FOLLOWING HEAVY rains, the irrigation department discharged water in large volumes from Shetrunji and Bhadar dams, the two largest reservoirs in the water-starved Saurashtra region, on Sunday. The current monsoon marks only the 16th season in the 55-year-long history of the twin dams, and the first time in the past five years, when they have overflowed simultaneously.
Located at Rajasthali village in Palitana taluka of Bhavnagar district, Shetrunji dam has a designed gross storage capacity of 308.68 million cubic metre (mcm), the largest in Saurashtra region. Bhadar, located at Lilakha village of Gondal taluka of Rajkot district, has a gross storage capacity of 188.14 mcm, the second largest in the region. Their cumulative storage capacity of around 497 mcm constitutes almost 20 percent of the total 2,540 mcm cumulative capacity of 140 major dams of Saurashtra.
Following good rainfall in their catchment areas, Sehtrunji dam overflowed on August 19 and Bhadar dam followed on August 21. It was for the first time since 2015, and the 16th time overall, that the two dams overflowed simultaneously during the same season.
The two dams are across Shetrunji and Bhadar rivers. These rivers flow in opposite directions and the two dams have different catchment areas. While Bhadar originates from Jasdan taluka of Rajkot, Shetrunji originates from the neighbouring Amreli district. Parts of Amreli also drain into Bhadar. However, their geographical location in Saurashtra makes these two dams a good indicator of rainfall distribution in the region, according to officers of the irrigation department.
“These dams are located in basins of two different rivers and have little correlation in them overflowing simultaneously. But the fact remains that they overflow simultaneously only when most of Saurashtra region gets fairly widespread rainfall,” says HN Kapdi, superintending engineer of Rajkot irrigation circle.
Saurashtra region has received more than 100 percent of its average rainfall this year. But in the peninsular region, almost every fourth monsoon remains a deficient monsoon. Even within 11 districts of Saurashtra, spatial distribution of rainfall remains skewed, as evidenced by 12 different years in which either only Bhadar or Shetrunji dam overflowed, officers said.
In their 55-year history, the twin dams have overflowed only 22 times each. More interestingly, it is only during 16 seasons that these dams overflowed simultaneously, data available with Rajkot and Bhavnagar irrigation circles showed. The dams overflowed simultaneously for the first time in 1965. The occurrence repeated itself only five years later in 1970. But after that, it was only after seven years — in 1977 — that the two dams overflowed together.
The longest streak of them overflowing together, for three consecutive seasons, was recorded only in 2005, 2006 and 2007. The two consecutive seasons have been recorded only once when the dams had overflowed together in 1979 and 1980.
Overall, the dams overflowed simultaneously in 1965, 1970, 1977, 1979, 1980, 1983, 1988, 1994, 2002, 2005, 2006, 2007, 2010, 2013, 2015 and 2020. The longest period between two seasons when the dam did not overflow was recorded between 1994 and 2002 in case of Shetrunji and 1970 and 1977 in case of Bhadar.
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