Cloud
Seeding May Not Help Some Water-Poor Countries
By Dr.
Michael A. Bengwayan, Ph.D. Environmental Science
Environment News Network
, Some 1.2
billion people or 20% of the world’s 7 billion-population, are prone to
diseases due to water poverty. Anthropologists dub some of whom
as “water-refugees”. This is because they don’t only lack water, but they
are on the move across borders in search for water.
The
assessment comes from the International Water Management Institute (IWMI) and
Earthscan. They produced the 2016 “Water for Food, Water for Life: An
Assessment of Water Management in Agriculture”.
The continuing
severity of water shortage has led Fred Pearce, author of the
globally-recognized book “When the Rivers Run Dry” to conclude that, “the
world water crisis has caught us unaware.”
Pearce says:
“With a series of local hydrological pinch-points rapidly escalating into a
global pandemic of empty rivers, dry boreholes, and wrecked wetland. There is
very little we can do to reverse the situation.”
How serious
is the water problem worldwide? IWMI defines water scarcity as human’s’
inability to secure and access safe and affordable water for drinking, washing,
and food production that affects 1/4 of the world’s area.
Sandra
Postel of the World Watch Institute warned there will be potential water wars.
Using the UNFAO and UNICEF figures, the IWMI announced that in the
water-starved regions, more than 1 billion people live below the one
dollar a day poverty line, majority of whom are women and children.
The majority
of them have no access to improved sanitation. The report added that the reason
behind these is the lack of water and long absence of rain.
Rainfall Absence & Biodiversity Extinction
According to
IWMI, out of the world’s more than two billion hungry people, 850 million
are dependent on agriculture. Their agriculture is dependent on rain for
irrigation.
In the
Sub-Saharan Africa, 95 per cent of farmers rely on rain, as well as 90 per cent in Latin America,
less than 70 per cent in the Near East and East Africa, in addition to 60
per cent in South Asia, while, in Southeast Asia, the picture is more mixed.
The
statistics mean that some yields from crops such as tubers which is a staple
crop, have decreased significantly. People dependent on rain-fed
agriculture are highly vulnerable to both short-term (2-3 weeks) and long-term
(seasonal) droughts, the IWMI report explained.
But not only
are humans but also biodiversity is suffering as well. The Millennium Ecosystem
Assessment reported that diminishing water availability has devastated many
ecosystems.
It said some
500 to 1,000 vertebrate species suffer in tropical and subtropical moist
broadleaf forests. After them comes those in grasslands and
shrublands. Afterwards, those in desert and xeric shrublands, followed by
the ones native to tropical and subtropical grasslands. That’s in addition
to savannas and tropical and subtropical coniferous forests and mangroves.
Wanted: Magic from Sky
The absence
or shortage of rainfall has been of increasing concern since the 1970s.
One of the most popular weather modification discoveries is cloud seeding. This
method initiates rainfall by targeting clouds. Seeding can occur from an
aircraft or from the ground with as silver iodide, dry ice and salt.
But if cloud
seeding works, why isn’t it implemented in many of the world’s regions that are
water scarce? “Simple, there aren’t enough clouds or there is unfavorable cloud
formation. Cloud seeding cannot happen without clouds”, a scientist from the
Philippine Atmospheric, Geophysical and Astronomical Services Administration
(PAGASA), said.
“Artificial
rainmaking, one must understand, aims to create rainfall by inducing
precipitation in clouds”, he said. The use of silver iodide salts or dry ice is
useless without cloud presence, he added.
Scientists
from the Australian Commonwealth Science and Industrial Research Organization
(CSIRO) said cloud composition, temperature and cloud diversion also have
direct relationship to the success of artificial rainmaking.
Clouds are
classified according to their appearance and height from the ground. This
classification system is: 1) Cirro. 2) Alto. 3) Strato. 4) Nimbo. 5) Cumulo.
How Does It Work?
A World
Meteorological Organization (WMO) primer explains that not all types of cloud
favor cloud seeding. The most likely to allow artificial rainmaking are Cumulus
Clouds, a cauliflower-like type of clouds.
The cloud
forms from updrafts of warm, moist air into an atmosphere that is unstable.
Intense daytime heating of the near-surface layer of air, or a wedge of cold
air moving across the state (as a cold front), usually triggers the formation
of convective clouds.
Normally, a
small percentage of cumulus clouds are needed to yield an appreciable amount of
rainfall. But these clouds that do produce rainwater are often inefficient.
Practical?
For all the
moisture they incorporate from below, only a tiny fraction of that moisture (as
cloud droplets) is ever used to grow large raindrops, which ultimately fall to
the ground as rainfall.
Tiny cloud
droplets must collide with neighboring droplets enough number of times to yield
larger drops and eventually rainwater. Seeding, using silver iodide is placed
in the upper portion of the growing convective cloud rich with supercooled
droplets. The silver iodide crystal can grow rapidly by tapping that vast field
of available moisture.
Because the
vapor pressure gradient over ice is less than that over water, the crystal such
as silver iodide will more readily attract the tiny cloud droplets. In a matter
of moments, the ice crystal transform into a large raindrop which is heavy
enough to fall through the cloud mass as a rain shaft.
The silver
iodide particles are released from below cloud base, using the strong
updraft of the cloud to transport the “seeds” high into the core of the cloud
where supercooled cloud droplets are plentiful.
To seed
clouds, pyrotechnics or flares consisting of silver iodide burn while mounted
on the wings of an aircraft that maneuvers within the updraft field below the
bottom of the cloud.
Seeding Time
At times the
seeding material can be dispensed below cloud base from an aircraft that is
equipped with wing-tipped generators that contain a solution of acetone mixed
with seeding material.
Cloud
seeding can take place above the cloud top, using an aircraft equipped
with a rack containing pyrotechnics. These droppable flares are ignited as they
fall from the plane’s belly into the upper region of seedable convective
clouds.
Either way,
from above cloud top or below cloud the base, seeding with silver iodide gives
an ample number of “seeds” with which to grow rainwater: one gram of silver
iodide can supply as many as ten trillion artificial ice crystals!
For now,
many countries continue to conduct researches and studies on more effective
methods of producing artificial rain because the demand has become greater
especially for agricultural and domestic use. Others, like China, in fact claim
to have done the opposite; stop rains, rather than produce some, which actually
happened during the Beijing 2008 Olympic Games.
But
meteorological science is more concerned in producing water in light of the
worsening climate changes. Water productivity policies dot many countries’
national plans and these include looking at cloud seeding either as a band-aid
or cure-all for their water headaches.