The end of the beginning...

Climate change manifests itself in a number of ways in the areas I have examined, and the impacts of this on East Africa’s water are multi-faceted and complex. There is a fundamental need to increase hydrological and meteorological measurements, improving available meltwater, groundwater and river discharge data. This is essential if we are to improve understanding of relationships between climate change and water availability in vulnerable parts of East Africa. With increased data, it may be possible to anticipate when large recharge events, that sustain groundwater abstraction, will occur.

Regional and local aspects of climate change mustn't be overlooked, as hydroclimatic changes are non-uniform across the continent. Entire livelihoods can be based on one seasonal flood. If that flood doesn't arrive in a warmer, uncertain future, crops will fail, livestock will starve, and farmers will lose money. Economic development, without promoting fossil fuel consumption, should be a paramount consideration in policies (UNEP 2012).

An explicit message is sent by the rapid loss of some of Africa's key glaciers: our climate is rapidly changing within the time-frame of human lifetimes. With anthropogenic GHG emissions expected to continue rising indefinitely over the next decade, natural Earth Systems will continue being perturbed. The mountains in tropical East Africa have wider importance to surrounding communities, and climate change impacts local people and their religious traditions as well as affecting physical water availability. Before all ice is lost on Kilimanjaro and the Rwenzoris, we must endeavour to improve understanding of atmospheric drivers behind glacier decay, and apply this knowledge to our planet's other vulnerable tropical regions (Kaser et al 2004). The book of Africa's future water supply is still largely unwritten with uncertain conclusions. Could regularly replenished groundwater from an intensified hydrological cycle be a glimmer of hope in what seems like a desolate future? One thing seems fairly certain: in a warming world, not all of Africa's taps will run dry.

The Breadbasket of Tanzania

The focus of this blog post is policy documentation from the International Union for Conservation of Nature (IUCN) Water and Nature Initiative (WANI) case study, looking at the Pangani River Basin (PRB) in North-East Tanzania (Welling et al 2011). The basin covers an area of 56,300 km² (95%) in Tanzania, with 4,880 km² (5%) of this situated within Kenya (Welling et al 2011). In order to improve management of the limited water resources available for the basin's 3.4 million inhabitants and gather technical information, with an overarching aim of strengthening Integrated Water Resources Management (IWRM), the Pangani River Basin Management Project (PRBMP) was set up in 2002.

A map of the Pangani River Basin (Source: Pangani River Basin, Tanzania Report)

Fertile soils and abundant rainfall mean this basin has been referred to as the 'breadbasket of Tanzania' (Welling et al 2011). In 2011, it was estimated by the WANI case study that ~55,000ha of the basin was being intensely irrigated with inefficient furrow irrigation. As well as irrigation, water from the multiple rivers constituting the basin serve several hydroelectric power (HEP) stations, collectively providing 17% of Tanzania's electricity demand (Welling et al 2011). Together, irrigation and HEP use nearly 90% of surface flow in the Pangani (Barchiesi et al 2011).

Problems within the basin

The basin is already defined as water-stressed (<1200m3 water per person, per year), and thus climate change is exacerbating the problem of there not being enough water supply to meet demands (PRBMP 2015; Welling et al 2011). We saw in my last post that Mount Kilimanjaro's glaciers are receding at dramatic rates due to impacts of climate change, and this is impacting flows in the nearby PRB (IUCN 2011). Flows which used to be several hundreds of metres per second have diminished to below 40m3 (Welling et al 2011; IUCN 2011)! The combined effects of 1.8-3.6°C temperature rise in Tanzania, intensified and unpredictable precipitation patterns, and increased evaporation and evapotranspiration are expected to cause a 6-10% decline in annual basin flows (PRBMP 2015). The reduction in river flow has already caused seawater intrusion 20km upstream from the estuary (PRBMP 2015) and thus future additional reduction will put livelihoods, industry and the economy of Tanzania at stake.

A warming world, with urbanisation, population growth, intensified agriculture, and rising energy demands have all led to increased competition and overexploitation of water resources in the basin (Barchiesi et al). This has caused conflicts to emerge between various stakeholders, such as large-scale and small-scale farmers, livestock keepers, coastal communities, and HEP producers downstream (Welling et al 2011; PRBMP). There is not enough physical water available in the basin to meet the allocations made, thus over-allocation of limited supplies is a key issue to be resolved by the PRBMP.

How to manage these issues?

