In the just concluded pre monsoon season (March 1 to May 31, 2021) India received 155.2 mm rainfall, 18% above the normal rainfall of 131.7 mm as per the India Meteorological Department (IMD). This is similar to the case in 2020[i] when India received 158.5 mm or 20% above normal rainfall.
Month wise distribution However, when we look at the month-wise distribution of rainfall we find that in March there was just 16.7 mm or 45% below normal rainfall when normal rainfall was supposed to be 30.4 mm. In April, the rainfall was 31 mm, 21% below normal rainfall of 39.3 mm. The lion’s share of rainfall of the season was in May 2021, at 107.5 mm, or 73% above the normal rain of 62 mm.
On June 10, IMD reported in its monthly report that May 2021 rainfall was 107.9 mm, second highest in last 121 years for which records are available. Earlier highest was 110.7 mm in 1990.
ALL INDIA State wise rainfall distribution As we can see the map of IMD showing state wise rainfall distribution during pre-monsoon season 2021, we see that thirteen States (and Union Territories) had Large Excess (over 60% in excess of normal rainfall), eight States and UTs had Excess (20-59% above normal rainfall), Seven states had Normal (between 19% excess and 19% deficit compared to normal), Eight states had Deficit (20 to 59% below normal rainfall) and one state (Mizoram) had Large Deficit (over 60% below normal) precipitation. Mizoram had 67% below normal rainfall of 578.8 mm, the highest deficit rainfall among all states of India in the season.
Kerala had the highest rainfall at 752 mm and Ladakh had the lowest at 20.2 mm. Daman & Diu had the highest excess % in rainfall at 3258%.
ALL INDIA Sub Division wise Rainfall distribution As can be seen from the IMD map below, out of 36 meteorological sub divisions of IMD, Seventeen had large Excess, Nine had Excess, Six had Normal and Four had below Normal rainfall.
NMMT (Nagaland-Manipur-Mizoram-Tripura) had the highest deficit % in rainfall at 55%. Saurashtra and Kutch at 1013% had the highest surplus %. Western Rajasthan had the lowest rainfall at 39.2 mm, Kerala had the highest.
ALL INDIA River Basin wise Rainfall Distribution As we have been highlighting for some years, IMD also provides River Basin wise rainfall distribution.
For Pre Monsoon 2021 season, as we can see from the IMD map, it is surprising that for a number of river basins, IMD has reported ZERO rainfall including: Narmada, Middle Yamuna, Ganga (main stem in the central UP), Tons, Vamsadhara, Nagvati, Lower Tungabhadra, Lower Krishna, Lower Bhima, Pennar, Ponnaiyar Palar, East Flowing Rivers between Godavari and Krishna, East Flowing rivers between Krishna and Pennar and Vaippar Pamba. This seems unlikely to be true for many of these basins, this only means that the IMD has been callous in collecting and calculating information about rainfall in river basins. For example, in case of vast Narmada basin, while IMD reports zero rainfall, for every single basin surrounding the Narmada basin, the rainfall reported is LARGE EXCESS. It seems totally impossible that the Narmada basin would have had zero rainfall in this situation. Even from its district wise rainfall figures, one can see that the IMD saying that Narmada Basin has had ZERO rainfall is absurd.
Strangely, IMD reports NO DATA for a number of basins like Jhelum and Upper Indus.
The composite River Basin “West flowing rivers South of Tapi” seems to have the highest rainfall at 690.7 mm. Mahi basin, just north of Narmada basin, has reported 318.7 mm rainfall, massive 4099% above normal, possibly the highest surplus % this season among all the river basins.
STATE WISE DISTRICT WISE RAINFALL: NORTH ZONE: Jammu & Kashmir
EAST ZONE: Uttar Pradesh
NORTH EAST INDIA: Sikkim
WEST INDIA: Rajasthan
SOUTH INDIA: Andhra Pradesh