Strong sediment deposition at the reservoir delta

Storage capacity reduction and sedimentation rate between the years of control survey

Bathymetric surveys of the Barasonareservoir: (a) in 1986; (b) in 1993; (c) in 1998; and (d) in 2006

a) Water routing b) Sediment transport• Reservoir routing: weighting factor calculated from the volume represented by the respective cross section•• River routing: based on the standard step River routing: based on the standard step methodmethod for a gradually varied flowfor a gradually varied flow

• Non-equilibrium sediment transport equation as proposed by Han (1980) •• Sediment carrying capacity computed by four Sediment carrying capacity computed by four different equationsdifferent equations

FormulasLimits of

applicability (mm)

Wu et al. (2000) 0.004 to 100

Ashida & Michiue (1973) 0.001 to 100

Tsinghua University (1985, IRTCES) 0.001 to 100

Ackers & White (1973) 0.040 to 100

c) Sediment budgetd) Bed elevation changes

• For three conceptual layers above the original bed• Deposition: using of a weighting factor, computed as a ratio between the water depth represented by each point and the maximum water depth at the cross section• Erosion: symmetrical distribution of bed Erosion: symmetrical distribution of bed thickness at the active layer is assumed thickness at the active layer is assumed adapted from the equilibrium channel adapted from the equilibrium channel width model proposed by Foster & Lane width model proposed by Foster & Lane (1983)(1983)

Erosion and Sediment Transport –Measurement and Modelling from Headwaters to large Catchments: A Research Project to reduce

Reservoir Sedimentation in semi-arid EnvironmentsA. Bronstert (1), E.N. Müller (1), J.C. de Araujo (2), R.J. Batalla (3,4), T. Francke (1), A. Güntner (5), G. Mamede (1,2)

(1) Institute of Geoecology, University of Potsdam, Germany, (2) Department of Hydraulic and Environmental Engineering, Federal University of Ceara, Fortaleza, Brazil, (3) Department of Environmental and Soil Sciences, University of Lleida, Spain, (4) Forest Technology Centre of Catalonia, Solsona, Spain, (5) GeoForschungsZentrum Potsdam, Germany (enmue@uni-potsdam.de / Phone: 0049-331-977-2975)

Ribera Salada

Ésera/Isábena

�

10°0'0"W

5°0'0"W

5°0'0"W 0°0'0"

0°0'0"

40°0'0"N 40°0'0"N

In dryland environments, the water supply depends strongly on the water stored in artificial reservoirs. However, storage capacity of the reservoirs is often threatened by severe sedimentation due to upland soil erosion. An international research group is currently developing and applying a modelling system for the quantitative assessment of sediment mobilisation in catchments, sediment transport in the river system, and sediment retention in reservoirs. The focus is laid on meso-scale river basins (several hundreds to thousands of square kilometres in size) in semi-arid regions. An existing hydrological model tailored for specific semi-arid characteristics is extended with components representing erosion and sediment transport processes.With the aim of implementing adequate process formulations, hydrological multi-scale data sets from dryland catchments, rivers, and reservoirs in Spain and north-eastern Brazil are used and expanded by own measurements. Modelling approaches and supporting measurements are designed according to a multi-scale approach in order to capture the effect of small scale processes and landscape features on the large-scale overall hydrological dynamics.

