**2. Water availability and scarcity**

There are various definitions for water availability divided into blue and green parts e.g., "*blue water availability is defined as total natural runoff net of 20% assigned to environmental flow requirements*" [39], "*Green water availability is defined as total rainfall infiltration in agricultural land minus runoff from this area multiplied by a reduction factor for minimum evaporation losses in agriculture of 0.85*" [ibid]. The same authors argue that water accessibility is even more important as water sources are often far from their point of use due to issues of spatial population or/and productive land distribution and industry. For instance, it is reported that the Amazon river has a 95% flow inaccessibility [40] while only less than 50% of the Congo River's flow can be assessed by the population due to infrastructure challenges despite being one of the largest rivers in Africa [41].

As seen in [42] water scarcity is divided into physical scarcity and economic scarcity. Physical scarcity occurs when, due to the global interconnectedness of the hydro-climatic system [43], water fails to satisfy consumption demand as well environmental flows [44]. Economic scarcity occurs when failure to satisfy the aforementioned demands is attributed to the socio-economic system's failure in water utilisation [ibid] either due to inadequacies in storage, timely distribution and access (infrastructure development) [45] or as seen in [46] in case human/ institutional actions or lack of capital place limits to water access.

An apt definition of water scarcity, among many seen in the relevant literature, is the one employed by the EU "*water demand exceeds the water resources exploitable under sustainable conditions*" [47]. According to Shiklomanov [48], 75% of the earth's surface is covered with water, but only 3 per cent of the earth's water is available as freshwater for human use with the other fraction locked up in oceans and hence salty. The quantity of usable water available is further constrained by a number of factors exacerbated by continued economic growth, population growth, climate change and rapid urbanisation that have increased pressure on the resource [49].

**Figure 1** shows water withdrawals across the globe as projected from 1995 to 2025 [50]. It is interesting to note from the figure that water withdrawals continue to rise especially in Africa, China and South Asia and South East Asia. Alcamo, and his colleagues [ibid] report that water withdrawals are prone to grow in these regions due to rapid population and economic growth. For instance, Hoekstra, Mekonnen [51] allege that the increased need for food to feed the growing population will lead to more water withdrawals in the agriculture sector which is the driving force behind economic development in these regions. At the same time, the rate of urbanisation especially in the developing world has led to increased domestic water demand, a situation described by Serageldin [52] as worrisome due to multifaceted implications this has on the social well-being of urban populations. Consequently,

**Figure 1.** *Graph showing Water Withdrawals projected from 1995 to 2025 [50].*

the increase in population coupled with increased water withdrawals has seen approximately 2.1 billion people living in severely water stress basins [50] with Dzikus [53] warning that a total of 1.1 billion people in African countries will be greatly affected by the dwindling water availability if the status quo is maintained.

**Figure 2.** *Map showing freshwater availability across the globe.*

*Incentives for Managing Water Demands: Lessons from the Umgeni River Basin, KwaZulu-Natal… DOI: http://dx.doi.org/10.5772/intechopen.106238*

The question that remains is whether the available water will be able to meet the growing demands if the situation remains the same [51], and this has led to some authors claiming of an impending global water crisis. However, Lall and Heikkila [54] has acknowledged in their report that the existence or emergence of a global water crisis still remains a topic of controversy among scientists, with some scholars claiming that it is being overstated while raising are questions regarding available data [55]. This not-withstanding, Brown and Lall [13] argues that it is the ability of states to manage their available water resources that affect economic development and social well-being of the society.

**Figure 2** is the map showing the availability of freshwater across the globe. While **Figure 1** indicates that global water withdrawals continue to rise in developing countries, it can be observed from **Figure 2** that most African countries including South Africa are heading towards stress levels with some countries especially in North Africa in critical situations of water scarcity.

All this points to the fact that increased water management efforts are imperative and more proactive measures should be sought [56]. However, it has to be admitted that managing the scarce water resources for increasing demands in an equitable and sustainable manner is one of the greatest challenges facing the world in the 21st Century [57, 58].
