Global Climate Change and Water: What Might the Future Hold?
Imagine for a moment a California where the average daily temperature is 5 degrees warmer, where the typical long, dry summer is altered by rainstorms, where winter in the Sierra Nevada brings less snow and more rain and where the Pacific Ocean has risen several feet, forever altering the coastline. It is a future in which droughts and floods could be more severe, unseasonal rain could arrive during a crucial crop or harvest period and levees in the Sacramento-San Joaquin Delta could be overcome by rising sea levels.
Or, then again, maybe not.
That is the underlying dilemma when it comes to predicting climate change. There are no absolutes, only computer projections, hypotheses and scenarios as scientists try to develop a forecast of how global warming will affect climate in the 21st century. The issue is further complicated by the West’s variable weather. There is no “normal” rainfall, only precipitation averages based on a past replete with drought and flood, flood and drought. And the historical record in some areas goes back less than 100 years, an eyewink in geologic time.
Leaving aside the debate of how to reduce manmade carbon dioxide (CO2) emissions – believed to be a leading cause of global warming – the majority of scientists say that existing CO2 emission levels will continue the trend toward warmer temperatures throughout the world. In 1995, the Intergovernmental Panel on Climatic Change (IPPC) determined that average global temperatures had risen between 0.3 and 0.6 degrees Celsius (C) since the late 19th century, equivalent to about 1 degree Fahrenheit (F). (The IPPC was established in 1988 by the United Nations Environment Programme and the World Meteorological Organization.) Sea levels have risen 4 to 10 inches during that same time frame. If CO2 buildup continues, the IPPC estimates that the average daily temperature will be 1 to 3 degrees C higher in 2100, about 2 to 5.4 degrees F. For the Western United States, some researchers say the rise in temperature would be at the high end. The warming is expected to cause thermal expansion of the oceans, which, along with melting glaciers, could cause sea levels to rise from 6 inches to 3 feet.
Globally, scientists predict that warmer temperatures will increase overall precipitation. Regional changes, however, may be quite different from changes in global averages. In the West, snowfall is expected to decrease even as precipitation increases, with a pattern that is likely to be highly variable. There is some speculation that El Niño events could occur more frequently.
“…[California's] complex natural systems and extensive human activities are highly susceptible to climate variability and change,” said a white paper on climate change prepared for a recent workshop at the University of California, Santa Barbara, sponsored by the National Science Foundation. “The prospect of increased variability in climate patterns should therefore be a major consideration for all Californians in planning the state’s future.”
The computer models and hypotheses developed in a number of climate change studies project a sobering future for the region. For rivers in the Sacramento-San Joaquin River Basin, researchers generally predict a future of more winter runoff – increasing flood risks – and less summer runoff, increasing risks of water cutbacks. For the Colorado River Basin, even if precipitation increases, a number of hypothetical scenarios point to a reduction in streamflow and a greater risk of drought if average daily temperatures increase.
The results and/or uncertainties in the results of such studies, however, are difficult to quantify. The most direct means of estimating future water supplies with a scenario of warmer temperatures is to use a computer model in which changes in climate are plugged into an equation to predict changes in streamflow. The problem with this approach is it assumes the relationship between the two sets of data will not change – an assumption that flies in the face of the belief that climate change will increase variability. And researchers are cautious about the accuracy of some of the earlier computer models.
Another approach builds upon those mathematical models by factoring in various scenarios, for example reservoir storage, and their relationship to the empirical data of temperature increase and change in overall precipitation. These scenarios, however, are based on hypotheses, which, by definition are unproved theories, propositions or suggestions.
All of these ifs, maybes and coulds make it difficult to determine what the actual effects of climate change and variability will mean for water systems in the Western United States. As with other issues such as ecosystem restoration, the quest for absolutes by the water industry, which is dominated by engineers, can collide with the hypotheses and scenarios commonly developed by hydrologists, climatologists, meteorologists and economists.
“Among the engineering community, I think there is a great deal of skepticism about climate change and global warming,” said Maurice Roos, chief hydrologist at the California Department of Water Resources (DWR). “There are also a lot of pressing, short-term problems to focus on and these issues are 50 to 100 years out in the future.”
“The possible changes are not at all sure and the range of forecasted changes is large,” said Raymond Hart, deputy director at DWR. “The most important parameter is detailed precipitation information at the regional level which is poorly modeled by the existing climatic models, at least from what we have seen. A rather small shift in precipitation can have large impacts on runoff and therefore water supply. Because of the uncertainty on possible future climatic change, major outlays or efforts to prevent what may only be a possible problem during the design life of facilities do not seem warranted now.”
The history of water development in California, however, illustrates a focus on the future. Engineers, water planners and policy-makers foresaw the need for building surface water systems to capture, store and distribute water for agricultural and industrial use, helping the state develop a trillion dollar economy, the seventh largest in the world.
Yet how do you plan an adjustment to climate change when its actual effects are unclear? No model or study can provide a precise picture of future climate change or determine exactly when its force will be felt. Add to the complexity of climate change the pressing short-term issues of the day, and the apparent course of action becomes even less clear.
