ANNE LAURE BESNIER1, OKECHUKWU AMOGU1, DAVID VIRAMONTES3 & JOSE LUIS GONZALEZ BARRIOS4

1 IRD-Niamey BP 11 416, Niamey, Niger andLTHE, Laboratoire d’étude des Transferts en hydrologie et Environnement, BP 53, F-38041 Grenoble, [email protected]

2 Laboratoire de Géographie Physique, Université Paris 8 et CNRS, F-92195 Meudon Cedex, France3 Instituto Mexicano de Tecnología del Agua, P. Cuauhnahuac 8532, 62 550 Jiutepec, Morelos, Mexico4 Centro Nacional de Investigación Disciplinaria en la Relación Agua Suelo Planta Atmósfera, AP 225-3, 35 071,

Gomez Palacio, Durango, Mexico

Abstract Two sediment budgets, for two widely different hydrological settings, have been prepared, compared and analysed to determine altered hydrological conditions resulting from land-use changes, over extended time periods. French alpine rivers are currently undergoing severe channel entrenchment. This has resulted from the accumulated effects of anthropogenic activity and climatic factors. Bridges and dikes are threatened by the entrenchment, which is the consequence of a major decline in hillslope erosion that began toward the end of the 19th century. On the other hand, in the Western Sierra Madre (northern Mexico), river channels have been rising for some decades, and at the same time widening; this is a consequence of severe hillslope erosion, which is both linear and laminar, and mainly due to overgrazing and deforestation. Both cases clearly demonstrate the impact of anthropogenic activities and, to a lesser extent, climate change, on hydrological conditions. Key words Alps; erosion; land uses; Mexico; overgrazing; sedimentation


Climate change and changes in sediment transport capacity in the Colorado Plateau, USA

ROBERT T. MILHOUSFort Collins Science Center, US Geological Survey, 2150 Centre Avenue Building C, Fort Collins, Colorado 80526, [email protected]

Abstract Information is presented on changes in the sediment transport capacity of streams of the Colorado Plateau region of the United States. The changes in transport capacity may be due to changes in climate. Changes in the ability of three rivers in the Colorado Plateau to transport sediment were investigated (Paria River at Lees Ferry, Arizona; Sevier River at Hatch, Utah; and Little Colorado at Woodruff, Arizona) using an index to sediment transport potential (or capacity) of the rivers. The index is called a Sediment Transport Capacity Index (STCI). The parameters in the index are calibrated to measured sediment concentrations. Other investigators have postulated that there have been three climate regimes in the Colorado Plateau during the 20th century: 1905–1941, 1942–1977 and 1978–1998. Time series analyses of the STCI showed reasonably clearly that there was a change in the climate about 1941 and a high probability of a change about 1923–1929. The STCI time series for the Sevier River had the expected pattern because the STCI increased in the years following 1997 nearly to the pre-1942 values from lower 1942–1977 values. The Little Colorado River showed a similar pattern, but not nearly to the magnitude suggested by the change in precipitation. The STCI for the Paria River essentially did not change. Changes in sediment transport also are investigated in the lower San Juan River where alterations in the sediment balance of the river may be due to variations in the character of summer precipitation.Key words climate change; Colorado Plateau, USA; sediment transport


Regulation du Fleuve Senegal et flux de matieres particulaire vers l’estuaire depuis la construction du Barrage de Diama

ALIOUNE KANEUniversité Cheikh Anta Diop, BP. 5005, Dakar-Fann, Séné[email protected]

Résumé Les observations et les mesures permettent de quantifier les volumes de matières en suspension qui aboutissent vers l’embouchure du fleuve Sénégal et mettent en évidence les principaux changements dans l’hydrologie et la morphologie de l’estuaire. Les échantillons sont récoltés au cours de la saison des hautes eaux, pendant les saisons hydrologiques de 1989 à 1993 et comparées aux résultats obtenus à Saint-Louis en 1981 et 1982 avant la mise en eau du Barrage de Diama (1985).Mots clés barrages; Diama; estuaire; matières en suspension; régulation hydrique; Sénégal River

