It is a statement of the obvious that water is the most critical factor related to drought. Whilst lack of water is the primary cause of drought, there are a large number of factors which exacerbate and intensify the effects of lack of water. If these factors, many of which have little to do with water per se, are adequately managed, the consequences of the lack of water can be greatly reduced. For this reason drought management policy must take into account a wide variety of factors.
"In popular usage, "scarcity" is a situation where there is insufficient water to satisfy normal requirements. However, this common-sense definition is of little use to policy-makers and planners. There are degrees of scarcity: absolute, life-threatening, seasonal, temporary, cyclical, etc. Populations with normally high levels of consumption may experience temporary scarcity more keenly than other societies accustomed to using much less water. Scarcity often arises because of socio-economic trends having little to do with basic needs. Defining scarcity [and drought] for policy-making purposes is very difficult."
Four terms have been developed for the purposes of greater clarity: water shortage, water scarcity, water stress and water security. The use of these terms is the subject of considerable international debate.
Water shortage is used to describe an absolute shortage where levels of available water do not meet certain defined minimum requirements. The actual quantity that determines a per capita minimum may differ from place to place.
Water scarcity is a more relative concept describing the relationship between demand for water and its availability. The demands may vary considerably between different countries and different regions within a given country depending on the sectoral usage of water. A country with a high industrial demand or which depends on large scale irrigation will therefore be more likely to experience times of scarcity than a country with similar climatic conditions without such demands. Countries such as Rwanda, for example, would be classified by most standards as suffering water shortage but, because of low industrial and irrigation utilisation, would not be classified as water scarce.
Water stress is the symptomatic consequence of scarcity which may manifest itself as increasing conflict over sectoral usage, a decline in service levels, crop failure, food insecurity etc.. This term is analogous to the common use of the term "drought".
Water security is a situation of reliable and secure access to water over time. It does not equate to constant quantity of supply as much as predictability, which enables measures to be taken in times of scarcity to avoid stress.
Determining water shortage and water scarcity
There are a number of problems related to determining water shortage and water scarcity. In general, national average figures are used which mask annual variability from year to year, seasonal variability and the regional variability within countries.
The Food and Agriculture Organisation (FAO) of the United Nations regards water as a severe constraint on socio-economic development and environmental protection at levels of internal renewable water availability of less than 1 000 m3/capita. At levels of water availability of less than 2000 m3/capita, water is regarded as a potentially serious constraint, and a major problem in drought years. Water scarcity provides a measure of the sensitivity of a given situation to drought. In situations where the average availability of water per capita is low, even slight variations can render whole communities unable to cope and create disaster conditions.
Water scarcity is a relative concept – it is partly a "social construct" in that it is determined both by the availability of water and by consumption patterns. Because of the large number of factors which influence both availability and consumption, the determining of water scarcity will vary widely from country to country and from region to region within a country. Adopting a global figure to indicate water scarcity should therefore be done with great caution. Whilst a threshold such as 1000m3/capita may be useful for purposes of comparison, it should be carefully used because it may understate situations of potentially serious water stress.
Because the concept of water scarcity is a social construct or, put in other terms, a matter of political and economic perception, it may be more useful to describe water scarcity as a particular mix of availability and demand at which water stress occurs, rather than a per capita figure. This means that its determination is more qualitative than quantitative, as the point at which water scarcity occurs may vary widely from one situation to another. In a semi-arid highly industrialised country or in a country where food security is dependent upon the extensive use of irrigation, the aggregated per capita figure at which water becomes sufficiently scarce to cause internal or transboundary conflict may be a lot higher than in a temperate, less highly developed country.
Causes of water scarcity
The causes of water scarcity are varied. Some are natural and others are as a result of human activity. The current debate sites the causes as largely deterministic in that scarcity is a result of identifiable cause and effect. However, if water scarcity is the point at which water stress occurs (the point at which various conflicts arise, harvests fail and the like), then there are also less definable sociological and political causes. Many of the causes are inter-related and are not easily distinguished.
Climatic change and variability
Sectoral resources and institutional capacity
Poverty and economic policy
Legislation and water resource management
Sectoral professional capacity
Managing Water Scarcity for Water Security - FAO Article