Kerala receives 81.26 cubic km rainfall since June 1, over half the volume of the Dead Sea

Since the onset of the southwest monsoon, Kerala has received abnormal amounts of rainfall, causing floods in almost all districts of the state. Between June 1 and August 15, Kerala got 2,091 mm of rainfall, 30 percent more than the 50-year average for the period, according to Indian Meteorological Department (IMD) data.

The volume of water that fell over the coastal state amounts to 81.26 cubic km. To put this in perspective, in the space of two-and-a-half months, Kerala received enough rainfall to fill Srinagar’s Dal Lake 82 times over. Also, this figure is more than half the 147 cubic km of saline water that fill the Dead Sea basin.

All of the 14 districts of state have witnessed excess rainfall, while Idukki recorded a large excess. The hill district saw 70 percent more-than-normal rainfall. Kottayam and Ernakulam received 41 percent and 38 percent more rainfall than the historical average. The IMD classifies rainfall patterns by comparing with the 50-year average.

Idukki is home to several dams like the Mullaperiyar, which has been the bone of contention between Kerala and Tamil Nadu. Reservoirs which were operating below half the maximum storage capacity are now having to open the sluice gates to keep up with rising water levels. Several villages and towns in the vicinity have been inundated.

Kerala is the only state in the country to have received excess rainfall this monsoon season. The monsoon has played truant in other parts of the country. Twelve sates recorded deficient rainfall. Mizoram had a large deficiency, getting less than 66 percent of the 50-year average.

Rainfall between 30 percent and 59 percent of the historical average is considered excessive. Rains are deemed normal if they fall in the -19 percent to +19 percent bracket.

In 2017, Kerala received 2,664.9 mm rain, only marginally greater than the 2,091 mm recorded in the two-and-a-half months since June 1, 2018. The IMD reckons that 2039.7 mm rainfall is normal for the four-month window between June 1 and September 30.

Ironically, Kerala received only 1855.9 mm rainfall during this period last year, a deficiency of 9 percent. Halfway through the monsoon season, rains in Kerala have already breached the historical average for the four months ending September.

The deluge has claimed over 350 lives and caused widespread damage to property. Several strategic installations have also been rendered inoperable due to flooding. The Kochi airport was shuttered for a week, and efforts are on to clear the airstrip.

Even if the rains subside, authorities will have to keep a check on water level in dams. According to Kerala State Electricity Board data, all but three of the dams used for generating hydroelectric power have their reservoirs filled to over 90 percent of maximum capacity.

Incessant rains had caused the water level in the Idukki dam to veer close to the danger mark. At present, its storage is 99 percent of total capacity. India Today had reported that on August 10, authorities at the Idukki dam let out six lakh litres of water every second.

The ordeal is yet to end for Keralites. The floodwaters have started to recede but the IMD has forecast heavy rains at several places, including Alappuzha and Ernakulam districts.

Experts believe that if dams had started releasing water earlier, the situation would not have deteriorated to the present level. Water level has been rising in dams since mid-July. Most rivers in Kerala empty out into the Arabian Sea.