A growing awareness of problems in the PRB has stimulated action, both in the form of governments and stakeholders. The PRBMP have undertaken climate change modelling assessments, groundwater studies, and integrated flow research in order to improve understanding of environmental flows and thus to better inform decision making for allocation of water in the basin. I believe that encouraging community participation and IWRM, getting opinions and perspectives from all stakeholders, will hopefully reduce conflict between users of the basin in a modifying climatic future.

Kilimanjaro: an ice-free Africa?

Over the last few posts we've seen the dramatic extent of glacier loss in the Rwenzori Mountains, affecting not only agriculture and ecosystems, but also community tourism and tribal traditions. Today, we're going to take a look at glaciers on Africa's most famed mountain: Mount Kilimanjaro.

An iconic view of Mt Kilimanjaro and it's snowy peaks (Source)

Mount Kilimanjaro, a dormant stratovolcano in Tanzania, is Africa's tallest mountain, rising nearly 20,000 ft above sea level. In recent decades, the mountain has attracted a multitude of attention, becoming a symbol for global warming in Africa (Thompson et al 2009). The reason for this is the glacial extent crowning the mountain of ~12km2 in 1912, is roughly 85% more than what exists today (extent was just 1.76km2 in 2011) (Cullen et al 2013). The famous ice-climber, Will Gadd, was shocked after arriving at the summit of Kilimanjaro last year and realising the ice he had planned to climb (from looking at photos), no longer existed (Lindzon 2015).

The ice-fields that have persisted throughout the Holocene (the last 11,700 years) are notably shrinking, and the finger is pointing towards global warming as the blame. Climate change on a global scale has the ability to locally affect Kilimanjaro due to changes in large-scale circulation systems that transport moisture to East Africa (Mölg et al 2013). In the scientific community, there is no longer of question of whether ice will disappear on the mountain, but a question of when it will all be gone. Though some uncertainty remains regarding the evolution of future precipitation patterns in East Africa, Cullen et al (2013) propose that if current trends continue, most of the remaining ice-cover on Kilimanjaro will be gone by 2040, and all ice will have sublimated and/or melted by 2060. If you can't envisage the changes to Kilimanjaro in writing, watch the video below from Cullen et al (2013) showing glacier loss from 1912 to 2011 using a 3D model with satellite imagery - very powerful!

Kaser et al (2010) argue that the primary cause of Mt Kilimanjaro's primarily sublimating glaciers is reduced atmospheric moisture, as opposed to rising air temperatures (most often associated with global warming). However, this is unlikely to be the only cause of thinning, melting and sublimating ice. A widespread drought 4,200 years ago, lasting ~300 years (recorded in a dust layer in ice cores), was not sufficient enough alone to remove the ice fields (Thompson et al 2009). Thus, it must be a complex combination of climatological factors such as warmer surface temperatures, reduced humidity and altered cloudiness, alongside terrestrial changes in land-use that are causing the loss of ice on this tropical mountain (Kaser et al 2004). Thompson et al (2009) argue that the climatological conditions driving the disappearance of Kilimanjaro's glaciers are unique within the Holocene epoch.

What are the implications of an ice-free East Africa?

A warmer world is certainly impacting vulnerable tropical alpine zones in East Africa, and having widespread implications for the 1.5 million people living around Mt Kilimanjaro (UNEP 2012). Elsewhere in the world, increased glacial meltwater from melting glaciers would increase river discharge, followed by a sharp decline as glaciers shrink (UNEP 2007). In Africa, however, the situation is somewhat different (as we touched upon in my last post). Shrinking glaciers appear to have a negligible impact on water resources at the base of the mountain, as ice is primarily lost through sublimation and glaciers are too small to act as water reservoirs (UNEP 2012; Mölg et al 2013). Sublimation means that even when ice is melting, it immediately dries up and evaporates directly into the atmosphere.

The impacts for people in this part of East Africa focus on a loss of tourism - a vital industry providing significant income to Tanzania's economy (UNEP 2012). People may no longer travel to Tanzania, in awe of the beautiful year-round snow-capped mountains, standing tall amongst the arid plains near the equator. There may indeed be a surge of tourism for the next decade or so as people rush to seize a final opportunity to witness tropical glaciers before they become a myth of the past. But once these glaciers have gone, tourism will undoubtedly suffer a grievous aesthetic loss, as will established alpine ecosystems on the mountain. Policies and agendas regarding climate change in East Africa must address ways to adapt to these impacts which promote economic development, without encouraging the main cause of global warming in the first place: fossil fuel combustion (UNEP 2012). Additionally, before all ice is lost from Kilimanjaro, we should try to clarify and extend our understanding of the atmospheric drivers behind glacier decay in vulnerable tropical regions (Kaser et al 2004).

