Geoscience Reference
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simulation models, several efforts have been made to link the climate change
with the hydrology of India, and to project the future climate scenarios (e.g.,
Singh and Kumar, 1997; Kumar et al., 2006; Tripathy et al., 2006). Although
intensification of the hydrological cycle is a unanimous projection for India,
there still remains considerable uncertainty about the regional variations and
projections of the response of hydroclimatic variables. The uncertainty may
be due to the complex physiography and large spatial and temporal variations
of the climate, which include the subfreezing Himalayan range, the tropical
coastal climate, the rainy climate of the northeastern states, and the arid Great
Indian Desert. Furthermore, the GCMs do not resolve the mesoscale processes
that play key role in the climate feedback processes (Pan et al., 2004).
Additionally, the Indian summer monsoon being the prime modulator of the
hydroclimatic variability, is influenced by the action and interaction among
the factors such as El Nino/southern oscillation (ENSO) (Kumar et al., 1999;
Ashrit et al., 2001), sea surface temperature (SST) (Krishnan et al., 2003);
deforestation (Gupta et al., 2005); Eurasian snow cover (Bamzai and Shukla,
1999); and the aerosols (Menon et al., 2002; Ramanathan et al., 2005;
Ramanathan et al., 2007).
References to trend analysis of hydroclimatic variables of India are mostly
confined to the study of temperature patterns. A general warming temperature
trend was observed for India given substantial spatial and temporal differences
in trend magnitude (e.g. Arora et al
.
, 2005; Kothawale and Kumar, 2005;
Fowler and Archer, 2006). However, bringing consensus about the rainfall
trends of India possess difficulty, may be due to the high spatial and temporal
variability of rainfall. Different parts of the country exhibit significant increasing
and decreasing trends in monsoon rainfall during different timescales (Dash et
al., 2007; Ramesh and Goswami, 2007). Recently several studies show a
significant increase in the occurrence of extreme rainfall events (Sen Roy and
Balling Jr, 2004; Goswami et al., 2006; Rajeevan et al., 2008). However, the
rainfall amount and the number of rainy days in both the early and late
monsoon exhibit a decreasing trend implying a shorter monsoon over India
(Ramesh and Goswami, 2007).
The Orissa state of India is the most climate change-affected region due
to frequent occurrence of hydrologic extremes in the recent past (Swiss Re,
2002; Mirza, 2003). The Centre of Environmental Studies (CES, 2007) reported
that the erratic behaviour of climate of Orissa is primarily due to the combination
of anthropogenic factors such as deforestation, extensive construction activities,
uncontrolled mining, elimination of water bodies and extensive carbon
consumption over a period of time. Further, a minor change in the pressure
anomaly of the Bay of Bengal can have profound hydrological impact on the
land mass of Orissa due to its geographical location (Fig. 11.1) at the head of
the Bay where the weather forms (CES, 2007). Applying nonparametric
methods to the GCM output, Ghosh and Majumdar (2007) predicted a severe
drought condition for Orissa. They attributed this future drying scenario to the
global warming due to greenhouse effect, sensitivity of rainfall to ENSO, and
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