2013; Pingale et al. 2014; Jaiswal et al. 2015; Mayowa et al. 2015; Singh et al. 2020).
These tests were performed by means of XLSTAT 2017 software.
Spatial Interpolation
To study the spatial pattern of rainfall characteristics, the inverse distance weighting
(IDW) interpolation technique has been employed. The IDW technique is a simple
and widely used interpolation technique. This spatial interpolation technique considers the role of each input point by a standardized inverse of the distance from the
control point to the interpolated point. This technique assumes that each input point
has a local impact that lessens with increase in remoteness. It weighs more on points
nearer to the processing points than those at a distance, meaning a rainfall or its
derived quantity at any desired location is interpolated from the given data using
weights that are based on the distance from each rainfall station and the desired
location (Burrough and McDonnell 1998). This technique gives a smooth pattern of
rainfall along with undesirable troughs and peaks. Interpolation of rainfall characteristics using the IDW technique used ArcGIS 10.2 software.
Results and Discussion
Temporal Variations in Rainfall
Annual Variations
The mean annual rainfall over Sahibi Basin during 1961–2017 is demonstrated in
Fig. 12.2a. The mean annual rainfall has shown a very high interannual variability,
varying from 217.33 mm in 2002 to 1214.96 mm in 1996, with a mean annual value
of 633.95 mm (SD ¼ 204.93, CV ¼ 32.33) in the basin (Table 12.2). The MK test,
Sen’s slope, and regression analysis have not shown any significant increasing or
decreasing trend in the mean annual rainfall over Sahibi Basin during the 57-year
period. Likewise, the time-series of mean annual CV has shown an almost constant
trend with high variability (Fig. 12.2b). During the 57-year period, a total of 8 rainfall
excess years and 7 rainfall deficit years have been observed over the Sahibi Basin
(Table 12.3).
The station-wise analysis has shown that the highest mean annual rainfall
occurred over Thanagaji station (708 mm/year; SD ¼ 239.48; CV ¼ 33.83), whereas
the lowest was over Tapukara station (575 mm/year; SD ¼ 291.94; CV ¼ 50.78)
(Table 12.4). The trend lines have shown an increasing trend over Bairath and
Kotkasim stations, whereas a decreasing trend occurred over Tijara and Tapukara
stations (Fig. 12.3). However, Kotkasim and Tapukara stations have shown significant increasing and decreasing trends, respectively (Table 12.5). Kotkasim station
12 Trends and Pattern of Rainfall over Semiarid Sahibi Basin in Rajasthan, India
279
These tests were performed by means of XLSTAT 2017 software.
Spatial Interpolation
To study the spatial pattern of rainfall characteristics, the inverse distance weighting
(IDW) interpolation technique has been employed. The IDW technique is a simple
and widely used interpolation technique. This spatial interpolation technique considers the role of each input point by a standardized inverse of the distance from the
control point to the interpolated point. This technique assumes that each input point
has a local impact that lessens with increase in remoteness. It weighs more on points
nearer to the processing points than those at a distance, meaning a rainfall or its
derived quantity at any desired location is interpolated from the given data using
weights that are based on the distance from each rainfall station and the desired
location (Burrough and McDonnell 1998). This technique gives a smooth pattern of
rainfall along with undesirable troughs and peaks. Interpolation of rainfall characteristics using the IDW technique used ArcGIS 10.2 software.
Results and Discussion
Temporal Variations in Rainfall
Annual Variations
The mean annual rainfall over Sahibi Basin during 1961–2017 is demonstrated in
Fig. 12.2a. The mean annual rainfall has shown a very high interannual variability,
varying from 217.33 mm in 2002 to 1214.96 mm in 1996, with a mean annual value
of 633.95 mm (SD ¼ 204.93, CV ¼ 32.33) in the basin (Table 12.2). The MK test,
Sen’s slope, and regression analysis have not shown any significant increasing or
decreasing trend in the mean annual rainfall over Sahibi Basin during the 57-year
period. Likewise, the time-series of mean annual CV has shown an almost constant
trend with high variability (Fig. 12.2b). During the 57-year period, a total of 8 rainfall
excess years and 7 rainfall deficit years have been observed over the Sahibi Basin
(Table 12.3).
The station-wise analysis has shown that the highest mean annual rainfall
occurred over Thanagaji station (708 mm/year; SD ¼ 239.48; CV ¼ 33.83), whereas
the lowest was over Tapukara station (575 mm/year; SD ¼ 291.94; CV ¼ 50.78)
(Table 12.4). The trend lines have shown an increasing trend over Bairath and
Kotkasim stations, whereas a decreasing trend occurred over Tijara and Tapukara
stations (Fig. 12.3). However, Kotkasim and Tapukara stations have shown significant increasing and decreasing trends, respectively (Table 12.5). Kotkasim station
12 Trends and Pattern of Rainfall over Semiarid Sahibi Basin in Rajasthan, India
279