Mountains of the Moon: Reduced riverflows?

Last week we looked at how the Rwenzori Mountain's melting glaciers are having dramatic societal and agricultural impacts. This post explores the direct effects of a reduction in glacial ice on alpine riverflow in these Ugandan Mountains, focusing on Taylor et al's (2009) paper in the Journal of African Earth Sciences. What are the effects of a warming world (and thus glacier loss - covered here) on alpine water supply?

River Mubuku, the principle river
recieving meltwater discharges at
the base of the Rwenzori Mountains.
(Source)

As covered in an earlier post, these glaciers are vital to sustaining meltwater discharges, especially during the dry season, and also act as a store of seasonal precipitation (Taylor et al 2009). Thus, concerns have arisen over potential reductions in river discharge following the recent loss of Uganda's frozen reservoir. Our understanding at present is somewhat limited due to a lack of hydrological measurements in the East African Highlands (Taylor et al 2009). Besides a few spot measurements taken by Temple in 1968, no other data exists for glacial meltwater discharges in the Rwenzoris.

By taking spot measurements of alpine riverflow along numerous altitudinal cross-sections of River Mubuku (the mountain's principal river), draining alpine icefields, Taylor et al (2009) assessed the contribution of glacial ice on the Rwenzori Mountains to river flow. Using this newly collected dataset alongside historical records, the authors found that accelerated glacial retreat since the 1960s has had minimal impact on alpine riverflow. Through their study, they conclude that meltwater from glacial ice contributes to under 2% of river flow in the Mubuku during both wet and dry seasons. So although glaciers continue to rapidly recede in the Rwenzori Mountains (see my first post in this 'mini-blog' series), it seems this is having a minor impact on alpine riverflow. River Mubuku's headwaters are provided by glacial meltwater from the Rwenzori Mountains. Thus, one may presume that due to a disproportionately high specific discharge (1730mm/year), a significant amount of riverflow originates from meltwater (Taylor et al 2009). However, this high specific discharge is actually attributed to high precipitation rates in Heath-moss and Montane forest areas (below the icefields), which occupy over 50% of the river's catchment.

The authors also argue that trivial contributions of glacial meltwaters to alpine riverflow found in the Rwenzoris may apply to similar tropical alpine regions, where glaciers contribute a small percentage of the basin area, e.g. Mount Kilimanjaro and Mount Kenya. If this is true, how is a reduction in dry season riverflow on Kilimanjaro (Desanker 2002) explained, if not due to deglaciation? Taylor et al (2009) argue this is likely to be from declining rainfall and land-use changes on the catchment (e.g. deforestation), rather than a loss of alpine glaciers.

Thoughts and reflections:

I think Taylor et al (2009)'s research is a great contribution to existing literature on this topic, and reveals that glacial recession does not impact alpine riverflow as one might initially expect. It appears that climate change's impact on the hydrological cycle (intensification and altered precipitation patterns) is more of an influence on alpine riverflow in this location than changes to alpine icefields, caused by temperature rises. However, just because glacial meltwater discharges do not have a large contribution to alpine riverflow does not mean that riverflow will not be affected in other ways by climate change in the near-future. For example, increased evapotranspiration will reduce surface water availability, and less frequent, but more intense rainfall will alter patterns of seasonal discharge in River Mubuku. All these changes, regardless of whether they result from glacial loss or through changing hydrological patterns, will have significant direct impacts on those communities who rely on water from and around the Rwenzori Mountains. Climate change is manifesting itself in a number of ways, and the impacts and consequences of this are not entirely straightforward. There is clearly a great need to increase hydrological and meteorological measurements, improving the data available for meltwater and river discharge in this area, if we are to learn more about the impact of climate change and water supply in this vulnerable part of East Africa.

I highly recommend delving into the rest of Taylor et al's paper if you're interested in this topic regarding the Rwenzori Mountains, and fancy something intellectually stimulating for a bedtime read!