Regulation of the Senegal River and the suspended sediment flux near its estuary since construction of the Diama barrageAbstract The daily and monthly regimes of total suspended solids (TSS) transport of the Senegal River (280 000 km2) to the ocean (1989–1994) is now regulated by the Diama barrage (established in 1986) located near the estuary. Since 1988, the Manantali reservoir, situated in the (high) basin has also controlled the riverine fluxes. The annual TSS loads vary between 0.63 and

1.9 Mt year-1, depending on the hydrological year and reservoir operation, with weighted TSS averages of between 90 and 218 mg l-1 at Diama. Specific solid transport in this Sahelian basin is very limited.Key words barrages; Diama; estuary; suspended matter; riverine flux regulation; Senegal River


Impact des modifications climatiques et anthropiques sur les flux de matières de quelques bassins fluviaux du Cameroun

L. SIGHA-NKAMDJOU1, D. SIGHOMNOU1, G. LIENOU2, J. R. NDAM2, M. BELLO2, R. KAMGANG2, G.E. EKODECK2, M. R. OUAFO3, G. MAHE4, J. E. PATUREL4 & E. SERVAT4

1 Centre de Recherches Hydrologiques de l’IRGM, BP 4110 Yaoundé, [email protected]; [email protected]

2 Université de Yaoundé I, Yaoundé, Cameroun3 Université de Dschang, Dschang, Cameroun4 UMR Hydrosciences, IRD Montpellier, France

Résumé En s’appuyant sur les résultats des travaux antérieurs, l’étude montre, à partir des résultats obtenus sur quelques bassins versants représentatifs des principaux écosystèmes du Cameroun, l’impact de la variation climatique récente et celui des activités anthropiques sur les régimes de flux des Matières En Suspension (MES). A l’échelle spatiale, la dégradation spécifique augmente de la zone forestière du sud (5 à 10 t km -2 an-1) vers la savane du nord (180 t km-2 an-1). A l’échelle temporelle, sur le bassin du Mayo Tsanaga (zone de savane), la dégradation spécifique décroît de 214 t km-2 an-1 en 1968–1969 à 180 t km-2 an-1 en 2003. Ces résultats indiquent une diminution du taux d’érosion liée probablement à la baisse des précipitations et aux techniques de lutte contre l’érosion. L’étude met également en évidence le rôle protecteur de la végétation contre l’érosion mécanique et montre que la baisse des MES, imputable à celle des précipitations est moins perceptible du fait de l’action anthropique qui porte sur la dégradation ou la protection du milieu.Mots clefs bassin fluvial; Cameroun; dégradation et protection des sols; érosion; flux de matières

Climatic and human impacts on sediment fluxes of river basins in Cameroon with contrasting land coverSuspended solids loads have been studied in six Cameroon rivers (basin areas of 1535–18 100 km2), having contrasting land cover ranging from wet tropical forest to savannah. Their specific solid transport ranges from 5 to 10 t km-2 year-1 for the wet forest to 180 t km-2 year-1 for the savannah, despite the markedly lower annual runoff from the savannah, 3.4 l s-1 km-2, cf. 68 l s-1 km-2 from the forest. In the savannah basin, a decrease of specific transport was also noted between 1968–1969 (214 t km-2 year-1) and 2003 (180 t km-2 year-1), and attributed to lower precipitation and anti-erosion techniques. Our study shows the importance of the protective land cover against erosion and the sensitivity of savannah basins to anthropogenic impacts.Key words river basin; Cameroon; soil degradation; erosion; suspended solids


Influence of reservoir sedimentation on water yield in the semiarid region of Brazil

JOSÉ CARLOS DE ARAÚJO1, AXEL BRONSTERT2 & ANDREAS GÜNTNER3

1 Professor Adjunto at the Department of Hydraulic and Environmental Engineering, Federal University of Ceará, Campus do Pici, bl.713, 60.451-970, Fortaleza, CE, Brazil [email protected]

2 Institut für Geooekologie, Universität Potsdam, Postfach 60 15 53, D-14415 Potsdam, Germany3 GeoForschungsZentrum Potsdam (GFZ), Section 5.4: Engineering Hydrology, Telegrafenberg, D-14473 Potsdam,

