Cloud seeding is a form of weather modification which involves the introduction of silver iodide (or sometimes dry ice) into the clouds to activate the formation of precipitation in the form of rain or snow. Cloud seeding has evolved over the years and scientists now know more about the process and what works and what doesn’t.
The technology of seeding clouds was introduced 70 years ago by the experiments of Vincent Schaefer. In 1946, this self-taught chemist seeded clouds over the mountains of Massachusetts with six pounds of dry ice. This experiment resulted in snowfall. Since then, his experiment has led to the belief that cloud seeding could be an answer to the ongoing problems of drought, control of forest fires, control of mega storms and the reduction of damaging hail.
Los Angeles County has attempted to increase precipitation by using cloud seeding since 1950‘s. In the recent rainfall in early March, 2016, clouds were seeded over Los Angeles. This was the first cloud seeding in LA done by the Department of Public Works since 2005.
How Is Cloud Seeding Done?
There are a couple ways to seed clouds. One way is via an airplane flying into the clouds with flares on the wings to release aerosolized silver iodide to stimulate rain and snow. Another way is using generators, which resemble mini missile launchers that sit on the ground and shoot silver iodide smoke into the clouds. The particles in the smoke attract water vapor which freeze onto the particles. When the frozen particles become heavy enough, they fall as rain.
Is Cloud Seeding Safe?
Because the small amount of silver iodide that is used, it is generally conceeded that cloud seeding does not harm the environment. According to the Centers for Disease Control and Prevention, “there is no reason to fear any toxic effects.”
Does Cloud Seeding Really Work?
The process of cloud seeding has improved over the years, but there is a difference of opinion as to whether or not cloud seeding really works, and if there are any long-term negative repercussions on the environment from the use of this process. In an article published in the LA Times, the Los Angeles County officials stated that their studies show that cloud seeding results in about a 15 percent increase in rainfall. However, there is is some disagreement coming from the scientific community regarding this figure. To quote from Lynn Russell of Scripts Institute’s Department of Atmospheric Chemistry, “there is no scientist who actually thinks that cloud seeding works.” She stated in an interview with NBC San Diego, that “there is has been no scientific increase in rainfall totals when seeding techniques are used.” In addition, there are still questions about how much extra precipitation seeding actually creates. The Desert Research Institute of Nevada has estimated that cloud seeding has produced an increase of ten percent in the snowpack. However, in 2013, the California Department of Water Resources issued a report that stated that cloud seeding only produced an average snowpack of four percent.
The Future of Cloud Seeding
Cloud seeding programs across the country are awaiting the completion of a 13 million dollar study started in 2005 by the state of Wyoming. This is the first truly exhaustive, in depth study of the technology. It will attempt to determine whether or not cloud seeding will increase the snowpack in the state’s mountain ranges. It is believed by many in the field that this study will bring new credence to the process.
However, Robert Moore of the National Resources Defence Council (NRDC) states that “the efficient use of water is the cheapest and most reliable way of making more of it available for future use.”
Sources:
https://weather.com/science/environment/news/california-cloud-seeding http://www.governing.com/topics/transportation-infrastructure/gov-california-tries-to-make-snow.html https://www.youtube.com/watch?v=zlX7rJv_m0g http://touch.latimes.com/#section/-1/article/p2p-86155840/
[Sacramento] – As winter storms slowly boost water supply, the Department of Water Resources has increased its water delivery estimate for most recipients from 10 percent of requests for the calendar year, as announced in December, to 15 percent.
“Our modest increase underscores the fact that we still have a critical water shortage after four-plus years of drought that we don’t know when will end,” said DWR Director Mark Cowin. “One look at our low reservoirs tells us that we need a lot more wet weather before summer.”
Although there is no exact formula for ending the drought and conditions vary region by region, a rough guidepost is that approximately 150 percent of average winter precipitation – rain and snow – would significantly ease statewide conditions, with the major exception of groundwater depletion.
