GroundWater potential in East Africa

Groundwater

Groundwater is the most abundant and readily available source of freshwater, and in fact accounts for > 90% of accessible freshwater worldwide (Figure 1). The abundance of groundwater is largely influenced by climate variability and change through replenishment by recharge, and indirectly through groundwater use. These impacts can be modified by human activity such as land-use change (Taylor, 2012).

Figure 1: Groundwater storage for Africa based on the effective porosity and saturated aquifer thickness

source: http://iopscience.iop.org/article/10.1088/1748-9326/7/2/024009

Potential for ground Water recharge

A shift towards few but heavier rainfall events is expected due to climate change in the East African region, this is expected to lead to more frequent and intense floods as well as variable and lower soil moisture. 

Based on records from the Makuyapora Wellfield, Tanzania 1955- 2010, Taylor (2013) finds that groundwater levels have been declining due to over abstraction. People have been removing water from the deep granite aquifer to provide water to the capital. Abstraction has increased from 0.1million m³ to 0.9million m³ per month in this time period, however supplies have not. This appears to be because episodic recharge events are sustaining intense abstraction.

Figure 2: Analysis of the relationship between groundwater recharge and rainfall

Source: http://www.nature.com/nclimate/journal/v3/n4/full/nclimate1731.html

As shown in figure 2, for a large proportion of the record, there is no recharge. Recharge only occurs when there is highly intense seasonal rainfall. Recharge results disproportionately from > the 80th percentile. A non- linear relationship between rainfall and recharge is demonstrated, where intense seasonal rainfall associated with ENSO and the IOD contributes disproportionately to recharge. 

Taylor (2013), shows that projected intensification of rainfall under climate change may favour recharge. Therefore, in a warmer world, where we see more intense rainfall events, groundwater may be a viable adaptation to support longer droughts and lower soil moisture. However, there are many problems that arise.

Problems

Uncertainties

Long- term monitoring data is generally lacking across the East African region, and in cases where data is available, there is more often than not, inconsistencies due to varying methodologies used. This can make comparisons and identifying trends challenging (Comte, 2016). One key uncertainty is whether soil infiltration capacities will be able to transmit heavy rainfall, and therefore actually generate increases in groundwater recharge as the models show (Taylor, 2013). There is also uncertainties of whether increased rates of potential evapotranspiration from warmer air temperatures will induce groundwater recharge (Kingston, 2009). A very important uncertainty, lies in the assumption that all increasing intensive rainfalls will contribute equally to groundwater recharge. 

Barriers to development 

Socio- economic and political factors can cause groundwater development costs to be higher than they would otherwise. According to Giordano (2006) the typical reasons for this include lack of local manufacturing capability, high duties on imported equipment, high energy costs, and poor supporting infrastructure such as road networks and electricians.

Furthermore, in some cases there has been national and donor policy that has undermined groundwater development. The push by donors and governments to invest in large scale irrigation schemes for example dams, may have drawn financial capital away from groundwater development. Furthermore the numerous large scale schemes that have failed in the past, may turn 'farmer sentiment away from irrigation expansion' (Giordano, 2006).

Influences on supply

Changes in total volume in precipitation largely influences the supply of Groundwater.

The recharge of groundwater due to climate change can also be affected by other influences such as over abstraction and land- use change. Increasing demand due to population growth and economic development, can lead to an increase in the use of groundwater supplies. If demand outstrips supply, these resources will be depleted.  (Carter, 2009).

At the continent level East Africa has the second highest rate of population growth. In contrast to inland areas where abstraction is only limited by aquifer productivity and available recharge. Coastal aquifers are susceptible to seawater intrusion, if not managed carefully due to being low- lying and shallow water tables. Salt water intrusion is already a risk to groundwater supplies if over abstracted, however, it is higher in coastal regions.

The combination of increasing rainfall extremity, increase in sea level rise (cause saltwater intrusion), increased urbanisation (results in increased surface runoff from land clearance), and increased demand for water (increased abstraction), puts coastal regions of East Africa at risk. All these factors have already, but will have further negative implications on groundwater recharge. Although recharge is projected to increase with climate change, fresh groundwater availability will likely decrease in coastal areas if an effective management regime, involving communities is not introduced (Comte, 2016).