“With all of these climate change scenarios, you have to take them with a big grain of salt because we don’t know what the precipitation and the temperature will be. But these studies all point in the same direction,” said Kathleen Miller, an economist at the Environmental and Societal Impacts Group at the National Center for Atmospheric Research. Miller reviewed climate change studies in preparation of a report, Climate Variability, Climate Change, and Western Water, on global warming and climate change for the Western Water Policy Review Advisory Commission. “The point I’ve been trying to get across is, ‘We can’t give you the specifics and you need to be prepared to deal with the uncertainties.’ I think everyone would be better off if they were aware that big changes are possible.”
This issue of Western Water explores the topic of global warming and its possible effects on water resources in California and the Colorado River Basin. It offers an overview of global warming and projected impacts; discusses the natural variability of Western climate, including El Niño and La Nina events; outlines ongoing research to develop past flood and drought records; and discusses the predictions of some climate change studies.
by Sue McClurg
A complete copy of this article is available for $3. Contact the Foundation and request a copy of the May/June 1998 Western Water.
Our new California Water Map is showing up at highway rest stops. Look for the water map as you travel around California. Staff member Lois Rein has been doing a great job working with the 30 Caltrans district maintenance offices to get the map up at every rest stop in the state. I met recently with Caltrans Director James van Loben Sels to get him on board with this project and present him with a copy of the map. By coincidence, his dad worked on the building of the State Water Project in the 1960s so Mr. van Loben Sels remains interested in water project locations and water resource issues. If you don’t see a water map at a rest stop in California, please call Lois. She’s now working on getting the Colorado River Water Map at rest stops around the West.
Climate change and how it affects water is the topic of this magazine. In the last couple of years Chief Writer Sue McClurg and I have heard a number of intriguing presentations about climate change and water resources in the West. It seems to us as laypersons that the majority of scientists agree something in this area is happening, they just can’t agree on what. In this El Niño year, it seemed timely for the Foundation to give this topic a journalistic review. While there are many uncertainties, I liked the advice of Dr. Kathleen Miller when she says not to take these predictions too seriously but that water managers should be prepared to deal with the uncertainties and be aware that change is possible.
Change is certainly coming to the Foundation with the announcement that Program Director Valerie Holcomb is leaving us to go to CALFED and assist them in solving a long-term California water problem – finding a Delta solution. I’m sad that CALFED is taking one of our valuable staff members but happy for them since they will be assisted by such a good organizer and communicator. During the eight years she spent with us, Valerie was a big part of our growth and success. When she came on board, we had an annual budget of about $400,000 and now, at $1.2 million, we’ve tripled that amount. During these years, she’s written and managed our grants, and developed and assisted us with some great programs. One of those programs was our series of town hall meetings on local water issues. I remember the summer we had such good times traveling around California to town hall water meetings with our young children, getting them to hand out Foundation materials.
Foundation board members, staff and supporters have had some great times with Valerie in between the serious issues, especially on the many water tours she organized. So its with deep affection that we say goodbye to Valerie Holcomb. Valerie recently married Byron Buck, executive director of the California Urban Water Agencies. So she’s on to a new job and a new life.
In the News
A decade after it was authorized by Contra Costa County voters, Los Vaqueros Reservoir began to fill with El Niño runoff and Delta inflow just in time for its May 2 dedication ceremony. The offstream storage reservoir is the first major water project built in northern California in 10 years.
The 100,000 acre-feet reservoir will allow Contra Costa Water District (CCWD) to improve the quality of the water it delivers to 400,000 customers in the east bay area. The district diverts water directly from the Sacramento-San Joaquin River Delta, which, in times of low outflow, is influenced by the salt water from San Francisco Bay. This was especially true during the 1987-1993 drought. Now, water district managers can divert better quality water during periods of high flow, store it in Los Vaqueros, and tap the better quality, stored water during the summer and fall months, reducing the salt content of the water that flows from customers’ faucets.
The district’s goal is to provide customers with water with 65 milligrams or less of sodium per liter. Customers can taste the salt when it reaches 100 milligrams per liter.
“Throughout its 60-year history, this water district has had to contend with high salinity in its Delta water supply,” said CCWD board President Joseph Campbell. “Los Vaqueros will solve that problem. It allows the district to capture good-quality Delta water, store it, and use it for blending or an emergency supply.”
CCWD voters approved the $450 million project in 1988, which was funded by increases in water rates. About $10 of the average single-family monthly water bill of $42 goes toward the reservoir. Along with the reservoir, the project included construction of a new pipeline and diversion point in Old River.
Construction on the project began in 1994. The reservoir, which could take 18 months to fill, is formed by the 192-foot high Los Vaqueros Dam located in the East Contra Costa County foothills near Brentwood. At its base, the 900-foot-long earthfill dam - composed of rock, clay and sandstone excavated from the reservoir site – is 1,000-feet thick.
Because the reservoir is a drinking water source, no body contact (swimming) or gasoline-powered boats will be allowed at Los Vaqueros, although electric boats and fishing may be allowed. Water district officials are still developing a recreation plan, but hiking and picnicking areas will be available. CCWD is developing 55 miles of hiking trails in the reservoir’s watershed, which includes 18,500 acres of dedicated open space, and a watershed education and stewardship program.
CCWD also was required to develop 19 acres of new wetlands and enhance 30 acres of existing wetlands for environmental mitigation. Several endangered and threatened species live at the site, including the red-legged frog, California tiger salamander and San Joaquin Valley kit fox.