Water security

The hydrologic environment is important for water security. The term hydrologic environment refers to the "absolute level of water resource availability". But it also refers to how much it varies in time and location. Inter-annual means from one year to the next, Intra-annual means from one season to the next. We can refer to location as spatial distribution. Scholars distinguish between a hydrologic environment that is easy to manage and one that is difficult.

An easy to manage hydrologic environment would be one with low rainfall variability. In this case rain is distributed throughout the year and perennial river flows sustained by groundwater base flows. For example, many of the world's industrialized nations have a hydrologic environment that they can manage quite easily. This has helped them achieve water security early in their development.

A difficult to manage hydrologic environment is one with absolute water scarcity such as deserts or low-lying lands prone to severe flood risk. Regions where rainfall is very variable from one season to the next, or regions where rainfall varies a lot from one year to the next are also likely to face water security challenges. We call this high inter-annual climate variability. An example would be East Africa, where there have been prolonged droughts every two to three years since 1999. Most of the world's developing countries have difficult to manage hydrologies and have not achieved water security. This is not a coincidence.

The poverty and hydrology hypothesis states that there is a link between poverty and difficult hydrologies. It postulates that regions with a difficult hydrology remain poor because the respective governments have not been able to make the large investments necessary to achieve water security. Examples of such regions would be those with rainfall variability within one year and across several years. The resulting water insecurity constrains economic growth. There is a statistical link between greater rainfall variability and lower per capita incomes.

The socio-economic environment also determines the potential of a society to sustain water security. This refers the structure of the economy, behavior of people and organisations, natural and cultural legacies, and policy choices. It also includes water infrastructure and institutions, macroeconomic structure and resilience, risk, and the behavior of economic actors.

Water-related impacts from climate change affect people's water security on a daily basis. They include more frequent and intense heavy precipitation which affects the frequency, size and timing of floods. Also droughts can alter the total amount of freshwater and cause a decline in groundwater storage, and reduction in groundwater recharge. Deterioration in water quality due to extreme events can also occur .

Global climate change will probably make it more complicated and expensive to ensure water security. It creates new threats and adaptation challenges. This is because climate change leads to increased hydrological variability and extremes. Climate change has many impacts on the water cycle. These result in higher climatic and hydrological variability, which can threaten water security. Changes in the water cycle threaten existing and future water infrastructure. It will be harder to plan investments for future water infrastructure as there are so many uncertainties about future variability for the water cycle. This makes societies more vulnerable to extreme water-related events and therefore reduces water security.

Climate change is about uncertainty. So it is an important long-term risk to water security. On the other hand, future climate change is only one of many existing challenges for water security. These include existing high levels of climate variability at low latitudes, population growth, increased demand for water resources, political obstacles, increased disaster exposure due to settlement of hazard-prone areas, and environmental degradation. Water demand for irrigation in agriculture will increase due to climate change. This is because evaporation rates and crop transpiration rates will be higher due to rising temperatures.

Climate factors are a major driver of water security across different scales. Geographic variability in water availability, reliability of rainfall and vulnerability to droughts, floods and cyclones are inherent hazards that affect development opportunities. These play out at international to intra-basin scales. At local scales, social vulnerability is a factor that increases the risks to water security, no matter the cause. For example, people affected by poverty may have less ability to cope with climate shocks.