H. KARAMBIRI(1), H. YACOUBA(1), B. BARBIER(1), G. MAHE(2) & J-E. PATUREL(2)

(1) International Institute for Water and Environmental Engineering (2iE), 01 BP 594 Ouagadougou 01 Burkina Faso, E-mail : harouna.karambiri@2ie-edu.org, Web : www.2ie-edu.org (2) HydroSciences IRD, MSE Université Montpellier 2, F-34095 Montpellier Cedex 5, France

African Basins Session, IFWF3 Conference, 16 Nov 2011

From plot to basin erosion in the Sahel: an alternative method to assess siltation

risks for small reservoirs in the Volta Basin

Background• Goal and Purpose : Assess the risks of small

reservoirs siltation for a better water management• Location: Nakambe basin in Burkina Faso (upper

part of the Volta basin)• Target Groups: Local communities (farmers,

fishers, breeders, others users)• Approach: Upscaling soil erosion from plot to

basin scale based on soils surface characteristics

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Plot scale (1 m²) Catchment scale (37 km²)

Basin scale (418 km²)

Outlet

Small reservoir at outlet

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Findings / Highlights

0%

2%

4%

6%

8%

10%

12%

14%

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

2004 2005 2006

Cum

ulati

ve lo

ss o

f res

ervo

ir ca

paci

ty (%

)

Annu

al so

il lo

ss (T

ons/

ha)

Year

Annual soil lossCumulative loss of reservoir capacity

Soil erosion and degradation is significantly increasing from one year to another.

This represents a serious threat for small reservoirs. The potential accumulation in the reservoir shows a loss of capacity about 12% over three years studies.

A need for actions

Figure 1: Evolution of soil loss by water erosion on the reservoir watershed (418 km²) for three years of study (2004,

2005 and 2006). 4

Evidence / Solutions

Figure 2: A small reservoir under intensive and multiple uses (Djibo, North of Burkina Faso)

Picture: H. Karambiri, 2iE

A particular attention should be given to the protection of these water resources (uplands soils and water conservation techniques, no farming buffer zones, pollution control, reforestation, etc..)

Integrated management of small reservoirs (resources, uses, users, consultation framework, legislation and policies, …)

Small reservoirs in the Volta Basin are vital for socio-economic development of local communities, mainly in Sahelian areas under water scarcity and high spatio-temporal variability

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Gaps / Challenges What is the state of siltation of small reservoirs in the Volta Basin?

What is the situation of water quality of small reservoirs in the Volta Basin?

How to take into account the dynamics at the basin scale (land uses, socio-economic activities, agriculture, …) in assessing siltation risks (including water quality issues) of small reservoirs?

Tools/methods to be developed for a better siltation forecast/prediction in small reservoirs?

Hydrological inter-relations of ensemble of small reservoirs in the Volta Basin?

How to integrate siltation risks in water resources management of small reservoirs?