What Happens Downstream from Disappearing Glaciers?

Posted on 18 November 2012 by Jerry

History is full of civilizations which grew up around predictable sources of water.  Glaciers, in conjunction with winter snows, store water in the form of ice and create consistent sources of fresh water for downstream use.  But what happens in an age of global warming to downstream populations when glaciers disappear upstream?  This is precisely the question a research team is seeking to answer using glaciers in the Andes of Peru as the basis for their major study.

The study, funded by a grant from the U.S. National Science Foundation, will be used to develop a baseline for computerized climate models to predict the effects on human population centers that depend on mountain runoff as their main source of water.  As the most comprehensive study of the climate change impact on glaciers funded to date, the study will also provide specific information for Peruvian leadership so they can prepare for the more limited water supplies in the future.

There are glaciers on all of the continents of the world (see link below).  Peru was selected because it has the largest mass of tropical mountain glaciers in the Cordillera Blanca (or White Mountain) range.  The majority of water supplied flows down the Santa River Valley, known as the Callejón de Huaylas, to hundreds of thousands of people in the valley.  By measuring for example, how the rocks, water and ice react as the heat of the day rises, how they behave as the area cools at night and correlating this with measurements of the thickness of the glaciers measured by satellites and aircraft, the researchers will construct a model of how glaciers will change.  By adjusting for local conditions like altitude, average temperature and historic downstream water use scientists believe their model will be useful all around the world.

Past studies have shown that glaciers have been shrunk between 20-30% since 1970.   The rate of shrinkage appears to be accelerating with recent assessments by the French Institute for Development showing the total mass of glaciers in the tropical Andes shrinking by roughly 3% per year.  Preliminary study results indicate these glaciers in the Andes will not completely disappear in the summer months.  This is due to their high altitude.  Were they farther down, they would disappear completely.   The projected future water flow however, will not meet forecasted future needs which include needs for basic drinking water, electricity generation and agricultural irrigation. 

A recent article appearing in the November 8, 2012 issue of Nature magazine which talks about the study in Peru indicates “glaciers serve as a buffer, locking up precipitation during the rainy season and releasing water slowly during the dry season, between June and September, when almost no rain falls.” The article further quotes Jeffrey McKenzie, a hydrologist at McGill University in Montreal, Canada as stating “You can think of glaciers as hydrological Prozac – they smooth out the highs and the lows.”  Without glaciers water use will have to adapt to greater seasonal variation between wet and dry seasons.

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2 Comments For This Post

  1. Laurie Lewis Says:

    Thank you so much for intriguing me with talk of your book. I imagine you already know of James Balog, and EIS (Extreme Ice Survey), but if not, you must see the film Chasing Ice. The cinematography and time lapse photography are amazing–and the message so pertinent. I saw it last evening at the Embarcadero Cinema, and would highly recommend it. A great example of research and science informing beliefs.

  2. Jerry Says:

    Hi Laurie:
    I have seen interviews on TV with James Balog where he talked about his experiences filming his movie. I also saw him on Bill Maher, I think he was a guest at the beginning of the segment. Thankyou for telling me where you saw Chasing Ice. I will try to see it. I hope your husband finds my book thought provoking. I enjoyed seeing you again but would hope for better circumstances next time.
    Thanks again.

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