The State Water Project (SWP) delivery estimate (allocation) may be increased further if storms continue to build rainfall and snowpack totals. The 29 public agencies that receive SWP water (State Water Project Contractors) requested 4,172,786 acre-feet of water for 2016. With today’s allocation increase, they will receive 631,115 acre-feet.
Collectively, the SWP Contractors serve approximately 25 million Californians and just under a million acres of irrigated farmland. It is important to note that nearly all areas served by the SWP also have other sources of water, among them streams, groundwater and local reservoirs.
Key reservoirs are beginning to rise from early winter storms, but remain low. Lake Oroville in Butte County, the State Water Project’s principal reservoir, early this morning was holding 1,366,061 acre-feet, 39 percent of its 3.5 million acre-foot capacity and 60 percent of its historical average for the date. Shasta Lake north of Redding, California’s and the federal Central Valley Project’s (CVP) largest reservoir, was holding 2,138,566 acre-feet, 47 percent of its 4.5 million acre-foot capacity and 71 percent of its historical average. San Luis Reservoir, a critical south-of-Delta pool for both the SWP and CVP, reflects the same trend of lower reservoir storage this year. San Luis was holding 641,729 acre-feet, 31 percent of its 2 million acre-foot capacity and 41 percent of normal for the date. Folsom Lake, a CVP reservoir near Sacramento, is holding 398,523 acre-feet of its 977,000 acre-foot capacity, 79 percent of average for the date.
Though still critically low, many reservoir levels have dramatically risen from recent storm runoff. Groundwater aquifers recharge more slowly, with many in the Central Valley sinking toward record levels.
Last year’s (2015) 20 percent allocation was the second lowest since 1991, when agricultural customers of the SWP got a zero allocation and municipal customers received 30 percent of requests. In 2014, SWP deliveries were five percent of requested amounts for all customers.
The last 100 percent allocation – difficult to achieve even in wet years largely because of Delta pumping restrictions to protect threatened and endangered fish species – was in 2006. SWP allocations in recent years:
2015 – 20 percent
2014 – 5 percent
2013 – 35 percent
2012 – 65 percent
2011 – 80 percent
2010 – 50 percent
2009 – 40 percent
2008 – 35 percent
2007 – 60 percent
2006 – 100 percent
Governor Edmund G. Brown Jr. declared a drought state of emergency on January 17, 2014 and followed up with statewide water conservation mandates. Since then, the state has been swept by drought-fueled forest fires, vast tracts of farmland have been fallowed and some communities have scrambled for drinking water.
Long-range weather forecasts are uncertain, and there is no way to know if this winter will deeply dent the state’s historic drought.
So far the recent El Nino storms have only slightly increased the levels of reservoirs in California,
reaching half of historic depths for this time of year. The federally operated reservoirs that supply California's farms and cities, are now 49 percent full, compared with 47 percent on Oct. 1, according to the U.S. Bureau of Reclamation.
The good news is that the Sierra Nevada snowpack is seeing an increase after 4 years of drought conditions, and when this starts to melt off, it will help replenish the critically low reservoirs. There are also more El Nino storms coming to California in the next two months which will also help add to water and snow levels.
This month the California Department of Water Resources and the U.S. Bureau of Reclamation have finalized the 2016 Drought Contingency Plan that outlines State Water Project and Central Valley Project operations for February-November 2016.
The plan was developed in coordination with staff from State and federal agencies, including the U.S. Fish and Wildlife Service, National Marine Fisheries Service, California Department of Fish and Wildlife, and the State Water Resources Control Board (SWB). It focuses on water project operations as related to SWB Water Rights Decision-1641 and the potential modification requests needed to balance the competing needs and benefits of our limited water supplies in the context of consecutive dry years. One of the key purposes of this plan is to communicate overarching goals for 2016 water management and the potential operations needed to achieve those goals for water resources stakeholders and the public. Read more: 2016 Drought Contingency Plan