Nearly one billion people who depend on the Indus, Ganges and Brahmaputra river basins for their lives and livelihoods are threatened by the impact of global warming in the Himalayan-Karakoram Mountains. Melting snow and glaciers will swell rivers, but the change in seasonality will affect agriculture, other livelihoods and the hydropower sector, while causing downstream flooding, according to a new multinational study by researchers from ‘Indore, Roorkee, Delhi, Bengaluru, Ahmedabad and Nepal, among others, found.
In India, the Union Territories of Jammu and Kashmir and Ladakh, the States of Himachal Pradesh and Punjab and parts of northern Haryana and Rajasthan lie in the Indus Basin . Uttarakhand, Delhi, the rest of Haryana, Uttar Pradesh, Bihar, Jharkhand, West Bengal and much of Rajasthan and Madhya Pradesh lie in the Ganges basin. Sikkim and Arunachal Pradesh, as well as most of Assam, Meghalaya and Nagaland lie in the Brahmaputra Basin. Those affected, particularly in the mega-cities of Delhi, Lahore, Karachi, Kolkata and Dhaka, represent nearly 13% of the world’s population in 2021, or one in eight people.
Base river runoff (water flowing into rivers) in the Himalayan-Karakoram (HK) region includes snowmelt, glacier melt, precipitation, and groundwater base flow , according to the study. Half of the ice in the Hong Kong region is contained in glaciers. The rate at which and when these glaciers melt affects the flow of river water in different seasons. Usually, rivers carry the snowmelt of the Hong Kong mountains in the summer, from April to June, then the glacier melt until October, before the winter hardens the snow and ice again.
Global warming, which affects glaciers, snowfall as well as precipitation regimes in the Hong Kong region, will have downstream consequences on river basins. The study predicts that there will be an increase in glacier melt, total river runoff and flows in different seasons until the 2050s.
Hong Kong’s river basins cover an area of 2.75 million km², have an irrigated area of 577,000 km² and an installed hydropower capacity of 26,432 MW, according to the study. Potential changes in river runoff will impact the timing and volume of meltwater available for irrigation, which is essential during the spring planting season, and for reliable hydroelectric power generation during the season. period leading up to the monsoon, according to the study.
“When we have more meltwater in the future due to a [glacier] as the monsoon rains melt and increase, we will have more water in the rivers. At the same time, glaciers are melting earlier in the summer. Instead of June, they melt in April. This means that the seasonality of meltwater changes. This change in the seasonality of meltwater will affect livelihoods and the economy, ”Mohd told IndiaSpend. Farooq Azam, senior research author and assistant professor at the Indian Institute of Technology, Indore.
The Karakoram anomaly
According to the study, changes in local, regional and global climate patterns due to global warming will have varying impacts on glaciers in the Hong Kong region. While river runoff in the Indus basin is more dependent on meltwater from glaciers and snowmelt, the Ganges and Brahmaputra basins are more dependent on monsoon rainfall, Azam explained. Thus, earlier melting of glaciers means a more negative impact for people living in the Indus basin.
The estimated contribution of melting ice and snow to the total Indus runoff varies between 21 and 40% and 22 to 49%, with estimates varying due to the different methodologies, modeling and time period considered for each study, have shown previous research. In contrast, in the upper Ganges basin, the combined melting of snow and ice accounted for 20% of total runoff, while precipitation and groundwater contributed 66% and 14%, respectively, according to this study.
Melting glaciers are already changing the hydrological regimes of Himalayan rivers and some of the immediate effects are seen in terms of the drying up of springs, which are the main source of drinking water for mountain dwellers, climatologist Anjal Prakash said. The increased runoff would contribute to downstream flooding and affect lives and livelihoods. Prakash is Research Director and Assistant Professor at the Bharti Institute of Public Policy, Indian School of Business in Hyderabad and lead author coordinating the special report of the Intergovernmental Panel on Climate Change on the Ocean and Cryosphere in a Climate in evolution, published in 2018.
“Mountain communities and people living downstream are more exposed to climate risks and the incidence of such climate-related disasters has increased in the region over the past two decades. This would greatly affect the populations as the Hindu Kush-Himalayas is one of the most densely populated and poorest mountainous regions in the world and any small climate change will affect a large part of the population, ”Prakash told IndiaSpend.
The varied impacts of warming on glaciers are well illustrated by the ‘Karakoram anomaly’, a term used by the scientific community to denote the trend of stable or increasing glaciers in the Karakoram mountain range, as opposed to retreating glaciers. of the Himalayas, in the face of climate change.
The shrinkage or growth of glaciers is called glacier mass balance, which refers to the sum of the accumulation of snow and the loss of snow and ice during the summer. When the accumulation exceeds the loss, it is called a positive mass balance.
“Compared to other parts of the Himalayas, the Karakoram has a positive mass balance and, therefore, it is abnormal. Some say it is due to special weather conditions, snowfall or warmer temperatures. Its glacial terrain is also at a higher elevation, “said Anil Kulkarni, co-author and distinguished visiting scientist, Divecha Center for Climate Change, Bengaluru.
Jeffrey Kargel, study co-author and senior scientist at the Planetary Science Institute in Tucson, Ariz., Explained that the impact of climate change on glaciers is complex when it comes to the Hong Kong region. Kargel said the climate is warming at different rates in different parts of the Himalayas and summer temperatures in the Karakoram, for example, are stable or may decrease in some valleys due to increased cloud cover, which in turn adds an influx of moisture.
“These parts of the Karakoram are among the very few places in the world where this (positive mass balance of glaciers) occurs. But overall, temperatures are rising rapidly. This is in part due to the increase in greenhouse gases. greenhouse, as in other parts of the world, but part of the increase in temperature is due to the absorption of sunlight into the “brown cloud” of pollution. another very important effect, but in detail, climatologists do not agree on what is going on specifically, ”said Kargel.
Kargel, meanwhile, explained that the short-term increase in glacier meltwater is akin to a bank account that has increased cash flow in the short term but will dry up in the long term. “The water they have stored in the form of ice can produce a large increase in short-term water reserves as the climate warms, but the long term is made more precarious, because ultimately the” bank account ” ice is drying up, and that’s something water managers need to take into account, ”added Kargel.
Look for gaps and prepare for changes in runoff
The findings of the multinational study are also based on a review of major studies on the region, with the aim of highlighting the issues regarding glaciers and climate change in the Hong Kong region and its impact on hydrology, as well as to identify research gaps in glaciology and hydrology. . With millions of people dependent on the three river basins, the authors say these research gaps on the effect of warming on glaciers in this region need to be addressed.
“Precipitation is a key factor that we need to study. It varies from valley to valley and currently information on precipitation is widely available at elevations below about 1000m above sea level. Hong region Kong has a lot of variability in topography with different precipitation regimes. This is not captured well in the models, ”Azam said.
Develop observation networks at higher altitudes; establish fully automatic weather stations at higher altitudes to monitor temperatures and precipitation; and the development of projects to study the area and volume of glaciers were some of the recommendations made in the document. He also suggested a multinational collaboration equivalent to the National Aeronautics and Space Administration (NASA) polar-oriented Icebridge mission that involves an airborne survey of polar ice.