Changes in land use/ land cover and water balance components before and after dam construction in the Mono River Basin, West Africa

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Abstract The intergovernmental Panel on Climate Change has predicted sub-tropical region to be more vulnerable to the effects of Climate Change(CC). Additionally, to CC, land use and land cover (LULC) changes and dam contruction often neglected, plays and important role on the spatial and temporal distribution of water balance components(WBC) for agriculture production and socio-ecological equilibrium. The aim of this study wa sto analyze and compare the changes in LULC and WBC for the periode before Nangbeto dam construction (1964-1986) and the period after its construction (1988-2010) in the Mono River Basin(MRB). To this end, the study used mainly WBC extracted from the validated Soil and Water Assessment Tool and LULC data of the years 1975 and 2000 in the MRB to explore their temporal distributions and the link in their changes. The results showed that the mean monthly actual evapotranspiration, percolation, water yield, surface runoff, groundwater and lateral flow represent 51.05%, 17.53%, 15.93%, 9.43%, 5.67% and 0.42%, respectively of total water balance between 1964 and 1986. The same components represented 51.02%, 9.17%, 20.43%, 6.30%, 10.56% and 2.59%, respectively between 1988 and 2010. The contribution of these WBC in mean-annual (1964-1986) period were for actual evapotranspiration (31.33%), water yield (25.95%), percolation(17.67%), groundwater(14.71%), surface runoff (9.94%) and lateral flow (0.40%). Meanwhile, between 1988 and 2010, the contribution of actual evapotranspiration, water yield, percolation, groundwater, surface runoff and lateral flow are 49.85%, 19.97%, 11.17%, 10.34%, 6.15% and 2.52%, resepctively. The results showed that the peaks of the evapotranspiration, surface runoff, percolation and water yield appeared in September corresponding to a month after the maximum of rainfall in August. However, our more detailed analysis showed that a significant decrease of forest and savanna and increase of cropland let to a decrease in actual evapotranspiration and lateral flow over the second period of simulation compared to the first period of simulation over the MRB scale. These findings showed that sustainable management and conservation of natural vegetation is crucial for integrated water resource management and conservation in MRB.

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