Hydropolitical issues 

There is an issue that aquifers may be transboundary, this creates hydropolitical issues (Taylor, 2009).  A transboundary aquifer is a body of groundwater which is intersected by two or more countries with the potential threat of dispute over shared groundwater resources. Abiye (2010) examined the transboundary aquifers in 6 East African countries (Ethiopia, Eritrea, Sudan, Kenya, Somalia and Djibouti). Although these countries are yet to give major attention to the groundwater contained in these transboundary aquifers, the author stresses the need for a change. They state the future trend is steering towards increased exploitation of these reserves due to water shortages. Therefore, systematic development of these resources is needed to strengthen cooperation, and reduce the potential for conflict.

Concluding thoughts

Through increased recharge from more intense rainfall events, Groundwater can enhance the resilience of domestic, agricultural and industrial uses of freshwater in the face of increasing climate variability and change. There are many issues that arise especially from increased population growth and economic development, that puts groundwater resources at risk from over abstraction, salt water intrusion and pollution. There is also the potential for conflict over transboundary resources. Therefore, for groundwater to be sustainably seen as a solution, it needs to be integrated into national policy and requires development of adequate cross- sector dialogue within government, as well as enhancing communities in the management process.

Irrigation in Kenya

Coefficient of Variation (c.v)

In last week's post i mentioned the C.V in order to describe the seasonal variability of rainfall in regards to Maize Farming.  

C.V is the formal definition of intra-annual or seasonal variability defined through 'normalised' spread of average rainfall over the year.  The CV is the average of 12 monthly rainfall values for a country (k) defined as CVMk = σ(Pj,k)/μ(Pj,k); i.e. as the ratio of standard deviation of calendar month (j) average rainfall to its grand mean across all calendar months (Brown, 2006).

Climate change is increasing rainfall variability, and is therefore making conditions for agriculture and economic development very difficult (Brown, 2006). Greater rainfall variability highlights a greater need for irrigation. It brings to attention the areas that may need supplementary irrigation to 'regularise' crop yields (Challinor, 2006). CV therefore enables solutions to increase reliance to these changes to be put in place, and therefore mitigate some of the expected impacts of climate change (Brown, 2006).

Irrigation in Kenya

Agriculture is the leading sector in the Kenyan economy, contributing to 24% of GDP, and is the largest contributor to employment (with > 70% of the labour force based in rural areas), and accounts for about 50% of principal export earnings (Kabubo- Mariaria, 2007).

In Kenya, traditional irrigation dates back 400 years, which is longer than most countries in Eastern and southern Africa. According to the Fao, in terms of utilising low- cost technologies (including rainwater harvesting, bucket irrigation, gravity fed sprinkles and drip, treadle and pedal pumps, rope and washer, mortised pumps, wind power and construction of small earthen dams), Kenya is well ahead of other countries in the sub- region.

Irrigated lands are up to 2.5 times more productive in comparison to rain-fed agriculture. They play an important role in the agricultural sector in SSA, and are often favoured by governments and donor agencies for their high return rate.

Models predict that global warming will lead to increased temperatures ~4℃ and rainfall variability up to 20% by 2100. Using Ricardian analysis, a study on the economic impact of climate change on Kenyan Agriculture, shows that climate does affect agricultural activity. They show that adaptation to climate change in Kenya is important, if households want to counter the impacts of long- term climate change. Results of perceptions and adaptation of farmers to climate change showed that Kenyan's are aware of both the long and short term changes in climate and have implemented various adaptation mechanisms. They do show that coping strategies must be tailored specifically to different factors including physical, economic and sociocultural. They found that irrigation is adopted in the drier regions, but not the areas that have a high potential for evaporation, in which the most common adaptation measure is diversification.

