Cloud Seeding in the Snowy Mountains Graphic.

Cloud Seeding in the Snowy Mountains

The New Zealand Hydrological Society Technical Workshop was held in Dunedin, NZ from April 3rd to 6th this year. These technical workshops are tightly focused around problems and opportunities in field of hydrology, providing great inspiration for the betterment of water measurement and monitoring.

I have written about Mic Clayton from Snowy Hydro previously so I don’t need to go into detail about who he is apart from him being a very entertaining individual who is continually pushing the envelope of possibility in water monitoring. He gave a couple of talks in Dunedin and one talk in particular has stuck in my mind.

Snowy Hydro has embarked on a cloud seeding program to increase the snowpack to enhance the inflow to their reservoirs.

Cloud seeding is not an endeavor commonly associated with consistent and reliable results. This perception may date back to the saga of Charles Hatfield who, in 1915, promised San Diego he could fill the Morena Dam Reservoir. The subsequent (coincidental?) flooding destroyed bridges and broke a dam causing about 20 fatalities.

Whereas the methods of cloud seeding have become more sophisticated over the past century, quantification of benefits has been elusive. This is why Mic is needed.

The problem for Snowy Hydro is their water license. There is no benefit to making snow if they cannot use the water. In order to justify an increase in water use to the regulating authority they must precisely quantify the amount of water they are adding to the catchment.

For a variety of environmental reasons the program was tailored specifically to snow-making not rain-making. Mic and his team therefore needed to measure the snowpack accumulation and attribute the measured quantities to natural or artificial causes. The ambitious measurement and monitoring campaign was run with a blind control where one out of every four events used a blank rather than silver iodide. Mic and his team had to successfully identify which events were which using a combination of quantitative, qualitative (e.g. snowflake structure), and analytical measurements (e.g. silver iodide concentrations at 1/trillionth resolution).

The results are impressive.

The measurements revealed a 14% increase in snowfall under suitable conditions. Depending on the weather conditions, approximately 1 to 2 kg of silver iodide dispersed over a 2,200 km2 region resulted in 1 gigaliter increase per event. There were 20 suitable events over the winter so the net addition of water was about 20 gigaliters. That represents a large dollar value when Snowy Hydro’s turbines can use that water to generate electricity.

However, the Snowy Hydro’s profits are not what interested me about this project. The cryosphere is shrinking at an alarming rate. A double whammy of shrinking snowpack and longer melt season is resulting in massive rates of glacial melt. New snow is like sunscreen for glaciers. New snow reflects the sun’s energy with high efficiency compared to bare glacial ice. Glaciers are extremely sensitive to the presence of snow. When the snow melts before the summer solstice then the glacial ice is exposed to high-angle high-intensity radiation that cuts through the ice like a hot knife through butter.

Suppose that artificially enhanced snowfall could provide some shielding protection for our glaciers. We wouldn’t be able to reverse climate change but we might be able to retard the rate of sea level rise enough to where we may have a small chance of implementing successful adaptation strategies in time.

I suggest this knowing it is probably a bad idea. However, to paraphrase Winston Churchill: “cloud seeding is the worst idea for climate mitigation, except for all of the others.” Our glaciers are on a fatal trajectory. If there can be any optimism it is in the expression, “the crash site is where the pilot ran out of altitude, airspeed, and ideas all at the same time.” In other words, up until the very moment before impact the right idea can save the day. We in the monitoring community, by the nature of our work, are watching the gauges – literally. We should be a good source of ideas for how to avert unwanted impacts.

My opinion is based on 9 parts angst and 1 part science. What is needed is for a real glaciologist to examine the data from Snowy Hydro and make an informed opinion about whether the idea has enough merit to warrant further investigation for glacier protection. Anyone who lives in a low-lying coastal region should be hoping that it does.

Photo Credit: Snowy Hydro, “How Cloud Seeding Works.”

  • Matthew Mabey
    Posted at 9:17 am, May 16, 2017

    “Our” glaciers have been on a fatal trajectory since the beginning of the Holocene. The rate of “blood loss” is a bit greater now, but the water from steadily shrinking glaciers is a part of what we consider “normal” stream flow. If we were to successfully start growing “our” glaciers, one result could actually be reduced stream flow. We could actually start locking up water in glaciers that we depend on. It is true enough that the more likely scenario would be that only a fraction of any increased snow fall would get stored inter-annually in the cryosphere. Never the less, we must remember that it is one big mass-balance equation. Extra water that falls on the Snow Hydro watersheds is water that can’t fall somewhere else. Water that we lock-up in glaciers is water that isn’t available somewhere else. Equally true is the fact that the water removed from storage in major aquifers that we have been depleting for the past 50+ years has to have gone somewhere too.
    By the way, looking for the silver-iodide in the snow is cheating. It takes the blinders off the blind control. Sorry, but the fact that they were checking for the silver-iodide invalidates the the results from my perspective. It isn’t blind if you are peeking.

  • Mark F Heggli
    Posted at 8:37 pm, February 8, 2018

    Hi Matthew and Stu,
    I helped design the SHL precipitation enhancement project. Quite a place to work. The initial experiments were held in 2004, 2005, and a bit beyond before going operational. The initial “exploratory” phase was completely randomized, with some events being seeded, and others not. It was a single blind experiment. After the results of the exploratory years came in, it was decided to go operational, so no more randomization, since it simply wastes opportunity.
    The robbing Peter to pay Paul concept must be put in context with the Snowy Mountains. The air mass that crosses the Snowy, starts descending, thus warming, and thus evaporating, and soon the air parcel is out over the South Pacific. Yes, an amount of condensate is removed from the atmosphere, but compared to the quantity of condensate passing over the crest, it is rather small. One could closely relate the situation to the Sierra Nevada, where the air mass is lifted on the windward (thus condensing), and evaporates on the leeward side (Nevada).
    Precipitation enhancement has never been sold as a “cure all”, but only one step in many steps to help water availability. In SHL’s case, there sounds like there were other factors, which I find interesting. The idea that one just seeds and hope for the best, is how some projects are run, especially in warm cloud seeding. Winter orographic cloud seeding has a very nice set of models, and a good deal of remote sensing to help identify opportunities, so it is well beyond the point of throwing darts on a spinning dart wheel. By the way, I worked with Mic back in the day. Good to year he is still at it.
    Stu, I consult with The World Bank these days, and use your five essential elements diagrams quite a bit. Very nicely done.

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