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].