Some of the types of irrigated agriculture found in Kenya are:

• Large- scale surface irrigation schemes by the Government, in which smallholder farmers play a very small role in management.
• Smallholder irrigation, either by individuals or small groups, that have been able to exploit water in streams and irrigate small areas in valley floors. This is mainly subsistence, but also cash crops for local markets.
• Agro-industrial irrigation of high- value crops, finance and developed by private corporations or individuals. These rely heavily on pump- based technologies in conjunction with drip or sprinkler irrigation.

Irrigation potential 

However, Kenya is still heavily dependent on rain-fed agriculture. With 17% of the land considered to have medium to high potential for irrigation, less than 10% is utilised, which amounts to only 2% of total arable land in Kenya (FAO, 2005).

A study on the potential for irrigation in Kenya, has showed that there is high potential for the expansion of both dam-based (water stored in large reservoirs) and small- scale irrigation (surface runoff based) in Kenya. The analysis of the potential investment for Small- scale irrigation project expansion in Kenya ranges from 54,000 ha to 241, 000 ha, with an internal return rate of 17-32%. For the dam- based investment analysis, under low- cost assumption, 58/ 73 damn are profitable. At high cost level, 32 of these dams are economically feasible.

Irrigation does not come without its environmental problems. For example, development of irrigation systems can increase the salinity of cultivated land in the area- this affects 29% of irrigated land in Kenya (FA0, 1997). The main challenges however facing irrigation expansion in Kenya is the cost of implementing projects. Kenya's agriculture sector (75%) is dominated by small- scale farmers, who do not have the capacity to invest in gravity- led or pump- fed irrigation canals (You, 2014). The problem found with large scale irrigation projects, is that often government and donor interests come first before smaller famers. The capacity for governments to manage these systems effectively has often collapsed.

Concluding thoughts

There is potential for both small and large scale irrigation schemes. However, for this to be effective, there needs to be better management and incentives to small scale farmers like subsidies, so that they can invest in technology.

Increasing variability in rainfall, is seeing exceptional high rates of precipitation, which may lead to groundwater recharge which can be harnessed during dry periods. However, the decrease/ lack of precipitation in the dry periods and increased demand may not only lead to decreases in runoff and streamflow downstream, but may also deplete groundwater supplies. As this post never explored groundwater as a source of water for irrigation, next week's post will look closely at the Groundwater potential in East Africa.

Maize Farmers in Tanzania

Rainfall Variability

The most important factor in sustaining crop productivity is water availability. Rainfall variability from season to season largely impacts soil water availability to crops, and therefore face crop production risks. Ideally, crop cultivations should be situated in areas with high rainfall and low variability. However, as shown in figure 1, in SSA about 37% of maize- growing areas are located in areas where there is high seasonal rainfall variability- coefficient of variation (C.V.) >0.2 (HarvestChoice, 2010).

Figure 1: Map of sub- Saharan Africa showing the coefficient of variation (C.V.) of seasonal rainfall at major maize growing areas during 1955-2004.

Source http://harvestchoice.org/labs/rainfall-variability-and-crop-yield-potential

As shown in the previous posts, with climate change will come increased rainfall variability, and this will have further implications for Maize farmers.

Maize in Tanzania

In Tanzania, up to 95% of food production depends on rainfall, which is highly affected by climate variability, and this will likely change due to global warming (Sixbert, 2016).  In Tanzania Maize is the 'staple food'. According to the (FAO, 2015), 80% of maize in Tanzania is produced by small-scale farmers and is usually grown under low input, rain-fed conditions. Maize is grown for both substance (65-80%) and cash crop (20-35%).

Hai District 

In a study on the 'Decline in maize and Beans production in the face of climate change at Hai District in Kilimanjaro Region, Tanzania', it was found in the Hai district that in the non- drought years, Maize has the highest yield in comparison to other crops (Figure 2). However, in the years 2003 and 2009- where there was lower annual rainfall- almost 98% of maize crops failed, but the same extreme impact was not felt in low rainfall years of 2005 and 2007.  The study found that there is a strong and significant association between climate change and high variability in yield patterns of maize in the Hai District. The reductions in maize yield are primarily due not only to the increases in temperature and decreases in rainfall amount, but also the distribution during the growing season (rainfall variability).

