Serious Water Shortage Facing California, Researchers Warn

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Energy may not be the only utility Californians should be worried about, warn UC Berkeley scientists who sugggest that the state could be on the verge of an impending water shortage.

According to predictions by researchers from the Lawrence Berkeley National Laboratory, the continual global warming associated with increasing atmospheric levels of carbon dioxide may leave the state of California with serious water problems over the next 50 years.

Using regional climate models based on a numerical model simulations of the earth system, scientists found that by the year 2049, the overall warming of the western region of the United States may cause water to become a scarcity.

"Climate projection have a large amount of uncertainty, but if this projection turned out to be true, then we may find California with increased winter storms and floods, warmer winters and hotter summers," said Norman Miller, an LBNL scientist. "There may be less water from the northern Sierra Nevada for agriculture and other summer time needs."

Increased atmospheric levels of carbon dioxide are a result of the burning of fossil fuels caused by human activities such as power generation, driving automobiles, heating and industrial production.

Elevated levels of the gas contribute to warmer overall temperatures and climate changes that affect the frequency and type of precipitation in affected regions.

"We may see increases in winter flooding and short water supply for the summer," said LBNL researcher Jinwon Kim. "There are other environmental and agricultural impacts associated with it."

According to Miller and Kim, if carbon dioxide levels continue to rise at the rate of 1 percent per year, the climate in western United States may consist of more rain and less snow-a combination that could lead to major water shortages during the warm season.

Snow is important because it acts as a storage system during the cold months and as a source of runoff water during the spring and summer when California typically receives little to no precipitation. Higher temperatures resulting from global warming acts to decrease the amount of snow.

"Increases in the low-atmospheric temperature raises the freezing level, reducing the amount of snowfall on the ground," Kim said. "Increased temperature also accelerates melting of snow. Combined, these effects generally reduce the amount of snow in the elevation range between one and two kilometers. Increased snow accumulation occurs only in very high elevation are where, despite the warming, near-surface temperature remains below freezing."

Whereas excess snow can serve as a water source later, increased rainfall could lead to flooding and may contribute to water shortage.

"The western United States region heavily relies on snow accumulation for water supply from the late spring to early fall," Kim said. "The projected effects show that there will be significant increase of winter rainfall while snowfall decreases due to the projected increase in low-atmospheric temperature. As a result, even though winter rainfall increases substantially, the amount of snow decreases. Unless more reservoirs are built to store increased winter time runoff, there will be a water shortage during the dry season. Building more reservoirs requires careful consideration on environment, in addition to the cost."

The high levels of water after intense rainfall cannot be saved for later use, Miller said.

"The potential for increased winter precipitation under warming future scenarios implies that snow storage that is usually available during the dry summer months may not be available," Miller said. "If there is an increase in heavy winter storms, then reservoirs will release water to protect their structural integrity when large amounts of runoff enter reservoirs. This potential increase of winter time storms also suggests potential flood increases and decreased storage."

Although the findings are only projections and may contain uncertainties, the research can still help Californians realize that fossil fuel burning has a very significant impact on the climate.

"The main goal of this paper is to report an estimated effects of increased carbon dioxide on the hydrologic cycle of the western United States," Kim said. "I believe the projections in this study is plausible, at least qualitatively. There have been plenty of warning in recent years about the potential impacts of human-induced climate change."

The findings should serve as a warning to California residents, who may not realize that the current abundance of water could soon be a luxury of the past, Miller said.

"There have been numerous reports and public oriented articles that serve as quasi-wake-up calls," Miller said. "This is not a doomsday report, but a scientific study of the potential impacts of increased greenhouse gasses and natural stressors on our already strained system. More often than not, it requires a crisis for society to wake up."

Currently, California is experiencing a period of above average precipitation, but residents need to be aware that it could be entering a period of dryness.

"The public tends to forget these natural oscillations and maintain a short term memory assuming an unlimited water supply," Miller said. "Educating the public and policy makers in a scientifically objective and understandable way will help to increase water and energy conservation and perhaps bring legislation that will increase efficiency."

In response to their projections, Miller said that there is no fast way to halt the problem.

"There is no quick fix to a potential water shortage," Miller said. "Land use change, increasing population, and other factors will continue to stress this system."

To combat global warming is a difficult and large endeavor because reducing carbon dioxide levels requires action on large levels, scientists said. They did, however, suggest actions that people can take to help stabilize levels.

Increasing levels of earth-warming gas can be combated by driving smaller cars, consuming less energy, and conserving energy use, researchers said.

"Decreasing carbon dioxide levels is not an easy task," Kim said. "Carbon sequestration has become one of a leading projects at the (Department of Energy). The best way is to reduce emission. Since reducing emission requires conservation, it also has large effects on industrial activities and economy."

The work is part of a series of studies and Miller pointed out that it is important to mention that many uncertainties exist.

"The (model) that we used was one of several that give different results," he said. "There needs to be more research with longer climate simulations using a larger number of models. The paper I presented focused more on uncertainty than just a result. We need to tell the public that there are possible outcomes and this represents only one."

For the future, both scientists plan to continue to expand their climate research by simulating other climate scenarios and critically analyzing the uncertainty for a number of past and future time periods.

"My continued research topic is to better understand dynamical and physical processes in the atmosphere and land surface, especially precipitation physics, vegetation effects, soil moisture, and improving model formulation to improve the quality of simulations," Kim said.


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