RELATED PUBLICATIONSPublished•A. Bronstert, A. Güntner, J.C. de Araujo, A. Jaeger, M. S. Krol (2005) Possible climate change impacts on water resources availability in a large semi-arid catchment in Northeast Brazil. IAHS-Publications 295, Wallingford (GB), pp. 221-230.•J.C. de Araujo, A. Güntner, A. Bronstert. (2006) Impact of reservoir silting on water availability in a semiarid region. Hydrological Sciences Journal, 51, 157-170•J. C. de Araujo, A. Bronstert, A. Güntner. (2005) Influence of reservoir sedimentation on water yield in Brazilian semiarid region. IAHS-Publications. 292, Wallingford (GB), pp. 301-307.•A. Güntner, M. S. Krol, J. C. de Araujo, A. Bronstert. (2004) Simple water balance modelling of surface reservoir systems in a large data-scarce semi-arid region. Hydrological Sciences Journal, 49 (5), 901-918.•M. S. Krol, A. Jaeger, A. Bronstert, A. Güntner. (2006) Integrated modelling of climate, water, soil, agricultural and socio-economic processes: a general introduction of the methodology and some exemplary results from the semi-arid Northeast of Brazil. Journal of Hydrology, 328, 417-431 doi:10.1016/j.jhydrol.2005.12.021•G. L. Mamede, A. Bronstert, T. Francke, E. Müller, J. C. de Araújo, R. J. Batalla, A. Güntner. (2006) 1D Process-based modelling of reservoir sedimentation: a case study for the Barasona Reservoir in Spain. Conference Proceeding River Flow 2006. International Conference on Fluvial Hydraulics. Lisbon September 06 ? 08, 2006•E. N. Müller, R. J. Batalla, A. Bronstert. (2006) Dryland river modelling of water and sediment fluxes using a representative river stretch approach. Book chapter IN: Natural Systems and Global Change, German-Polish Seminar Turew, Poznan

• Complete WASA update• Analysis of temporary sediment storage (Ésera/Isábena River)• Analysis of measured bedload data (Ribera Salada)• Testing / Scenario studies (Ésera,Ribera Salada, Bengue)ephemeral river modelling (Bengue)

• Assessment of vertical distribution of suspended sediment concentration close to the dam (Barasona Reservoir)

• Analysis of the effects of small reservoirs on water and sediment budget in semiarid areas (Bengue)

1. Riverbed gradation at Ribera SaladaMotivation:Evaluation of the spatial variability of the D50 parameter and of the bimodality index of the riverbed gradation1. Method: Wolman Pebble Count, sampling of ca. 50 - 100 grains,

randomly, measurement of the intermediate axes with ruler2. Method: Facies mapping: estimate areal extent of patches (along

perpendicular transects, measurement of areal extent or usage of spatially segregated sampling)

Calculation of Sediment budgets using randomForest-models

0

10

20

30

40

50

60

70

80

SSC

[g/l]

0

0.05

0.1

0.15

0.2

runoff[m

3/s]

B1

rainfall

runoff

S S C (obs )

S S C,HERMintpl

data bounds

S S C,NNintpl

Interpolation method Pros Cons

Hermite, nearest

neighbour

easy, straightforward

no implausible values

not reflecting rapid

dynamics

SSC=0 for

unmonitored events

Sediment rating curve Easy, continuous Explains <17 %

variability

Generalised linear

models

Can Include additional

driving forces

Good fit in training

data

Unstable estimates,

implausible values

randomForest additional driving

forces

robust

good performance

Computationally

intensive

Restricted range of

values

20/09 30/09 10/10 20/10 30/10 09/11 19/11 29/11 09/12 19/12 29/120

0.5

1

1.5

2

x 104

flood 1

flood 2

flood 3

flood 4

flood 5

flood 6

flood 7

flood 8

sedim

ent budget [t]

0.0

t16073.2

t

126.5

t

2081.4

t

313.5

t

70.2

t82.0

t359.0

t

347.1

t

359.2

t

61.8

t

43.5

t

54.0

t

33.7

t4.4

t76.9

t

Flood-based sediment budget Cabecera (qrf)

0

5

10

15

20

25

30

35

40

45

runoff [m

3/s

]

flood period

SY, CIhi

Sediment yield

SY, CIlo

Unimodal D50Bimodal D50 Threshold

Time series for measured and simulated bedload transport rates (submerged weight) for the storm event on 04.04.2002 at the Terrassolasection (Ribera Salada) for parameterisation Scenario 1 (unimodal), Scenario 2 (bimodal) and Scenario 3 (threshold).

2. Spatial estimation of temporary sediment storage in Isábena River (along ca. 33 km)Motivation:Investigation of the sediment transfer and storage processes by quantifying the total amount and its spatial distribution of fine sediments in the Isabena riverbed.

3. Temporal estimation of sediment storage at specific cross-sections in the Isabena RiverMotivation:Estimation of the temporal variations of fine sediments stored river bed method: frequent monitoring of steel bars installed in riverbed.