Germany

Abstract The semiarid region of Brazil (106 km2) is densely populated and highly vulnerable to droughts. Governmental water policy has long been oriented towards the construction of reservoirs to reduce the impacts of droughts. Nonetheless, continuous reservoir sedimentation not only affects water quality, but also reservoir morphology, thus reducing water yield for a given reliability level. This research assesses the effect of reservoir silting on water availability in the State of Ceará. Yield-reliability curves were calculated for selected reservoirs, using a stochastic approach, in two different morphologic states. The methodology was applied to four impoundments in Ceará, where long-term (an average of seven decades) sedimentation rates were determined. The results indicate that basin management, rather than only reservoir management, is necessary to avoid substantial reductions in water-yield reliability due to regional reservoir siltation.Key words Brazil; reservoir sedimentation; semiarid; stochastic modelling; water availability


Reassessment of Porto Primavera Reservoir sedimentation in view of updated sediment measurements

ALOÍSIO CELERI1, CARLOS F. CASTRO ALVES2 & NEWTON DE OLIVEIRA CARVALHO3

1 CESP, Companhia Energética de São Paulo, Caixa Postal 145, 15385-000 Ilha Solteira, SP, [email protected]

2 Drenatec-Regea, Engenharia, Geologia e Estudos Ambientais, Av. Eng. Heitor A. E. Garcia, 340, 05588-000 São Paulo, SP, Brazil

3 Adviser on Water Resources and Sedimentology, Rua Conde de Baependi, 112, ap. 904, 22231-140 Rio de Janeiro, RJ, Brazil

Abstract The Porto Primavera Dam is located on the Paraná River, Brazil, downstream of the Jupiá dam and upstream of the Itaipu dam. The reservoir capacity is 15.7 km3. The sediment load impounded in the reservoir mainly comes from six tributaries located in a drainage area of 574 000 km2. Low dam height and high intake flow have led to a very low intake crest elevation, which can affect dam operations due to sediment deposition at the dam. Previous sedimento-logical studies did not take into account two tributaries with significant sediment yields. A re-evaluation of present reservoir capacity, taking into account the additional tributaries and more recent sediment monitoring data, indicates that the sediment deposits at the dam will not reach the intake crest during the projected life expectancy of the Porto Primavera Dam and Reservoir. However, it is clear that a soil conservation plan could substantially extend the utility/life

expectancy of the facility. Key words Brazil; Paraná River; Porto Primavera Reservoir; sedimentation


Estimation of soil erosion and sedimentation in Ramganga Reservoir (India) using remote sensing and GIS

SANJAY K. JAIN, SHARAD K. JAIN & K. D. SHARMANational Institute of Hydrology, Roorkee 247 667, [email protected]

Abstract Accumulation of sediment reduces the storage capacity and the capability of a reservoir to conserve water for its intended purpose. To limit siltation, it is essential that soil conservation measures be undertaken in the drainage basin upstream of the reservoir. In this study, the catchment of the Ramganga Reservoir has been divided into nine sub-basins to determine which ones are prone to extensive soil erosion. Different parameters that influence soil erosion, such as slope, soil type and land use were analysed using a Geographic Information System (GIS). Siltation in Ramganga Reservoir has been assessed using multi-date remote sensing data. The revised capacity of the reservoir between 364.4 and 339.05 m water levels, due to siltation over a period of 12 years (1988–2000) was assessed to be 2391.63 106 m3, which gives an average sedimentation rate of 4.28 106 m3 year-1. The average siltation rate, based on bathymetric surveys over a time period of (1974–1997), was 4.78 106 m3 year-1. Thus, the estimated siltation rate, obtained using both the methods gave fairly similar results. This agreement confirms that remote sensing is a viable, inexpensive, and fast alternative to conventional bathymetric surveys.Key words sediment, reservoir, soil erosion, GIS, sedimentation rate


Sediment delivery and budgets in reservoir watersheds

SU-CHIN CHEN & YI-CHENG LAIDepartment of Soil and Water Conservation, National Chung-Hsing University, Taichung 402, Taiwan [email protected]

