What are the causes and effects of drought?

What is drought?

It feels like we've been hearing about extreme weather a lot more in the news in the last few years. One issue on many people's minds is the increased likelihood of drought. Drought is a natural climatic phenomenon characterised by a lack of water over a long period. Depending on the region, droughts can be one-off or cyclical. While drought certainly isn't a new challenge in some areas of the world, climate change has been causing more droughts to happen recent years, even in parts of the world that are used to higher levels of precipitation.

What’s more, drought is defined at a national rather than a global level. Different countries have their own definitions: in England, an absolute drought is currently defined as a period of at least 15 consecutive days when there is less than 0.2 mm (0.008 inches) of rainfall.

What causes a drought?

Different types of drought

• Meteorological or atmospheric drought: Meteorological drought is when there is very little precipitation (rain, snow, etc.) over a long period of time in an area.  An episode like this can vary in length from several months to a whole year.
• Edaphic drought: Edaphic drought is due to increased soil dryness. It occurs when there isn’t enough water in the soil to meet the needs of plants and the organisms that depend on them. Edaphic drought can be caused by a lack of rainfall, high evaporation due to increased temperatures, strong winds, poor levels of water retention in the soil, excessive water use by plants, or a combination of these factors.
• Hydrological drought: Hydrological drought happens when the water levels in rivers, lakes, water tables and reservoirs get too low. This type of drought occurs when there’s not enough rainfall to maintain adequate water levels in these systems, or when the demand for water significantly exceeds the quantity available.
• Hydrological drought is often the consequence of a prolonged meteorological drought, where there is a shortage of precipitation over a long period. This can lead to reduced flow in rivers and lakes, lower water tables and reduced reservoir storage capacity.

What impact does drought have on the environment and society?

Drought can have varying degrees of impact on the environment and society. Here are some of the main effects of drought:

Effects on agriculture and food security

When drought affects an area, there is less water available for people to irrigate their land and grow crops. This can lead to crop losses, reduced food production and consequently higher food prices. These conditions can jeopardise food security, particularly in parts of the world that rely heavily on agriculture.

Deterioration of water resources

Drought means dwindling freshwater resources in rivers, lakes, water tables and reservoirs. This can lead to shortages of water for people to drink, as well as for industry and agriculture. Water quality can also deteriorate due to the concentration of pollutants caused by reduced river flow.

Effects on ecosystems

Drought can have serious consequences for natural ecosystems such as forests, wetlands and aquatic habitats. When there is less water available, this can lead to increased mortality of plants, animals and aquatic organisms, as well as a reduction in biodiversity. In addition, very dry conditions can result in more frequent and more intense forest fires.

Impact on the economy 

Drought can have a significant economic impact. It can affect the agricultural and agri-food sectors, leading to economic losses for farmers, related industries and rural areas where people rely on farming. Water-dependent industries such as hydroelectric power generation may also be affected. In addition, dwindling water resources can lead to disruptions in commercial and industrial activities.

Effects on public health

Drought can cause serious health problems. When access to clean water is limited, this can lead to an increase in hygiene-related health problems, encouraging the spread of water-borne diseases. In addition, drought creates conditions that promote the spread of diseases, such as malaria carried by mosquitoes, due to the stagnation of residual water. These factors pose significant health risks to people in drought-affected areas.

How can we combat drought?

Combating drought requires a global approach, with governments and people taking appropriate measures to reduce its impact. Here are some strategies and measures that can be taken in the fight against drought:

Optimising water management

Efficient water management is essential for coping with drought. This includes saving water, improving irrigation efficiency, promoting sustainable agricultural practices, reusing treated wastewater and rainwater harvesting. Infrastructure such as reservoirs, dams and water storage systems can also be developed to increase water storage and regulation capacity.

Adopting resilient farming practices

 Adopting drought-resilient farming practices, such as selecting drought-resistant crops, crop rotation, agroforestry and conservation agriculture, can help lessen the effects of drought on agriculture. Using precise, efficient irrigation techniques, such as drip irrigation, can also save water.

Soil conservation

Soil conservation can help improve the soil’s ability to retain water and prevent erosion. This involves paying more attention to the structure of the soil. Soil conservation can be optimised by adopting practices such as vegetation cover, minimum tillage and reforestation. In areas where drought is a relatively new challenge, it's important for farmers to have all the information they need to learn about these new techniques.

Awareness-raising and education

We need to raise awareness of drought issues through public information campaigns from an early age, and promote responsible behaviour in terms of water use. Educating people in saving water and using it wisely in the home, as well as encouraging them to learn about water science and water resource management, will help them to use water more sustainably.

Planning and policies

Effective planning and appropriate policies are needed to cope with drought. This includes setting up drought management plans, incorporating climate resilience into water policies, promoting research and developing water-related technologies, and coordination between government players, local communities and relevant stakeholders.

Adapting to climate change

Given that the drought situation is likely to get worse due to climate change, it’s important to develop strategies for adapting to droughts. This can include diversifying water sources, planning drought-resistant land use, promoting water conservation and integrating climate risk management into development policies and plans.

Global drought

In the UK, the South of England is generally more drought-prone due to its relatively dry climate. In recent years, however, droughts have become more common, even in areas where the average rainfall was traditionally higher. These recent changes are mainly due to global warming and these conditions are likely to continue for years to come.

Droughts are not just a national problem: climate change and the resulting extreme temperatures are a global challenge. To deal with these more frequent droughts, authorities in many countries are taking measures such as restricting water use in dry periods. In some regions of France considered to be in crisis, the government has banned non-priority water use, including for agricultural purposes*. Water can only be used for health purposes, drinking water, sanitation, etc. Meanwhile in England, water companies in many areas introduce hosepipe bans during long periods of hot, dry weather.

* Source: http://propluvia.developpement-durable.gouv.fr/propluvia/faces/index.jsp