Relentless monsoon rain has left 33 million people across Pakistan affected by flooding, according to Pakistan’s Federal Minister for Climate Change, Senator Sherry Rehman. Although very little rain is expected through the coming weeks the levels of the Indus and Kabul Rivers will continue to leave many lives and livelihoods at risk.
The Asian summer monsoon season runs from June to the end of September, and much of south Asia depend on this rainfall following the dry season. However, this year Pakistan has seen this rain come in unmanageable volumes.
Deputy Chief Meteorologist at the Met Office, Ele Hands, said: “Pakistan started the season with its wettest July on record, followed by a very wet August. These added together means that they have already seen three times the average monsoon rainfall, and more locally areas have received up to five times the amount of rain they would usually see, and we still have another month of the monsoon season left.”
River levels are slowly retreating from that of a 1 in 100-year event, very little rainfall is expected this week, but levels are forecast to be that of a 1 in 20-year event even into this weekend.
The Indus River rises in Tibetan Plateau, while the Kabul River rises in the Hindu Kush mountains in Afghanistan. The Indus drains an enormous area of Pakistan, and extreme rainfall has resulted in the main river channel becoming overwhelmed. Mountain glaciers to the north feed these large rivers flowing south, and during mid-July to mid-August peak snow melt and rainfall coincide to result in the highest river levels.
The drivers of flooding
Throughout July and August, a succession of monsoon depressions tracked west across India and into Pakistan bringing waves of very heavy rain. This weather pattern is typical during monsoon season, but the frequency has changed this year.
Monsoon conditions are driven by a simple mechanism that drive a dramatic change, every year. Heat builds up across the Tibetan Plateau through the spring and summer months causing air to rise. This means low-pressure depressions develop at the surface. These depressions drag in moist southwesterly air which lead to heavy rainfall.
Ele explained: “In a typical monsoon season, we would expect around four waves of this heavy rain but there have been eight of them so far. These waves have moved into a similar area each time and that means the rain has accumulated over the same areas.”
Not only have these pulses of rain arrived at an unmanageable rate, but they have also pushed into more northern parts of Pakistan. The increase in spatial coverage means that far more people compared to usual as well as other extreme monsoons events, have been affected.
Is this climate change?
The south Asian monsoon is known to exhibit a high degree of natural variation with some extreme years producing much higher rainfall totals across the region, and the ongoing La Nina conditions are likely to be a contributing factor to the wetter-than-average season.
The natural variability creates challenges for climate scientists trying to examine the impacts of climate change on this weather system. This is largely because the differences between extreme wet and dry years can be larger than any influence that could be expected from climate change at this stage.
We know that a warmer atmosphere holds more moisture, so this could be a contributing factor affecting those years which would already have been extremely wet. It is likely human influence has led to intensification of heavy precipitation across Asia but adding glacial and snow melt into the picture complicates the relationship between the south Asian monsoon and downstream flooding events. Any changes in land management of the catchments of southern Asia’s great rivers provides an extra complication which needs to be considered. Ongoing research into the evolution of the Indian Summer Monsoon is therefore vital to better understand what the future holds.
In 2010, an extreme monsoon caused devastating flooding to the Indus River in Pakistan. It was estimated that 20 million people were affected, so far, the 2022 monsoon has affected 33 million people. Human fatalities are currently estimated to be around 1000, so far less than the total from 2010. But the impacts from this year’s monsoon season are expected to continue well after the peak rainfall, as the rivers continue to react.
Flooding is always expected during monsoon season but this year’s flooding will leave damage that will take years to recover from. UN (United Nations) Secretary General Antonio Guterres has said “the people of Pakistan face the unrelenting impact of heavy rains and flooding – worst in decades.” On Tuesday, the Government of Pakistan and the United Nations launched a Floods Response Plan in the backdrop of devastating rains, floods, and landslides that have destroyed homes, caused over 735,000 livestock to perish, impacted two million acres of crops, and caused severe damage to communications infrastructure.