Mountains of the Moon: Community consequences

Last week I introduced one of East Africa's key landscapes affected by a warming world: the snow-capped Rwenzori Mountains, supplier of lakes which feed the Nile. In this first post in this 'mini-blog' series regarding the mountains we reviewed evidence of the extent of glacial retreat due to climate change, but we have yet to cover any wider societal implications of this. How are local tribal traditions affected by this rapidly modifying environment? How are agricultural practices around the mountains expected to alter due to climate change? So, today let's take a brief step away from the physical science of the issue, and instead try to understand how changes in climate are affecting the local population.

The Bakonzo People

Bakonzo way of life will be directly impacted by warming temperatures and glacial recession. (Source)

The large-scale loss of glacial ice in the Rwenzori Mountains has significant implications for the traditional beliefs of the Bakonzo people. The Bakonzo call the mountains their home and have done for many centuries; they hold strong religious ties with this high altitude landscape (Festa 2014). Glacial ice - Nzururu - is the father of the spirits, Kitasamba and Nyabiuya, responsible for human life and fertilisation of the land (Nakileza and Taylor). For them, the mountains are literally the source of life for the surrounding land. With a dramatic loss of their father of the spirits, Nzururu, in the past century, their belief system is directly at stake (Festa 2014). Furthermore, as temperatures are rising, declining ice cover means mountain guiding treks led by the Bakonzo people (a key source of their income) are becoming more dangerous, and thus this form of tourism livelihood is at risk (Nakileza and Taylor).

Agricultural Impacts

Arabica coffee, typically found above 1400m in Uganda (Jassogne et al 2013)
(Source)

For small-scale coffee farmers, already vulnerable livelihoods are at risk in a warming world. Coffee exports are a vital part of Uganda's economy, accounting for 20-30% of foreign exchange profits (Jassogne et al 2013). However, as the climate is changing, so are the niche tolerance areas certain coffee cash crops can be grown. For example, Arabica coffee (Coffea Arabica) has a specific and small tolerance range, only able to be grown in a cool tropical climate, such as that found in the alpine regions of the Rwenzori Mountains (Jassogne et al 2013). Climate mapping by an Oxfam research team found areas suitable for growing Arabica will drastically reduce in the near future as the climate of the mountains warms. Adaptation strategies, such as using shading to cool the coffee canopies, will be wholly necessary for small-holder farmers in the Rwenzori Mountains if the Ugandan people are to mitigate negative financial impacts from rising temperatures (Jassogne et al 2013).

Shifting wildlife patterns and spread of disease

Due to rising temperatures in the mountains, there have been major changes in the altitude range of plants and animals, with some serious human repercussions. Lets use the example of mosquitoes, which carry a parasite that causes malaria. One of the mountain villages, Ibanda, is where trekkers start their hike into the Rwenzori Mountains (Festa 2014). Historically, mosquitoes have never reached this altitude, and thus residents of the village have never been affected by malaria. However, since climate change and warming atmospheric temperatures, mosquitoes can now infiltrate higher altitudes and thus malaria is becoming a more serious common problem in mountain villages like Ibanda (Festa 2014).

Thoughts and reflections

I think to truly appreciate the significance of these mountains in tropical East Africa, you have to understand the wider importance of them to surrounding communities, and ways in which climate change impacts local people and their livelihoods', as well as the more obvious impact on water supply (which I will cover in my next post). Agricultural productivity, entire livelihoods, and religious traditions are all at stake in this part of East Africa as atmospheric temperatures climb and glaciers rapidly recede.

Mountains of the Moon: A final glimpse?

The Rwenzori Mountains, which stretch across equatorial East Africa, bordering Uganda and the Democratic Republic of Congo (DRC), were described by Ptolemy in AD 150 as 'Mountains of the Moon, whose snow feeds the lakes, sources of the Nile'. Though one doesn't immediately associate ice and snow with Africa, the glaciers found on this mountain range are indeed a key source for lakes which supply the (White) Nile (Taylor 2014). But in a warming world, how will this change?

The picturesque Rwenzori Mountains (Sources: left, right)

A study in 2006 by Richard Taylor et al revealed that if current trends of glacial recession continue, there will be no more ice in the Rwenzori Mountains within the next two decades. Our changing climate has caused an estimated reduction in glacier extent across the remaining three ice-covered summits (Mounts Speke, Stanley, and Baker) from 6.5km2 in 1906, to just 1km2 in 2003. In just under a century, the areal extent covered by glaciers has declined by ~84%. Taylor further estimates a decline in ice by ~0.2 square miles per decade (Carrington 2014). That's a pretty eye-opening prediction. 

