CalClim: California Climate Data Archive

CALIFORNIA CLIMATE WATCH
CURRENT ISSUE: April 2005

Read the full newsletter here: Word Format or PDF format

Today's Snow, Tomorrow's Tap Water

By Laura Edwards
Western Regional Climate Center

In California, water resources and their management are essential to our everyday lives. The snowpack stored high in the mountains is the state's largest "reservoir", naturally produced each winter, supplying up to 70% of our water for the year. As a result, climate impacts on that snowpack are integral to the management of this resource in the future.

Figure 1, right. The author on a snow survey in the Lake Tahoe area, spring 2005.

Dr. Dan Cayan and colleagues (1) have studied climate impacts on flora and snowpack concurrently. They found that indeed, spring melt has occurred earlier with increasing average temperatures, in parallel to first blooms on lilac and honeysuckle. The implications of earlier spring snowmelt are far-reaching when you take into consideration the climatological dry summers in the state and the water demands for agriculture and from the population. In the High Sierra, snow often lingers into the early summer at the mountain tops. A slower melt season is advantageous for water supply operators, in order for them to maintain the maximum storage in the reservoirs. An earlier snowmelt would drive higher streamflows earlier in the year as well, depleting the storage that mountain snowpack provides.

Foothills to the Sierra Nevada are the most vulnerable, as they are in the transition region from rain to snow. This region could become a rain-only zone in a warmer climate. Research has shown that with warmer annual average temperatures come warmer springs and autumns, seasons where snowmelt and snow accumulation are crucial. Dr. Jessica Lundquist has studied the snowpack in Yosemite National Park (see http://www.yosemite.org/naturenotes/naturenotes_synchsnow.htm, 2). In the mountains, there can be an onset date when the snow begins to melt at almost all elevations, what is term a synchronous melt. This date of spring pulse has been occurring earlier than in decades past, and is projected to continue this trend in the future, by as much as a month earlier by 2100. There are also nonsynchronous years, where the snow melts gradually from lower to higher elevations. Learning more about predicting which phenomenon will occur and, in the synchronous case, what that date may be are continuing areas of research for Dr. Lundquist.

Figure 2, below. March 29, or day 88, was the 2002 onset date of snowmelt in the Tuolumne River in Yosemite National Park. By Dr. Jessica Lundquist, http://www.yosemite.org/naturenotes/naturenotes_synchsnow.htm

Climate prediction models and observations over the last 50 years both point to more precipitation falling as rain than snow in a warmer climate (3, 4). This affects the amount of snow that is stored in the snowpack. Dr. Satish K. Regonda and colleagues found that "winter precipitation seems to be generally increasing, but there is no clear increase in spring streamflows", suggesting more rain and less snow. Dr. Phil Mote and his colleagues have determined that the average April 1 snowpack in western North America has been reducing. Climate modellers have run a number of different scenarios, with various combinations of greenhouse gas emissions, and all have shown changes in streamflow and snowmelt in the future.

Dr. Olli Varis and colleagues have written a paper on combining the work of climate modellers and integrating this into water resource management (5). It is a challenge to combine the research results with water management due to the other aspects they need to consider, such as changes in demography and land use. Downscaling global climate models to a regional scale have been one helpful tool for water managers. There are a few different methods in downscaling global climate models, and each has advantages and disadvantages. One somewhat formidable roadblock for water managers is the "very crude, unreliable, and often even inappropriate" output from the models. Perhaps fortunately more and more water managers are acknowledging work in changing climate scenarios and considering these studies in their long-term decision making and planning.

1. Cayan, D. R., S. A. Kammerdiener, M. D. Dettinger, J. M. Caprio, and D. H. Peterson, 2001. Changes in the onset of spring in the western United States . Bull. Am Meteor. Soc., 82 (3), pp 399-415.

2. Lundquist, J., 2005. Onset of snowmelt and streamflow in a warmer world. Bull. Am. Meteor. Soc., 86 (4), pp. 480-482.

3. Regonda, S. K., B. Rajagopalan, M. Clark, J. Pitlick, 2005. Seasonal cycle shifts in hydroclimatology over the western United States . J. Climate, 18 (2), pp. 372-384.

4. Dettinger, M. D., D. R. Cayan, M. K. Meyer, and A. E. Jeton, 2004. Simulated hydrologic responses to climate variations and change in the Merced , Carson , and American River basins , Sierra Nevada , California , 1900-2099. Clim. Change, 62 , pp. 283-317.

5. Varis, O., T. Kajander and R. Lemmela, 2004. Climate and water: from climate models to water resources management and vice versa. Clim. Change, 66 , pp. 321-344.

For further reading:

Stewart, I. T., D. R. Cayan, M. D. Dettinger, 2005. Changes toward earlier streamflow timing across western North America . J. Climate, 18 (8), pp. 1136-1155.

Page last updated 6/14/05.

HOME	Data & Products	Monitoring & Forecasts	Related Research	Links	Site Map
Contact Us/Data Request Form	© 2004-2008 WESTERN REGIONAL CLIMATE CENTER. ALL RIGHTS RESERVED.