Subcatchment event response (water/sediment export)Motivation:• Focus: Villacarli and Cabecera• monitor dynamics of sediment generation,

channel storage and sediment export from catchment

Methods:• survey of colluvium (1)• monitoring of hillslope

erosion,deposition (2) and yield (3)

• computation of trap efficiency

Methods:• Automatic rain gauge• Discharge and sediment flux monitoring

max depth

(3) (2) (1)

river

bridge

TruTrackWT-HR 2000

hosefilter cloth

PVC-pipewith cap

Bedload Modelling in the Ribera Salada

5 bedload formulas3 parameterisation approaches for the

spatial scaling of the D50 parameter

Medium-term sediment yield of badlands• elementary badland catchment, ~ 8.1 ha• preferrable settings for measurements:

‚check dam‘ (road) built 20 years ago

Study Areas

Bathymetric Survey of Barasona Reservoir Motivation: • Assess sediment deposition in Barasona reservoir Method: • Bathymetrical survey

Water and sediment transport in reservoirs

F I

E L

D W

O R

K

In review / in press / close to submission•A. Bronstert, R. J. Batalla, J. C. de Araújo, T. Francke, A. Güntner, G. Mamede, E. Müller. (2007, in press) Investigating erosion and sediment transport from head-waters to catchments to reduce reservoir siltation in drylands. Book chapter IN: IAHS-Publications No. xxx, Wallingford (GB)•T. Francke, A. Güntner, A. Bronstert, G. Mamede, E. N. Müller. (2007, in press) Automated catena-based discretisation of landscapes for the derivation of hydrological modelling units. International Journal of Geographical Information Science•G. Mamede, J. C. de Araujo, A. Bronstert. (2007, in press) Global change scenarios in the prediction of reservoir sedimentation and water availability. Book chapter IN: IAHS-Publications No. xxx, Wallingford (GB)•E. N. Müller, R. J. Batalla, A. Bronstert. (submitted) Modelling bedload transport rates during small floods in a gravel-bed river. to be submitted to Journal of Hydraulic Engineering

M O

D E

L L

I N

GO

U T

L O

O K

Name: Ésera/Isábena catchmentCatchment area: 1231 km²Climate: Mediterranean-mountainous

precipitation 600 - 1200 mm Land use/ Geology: heterogenous landuse including

pastures, agriculture and forested areas on Paleozoic rocks and easily erodible materials (marls, sandstones)

Reservoirs: Barasona reservoir (92 Mm3)

Name: Ribera Salada catchmentCatchment area: 225 km2

Climate: Mediterranean-mountainous,precipitation 700 - 800 mm

Land use/Geology: mainly forested areas on on conglomerates

Name: Bengue catchmentCatchment area 933 km2

Climate: semiarid, precipitation 430 mm, highly variable and seasonal

Land use/Geology: Caatinga (shrub), dry forests, agriculture on Precambrian and Proterozoic crystalline bedrock

Reservoirs: Bengue Reservoir (19.6 Mm3)

Acknowledgements: This research was carried out within the SESAM-project (Sediment Export from semi-arid catchment: Measurement and Modelling) funded by the Deutsche Forschungsgemeinschaft (DFG)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 500 1000 1500 2000 2500 3000Time [min]

Sed

imen

t su

bm

erg

ed w

eig

ht

[g/m

s]

0

2

4

6

8

10

12

14

16

Wat

er d

isch

arg

e [

m3

/s]

Measured bedload Measured water discharge

23/12/00 08/03/01 30/04/01 04/04/02 08/06/02

YearStorage capacity

(Mm3)

Storage capacity

reduction (Mm3)

Sedimentation

rate (Mm3/year)

1932 71,00 - -

1972 92,20 11.41* 0,29

1986 91,80 0,40 0,03

1993 75,92 15,88 2,27

1998 80,10 (-4.18)** (-0.84)**

2006 75,78 4,32 0,54

* value computed using a storage volume of 59,59 Mm3 corresponding

to the initial maximum reservoir level in 1932 (442.67 m)

** negative values can be explained by flushing operation at the period