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The Niger Inland Delta (NID) is a wetland of a seasonally flooded area of

approximately 30,000 to 40,000 km2 along the Niger River in Mali (Orange et al.,

2002). NID plays an important role in sustaining the livelihood of one (1) million

people, and its annual flood events have considerable influence on downstream flow

regimes due to water loss significantly impacting water availability of the basin

(Zwarts et al., 2005). However, this processes that occur in NID are not fully

incorporated in the conceptual development of many hydrological models of Niger

basin runoff.

Objective:

This study focuses on the analysis of NID’s water balance on monthly time steps,

taking into account remote sensing flooded area estimates. This analysis is based on

water loss estimation specifically the evapotranspiration and infiltration loss in view

of improving NID’s water budget.

Introduction

Data & Methods

Results

The annual flood dynamic observed through remote sensing was consistent with the

NID flow regime as shown in figure 5 providing a correct representation of the

flooding with good

correlation R2=0.90.

Fitted Power model for the

relationship between Area &

Flow regime (Figure 4).

Improving the Water Balance of the NID

References

Historical hydro-climatic

data of upper, middle, and

Inland Delta for the period

in between 1950 to 2010

(collected from the Niger

Basin Authority and the

national services of

Hydraulic and Meteorology

of Mali) were used in this

study (see figure1).

1. WASCAL Graduate Research Programme, Benin, 2. Center for Development Research, ZEF, Germany, 3. Regional center AGRHYMET, Niamey, Niger, 4. Department of Civil Engineering, University of Ottawa, Canada, 5. Water and Environment Division - DER Geology, ENI-ABT Bamako, Mali

Moussa Ibrahim1,*, Dominik Wisser2, Ali Abdou3, Abel Afouda1.4, Ousmane Seidou4, and Adama Mariko5

Flooded area characterization and loss estimates for improving water balance over the Niger inland delta (NID), Mali

Our Common Future Under Climate Change | Paris, France | 07 - 10 July 2015

Figure 2: Flood area extent

over ten years from remote

sensing data for the NID

Remote sensing derived flood maps extent of the NID that is inundated is used for

every month between 2000 and 2009 (Fig.2).

To characterize the extent of the flooded area using the depth of flow from the

monthly scale river flow input within a non-linear regression Model based.

Figure 1: Study Area

Description of system

Six main components of the water balance over the need were identified as part of the

physical hydrological process of the system (Figure 3).

Our water budget equation can be summed up based on the diagram below as follows:

∆S = Qi(t) + P(t) − AET(t) − I(t) +WCI(t) − Qo(t)

where:

ΔS = change of storage,

Qi = surface water inflow (KeMacina and Douna),

P = contribution of rainfall over the NID,

AET = actual evapotranspiration loss,

I = infiltration loss from flooded area,

WCI = Water contribution from irrigation,

Qo = surface water outflow at the station of Diré,

t = monthly time scale.

All units are in (km3 month-1).

Figure 4 Figure 5

The high level of correlation is coherent with a geometrical surface-stage-inflow

relationship, and provided partial confirmation of the ability to use remote sensing

area estimate to study NID’s flood dynamics. Where correlations were good (figure 6),

with maximum flooding occurring at the same time with the stage and inflow status.

Figure 6

Over the hydrological years studied, the

flooded surface area varied between a

maximum flood of 25 000 km2 in wet season

and a minimum of 2000 km2 during the dry

season.

The figure 8 clearly indicates the contribution of each terms to the water budget over

the NID’s wetland compare to the studies in the past.

The monthly change in storage of

the system was calculated using the

combined river flow regime as input

and the estimated remote sensing

flooded area (see figure 9).

Figure 8: Annual average water fluxes over the

NID for the period 1979 - 2004

Conclusion

This study illustrates how remote sensing data can be used to help conduct

hydrological process analysis at high temporal and spatial resolution across large

wetlands. This knowledge was applied to understand the variations at play in a flooded

area, and to refine evapotranspiration estimates, precipitation and infiltration over

the NID. Though relatively insignificant and often neglected, rainfall and infiltration

over a wetland are essential to explain inter-annual variations in the water budget.

Information on the propagation and dynamics of the flooding can be used to develop

and calibrate a dynamic model of the NID.

1.Mah, G., Bamba, F., Soumaguel, A., Orange, D., & Olivry, J. C. (2009). Water losses

in the inner delta of the River Niger : water balance and flooded area, 3160(August),

3157–3160. doi:10.1002/hyp

2.Orange, Didier, Mahé, G., Dembélé, L., Diakité, Cheik Hamalla, Kuper, M., & Olivry,

J.-C. (2002). Hydrologie, agro-écologie et superficies d’inondation dans le delta

intérieur du Niger.

3.Zwarts, L., Van Beukering, P., Kone, B., Wymenga, E. (2005). The Niger, a lifeline

Effective water management in the Upper Niger Basin. RIZA, Lelystad / Wetlands

989 International, Sévaré / Institute for Environmental Studies (IVM), Amsterdam /

A&W 990 Ecological Consultants, Veenwouden. Mali / the Netherlands, 169(Ivm), 169

* Contact Information:

imoussa47@yahoo.frThis research is done for the partial fulfilment of requirements for Doctoral Studies

GRP climate change and water resources, university of Abomey Calavi, Republic of Benin, 2013 -2015P 2212 a - 07