Climate Watch Archive All data in the Climate Watch is provisional and subject to change. Jan 2005 [PDF] [Word] Feb 2005 [PDF] [Word] Mar 2005 [PDF] [Word] Apr 2005 [PDF] [Word] May 2005 [PDF] [Word] For 2004 stories, click here Monthly Weather Summaries 2005 2004	CALIFORNIA CLIMATE WATCH CURRENT ISSUE: April 2005 Read the full newsletter here: Word Format or PDF format Today's Snow, Tomorrow's Tap Water By Laura Edwards Western Regional Climate Center In California, water resources and their management are essential to our everyday lives. The snowpack stored high in the mountains is the state's largest "reservoir", naturally produced each winter, supplying up to 70% of our water for the year. As a result, climate impacts on that snowpack are integral to the management of this resource in the future. Figure 1, right. The author on a snow survey in the Lake Tahoe area, spring 2005. Dr. Dan Cayan and colleagues (1) have studied climate impacts on flora and snowpack concurrently. They found that indeed, spring melt has occurred earlier with increasing average temperatures, in parallel to first blooms on lilac and honeysuckle. The implications of earlier spring snowmelt are far-reaching when you take into consideration the climatological dry summers in the state and the water demands for agriculture and from the population. In the High Sierra, snow often lingers into the early summer at the mountain tops. A slower melt season is advantageous for water supply operators, in order for them to maintain the maximum storage in the reservoirs. An earlier snowmelt would drive higher streamflows earlier in the year as well, depleting the storage that mountain snowpack provides. Foothills to the Sierra Nevada are the most vulnerable, as they are in the transition region from rain to snow. This region could become a rain-only zone in a warmer climate. Research has shown that with warmer annual average temperatures come warmer springs and autumns, seasons where snowmelt and snow accumulation are crucial. Dr. Jessica Lundquist has studied the snowpack in Yosemite National Park (see http://www.yosemite.org/naturenotes/naturenotes_synchsnow.htm, 2). In the mountains, there can be an onset date when the snow begins to melt at almost all elevations, what is term a synchronous melt. This date of spring pulse has been occurring earlier than in decades past, and is projected to continue this trend in the future, by as much as a month earlier by 2100. There are also nonsynchronous years, where the snow melts gradually from lower to higher elevations. Learning more about predicting which phenomenon will occur and, in the synchronous case, what that date may be are continuing areas of research for Dr. Lundquist. Figure 2, below. March 29, or day 88, was the 2002 onset date of snowmelt in the Tuolumne River in Yosemite National Park. By Dr. Jessica Lundquist, http://www.yosemite.org/naturenotes/naturenotes_synchsnow.htm Climate prediction models and observations over the last 50 years both point to more precipitation falling as rain than snow in a warmer climate (3, 4). This affects the amount of snow that is stored in the snowpack. Dr. Satish K. Regonda and colleagues found that "winter precipitation seems to be generally increasing, but there is no clear increase in spring streamflows", suggesting more rain and less snow. Dr. Phil Mote and his colleagues have determined that the average April 1 snowpack in western North America has been reducing. Climate modellers have run a number of different scenarios, with various combinations of greenhouse gas emissions, and all have shown changes in streamflow and snowmelt in the future. Dr. Olli Varis and colleagues have written a paper on combining the work of climate modellers and integrating this into water resource management (5). It is a challenge to combine the research results with water management due to the other aspects they need to consider, such as changes in demography and land use. Downscaling global climate models to a regional scale have been one helpful tool for water managers. There are a few different methods in downscaling global climate models, and each has advantages and disadvantages. One somewhat formidable roadblock for water managers is the "very crude, unreliable, and often even inappropriate" output from the models. Perhaps fortunately more and more water managers are acknowledging work in changing climate scenarios and considering these studies in their long-term decision making and planning. 1. Cayan, D. R., S. A. Kammerdiener, M. D. Dettinger, J. M. Caprio, and D. H. Peterson, 2001. Changes in the onset of spring in the western United States . Bull. Am Meteor. Soc., 82 (3), pp 399-415. 2. Lundquist, J., 2005. Onset of snowmelt and streamflow in a warmer world. Bull. Am. Meteor. Soc., 86 (4), pp. 480-482. 3. Regonda, S. K., B. Rajagopalan, M. Clark, J. Pitlick, 2005. Seasonal cycle shifts in hydroclimatology over the western United States . J. Climate, 18 (2), pp. 372-384. 4. Dettinger, M. D., D. R. Cayan, M. K. Meyer, and A. E. Jeton, 2004. Simulated hydrologic responses to climate variations and change in the Merced , Carson , and American River basins , Sierra Nevada , California , 1900-2099. Clim. Change, 62 , pp. 283-317. 5. Varis, O., T. Kajander and R. Lemmela, 2004. Climate and water: from climate models to water resources management and vice versa. Clim. Change, 66 , pp. 321-344. For further reading: Stewart, I. T., D. R. Cayan, M. D. Dettinger, 2005. Changes toward earlier streamflow timing across western North America . J. Climate, 18 (8), pp. 1136-1155. Page last updated 6/14/05.