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Humans are cause of diminishing water flow in the West


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The Rocky Mountains have warmed by 2 degrees Fahrenheit. The snowpack in the Sierras has dwindled by 20 percent and the temperatures there have heated up by 1.7 degrees Fahrenheit.


All could lead to dire consequences for the water supply in the Western United States, including California. Scientists have noted that water flow in the West has decreased for the last 20 to 30 years, but had never explained why it was happening.


Until now. Scientists from Lawrence Livermore National Laboratory’s Program for Climate Model Diagnosis and Intercomparison in collaboration with Scripps Institution of Oceanography, have pinpointed the cause of that diminishing water flow on a regional scale: humans.


The research appears in the Jan. 31 online edition of Science Express. The findings also were presented at last year’s annual fall meeting of the American Geophysical Union.


“We looked at whether there is a human-caused climate change where we live, and in aspects of our climate that we really care about,” said Benjamin Santer of LLNL and co-author of the paper. “No matter what we did, we couldn’t shake this robust conclusion that human-caused warming is affecting water resources here in the Western United States.”


By looking at air temperatures, river flow and snowpack over the last 50 years, the team determined that the human-induced increase in greenhouse gases has seriously affected the water supply in the West. And the future brings more of the same.


“It’s pretty much the same throughout all of the Western United States,” said Tim Barnett of Scripps and a co-author of the paper. “The results are being driven by temperature change. And that temperature change is caused by us.”


The team scaled down global climate models to the regional scale and compared the results to observations over the last 50 years. The results were solid, giving the team confidence that they could use the same models to predict the effects of the global scale increase in greenhouse gases on the Western United States in the future.


The projected consequences are bleak.


By 2040, most of the snowpack in the Sierras and Colorado Rockies would melt by April 1 of each year because of rising air temperatures. The earlier snow melt would lead to a shift in river flows.


The shift could lead to flooding in California’s Central Valley. Currently, state reservoirs are filled during the rainy season. As the water is drawn down, the reservoirs are replenished with snow melt from the Sierras.


If that snow melts earlier, as predicted in the climate models, the reservoirs could overflow.


“We are headed for a water crisis in the Western United States that has already started,” Barnett said. “A couple of decades ahead, we might not have that snowpack, making us more susceptible to flooding.”


Santer said the increase in predicted river flow should be a wake- up call to officials that the water supply infrastructure needs to be updated now, as opposed to waiting until the situation is urgent.


As for the warming, with the existing greenhouse gas in the atmosphere, the Earth will continue to warm for the next 80-100 years.


“For someone who has seven grandchildren, that scares the hell out of me,” Barnett said. “I’ve seen the future and I don’t like it.”


Other Livermore contributors included Celine Bonfils, Govindasamy Bala and Art Mirin.


Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by Lawrence Livermore National Security, LLC for the U.S. Department of Energy's National Nuclear Security Administration.


For more information contact Contact:Anne M. Stark

Phone: (925) 422-9799

E-mail: stark8@llnl.gov

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Water scarcity is an issue in the Himalayas as well. When we first began our research, the problems and issues of middle mountain watersheds

were thought to be deforestation, increasing erosion, declining crop yields, and farm incomes. Floods were seen as significant problems for both middle mountain inhabitants and downstream dwellers.


However, after nine years of research a different picture emerged, backed by interaction with watershed residents and farmers as well as by

exhaustive data collection and analysis. The research carried out is undoubtedly one of the most detailed and geographically widespread

environmental research projects undertaken in the Himalayas.


Land transformation may result in a wide variety of changes, many of which can be significant on the global scale – including greenhouse gases and potential global warming, loss of biodiversity and loss of soil resources, and the regional impacts contributing to climate change. In the mountains, watersheds can be considered as functional units of natural resource management for sustainable development.


Understanding the dynamics of watershed functions includes physical characteristics such as hydroecological linkages between land uses, resource

dimensions, and socioeconomic conditions. Socio-economic demands and natural resource use are interactive (Rai and Sharma 1998; Sharma et al. 1998). Increasing stresses on natural resource use and their impacts at the watershed level can also result in cumulative impacts at the regional level. Carbon is an important indicator for studying the mechanisms of change in watershed functioning as a result of changing land-use in mountain areas.


Of the estimated eight billion tons of carbon dioxide injected annually into the air by human activity, threefourths come from the burning of fossil fuel and the remainder from land-use change and cultivation of land for agriculture (Odum 1971).


Over the last three centuries, the total global area of forests and woodlands has decreased by 12 trillion sq km, grasslands and pastures have declined by 5.6 trillion sq km, and croplands have increased by 12 trillion sq km (Richards 1990). Such large-scale change has consequences on regional and global climate, more prominently through modification of global carbon, nitrogen, and water cycles, and increased rates of extinction of biological resources. Changes, in terms of both the conversion of land for cultivation and the intensification of agriculture on land already cultivated, have accelerated globally.


The importance of community involvement rather than government action is needed to improve domestic water supply. This involvement starts in the planning phase of a water supply scheme.


How is the watershed defined? By whom? What watershed services are perceived by different actors?


How do local people manage the ecosystem's capacity behind those services; viz., management practices, local institutions, and governance



How are local people affected by large-scale processes (state conservation and development policies, market economy, technology innovations,

and climate changes), and how do they shape or cope with the resulting changes?


What are the interactions between upstream and downstream? How do the local communities link with institutions and organisations on other scales

and what are the roles of social networks in resilient livelihoods?


Are there any win-win scenarios or good practices? Can they be duplicated and in which conditions?


How can macro-watershed regional perspectives and comparative analysis contribute to new dialogue and policy-making processes?

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