Fate of African water

Will African water be secured in the future?
Over the past few months, I have been exploring about the threats posed on African water systems, including land use/cover changes, demographic change and climate change impact on water. 
     Personally, it was very intriguing to find diverse sources emphasising the extensive impacts of land use/cover changes in Africa - which is one of the areas with most rapid urbanisation across the world - on water balance system. Although great amount of studies on impacts of climate change exist in the academic discourse, I felt that the case studies and analyses of land use change in Africa are relatively less, which may due to insufficient data collection in many African regions. Also, it seems to me that if we want to project the future of African water system, diverse factors (not only topics mentioned in previous posts but also other factors like national irrigation schemes) should be integrated in examination. 

Climate Change VS other factors

Would the impacts of CC on water balance outweigh other factors (e.g. Land use/cover change or demographic change) ?

While researching for climate change impacts on African water, I have found an interesting study by Favreau et al. (2009); it explores about different factors (apart from CC) that might have affected the water system in Africa, using a case study of Southwestern Niger. 

Southwestern part of Niger experienced rising water table for past few decades (1963 - 2007) despite a deficit in monsoonal rainfall from 1970 to 1998 (Favreau et al., 2009). Such 'paradoxical phenomenon' is related with changes in land use, mainly from natural savannah to millet crops since 1950s - which expanded by six times. Changes in land use caused soil crusting on slopes, enhancing the Hortonian runoff. Consequently runoff concentrates in closed ponds, leading to aquifer recharges. 

In order to investigate the factors affected such consequences in detail, the study used three different scaled methods: 
     First, a physically based distributed hydrological model in local scale (2 km2) revealed that land clearing happened in 1950s are has increased the runoff by threefold while rainfall deficit decreased runoff by twofold. 
     A larger scale (500 km2) historical aerial photographs between 1950 and 1992 showed an increase in the gully densities by factor of 2.5 in response to a 80% decrease in perennial vegetation. 
    Lastly, a entire study area-scale (5000 km2) analytical modelling of groundwater radioisotope data illustrated that recharge rate before the land clearing was approximately 2mm a􏰧-1, while it was about 2± 7 mm a􏰧-1 after the clearing. 

Hence, in the case of southwestern Niger, impacts of land use change on water balance were much greater than the direct influence of climate variability. 
     Yet, this study does not directly address the 'climate change' aspects related to climate variability, it is interesting to see how land use change can affect the water balance system in the area - varying in scale. Also, the study area was well equipped with appropriate information to conduct detailed study, which many parts of Africa lack still. 

Climate Change (CC) projections and adaptations to CC

Uncertainties involved in such CC projections

As mentioned briefly in the previous post, certain degree of uncertainties in Climate Change projections is inevitable. Although enhancements are being made continuously, it is difficult to say that there is an absolute and/or objective ways to assess different climate change projection models - so each model has equal probability of getting the projection 'right'. 

     Some scientists suggest that the uncertainties in CC projections should be discussed further in detail, since it can influence massively in the process of forming climate mitigation and adaptation policies around the world. For instance, IPCC Technical Report VI (Bates et al., 2008) discuss about the uncertainties involved in climate projections and how it can impact the results indicated in the report; it includes major uncertainty sources related to hydrological cycle such as limits in climate models produced by spatial resolution and ensemble size achieved by present computer resources (Bates et al., 2008). However, such approach of uncertainty based on ensembles of different GCM projections is often criticised due to lack of rigour in mathematical aspect since the probability function is not conditioned on measured values of the variables (Rougier, 2007 in Taylor et al., 2009). 

     Particularly in climate projections of African region, uncertainty in projected precipitation is a major concern because it can affect the water resources management significantly. Not only the impact of CC on atmospheric water-holding capacity derived from Clausius-Clapeyron relationship and precipitation intensities, but also the socioeconomic changes in land use/cover in the area can influence the uncertainties in future climate projections. Furthermore, many regions in African continent lack sufficient observational data, which is essential in climate model validation process. Hence, there are more diverse factors, which could be considered more extensively in uncertainty discussions of CC projections.