Impacts of global climate change on African water

Global climate change and water availability in Africa
The impacts of global climate change on Earth's system are increasingly acknowledged, particularly on the availability of water resources. 

Projection of future climate change and African water

Projecting future climate change usually involves processes like downscaling General Circulation Models (GCMs) into higher resolution Regional Climate Models (RCMs), then estimate the future water flows and stores. It is often validated with observation data, however in some regions particularly in Africa lacks most of its observed data (e.g. precipitation or river discharge), increasing the uncertainty in projection of future climate change. 

      One of the examples for predicting climate change and its impact of water resources can be referred to the project led by the Egyptian Ministry for Water Resources and Irrigation (MWRI), DHI and the UK Met Office Hadley Centre, which targets to conduct “Regional Climate Modelling of the Nile Basin: Preparation of climate scenario outputs for assessment of impact on water resources in the Nile Basin”(Butts and Lørup, 2009) since the impacts of climate change on the Nile river basin are expected to be very critical in managing the water sources for various countries sharing the basin water. Many activities were involved to assess the climate change impacts, and developing a RCM for the Nile Basin was part of the scheme (See figure 1); RCM covering the whole region of Nile river Basin has been developed by UK Met Office Hadley Centre, performed with PRECIS ( a modified RCM from HadRM3 model, designed to run on PCs - Jones et al., 2004).  

Figure 1 - RCM (left) and GCM (right) projections of Nile river Basin (from UK Met Office Hadley Centre in Butts & Lørup, 2009). 

The next phase of the project was to apply such climate projections to the grid-based hydrological model ('the Nile Forecasting System'), to assess more detailed impacts on Nile Basin water resources.

Although RCMs have advantage over GCMs, such as higher resolution and greater detail for climate simulations, it still incorporates high uncertainty in projections of climate change. This can be critical in planning the water management schemes especially in regions like Africa where high variability in hydrology exists inherently. 

Impacts of climate change on African water resources

Global climate change trends
Globally, seasonal precipitation range is expected to increase under warming climate scenarios, as well as the precipitation difference between Northern and Southern hemisphere in the boreal winter and summer. These are illustrated by the climate model simulations and past observation analyses, implying that there is a tendency of wet season getting wetter and dry season getting slightly drier or remains same as now (Chou et al., 2007).  

Impacts on Africa
For the climate change impacts specifically on African region, it can be divided into three major areas: 

1) The warming in Africa will continue, likely to exceed 2°C (mean annual temperature) under SRES (Special Report on Emissions Scenarios) A1B and A2 scenarios by the end of this century (Niang et al., 2014). Moreover, the land temperature over Africa is likely to increase faster than the global land average - especially in the more arid regions. 

2) The reduction in precipitation is likely over Northern Africa and Southwestern parts of South Africa by the end of twenty-first century (under SRES A1B and A2 scenarios) (Niang et al., 2014). 

3) Longer period of droughts especially in southwestern Africa and increased variability in river discharge (Niang et al., 2014). 

4) Intensification of precipitation from global warming in Africa will lead to fewer, lower and medium intensity rainfall events while more very heavy rainfall events - hence more extreme precipitation events. Also, in regions of high or complex topography (e.g. Ethiopian Highlands) will likely to experience increases in rainfall & extreme rainfall by the end of twenty-first century (Niang et al., 2014). 

Intensification of precipitation in Africa
Intensification of precipitation in Africa is partly resulted from global warming and associated impacts of 'Clausius Clapeyron relation'; warming air holds more moisture in the atmosphere, leading to increases in low-level moisture with rising temperature as a consequence of Clasius-Clapeyron relation (Allan et al., 2010). Thus, such increase in moisture contributing to the intensification of (extreme) precipitation. 


Furthermore, variable precipitation may lead to more variable soil moisture, impairing the crop yields in Africa. For instance, a study by Ahmed et al. (2015) illustrates that decreases in productivity of some crops are already observed in regions like West Africa - where vulnerability to climate change is relatively higher than other regions in Africa. Both projected increase in temperature and shift in patterns of precipitation are presented to be the major factors influencing the crop yield change. Also, inter-annual variability of crop yields are predicted to increase by the mid-21st century (Ahmed et al., 2015) in West Africa despite projected rise in precipitation in some areas. This is a crucial issue particularly in Africa since its projected population growth is massive (African population can reach 4.4 billion people by 2100 - mentioned in previous post) and regional food security problem can be exacerbated with such predicted intensification in precipitation (Challinor et al., 2007). 

