Here in Modesto, California, pilots are prepping this
plane to fly into the center of a storm.
Flares on the wings and fuselage will inject a
substance called silver iodide into the storm
clouds, causing water within the clouds to freeze
and increasing the amount of precipitation that falls.
We can't make a storm happen and we can't create
conditions in this storm that are ideal.
Those happen naturally. And what we're doing is just
taking advantage of existing conditions,
naturally occurring conditions, and trying to
make the storm again more efficient from a water
supply perspective.
It's called cloud seeding, and as futuristic as it
sounds, it's been around since the 1940s.
Today, states, utility companies, and ski resorts
alike pay companies like Weather Modification
International significant money to seed storm clouds
and increase snowfall in the drought-ridden American
West and worldwide.
The current project is about $4 million a year.
We're very well supported.
We have a lot of local stakeholders that are
investing in it.
Until recently, the evidence for cloud seeding's efficacy
was murky. But research has finally shown unequivocally
that it works, and there's been no evidence to show
that the seeding agent, silver iodide, is harmful at
the current level that it's used. Blestrud says that
Idaho Power sees an 11% or 12% increase in snowpack in
some areas that it seeds, while Carkeet says Turlock's
program results in about 60,000 to 90,000 extra
acre-feet of water every year.
While it's no cure for the West's historic drought,
dozens of cloud seeding programs across the country
are ramping up right now as winter gets underway.
These are the flares that we will use when we're above
cloud, and we need to get the flare down into the
cloud. When we're in cloud, we will be using the
burn-in-place flare, which can be ignited from the
cockpit one at a time.
They burn for four to four and a half minutes and they
just trail smoke out with the silver iodide.
The world's first cloud seeding experiment back in
1946 was a bit more simplistic than Zimmer's
current setup.
There was a group of scientists back in New York
that worked for the General Electric Company.
They released some dry ice into the top of a
super-cooled stratus cloud and caused ice to form, and
that ice formed and used up the available liquid water
of the cloud drops and cloud seeding was thus born.
Supercooled means liquid that is below its freezing
point, but hasn't yet crystallized. Injecting
silver iodide into clouds that contain supercooled
liquid water causes droplets to freeze together
and form snowflakes, which fall to the ground when they
reach a certain size. Absent the freezing process,
these supercooled droplets wouldn't become heavy enough
to precipitate as either rain or snow.
The cloud initially is all water.
Eventually, as it gets toward the summit of the
mountain, it may be 50% ice or maybe more than that.
Even if it is, there's still a lot of liquid water
left there. And the precipitation that's forming
has a very short time to get big enough to fall out
before it crests the mountain and starts to
descend and thus warm.
And so that's the window of opportunity.
For cloud seeding pilots, this is when they fly into
the storm, which is no easy task.
The first thing we do for safety is turn on all the
aircraft ice protection systems.
Weather radar is important for us so we don't get into
a convective environment like an embedded
thunderstorm or something like that.
An average flight lasts between two and four hours.
By the time the wheels are up, you're in cloud and
we're in cloud the entire mission until we're shooting
an approach back into an airport and then pop out of
the clouds and have a visual on the runway.
Yeah, it feels like you're a subcommander in the Navy.
You don't see anything.
Zimmer seeds clouds for the Turlock Irrigation District
in Northern California from November through April every
year.
We do a preflight check and take off and head to our
seeding area, which is over the Sierra Nevada mountains.
If we are flying in cloud with decent supercooled
liquid water, the most effective tool we have is
the burn-in-place flare on the back of the wing,
because it's going directly into the cloud and mixing
with that supercooled liquid water.
If we're just above cloud or at cloud top and we're a
little bit colder than where we want to be with the
burn-in-place flares, we can transition to the
injectable flares which shoot the silver iodide down
through a warmer layer below us to find that minus
five degrees Celsius level where they're most effective
in forming ice.
From a water supply perspective, it's most
valuable to seed clouds over mountains where the
water is stored as snow until the spring runoff.
If you put it in the mountains, the drainages
coming out of the mountains often have reservoirs on
them, and so you can capture it that way.
When it's out on the plains, such as North
Dakota, it's still a benefit because it helps
recharge soil moisture, but it can't be stored and used
for a later date.
Texas, for example, uses cloud seeding to help
irrigate fields for farmers, while states like
Idaho, California, Colorado, Utah, and Wyoming
use it to help fill up their rivers and reservoirs.
