Drought is not a new word to many people. Drought is the absence of rain for an extended period, often for a season or more. Climate change is associated with the significant reduction in rainfall and increase in droughts that is already apparent in some parts of the globe. Droughts have caused loss of human life, livestock and property, as well as migration of people.
Most of the agriculture in low-income countries is small scale and therefore highly dependent on rainfall and traditional technologies. Drought affects agriculture by damaging crops and decreasing crop yield (Figure 10.5), which causes food shortages not only in rural areas but also in towns and cities. In the worst periods of drought, there may be widespread famine, when the extreme shortage of food results in many deaths.
Global warming and alterations in rainfall patterns are believed to be the underlying cause of the trend towards more frequent and more severe droughts in many parts of the world.
Can you suggest why a climate which is gradually becoming warmer will result in an increase in the risk of droughts? (Hint: think back to Study Session 9.)
Increased air temperature will heat the surface of water bodies and make the soil warmer, resulting in increased evaporation of water into the atmosphere. Also, as plants die through lack of water (remember Figure 10.5), large areas of bare soil are exposed to the heating effects of higher air temperatures, so, even more, water is lost through evaporation.
There are many other interlinked factors that cause droughts, as a rapidly increasing demand for water to meet a larger population needs (Figure 10.7). The rising standard of living, economic growth and industrial development all increase water demand because they require more water for additional uses. Particularly in urban areas, the demand for piped water and flush toilets has increased because households aspire to achieve higher standards of hygiene and sanitation.
Population pressure also leads to high deforestation for agricultural expansion and to meet the growing demand for wood (Figure 10.8) to burn as fuel and also for building fences and houses.
Summarise the ways in which forests sustain the water cycle and locally available water resources.
Forests play a crucial role in stabilising soils, reducing water run-off during rainy periods and increasing the amount of water stored underground. Shade from trees also reduces surface water evaporation and trees add moisture to the atmosphere through the process of transpiration. Thus, forests can be considered an important part of the water cycle, and they contribute to sustaining the availability of water in the local area.
In summary, climate change leading to global warming and reduced rainfall, coupled with population pressure, deforestation and change in land use are all major factors in the increasing risk of drought in most low-income countries.
Impacts of drought on WASH
As well as causing shortages of food and surface water, droughts have a significant effect on the availability of safe water resources. Drought causes water scarcity, so people are more likely to use unsafe water sources such as polluted rivers, streams and lakes. During times of water scarcity, people may save whatever water they can find for drinking and cooking, and stop using it for hygiene activities such as handwashing after defecation (Kovats et al., 2003). Drought can also increase the concentration of pathogenic organisms in rivers and lakes because the lower volume of water cannot dilute the contaminants to below the infectious dose (Kovats et al., 2003). We will discuss the impacts on human health in Study Session 11.