Abstract Serious siltation of Taiwan’s reservoirs has occurred from natural landslides and over-development. Although reservoirs can be dredged to prolong their utility and there are treatments to improve water quality, it is far better to achieve these goals via effective watershed sediment management. The sediment budget concept represents the most basic framework for addressing sediment issues in reservoir watersheds. The Soil Erosion Index Model (SEIM) has been integrated into a geographical information system (GIS) to provide a basis to evaluate sediment delivery and budgets in reservoir watersheds. Soil losses estimated using SEIM have also been compared with estimates of soil movement using 137Cs. The sediment delivery processes occurring in the Shih-Men, Teh-Chi and Cheng-Wen reservoirs have been modelled using SEIM and landslide volumes. Results indicate that the sediment delivery ratios are 29, 67 and 75% for


the Shih-Men, Teh-Chi and Cheng-Wen watersheds, respectively, when fluvial transport is disregarded. Sediment budgets have been developed in the 18 sub-watersheds of the three reservoirs. The approach developed during the present study not only provides erosion and landslide information at the individual sub-watershed level, but also establishes overall watershed sediment budgets. Finally, sediment budgets for the Shih-Men, Teh-Chi and Cheng-Wen watersheds are discussed in terms of their implications for sediment/watershed management. Key words caesium-137; sediment budget; sediment delivery ratio (SDR); sediment yield; soil erosion index model (SEIM); soil erosion potential


Impact des lâchers du barrage El-Moustakbal sur l’envasement d’un barrage de prise d’irrigation, Blida, Algérie

BENINA TOUAIBIA1, MOHAMED TOUAIBIA2, BACHIR BENLAOUKLI1, ABDELAZIZ BESSALEM1 & MOHAMED FEWZI SIDI MOUSSA3

1 Ecole Nationale Supérieure de l’Hydraulique, BP 31, 09000, Blida, Algé[email protected]; [email protected]

2 Direction Générale, Office des Périmètres d’Irrigation de la Mitidja, 100 Rue de Tripoli, Hussein Dey, Alger, Algérie3 Agence Nationale de Ressources Hydriques. Route Nationale No. 29, Soumâa, Blida, Algérie

Résumé Conçu initialement pour l’irrigation de la Mitidja Ouest, le barrage El-Moustakbal sur l’Oued Bouroumi, d’une capacité de 188 Mm3, se voit, ces trois dernières années, alimenter en eau potable la capitale “Alger” via les infrastructures d’accompagnement des périmètres irrigation de la Mitidja Ouest. Les lâchers d’eau claire quasi quotidienne de ce barrage transitent par le cours d’eau naturel sur une distance de 13 km et arrivent turbides au barrage de prise de Mouzaïa. Les volumes lâchés varient de 20 000 à 188 000 m3 jour-1 selon leur destinée (Alimentation en eau potable, irrigation) et la période. En 2002, pour répondre à la crise d’eau qu’a connut la capitale, le problème d’envasement du barrage de prise, d’une capacité de 60 000 m3, et de ces ouvrages d’accompagnement s’est posé d’une façon accrue, paralysant le transfert d’eau. Une opération de dévasement s’est lancée en un temps record (deux mois) où 58 000 m3 de vase consolidée ont été enlevés du barrage de prise et de ses infrastructures d’accompagnement pour un coût très excessif. En 2004 (23 mois après cette opération de dévasement), ce barrage de prise se retrouve envasé à 65%, réduisant sa capacité de stockage et paralysant les infrastructures à l’aval. Devant cet état de fait, la quantification de l’apport solide et la connaissance de son évolution temporelle dans le transit Barrage El-Moustakbal—Barrage de prise de Mouzaïa deviennent nécessaire voire obligatoire pour une prise en charge effective de ce phénomène.Mots clefs transport solide en suspension; barrage de prise; barrage El-Moustakbal

Reservoir siltation caused by change of use of hydraulic works from irrigation only to urban water supply: Oued Bouroumi, Algeria Abstract Oued Bouroumi (Algeria) is now totally regulated by hydraulic works. Originally conceived to provide water only for irrigation, these works (El-Moustakbel Dam, Mouzaïa irrigation reservoir), have also been used for water supply to Algiers (the Algerian capital city) since the 2002 water supply crisis. These operational changes are now causing a major silting issue in the Mouzaïa irrigation reservoir: its volume has been reduced to 35% in two years, which has necessitated the removal of 45 000 m3 of deposited mud. Our study illustrates the difficulty of integrated water management in dry regions.Key words El-Moustakbel dam, Algeria; reservoir silting; suspended solids

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