Figure 2: Annual maize and rainfall/ temperature patterns in Hair District from 2000 to 2010 

source:http://search.proquest.com.libproxy.ucl.ac.uk/docview/1655266955/fulltextPDF/5E7207F4328C4936PQ/1?accountid=14511

Wami Ruvu Basin

Adaptation is the only way rain-fed farmers can survive the threat of climate change, and this is on the agenda of many countries around the world. However, before this can properly be thought out and implemented, it is important to know and fully understand the impacts of climate change at smaller scales. In a study on the 'Assessment of the impacts of climate change on maize production in the Wami Ruvu basin of Tanzania', they sought to do exactly this. Using detailed field and household survey information, data of current climate conditions and future climate projections (RCP 4.5 and RCP 8.5), they created a model. They assessed the impacts of climate change of maize production by analysing the changes in simulated maize yields (2010-2099) and compared them to the baseline period (1971-2000).

Results showed that due to climate change future maize yields over the Wami Ruvu basin will slightly increase relative to the baseline during the current century. However, maize yields will decline in the mid and end centuries. The report also highlights how different parts of the basin will be affected differently: The eastern parts of the basin will experience decreased yields, while part of the central region and the Western side of the basin will experience increased maize yields. They also show a high decline projected over lower altitude regions due to projected increase in temperatures.

It is important to note that different models provided different estimates of future maize yields, highlighting the uncertainties associated with the projections.

Manyoni District

Many Farmers have already adapted their farming practices due to changing rainfall patterns and amounts, and other land changes. Based on a study of two villages in Manyoni District in Singida region, Tanzania, the table below summarises how maize farmers have adapted their practices:

Table 1: Impacts of changes in rainfall pattern on maize cropping practices in Kamenyanga and Kintinku Villages

 Source: https://assets.publishing.service.gov.uk/media/57a08b47e5274a27b2000a75/Majule-and-Mary.pdf

This paper is highly reliant on data collected from local people and their perception on how the climate has changed. Results showed that this region has presented increased temperatures and a delay in the rainy season. Although the annual quantity of rainfall is reported to not have changed, rainfall variability has increased, seeing more droughts and floods. This has meant that local farmers, in particular maize farmers, have changed their farming practices, to suit the new changing climate. Thornton (2007) has shown that some farmers may even completely change the crop they grow, for example, due to a reduction in the growth period, maize might be substituted by sorghum and millet since they are more suited to their drier environments. Inclusion or change to drought resistant crops such as Casava or sweet potatoes may also be an option  (Munishi, 2015).

Concluding thoughts

High rainfall variation, is increasing the risk of short- run crop failures and long- run production declines, therefore with further projected changes, adaptation methods need to be strengthened, on a case by case basis.  Maize specifically has been shown to be very vulnerable, and receptive to changes in temperature and rainfall, and therefore continued reliance on this crop will be a high risk to farmers, especially in the face of climate change.

Next week's blog will look at how farmers can adapt to changes in rainfall, by using irrigation.

Donald Trump- Is this a new planetary disaster?

"We're going to cancel the Paris climate agreement- unbelievable- and stop all payments of the United States dollars to UN global warming programs."

Business man Donald Trump who believes that Climate Change is a Chinese hoax is now the new president of the United States.

What does this mean for the future?

Figure 1: Past and future projections of US carbon emissions based on US presidency

Source: http://www.luxresearchinc.com/news-and-events/press-releases/read/trump-presidency-could-mean-34-billion-tons-more-us-carbon

What does this mean for Water in Africa?

Moving East!

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

Source: https://saylordotorg.github.io/text_world-regional-geography-people-places-and-globalization/s10-05-east-africa.html

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

Source: http://onlinelibrary.wiley.com/doi/10.1002/fes3.61/full

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.*

Source: http://www.alliancesud.ch/it/politica/clima/copy_of_downloads/conflitti-aw.pdf

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.