Introduction
Rainfall is the most important climatic parameter affecting the temporal and spatial
distribution of available water. Knowledge of the rainfall received over a region
assists in estimating water availability for domestic, industrial, and agricultural
requirements (Kumar and Jain 2010). In recent decades, the changing climate has
significantly disrupted rainfall trends and patterns (IPCC 2014; Loo et al. 2015). The
changing rainfall patterns may cause unpredictable hydrological extremes such as
floods and droughts (Srivastava et al. 2015). The amount of rainfall controls aquifer
recharge and the availability of moisture in the soil for crops (Gupta et al. 2014). Any
change in the amount of rainfall may adversely affect agricultural production, food
security, and overall growth of the economy of a country such as India (Gadgil and
Gadgil 2006; Kumar and Jain 2011; Biswas et al. 2019). The rainfall over a
particular region is mainly controlled by both local and large-scale environmental
processes and therefore reveals noticeable spatial and temporal variability. The
fluctuations in rainfall pattern are not uniform over a region; rather, each has its
own distinctive local pattern. Knowledge of the spatiotemporal distribution of
rainfall can be beneficial in various hydrological and water resources management
applications. Thus, it is vital to examine the trends and pattern of rainfall to evaluate
water resources availability in a region.
River basins have been recognized as the principal natural hydrological unit of
analysis for planning and development of water resources. Therefore, researchers
have extensively studied the rainfall trends and pattern over different river basins the
world over (Kliment and Matoušková 2008; Muller et al. 2009; Kamruzzaman et al.
2013; Babatolu et al. 2014; Langat et al. 2017; Ninu Krishnan et al. 2018; Emmanuel
et al. 2019; Khaniya et al. 2019; Amoussou et al. 2020). Many reports are also
available on the trends and pattern of rainfall over the different river basins of India.
For example, Singh et al. (2008) have noticed a rising trend over 8 of 9 river basins in
northwest and central India in the past century. Ranade et al. (2008) have not
observed any trend in the beginning or termination dates, period, and total amount
of rainfall during the wet season over several river basins of India, whereas Kumar
and Jain (2011) have witnessed a decline in annual rainfall amounts and number of
rainy days in 15 of 22 basins in India. Raj and Azeez (2012) observed a substantial
decrease in annual, monsoon, and pre-monsoon season rainfall over the
Bharathapuzha River Basin. Deka et al. (2013) noticed a substantial declining
trend in monsoon and post-monsoon season rainfall over Barak Basin in the past
century. Abeysingha et al. (2014) observed a substantial rising trend in rainfall over
upstream areas, whereas a decreasing trend was recorded over downstream areas of
Gomti Basin. Taxak et al. (2014) have shown a decline in annual and monsoonal
rainfall over Wainganga Basin in the latter half of the twentieth century. Deshpande
et al. (2016) noticed declining trends in monsoonal rainfall over Ganga, Narmada,
Tapi, Godavari, and other west coast rivers, whereas Krishna and peninsular rivers
have shown increasing trends. Gajbhiye et al. (2016) have shown a substantial rise in
annual and monsoonal rainfall over Sindh River Basin. Bera (2017) observed
diminishing trends in annual, pre-monsoon, and post-monsoon season rainfall over
274
M. Chahal et al.
Rainfall is the most important climatic parameter affecting the temporal and spatial
distribution of available water. Knowledge of the rainfall received over a region
assists in estimating water availability for domestic, industrial, and agricultural
requirements (Kumar and Jain 2010). In recent decades, the changing climate has
significantly disrupted rainfall trends and patterns (IPCC 2014; Loo et al. 2015). The
changing rainfall patterns may cause unpredictable hydrological extremes such as
floods and droughts (Srivastava et al. 2015). The amount of rainfall controls aquifer
recharge and the availability of moisture in the soil for crops (Gupta et al. 2014). Any
change in the amount of rainfall may adversely affect agricultural production, food
security, and overall growth of the economy of a country such as India (Gadgil and
Gadgil 2006; Kumar and Jain 2011; Biswas et al. 2019). The rainfall over a
particular region is mainly controlled by both local and large-scale environmental
processes and therefore reveals noticeable spatial and temporal variability. The
fluctuations in rainfall pattern are not uniform over a region; rather, each has its
own distinctive local pattern. Knowledge of the spatiotemporal distribution of
rainfall can be beneficial in various hydrological and water resources management
applications. Thus, it is vital to examine the trends and pattern of rainfall to evaluate
water resources availability in a region.
River basins have been recognized as the principal natural hydrological unit of
analysis for planning and development of water resources. Therefore, researchers
have extensively studied the rainfall trends and pattern over different river basins the
world over (Kliment and Matoušková 2008; Muller et al. 2009; Kamruzzaman et al.
2013; Babatolu et al. 2014; Langat et al. 2017; Ninu Krishnan et al. 2018; Emmanuel
et al. 2019; Khaniya et al. 2019; Amoussou et al. 2020). Many reports are also
available on the trends and pattern of rainfall over the different river basins of India.
For example, Singh et al. (2008) have noticed a rising trend over 8 of 9 river basins in
northwest and central India in the past century. Ranade et al. (2008) have not
observed any trend in the beginning or termination dates, period, and total amount
of rainfall during the wet season over several river basins of India, whereas Kumar
and Jain (2011) have witnessed a decline in annual rainfall amounts and number of
rainy days in 15 of 22 basins in India. Raj and Azeez (2012) observed a substantial
decrease in annual, monsoon, and pre-monsoon season rainfall over the
Bharathapuzha River Basin. Deka et al. (2013) noticed a substantial declining
trend in monsoon and post-monsoon season rainfall over Barak Basin in the past
century. Abeysingha et al. (2014) observed a substantial rising trend in rainfall over
upstream areas, whereas a decreasing trend was recorded over downstream areas of
Gomti Basin. Taxak et al. (2014) have shown a decline in annual and monsoonal
rainfall over Wainganga Basin in the latter half of the twentieth century. Deshpande
et al. (2016) noticed declining trends in monsoonal rainfall over Ganga, Narmada,
Tapi, Godavari, and other west coast rivers, whereas Krishna and peninsular rivers
have shown increasing trends. Gajbhiye et al. (2016) have shown a substantial rise in
annual and monsoonal rainfall over Sindh River Basin. Bera (2017) observed
diminishing trends in annual, pre-monsoon, and post-monsoon season rainfall over
274
M. Chahal et al.