Interestingly, some studies suggest that such precipitation intensity change can affect groundwater recharge positively in the tropics; Study by Jasechko and Taylor (2015) related currently available long-term records of stable isotope ratios - of Oxygen (O) and Hydrogen (H) of modern groundwater - in 15 different tropical precipitation sites. The results indicated that 14 out of 15 tropical sites showed groundwater recharge biased to intensive precipitation (in monthly data), often exceeding the 70th decile (Jasechko and Taylor, 2015). Yet, the processes associated with transmitting intensive rainfall to groundwater systems and (accordingly) enhancing groundwater replenishment remain unclear. 
     Additionally, such results only signify the tendency of increased groundwater replenishment related with intensive rainfall as a result of global warming, and other factors influencing groundwater systems such as land-use/cover change or human disruption (Jasechko and Taylor, 2015) may have also included in the investigation. Nonetheless, such favour in groundwater recharge from intensive precipitation will place groundwater in a more crucial role particularly in regions like Sub-Saharan Africa where projected population growth in very high and food security problems likely to increase in the future (Taylor et al., 2009). 

Demographic change and African water

Demographic change in Africa and impacts on water

Population in Africa is rapidly growing, and projected to grow in near future as well. According to the population projection by UN population Division (2015), African population will likely to be more than doubled (about 2.5 billion) in 2050 compared to 2015 (1.19 billions). Then by 2100, the population could have doubled again to 4.4 billion people (shown below in the graph).  

UN Medium-variant population projections in billions, from 2015 to 2100 (Graph produced with data from UNPD).

 Not only the huge number of people will be added to African population in near future, but also the rate of regional population change will be fastest in Africa; a growth by 108.87% in 2050, compared to 2015 population. 

Regional population change in percentage from 2015 to 2050, graph used data produced by UN Medium-Variant Population projection 2015. 

Such projected increasing trend can be a result of different factors combined, including dramatic improvement in infant mortality and life expectancy in Africa is expected, while high Birth Rate remains. 

     Some people suggests that such growing and relatively 'youthful' population in Africa can be an 'opportunity' for regional development, as Asia has experienced massive economic growth with increasing population before. However, many problems are also projected with such growing population, particularly related to water resources. 


Overall, many resources including water will face rapidly increasing demands from growing population in Africa. Demands will increase not only for domestic use, but also for agriculture, for food production as well. Agricultural water use generally accounts for 75% of total global consumption while industrial and domestic uses account for the rest (UNEP, 2008). As population increases in Africa, more food production will be needed to feed the growing population and this will likely lead to greater share of agricultural use in water consumption - even greater than now. The main issue will be how to meet such increasing demands in a relatively fast rate of growth - both in domestic and agricultural use (maybe even in industrial use as well to produce goods for larger population) - in Africa. 
     However, studies like Alcamo et al. (2007) implied that according to the analysis of socio-economic driving forces (from A2 and B2 IPCC sceanarios) on future global water stress, 
the most important factor affecting the growing water withdrawals for domestic use is actually stimulated by income growth, while population growth exerting a much less impact. 
         

     Additionally, the growing population will have impact on the land uses in Africa, since competing demands for subsistence farming, commercial agriculture and other developments are likely to increase massively (Financial Times, 2016). Larger population means greater demands for food, while many states trying to develop areas with development projects involving infrastructure building, and this will heavily determine the changes of land use/cover patterns in Africa. 


     Furthermore, population growth in Africa can increase vulnerability of the region to climate change, as indicated in the IPCC AR5 for Africa (Niang et al., 2014); "Climate change will interact with non-climate drivers .... to exacerbate vulnerability of agricultural systems, particularly in semi-arid areas (high confidence)". IPCC report investigated that the changes in precipitation and increasing temperature is happening as a result of climate change and it is highly likely to reduce cereal crop productivity. Thus, it could have negative effects on food security, along with increased vulnerability from population growth. For example, lack of precipitation over several seasons and extreme climate events in the Horn of Africa like Somalia, have left humanitarian crisis including UN's declaration of 'famine zones'. This has been aggravated by factors like rapid population growth, compounding their vulnerability to adapt or mitigate the impacts of climate change. 


As illustrated above, demographic change in Africa is in a rapid progress and is affecting diverse aspects of African environment. Although it may seem like it is not directly related to water systems in Africa, it can exert huge impacts on issues like land use/covers and vulnerability against climate change - which can influence water systems in Africa massively. Hence, it can be effective to examine the association and extent of impacts of population on different issues related to Africa water. 


*Just to mention, population projections always involve limitations in its measurements, and in UN 'Medium-Variant population projection' used in the graphs above assumes that the global average fertility rate will fall from 2.5 children per woman (2015) to 2.4 (around 2030) and eventually 2.0 in 2100. Also, population projections likely to change even between few years, for example shown in the graph below:

Graph comparing UN world population projections between 2012 and 2015. 

Medium-Variant projections of world population have changed between 2012 and 2015, and this may due to different factors such as changes in investment or policies on reproductive health and family planning, migration, time commitment and cost of raising children affecting the fertility rates. However it also involves various factors that could change the projection figures significantly.