Abstract
Climate simulations in West Africa have been attributed with large uncertainties. Global climate projections are not consistent with changes in observations at the regional or local level of the Niger basin, making management of hydrological projects in the basin uncertain. This study evaluates the potential of using the quantile mapping bias correction to improve the Coupled Model Intercomparison Project (CMIP5) outputs for use in hydrological impact studies. Rainfall and temperature projections from 8 CMIP5 Global Climate Models (GCM) were bias corrected using the quantile mapping approach. Impacts of climate change was evaluated with bias corrected rainfall, temperature and potential evapotranspiration (PET). The IHACRES hydrological model was adapted to the Niger basin and used to simulate impacts of climate change on discharge under present and future conditions. Bias correction with quantile mapping significantly improved the accuracy of rainfall and temperature simulations compared to observations. The mean of six efficiency coefficients used for monthly rainfall comparisons of 8 GCMs to the observed ranged from 0.69 to 0.91 and 0.84 to 0.96 before and after bias correction, respectively. The range of the standard deviations of the efficiency coefficients among the 8 GCMs rainfall data were significantly reduced from 0.05–0.14 (before bias correction) to 0.01–0.03 (after bias correction). Increasing annual rainfall, temperature, PET and river discharge were projected for most of the GCMs used in this study under the RCP4.5 and RCP8.5 scenarios. These results will help improving projections and contribute to the development of sustainable climate change adaptation strategies.
Highlights
Climate change impacts are expected to exacerbate poverty in most developing countries and create new poverty pockets in countries with increasing inequality in both developed and developing countries [1]
The outputs of all Global Climate Models (GCM) underestimated and overestimated daily mean and monthly mean rainfalls. These outputs were adequately corrected by quantile mapping bias correction (Figure 2)
Mean and standard deviation of efficiency coefficients to observed among the 8 GCMs (Tables 2 and 3) were significantly (p < 0.05) improved by bias correction during seasonal (winter (December–February), spring (March–May), summer (June–August) and autumn (September–November)), monthly and daily climatological comparisons (Table 2)
Summary
Climate change impacts are expected to exacerbate poverty in most developing countries and create new poverty pockets in countries with increasing inequality in both developed and developing countries [1]. Water resources are fundamental for several sectors such as hydropower, crop production and fisheries in Africa [2]. Climate change has driven decreased discharge and increased drought in the Sahel, a transition zone between the Sahara desert and Sudan zones of west Africa, since 1970, with partially wetter conditions experienced since 1990 [1,3,4]. Niger river, which is the major source of water for some Sahelian countries Severe decrease of river flows in the basin was observed mainly due to the 1970s’ droughts [6]
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