Figure from Taylor et al (2006): a) Map of Uganda, Rwenzori Mts and meteorological stations, b) "Indicator glaciers", Elena and Speke, are shown with extent in glacial cover in 1955 compared to 1990, c) Visible declines in Elena Glacier's areal extent since 1906, d) LandSat7 ETM+ satellite image from 2003, showing Mount Speke's declining glacier extents since 1906.

A stark sight: retreat of Elena Glacier's terminus in just 2 years.
(Source: Richard Taylor)

When Taylor et al (2006) set out to measure the terminal positions of both Elena and Speke valley glaciers (see figure above), they found the recession trend between 1906-1990 appeared to be continuing at alarming rates. Elena's terminus has receded by ~400m since 1906, and 140m (+-17m) since 1990 alone (Taylor et al 2006). Speke's terminal retreat is somewhat more drastic, receding ~600m since 1906, and a vast 311m since 1993 (Taylor et al 2006)! Taylor et al (2006) attribute these differences in retreat due to dissimilar supplies of ice and snow from disparate elevation and morphology. These numerical values are informative, but as the saying goes, 'a picture is worth a thousand words', and I really feel the set of photographs taken by Taylor (above right) do exactly that. In just two years, there has been an enormous visible retreat of Elena Glacier's terminus.

What has caused this deglaciation? 

It is difficult to pinpoint the exact cause of glacial retreat in the Rwenzori Mountains, due to a lack of monitored meteorological observations in the area (Taylor et al 2006). However, Taylor et al (2006) find that air temperatures on land align with warming trends. Evidence does not support the idea that increased glacial recession is due to a reduction in precipitation (in this case, snowfall) (Taylor et al 2006). Conclusively, the team suggest that the observed decline in glacial extent in the Rwenzori Mountains is due to a rapidly warming environment, amplifying ice loss through evaporation, sublimation and melting. Albedo is also a significant player. As more of the glaciers are lost, more of the darkly-coloured rock is exposed, absorbing more solar radiation and thus enhancing warming trends; a positive feedback loop develops.

These mountains, amongst other frozen reservoirs in tropical East Africa, warrant increased efforts to monitor climatic variables and glacial volume and extent in the next crucial few decades. An explicit message is being sent by the visible loss of Africa's glaciers: the climate in this region is changing, and it is changing within the time-frame of our human lifetimes.

Why are these changes important for water?

Alpine glaciers situated near the equator are a vital freshwater reservoir, storing seasonal precipitation (due to the movement of the ITCZ). They act as a buffer, sustaining meltwater flows during dry seasons (Taylor et al 2009). Thus, the fact that a warming world threatens tropical glacier existence means that usage and amount of water available from the mountains will also change. Will alpine river discharge be drastically less during the dry season if deglaciation continues? Will flooding still occur at the base of the mountains during wet seasons? How will this impact the livelihoods of those who live within and around the mountains? Is it too late to reverse or slow these changes? These are all vitally important questions which I will be covering over the next couple of posts in a series of 'mini-blogs', focusing on the Rwenzori Mountains of East Africa. 

Kili's glacial retreat: a preview

The world is beginning to wake up to some of the realities of climate change. Some of the most pristine landscapes on Earth, such as glacial peaks, are diminishing at alarming rates. We're starting to realise that the snowy, ice-covered caps existing today may not stick around to be enjoyed by our grandchildren. This threat isn't just in the high latitudes of our planet; the tropical mountain ranges of East Africa are a key location being affected by climate change.

The first video from the National Science Foundation is a great summary of some of the impacts caused by shrinking glaciers in Tanzania - the home to Mt. Kilimanjaro, part of the Eastern Rift Mountain range. Though melting/sublimating glacial ice due to climate change is a phenomenon occurring globally, increasingly significant consequences are expected in tropical mountain ranges, due to Africa's preferential warming predicted in the near future (1.5 times the global mean) (Niang et al 2014). The diminishing glaciers of Kilimanjaro have become a symbol of climate change in Africa (Thompson et al 2009). The second video is fascinating; a clip of conservationist Ian Redmond expressing his feelings towards climate change, after witnessing first-hand the vanishing glaciers on Mt. Kilimanjaro.

If you have a spare 10 minutes, make yourself comfortable and sit down with a cuppa, because I really recommend watching these.

To keep this introductory post short and sweet, I'll be drawing back to Mt. Kilimanjaro's shrinking glaciers and impacts on water at a later date. Coming up next: climate change in the Rwenzori Mountains and implications for water supply.