Introduction - Hydrologic Time Series Analysis: Theory and Practice - page 2

1000 litres of water to produce one kilogram of wheat, whereas we need about
5000 to 13,500 litres of water to produce one kilogram of meat. The demand
for water is gradually increasing with growing population as well as rapid
urbanization and industrialization in different parts of the world (Postel, 1998;
Shiklomanov and Rodda, 2003; UNESCO, 2003, 2009; Grafton and Hussey,
2011). As a result, water demand is surpassing the available freshwater resource.
On top of it, in future, more people will need more water not only for food and
sanitation but also for fibre, livestock and industrial crops (bio-energy).
Unfortunately, the excessive use and continued mismanagement of
freshwater resources for human development (to supply ever-increasing water
demands for food, feed, fibre and fuel) have led to water shortages, increasing
pollution of freshwater, loss of biodiversity, and degraded ecosystems across
the world (e.g., Postel, 1998; de Villiers, 2001; Steffen et al., 2002; UNESCO,
2003; UN Water, 2007; Vörösmarty et al., 2010; Grafton and Hussey, 2011).
As a result, freshwater scarcity has emerged as one of the most pressing
problems in the 21 st century. According to Molden (2007), one in three people
at present face water shortages, around 1.2 billion people (almost one-fifth of
the world's population) live in areas of ' physical water scarcity ' (i.e., where
the available water resources cannot meet the demands of the population), and
500 million people are approaching this situation. Another 1.6 billion people
(almost one quarter of the world's population) face ' economic water scarcity '
(i.e., where countries lack the necessary infrastructure to harness water from
rivers and aquifers). Furthermore, about 2.5 billion people lack adequate
sanitation, and 884 million people are without access to safe water (UNICEF
and WHO, 2008). It has been estimated that half of the population of the
developing world is exposed to polluted sources of water that increase disease
incidence. Between 1991 and 2000, over 665,000 people died in 2557 natural
disasters, of which 90% were water-related disasters and a vast majority of
victims (97%) were from developing countries (IFRC, 2001).
If the present trend continues, based on the widely used Falkenmark
indicator for water scarcity, nearly 1.4 billion people will experience ' chronic
water scarcity ' (i.e., water supply less than 1000 m 3 /capita/annum) within the
first 25 years of this century, mostly in semi-arid regions of Asia, North Africa
and Sub-Saharan Africa. Also, 1.8 billion people will be living in countries or
regions with ' absolute water scarcity ' (i.e., water supply less than 500 m 3 /
capita/annum), and two thirds of the world's population could be under ' water
stress ' (i.e., water supply less than 1700 m 3 /capita/annum) conditions by 2025
(UN Water, 2007). Urban and industrial water use in the world is projected to
double by 2050. With increasing evidence of unsustainable water use in several
parts of the world, particularly in developing nations, India is under 'water
stress' conditions today and will face 'chronic water scarcity' by 2025. The
problem of water management in general and water shortages in particular
will worsen in many parts of the world due to global climate change. Higher
temperatures and changes in extreme weather conditions are projected to