Chapter 1:The Global Challenges of Desalination1.1 Fresh water stress: outlook of fresh water in the world The European Environment Agency (2016) defines freshwater stress as a measure of the strain that freshwater extraction for utility in diverse economic sectors puts on freshwater resources. On the other hand, the United Nations describes freshwater scarcity as a significant risk factor across all societies, as t contributes to extended systemic challenges like poor urban planning, extensive poverty, financial pressures on government institutions and structures and degradation of the environment. Cases of extreme water stress can lead to competition for the scarce water resources among users, and ultimately to a minimized water accessibility to downstream users, particularly during periods of drought or low water flow. A global outlook of the global freshwater situation by Few Resources (2016) reveals that only 2.5 percent of the entire water on the Earth surface is could be considered to be freshwater.
Few Resources (2016) further reveals that a majority of the amount of amount of water is saline water, which is in the oceans. Some 30.1 percent of the 2.5 percent of the freshwater is groundwater found in aquifers.
An additional 68.6% of the freshwater is from polar caps and glaciers, while a mere 1.3 percent of originates from rivers and lakes (See Figure 1) (Few Resources 2016). This implies that humans face significant freshwater scarcity, as they mostly rely on groundwater and surface water from rivers and lakes. Figure 1: Distribution of Earth's water (Few Resources 2016)In another study by Unesco (2015) of the distribution of water resources globally, it was concluded that runoff water and water from precipitation is unpredictable, as different regions of the earth receive diverse quantities of freshwater annually.
Unesco further revealed that the increasing climate change was actually exacerbating the risks linked to the disparities in freshwater resource distribution and accessibility. Figure 2: Renewable water resources per capita in 2013 (UNESCO 2015). The increased water temperatures because of warmer climate that result from climate change and increased release of waste heat is also projected to reduce accessibility to freshwater by increased forms of water pollutions, including release of salts and pesticides, nutrients and dissolved sediments and thermal pollution.
Greater focus has, therefore, been on groundwater as it has a significant function in diversifying freshwater supply. According to UNESCO (2015), of the overall global population, some 2.5 billion people are wholly dependent on groundwater resources for use. Despite this, there is a concern that the currently available groundwater resources are becoming increasingly depleted because of increased human population and their reduced rate of replenishment rates (El-Shamy & Said 2014). The depletion rate of the groundwater is estimated to be at least 20 percent due to over-exploitation.
This has led to severe implications, including intrusion into salt water and subsidence of land. There is a significant decline in the levels of groundwater globally. For instance, the withdrawal of freshwater in the Arabian Peninsula for instance is was approximated to be 505%, as a fraction of renewable water resources internally. Unesco (2015) also estimated that the overall quantity of groundwater footprint is nearly 3.5 times the size of aquifers, while some 1.7 billion people current reside in regions where they are at risk of freshwater scarcity because of depleted groundwater resources.
On the other hand, some 80% of aquifers contain groundwater footprint estimated to be less than their regions. This implies that the net global value is depended on the few available yet immensely overused aquifers.