Hydrologists on the roof of the world

It's the Holy Grail for mountaineers, but also an extraordinary field of research for hydrologists: the Himalayan range is a major reservoir of water that feeds large, densely populated river basins, such as the Ganges and the Indus.

Geopolitically sensitive, this area has long remained inaccessible to scientists, allowing only a handful of studies on the hydrology of the valleys. Since 2010, French researchers have undertaken a systematic study of Nepal's Khumbu region, taking advantage of the presence of an Italian laboratory at the foot of the world's highest peak. Each year, François Delclaux, an IRD hydrologist at the Hydrosciences Montpellier laboratory, travels from the village of Lukla, at an altitude of 2,860 metres, to the famous laboratory at 5,000 metres above sea level. This high-altitude scientific journey is designed to obtain sufficiently reliable hydro-climatic data to understand and model hydrological processes, and thus forecast the evolution of water resources in the Dudh Koshi valley. In 2012, photographer Olivier Boulanger accompanied him on this mission to the roof of the world.

Researchers and Sherpas: an indispensable partnership

After a 40-minute flight, the researchers reached the village of Lukla at an altitude of 2,860 metres. From here, all travel is on foot. To transport the 50 kilos of scientific equipment, the hydrologists hired the services of three porters. Partnership with the Sherpas, the main inhabitants of the upper Everest valley, is essential to the success of the mission. Throughout the year, they host, maintain and collect data from the various measuring stations.

Taking measurements at altitude

To understand the water cycle, hydrologists have installed hydrometric stations on major rivers. And to measure snowfall, they have installed a simple wooden plank topped with a metal rod. Every morning, a local resident measures the height of the previous day's snowfall and collects a calibrated sample to determine the corresponding volume of water.

Growing tourist pressure

Sagarmatha National Park welcomes 30,000 tourists every year. To accommodate them, the Sherpas have built lodges, installed sanitary facilities and modified their farming practices. In this part of the Himalayas, environmental changes linked to tourism are more significant than those due to climate change.

Photo Credit: Olivier Boulanger