"In March or April, this used to be 10 to 12 feet of snow here," RS Rana laments, as he trudges through mushy slush in the Dhauladhar range.

An avid trekker, he's been hiking what are called the "lesser Himalayas" for nearly half a century.

The change, he says, has been dramatic.

"I have never seen this area without snow in the month of March, April, May, even June," he says.

In the trekking camp of Triund, stall owner Suresh Sharma sells drinks and snacks.

Less snow means more tourists and sales, but Mr Sharma says it doesn't feel right.

"It is good for business, but somehow we are losing something," he says.

"I am nature lover person, so I want more snow and less people, you know."

Geology Professor Sunil Dhar from the Dharamsala's Government college, puts it simply.

"One thing is certain, that glaciers are retreating, they are melting fast," he says.

Wolfgang Schwanghart, a glacial researcher from Germany's University of Potsdam, says the whole Himalayas have around 60,000 square kilometres of glaciers, which are retreating at up to 66 centimetres per year.

Professor Dhar says a recent Indian Government survey backs that finding, casting doubt over the Himalayas' ability to continually feed green-energy hydropower projects.

"If it goes with this rate, as a matter of fact, it will definitely have some kind of effect on the magnitude of the generation of hydropower," he says.

Hydropower is projected to account for 20 per cent of India's planned emissions cuts, according to one United Nations website tracking various nations' pledges.

Dr Schwanghart says scientific consensus on climate change indicates those emissions are themselves jeopardising hydropower.

"The massive expansion of hydropower projects reflects the nexus between climate change, water resources and energy production," he says.

"The fast-growing economies, such as India and other South Asian nations, require reliable power sources to sustain growth.

"So climate change increasingly urges nations to use renewable energies, but harnessing hydropower entails several risks due to climate change too."

RS Rana says he has never seen the area without snow in March, April, May or June. ( ABC News: James Bennett )

'Time will come when there's no snow here'

The risk, Mr Schwanghart says, is that hydro projects won't deliver the power that India's banking on, to meet environmental targets and to electrify the developing nation.

"This problem seems to be appreciated by some environmental agencies, but not by the ministry of power," he says.

Precise modelling, though, is difficult, because India's Government keeps Himalayan river-flows classified.

Professor AR Ramanathan, a glaciologist and hydrologist from Delhi's Jawaharlal Nehru University, says many of the hydro projects contributing to those projected carbon cuts should only operate half the year.

"I think we have enough water for six months, in some of the river systems," he said.

"For the other six months, it may not be there."

Neither India's power ministry or national hydro power corporation responded to the ABC's requests for information or interviews.

Back in the mountains above Dharamsala, RS Rana predicts a grim future.

"The time will come when there's no snow here," he says forlornly.

"I believe that."