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. 

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. 

Land use/cover change and water in Africa II

Land use and cover change impacts on quality of African water

Last post explored about the impacts of land use/cover change on African water supplies. This time, the impacts on the quality of African water will be investigated. 
As mentioned at the end of the last post, the quality of water is crucial for both human socioeconomic development and conditions of environment; and land use/cover changes could lead to significant changes in water quality. 

Many scholars examined the effects of land use change on water quality, mostly suggesting strong relationship between them in the concluding remarks (i.e. Gburek & Folmar, 1999). For example, Bolstad and Swank (1997) suggested that consistent changes in water quality variables were accompanied by the changes in land-use and Tong (1990) also implied that the urban development in the watershed of study area (Little Miami River basin) caused substantial modification of flood runoff and water quality. To investigate further of such relationship, I would like to look closer on the study from Tong and Chen (2002) examining the hydrologic effects of land use at both regional and local scale of the study area:


Tong and Chen (2002) conducted statistical and spatial analyses to examine the relationships of land use, flow and water quality in receiving waters on regional scale (the State of Ohio). Also, in local scale (local watershed in the East Fork Little Miami River Basin) as well, by modelling effects of land use on water quality using BASINS method. The results in regional scale indicated that land use was related to many water quality parameters; correlation between different land-use types and water quality variables in the watersheds in the State of Ohio was statistically significant, with a probability level of <0.0001 (See Table below).

Table of results of the Spearman's rank correlation analysis on land-use types and water quality variables in all sub-watersheds in the State of Ohio, from Tong & Chen (2002). 

Moreover, the results of modelling impacts of land-use change on water quality of the smaller local watershed revealed that runoff from agricultural and impervious urban land-use had much more phosphorus and nitrogen. This may be related to the enrichment of nutrients and/or sediments from agricultural land and rubber fragments, heavy metals and sodium from road deicers (Tong & Chen, 2002). 
     Thus, the study signified that the changes in land use have resulted in altering the parameters of water quality in the study area. This could be helpful in understanding the land-use change impacts on African water quality since the region is experiencing rapid urbanisation and expansion in agriculture, which affects the water quality the most - as elaborated previously by other studies as well. 



As an applied case study in African region, a study by Du Plessis et al. (2014) - quantifying and predicting the relationship between water quality and land-cover change - can be an example.

The study aims to quantify relationships between selected water quality parameters and land cover change in the Blesbok Spruit Catchment in South Africa, with application of Partial Least Squares (PLS) Regression model to come up with model equations for predicting water quality. 

Map of South Africa showing the location of Blesbok Spruit catchment (dark orange shaded area), from Du Plessis et al., 2014. 

     The results demonstrated that the Blesbok Spruit catchment has very poor water quality levels, heavily influenced by the densely populated characteristics with economic growth and development, cultivated land, and mining land cover within the catchment. Particularly, the whole catchment area has been affected by the discharge of mining effluent, sewage, and other pollution sourced from urbanisation, industrial and agricultural growth over the past decades. Furthermore, the efforts of retransforming the land cover into natural areas have caused undesirable side effects because of the degradation of the region's buffering capabilities and failure in decommissioning the mining operations. Du Plessis et al. (2014) concludes with emphasis on the urgency of addressing the water quality issues affected from the land cover changes since it not only disrupts the water quality of the area, but also can limit the future economic growth and development in the region. 

There are already cases of water quality altered by the land-cover changes in Africa, especially from urbanisation and development, and it is expected to be faced by more regions as many of them are going through rapid development or yet to start. 



After exploring the impacts of land use/cover change on water in Africa - in different aspects of quantity and quality of water system - it seems to me that demographic change happening in Africa is inseparable in current discussion about relationship between land use/cover change and water in Africa, since it is one of the most influential factors altering the landscapes of Africa. Hence, I would like to explore a bit further on the impacts of  population growth on land use/cover change and availability of water in Africa in the next post.  

Land use/cover change and water in Africa I

Land use is referred as the different ways that humans use the earth's surface mainly driven by consumption and production dynamics related to socioeconomic activities, while land cover can be referred as the biophysical state of the earth's surface and its upper subsurface (Schulze, 2000). Land use changes often lead to inevitable modification in land cover and as land cover changes, whether it is due to changes human activities or from other natural factors like hazards, its impacts on environmental system are crucial to all living organisms. 

An exemplary land use and land cover changes in Senegal - major changes in agricultural expansion seems to drive fragmentation of wooded Savannas and woodland sin Southern part of country, leading to loss of habitat and degradation of habitat quality.
(Source: US Geological Survey - http://lca.usgs.gov/lca/africalulc/results.php#senegal_lulc). 

Although natural factors such as hazards can alter land cover, anthropogenic activities account for increasing part of land use/cover triggers. Such changes often led to negative impacts on Earth, loss of biodiversity through modification and fragmentation of the habitats and degradation of soil and water resources for example. Human activities account for one-third to one-half of the global ecosystem production (Du Plessis et al., 2014) and with continuing demands from population pressure and intensified economic activity particularly from African countries, conversion in land use patterns and hydrological cycles are highly likely to enlarge for few decades. 

Growing interests in relationship between land use and hydrology 

Rapid increase in human activities in Africa including expansion of agriculture and firewood industries have led to diverse changes in land cover. For example, increased agricultural demands for irrigation and cropland resulted in deforestation and conversion of some parts of indigenous forestlands. Also, demands for timber and pulp instigated commercial afforestation for species that are fast growing, and domestic water uses increased as the urban area develops. All of the examples show factors altering the land cover in Africa currently. Such different and diverse stakeholder demands are driving land use changes in Africa, and inseparably causing impacts on hydrology of the region. 

