Why East Africa?
As I said in last week's post, I am going to be focusing on East Africa. I have chosen this region, because since studying 'health and pollution in East Africa' and 'Development in East Africa', during my Geography A levels, I have had a deep-rooted interest in this region. What I particularly enjoyed studying and researching was how the physical landscape is core and an extremely important factor to its development- there are so many attributes that can lead this region to thrive. Although at the same time, some, especially in interest of this blog Climate and land use change that will limit this. However, I believe that this factor is often largely overlooked by human geography research in development, when it is fundamental to the development of this region.
Physical Geography
East Africa is the easterly region of the African continent, variably defined by geography or geopolitics. The different countries that belong to East Africa is disputed by many different sources (Figure 1).
Figure 1: Different disputed maps of East African boundaries
Sources: http://www.mapsofworld.com/africa/regions/eastern-africa-map.html;https://en.wikipedia.org/wiki/East_Africa; https://saylordotorg.github.io/text_world-regional-geography-people-places-and-globalization/s10-05-east-africa.html
Water Resources
East Africa has some of the greatest water sources in the world. The three most notable water sources in this region include:
- Lake Tanganyika- the greatest single reservoir on the continent and second deepest in the world.
- Lake Victoria- The continents largest lake and the world second- largest freshwater lake.
- The Nile River Basin- Source of the Nile, the longest river in the world.
Tectonic Rifting
The physical landscape of East Africa is largely characterised by tectonic rifting (Figure 2), which partially determines the hydro climatology.
Long, linear deep lakes such as Lake Malawi have been created by rifting. Tectonic activity has also seen the birth of the highest mountain in Africa, Mt. Kilimanjaro- located in Tanzania near the border of Kenya, and the second highest peak, Mt. Kenya- located near the North of Nairobi. They both provide fresh water to their surrounding areas.
Figure 2: East African Rift Valley
The East Africa region is by primarily arid and semi- arid lands, and parts cool and dry (GWI, 2011). The main reason for this is due to a rain shadow affect experienced on the leeward side of areas of high relief. The Rwenzori Mountains and Highlands of Ethiopia are great examples of this.
- The Rwenzori Mountains on the Congo- Ugandan border reach elevations >16,000ft. These ranges which have permanent snow and glaciers create a rain shadow affect that cuts off moisture for the region from the westerly equatorial winds;
- The highlands of Ethiopia which reaches a high of 15,000ft, restricts precipitation in areas to the east. This creates a Savanna- type landscape.
Rainfall
Figure 3: Percent of normal precipitation in East Africa, 2011
Source: Source: NOAA Climate Prediction Center via
Weather Underground
Rainfall seasonality in East Africa is complex, and high variability characterises the rainfall system (Galvin, 2004). The annual cycle is bi-modal, with wet seasons from March to May and October to December. The long rains (March to May) contribute > 70% to the annual rainfall and the short rains <20%. Much of the inter annual variability comes from the short rains (Butterfield, 2011).
ENSO and IOD (Indian Ocean Dipole) play an important role in the variability of precipitation in this region, especially the extreme events. Historically, East Africa face large variability in rainfall with occurrence of floods and droughts. However, there have been many changes: The climate of East Africa during the main March- May rainy season has steadily dried over the past 30 years leading to droughts, and increased rainfall in the October- December rainy season, which can cause flooding (figure 3).
The heating up of the Indian Ocean, which has altered the atmospheric circulation over East Africa is arguably what has caused these changes.
Climate Change in East Africa
Projected changes in Precipitation
Temperature and Precipitation variability are projected to increase in East Africa, however it is varied over the region. As shown in figure 4, projected increases in temperature are quite uniform over the region. There are however large uncertainties, and variations in precipitation (Adhikari, 2015). IPCC AR5 reported that 'the future precipitation projections are more uncertain but are likely to increase in Eastern Africa and decrease in the southern part' (Niang, 2014). The uncertainties in projections, are mainly since the seasonal weather in the region is highly influenced by ENSO.
Figure 4: Projected temperature and precipitation in east Africa
In a report on the Projected changes in East African rainy seasons, Cook (2013) uses a regional climate model to show C21st simulation:
- Southern Kenya- Tanzania: long rains (March- May) are reduced throughout the season due to a secondary response to changes in the Congo basin. The short rains period is lengthened by ~ 2 months in association with a northeast-ward shift of the South Indian Convergence Zone.
- Eastern Ethiopia- Somali: The long rains (start beginning of May) will end prematurely due to an anomalous dry, anticyclonic flow that develops over Arabian Peninsula and northern Arabian sea in response to strong warming over the Sahara.
Implications on water access
Climate change is strongly associated with water scarcity and Stress. Below are some of the impacts of climate change on water resources in the region:
Figure 5: Impacts of climate change in on water East Africa
Edit * There is a factual error in the 1st point in the figure above. Seasonality changes of rivers are entirely due to changes in rainfall patterns; the glaciers contribute negligibly to rive discharge. Not the 'loss' in icecap volume/ areas as stated in the figure.*
Concluding thoughts
The region of East Africa has already felt the impacts of climate change. Extreme Flooding and Droughts is a real problem that this region faces. Although future projections show that they are to see annual increases in rainfall, the seasonal changes, is what will bring devastation to many. The changes in frequency, intensity and predictability of precipitation, will ultimately affect water availability and may lead to decreased agricultural production and potentially widespread food shortages.
Next week's blog, will focus on Agricultural production, and how these changes in rainfall has and will affect the Maize production in Tanzania.
Interesting read, it's great that you are able to focus and learn more about a region that you have a personal interest in.
ReplyDeleteOther than the reason stated, why do you think that the IPCC are so conservative in their projections, when personally I think that the best thing to do is overestimate and prepare for the worst?
Hi Lewis, thank you for your comment. Sorry about this late reply, but in concern to your comment.
DeleteI agree with Richard, that in this case the IPCC have not necessarily been conservative. Although the IPCC has projected that East Africa will experience more rainfall, but in fact global averages are stayed pretty much the same, or in fact decreased. However, many regions have found that they're long rain season has seen shortages in the amount of rainfall, leading to drying.
Yes you are right that in many cases the IPCC has been found to be conservative, as it is important to note that they are not just a scientific body, but also a political one too. However, i do not believe that this is the case in this circumstance.
Rhona, be good to reply to Lewis! It is unclear to me why the suggest that IPCC is being conservative. Indeed, the IPCC suggests that East Africa will become wetter under anthropogenic warming yet it is currently becoming drier!Note that there is a factual error in the cited Swiss website which argues that the seasonality of rivers flowing from Rwenzori Mountains and Kilimanjaro has been affected by the loss (or reduction actually) in the icecap volumes/areas. Seasonality changes are entirely due to changes in rainfall patterns; the glaciers contribute negligibly to river discharge - see Taylor et al. (2009) Journal of African Earth Sciences Vol. 55, pp. 205-213.
ReplyDeletethank you Richard, i have now included that in the post about the mistake in the source.
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