Water scarcity

Water scarcity assesses the change in water availability per capita and the water consumption per capita for a certain period (for example the last 10 year period). The change in water scarcity can be affected both by increased consumption and/or decreased supply.  Scarcity, by definition means diminishing water resources and/or a pressure on the supply of available resources.

Aim of the method/technique	The proposed scarcity index is especially important for assessing land vulnerability to degradation and desertification.  Areas subjected to high water scarcity are subjected to higher desertification risk.
Scale – spatial and temporal	The river basin is more and more adopted as the appropriate unit to understand the key processes with increasing water scarcity as human use reaches the boundaries of the basins (Rijsberman 2005). Water scarcity can have high spatial and temporal change.
Brief description	The most widely used measure of water scarcity is the Falkenmark indicator or ‘‘water stress index’’ (Falkenmark et al., 1989). They proposed 1700 m3 of renewable water resources per capita per year as the threshold, based on estimates of water requirements in the household, agricultural, industrial and energy sectors, and the needs of the environment. Countries whose renewable water supplies cannot sustain this figure are subjected to water scarcity. When supply falls below 1000 m3, a country experiences water scarcity, and when supply falls below 500 m3, it faces absolute scarcity. Furthermore, water scarcity can be defined here as the ratio of water availability per capita (WAC) divided by the water consumption per capita (WCC) per year for the period of the past ten years. The following 5 classes can be distinguished: (a) no water scarcity, WAC/WCC=R>2; (b) low water scarcity, R=1.5-2; (c) moderate water scarcity, R=1.5-1.0; (d) high water scarcity, R=0.5-1.0, and (e) very high water scarcity, R<0.5.
Data requirements	Data required for assessing water scarcity are: the population density of the study area, (b) the water resources available in that area for a period of at least the past 10 years, and (c) the total water consumption for the same period.
Main applications in cropland and forests & shrubland regions	Water scarcity is an important indicator for assessing desertification risk in an area. The main processes of land degradation, particularly affected by water scarcity, are soil salinization and water stress in the growing plants.  Forested watersheds are exceptionally stable hydrological systems (FAO, 2003) and play a fundamental role in water cycle that directly affects the quality of people’s lives, their food security and their livelihoods. Water scarcity is an important indicator for assessing desertification risk in an area.
Strengths and weaknesses	Water resources data for an area usually are not easily available mainly because of the great number of organizations involved in water resources management. Furthermore, long term series of water resources data for a specific river basin are usually limited.

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