Significant changes in land cover have occurred in West Africa over the past few decades, and the reasons behind this range from population growth and increasing use of resources for agriculture and socioeconomic development (Abbas et al., 2010). As the land cover changes, it heavily affects the components of the water balance in the region including both surface and groundwater. Various studies analysing relationship between land use/cover change and water balance system in African countries are produced, and it is continuously being researched by many scientists due to its importance in water management and planning in Africa. 

A study by Albhaisi et al. (2013) analysed the impacts of land use change on groundwater recharge of the Upper Berg catchment in South Africa using WetSpa hydrological model. The results indicated that the change in land cover related to clearing of non-native hill slope vegetation is associated with systematic increase in groundwater recharge in the catchment area. Additionally, a study about examining hydrological responses of the watershed to land use/cover changes and management schemes practiced at Hare Watershed in Ethiopia by Mengistu (2009) suggested that the change of land use/cover pattern has affected the rainfall-run off relationship. Also, the results signified that the expansion of croplands in some parts of the watershed area has potential on causing a reduction on dry-season flows affecting the water demand during this period directly (Awotwi et al, 2014).  

As illustrated in studies above, land use/cover changes in Africa seems to have considerable hydrological impacts regionally. I would like to explore this relationship further, through case study of the White Volta Basin in West Africa adopted from study by Awotwi et al. (2014). 


The White Volta Basin is located across Burkina Faso and Ghana, in West Africa (Figure 1a and b). It is in the zone of semiarid and sub humid climate, and it supports tens of millions of people's livelihood. 

Figure 1a - White Volta Basin in Burkina Faso (Source: GLOWA Volta http://www.zef.de/publ_maps.html).  

Figure 1b - White Volta Basin in Ghana (Source: GLOWA Volta - http://www.zef.de/publ_maps.html).  

Awotwi et al. assessed impacts of land use/cover changes on water balance in the White Volta Basin using the Soil and Water Assessment Tool (SWAT) with two land use/cover map from 1990 and 2006 and two land use scenarios. Through examining the land use/cover classified maps from 1990 and 2006, reductions in Savannah/grass land and expansion of croplands were clear (figure 2). 

Figure 2 - Land use and land cover map of White Volta Basin of year 1990 (left) and 2006 (right).
(Source: adopted from Awotwi et al., 2015). 

The hydrological impacts of land use/cover change implied in the results of SWAT model were following: 
- Different land use/cover changes influence various water yields and Evapotranspiration (ET).
- With land cover changes from grassland and savannah land to cropland, both surface run-off and groundwater decreased between 1990 and 2006 in the catchment. 
- Also, such conversion may result in an increase in ET; this implies that land cover change is playing major role in ET change due to stomatal resistance differences and leaf area index (LAI) of various land cover controlling ET (Awotwi et al., 2014). 

Despite the uncertainties of the analysis (e.g. missing data in flow and climate), the study draws into conclusion that land use/cover change in the White Volta Basin in actually (and heavily) influencing the water balance system. 

Since adequate water supplies are key elements in good health and well being of humans, ecosystems and socioeconomic development of the region (Du Plessis et al., 2014), it seems to be crucial to assess hydrological impacts of land use/cover changes. Furthermore, not only the quantity of water for different sectors of the society are important, but also the quality level of the water are essential for both humans' development and environment as a whole. 

Hence, I would like to explore more about land use/cover change impacts in African water - focusing on water quality levels. 

References

Abbas, I.I., Muazu, K.M. and Ukoje, J.A. 2010. Mapping Land Use-Land Cover and Change Detection in Kafur Local Govern- ment, Katsina, Nigeria (1995–2008) Using Remote Sensing and GIS. Res. J. Environ. Earth Sci. 2(1): 6–12.

Albhaisi, M., Brendonck, L. and Batelaan, O. 2013. Predicted Impacts of Land Use Change on Groundwater Recharge of the Upper Berg Catchment, South Africa. Water SA. 39(2): 211– 219. 

Awotwi, A., Yeboah, F. and Kumi, M. 2014. Assessing the impact of land cover changes on water balance components of White Volta Basin in West Africa. Water and Environment Journal. 29(2): 259-267.

Du Plessis, A., Harmse, T. and Ahmed, F. 2014. Quantifying and Predicting the Water Quality Associated with Land Cover Change: A Case Study of the Blesbok Spruit Catchment, South Africa. Water. 6(10): 2946-2968.

Mengistu, K.T. 2009. Watershed Hydrological Responses to Changes in Land Use and Land Cover, and Management Prac- tices at Hare Watershed, Ethiopia. Universität Siegen, Research Institute for Water and Environment, Siegen, Germany.

Schulze, R.E. 2000. Modelling Hydrological Responses to Land Use and Climatic Change: The Southern African Perspective. Ambio. 29(1): 12–22.

Targeting AGwater Management Interventions (TAGMI). 2013. Overview. [online] Available at: http://iwmi-tagmi.cloudapp.net/overview.php#project-8 [Accessed 30 Oct. 2016].

US Geological Survey. 2013. Land Cover Applications and Global Change. [online] Available at: http://lca.usgs.gov/lca/africalulc/results.php#senegal_lulc [Accessed 30 Oct. 2016].