13.1 Introduction
The ever-growing population and fast urbanization is leading to over-utilization of the water
resources, exerting pressure on these commonalities which are on the brink of collapse. Consequently, the world climate is changing more
rapidly in recent years (Vijaya et al. 2011) and
causes difficulty in appropriate water management including storage plans. As the water
resources are inextricably linked with climate,
the global climate change has serious implications on them (Bates et al. 2008; Ghosh and
Misra 2010) and therefore, it has led to the vulnerable state of the water resources worldwide.
The Intergovernmental Panel on Climate
Change (IPCC) has projected rising trend of
Earth’s surface temperature of about 0.2 °C per
decade for the next two decades due to increasing
concentration of greenhouse gases in the atmosphere (IPCC 2007). Increased temperature leads
to irregular frequency and intensity of rainfall
that significantly increases the intra-annual variability of stream flow; in turn will have an impact
on water availability. The impact of climate
change in future would be quite severe for India
including Gangetic West Bengal (GWB) because
the IPCC recently reported that there is a high
confidence in a projected rise in temperature and
medium confidence in a summer monsoon precipitation increase in the future over South Asia
(IPCC 2013). It is also projected that the number
of rainy days may decrease by 20–30%, which
implies that the intensity of rainfall is likely to
increase. Consequently, it produces more frequent floods and has rendered millions vulnerable to their impacts as the intensity of monsoon
rainfall and large floods has been strongly associated. Although the subject area of climate
variability is vast, the changing pattern of rainfall
deserves urgent and regular attention as it affects
the socio-economic conditions especially food
production of India and the occurrence of waterrelated disasters triggered by extreme events
(Dore 2005; Kumar et al. 2010; Kumar and Jain
2010). The data of the Central Water
Commission (CWC), New Delhi demonstrated
that on an annual average, 7.21 million ha of land
is inundated and nearly 32 million people are
affected by floods in India (Kale 2014). Therefore, it is important to study the trend and pattern
of the distribution of rainfall where the growth of
an agro-based economy is linked to the rainfall of
the region in concern.
In recent decade, a great emphasis has been
given on the studies of trend in monsoon rainfall
pattern of India. Earlier, Lal (2001) reported
large fluctuations in Indian rainfall with no systematic change on either an annual or a seasonal
scale. However, areas of increasing trend in the
seasonal rainfall have been found along the West
Coast, north Andhra Pradesh and northwest India
and decreasing trend over east Madhya Pradesh,
Orissa and northeast India during recent years.
Guhathakurta and Rajeevan (2007) found the
significant decreasing trend in the three subdivisions (Jharkhand, Chhattisgarh and Kerala) and
significant increasing trend in monsoon rainfall
in eight subdivisions (Gangetic West Bengal,
West Uttar Pradesh, Jammu and Kashmir, Konkan and Goa, Madhya Maharashtra subdivision,
Coastal AP and North Interior Karnataka) during
the period of 1901–2003. Decreasing tendency in
the summer monsoon rainfall over Indian landmass and increasing trend in the rainfall during
pre-monsoon and post-monsoon months have
been reported by Dash et al. (2007). Kumar et al.
(2010) examined the monthly, seasonal and
annual trends in rainfall for 30 subdivisions in
India during the period of 1871–2005. They
reported that half of the subdivision showed
increasing trends and half showed decreasing
trend in annual rainfall. The fluctuations of
rainfall amount for the Indo-Gangetic region
have been studied by Singh and Sontakke (2002)
using the data of 1829–1999. Their study indicated a significant increasing trend from 1939
over the Central part, and a significant decreasing
trend over eastern parts of the country. Sen Roy
and Balling (2004) analyzed the trends in the
patterns of extreme precipitation events from
1910 to 2000 and showed an increasing trend
170
N. C. Jana et al.
The ever-growing population and fast urbanization is leading to over-utilization of the water
resources, exerting pressure on these commonalities which are on the brink of collapse. Consequently, the world climate is changing more
rapidly in recent years (Vijaya et al. 2011) and
causes difficulty in appropriate water management including storage plans. As the water
resources are inextricably linked with climate,
the global climate change has serious implications on them (Bates et al. 2008; Ghosh and
Misra 2010) and therefore, it has led to the vulnerable state of the water resources worldwide.
The Intergovernmental Panel on Climate
Change (IPCC) has projected rising trend of
Earth’s surface temperature of about 0.2 °C per
decade for the next two decades due to increasing
concentration of greenhouse gases in the atmosphere (IPCC 2007). Increased temperature leads
to irregular frequency and intensity of rainfall
that significantly increases the intra-annual variability of stream flow; in turn will have an impact
on water availability. The impact of climate
change in future would be quite severe for India
including Gangetic West Bengal (GWB) because
the IPCC recently reported that there is a high
confidence in a projected rise in temperature and
medium confidence in a summer monsoon precipitation increase in the future over South Asia
(IPCC 2013). It is also projected that the number
of rainy days may decrease by 20–30%, which
implies that the intensity of rainfall is likely to
increase. Consequently, it produces more frequent floods and has rendered millions vulnerable to their impacts as the intensity of monsoon
rainfall and large floods has been strongly associated. Although the subject area of climate
variability is vast, the changing pattern of rainfall
deserves urgent and regular attention as it affects
the socio-economic conditions especially food
production of India and the occurrence of waterrelated disasters triggered by extreme events
(Dore 2005; Kumar et al. 2010; Kumar and Jain
2010). The data of the Central Water
Commission (CWC), New Delhi demonstrated
that on an annual average, 7.21 million ha of land
is inundated and nearly 32 million people are
affected by floods in India (Kale 2014). Therefore, it is important to study the trend and pattern
of the distribution of rainfall where the growth of
an agro-based economy is linked to the rainfall of
the region in concern.
In recent decade, a great emphasis has been
given on the studies of trend in monsoon rainfall
pattern of India. Earlier, Lal (2001) reported
large fluctuations in Indian rainfall with no systematic change on either an annual or a seasonal
scale. However, areas of increasing trend in the
seasonal rainfall have been found along the West
Coast, north Andhra Pradesh and northwest India
and decreasing trend over east Madhya Pradesh,
Orissa and northeast India during recent years.
Guhathakurta and Rajeevan (2007) found the
significant decreasing trend in the three subdivisions (Jharkhand, Chhattisgarh and Kerala) and
significant increasing trend in monsoon rainfall
in eight subdivisions (Gangetic West Bengal,
West Uttar Pradesh, Jammu and Kashmir, Konkan and Goa, Madhya Maharashtra subdivision,
Coastal AP and North Interior Karnataka) during
the period of 1901–2003. Decreasing tendency in
the summer monsoon rainfall over Indian landmass and increasing trend in the rainfall during
pre-monsoon and post-monsoon months have
been reported by Dash et al. (2007). Kumar et al.
(2010) examined the monthly, seasonal and
annual trends in rainfall for 30 subdivisions in
India during the period of 1871–2005. They
reported that half of the subdivision showed
increasing trends and half showed decreasing
trend in annual rainfall. The fluctuations of
rainfall amount for the Indo-Gangetic region
have been studied by Singh and Sontakke (2002)
using the data of 1829–1999. Their study indicated a significant increasing trend from 1939
over the Central part, and a significant decreasing
trend over eastern parts of the country. Sen Roy
and Balling (2004) analyzed the trends in the
patterns of extreme precipitation events from
1910 to 2000 and showed an increasing trend
170
N. C. Jana et al.