Most use planes to do cloud seeding, but some programs
use ground-based flares.
There are multiple utilities, both south of us
and north of us that have cloud seeding programs.
It's a lot more common than people think.
More basins have a seeding program than do not have a
seeding program.
For much of cloud seeding's history, its success was
measured by comparing the snowfall in an area where
cloud seeding occurred to a nearby control area.
And then you look after cloud seeding happens and if
there's a shift in that so you get more than what's
expected in the target area, then you can equate
that to cloud seeding.
This method convinced many states and utility companies
like Idaho Power of cloud seeding's efficacy long
before tech was good enough to actually see the changes
taking place within the clouds themselves.
However, there were still plenty of skeptics, given
how hard it was to verify cause and effect due to the
many variables at play in a storm.
But a 2017 collaborative study between various
universities, Idaho Power Company, and the National
Center for Atmospheric Research, called SNOWIE,
gave researchers a clear visual of what happens as a
cloud seeding plane zigzags through a storm.
So you could actually see that cloud turn from what's
called a supercooled liquid water cloud, a cloud that
has a bunch of water that's below freezing but stays in
the liquid state, and then it started to turn to ice
and it started to grow to a snowflake.
And the radar can then see those snowflakes on it and
they could start to see that zigzag pattern there.
The ultimate impact of cloud seeding varies according to
location and the nature of the storm, though studies
show an overall 5% to 15% increase in precipitation
can be expected. A small percentage of that total
will be absorbed into the soil, while the rest will
become runoff that's hopefully stored in one of
the West's shrinking reservoirs. The Turlock
Irrigation District has a max budget of $475,000 per
year for its cloud seeding program, and says it's seen
a 3% to 5% increase in runoff since it started
seeding in 1990.
It's percentage wise and it's within the realm of
natural variability.
It's one of the things that makes it so hard to evaluate
is you don't see a doubling or tripling of the
precipitation. You see an incremental increase, but
you add that up over the course of a winter and then
it can be significant.
And cost-wise, Boe says that it's almost always worth it.
It's kind of, well, I won't say a no-brainer, but it
makes a lot of sense to water managers to go ahead
and do it even if the increase is on the order of
a few percentage points.
It's still cost effective to do it.
When you run the numbers, Blestrud says the
multimillion dollar cloud seeding program that Idaho
Power oversees yields billions of gallons of
additional water at a cost of about $3.50 per
acre-foot. That's compared to about $20 per acre-foot
for other methods of accessing water, such as
through a water supply bank.
States in the lower Colorado River Basin like California,
Nevada, and Arizona are even helping fund
out-of-state cloud seeding operations in the upper
basin states like Utah, Wyoming, and Colorado,
hoping excess water will make its way into their
lower basin reservoirs.
States are putting money into those programs, knowing
that they have no legal claim to any of that water.
But since the locals already have enough water,
they're figuring the additional water is likely
going to pass down into the Green and into the Colorado
and make it down their way. So to them, it's very
worthwhile to do it.
While cloud seeding is most commonly used to increase
precipitation for drought alleviation, it can also be
used to suppress hail and clear fog around airports.
Internationally, there's been concern that cloud
seeding has led to increased flooding, such as
in the UAE. This remains unproven, though some
experts are pushing for an international body to
regulate weather modification activities.
So far this year, the Turlock Irrigation District
has conducted six cloud seeding missions.
We're flying below average right now.
We're hoping we get that atmospheric river to show up
and bring bring more moisture to California.
Now that studies have validated the efficacy of
cloud seeding and as the drought in the West
persists, interest in this decades old tech is peaking
both nationally and globally.
We're busy right now. We have new contracts starting
in the Middle East. We operate in India, Canada,
Wyoming, Idaho, California.
Right now, we have deployed every aircraft that we have
access to that we, the company, owns.
We don't have anything sitting in reserve.
But as seeding operations ramp up for the winter, Boe
warns that this tech can only go so far when it comes
to alleviating our water woes.
For us, it's really important that people that
want to engage in cloud seeding technology do so
with the perspective of water management, not
solution to a drought.
Because when you're in the throes of a big drought,
you're going to have far less opportunities to
actually seed clouds.
So you need to view it long-term as a water
management tool, not as a knee jerk reaction because
you're in a drought.