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Title: Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century

Abstract

The Southwestern United States has a greater vulnerability to climate change impacts on water security due to a reliance on snowmelt driven imported water. The State of California, which is the most populous and agriculturally productive in the United States, depends on an extensive artificial water storage and conveyance system primarily for irrigated agriculture, municipal and industrial supply and hydropower generation. Here we take an integrative high-resolution ensemble approach to examine near term climate change impacts on all imported and local sources of water supply to Southern California. While annual precipitation is projected to remain the same or slightly increase, rising temperatures result in a shift in precipitation type towards more rainfall, reducing cold season snowpack and earlier snowmelt. Associated with these hydrological changes are substantial increases in both dry and flood event frequency and intensity. On one hand, the greater probability of drought decreases imported water supply availability. On the other hand, earlier snowmelt and significantly stronger winter precipitation events pose increased flood risk requiring water releases from reservoirs for flood control, also potentially decreasing water availability. As a result, lack of timely local water resource expansion coupled with climate change projections and population increases may leave the areamore » in extended periods of shortages.« less

Authors:
 [1];  [2];  [2];  [1]; ORCiD logo [2];  [2];  [2];  [3]
  1. Loyola Marymount Univ., Los Angeles, CA (United States); Univ. of California, Los Angeles, CA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Loyola Marymount Univ., Los Angeles, CA (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1325599
Grant/Contract Number:
AC05-00OR22725; 32112413
Resource Type:
Journal Article: Published Article
Journal Name:
Environmental Research Letters
Additional Journal Information:
Journal Volume: 11; Journal Issue: 9; Journal ID: ISSN 1748-9326
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Pagán, Brianna R., Ashfaq, Moetasim, Rastogi, Deeksha, Kendall, Donald R., Kao, Shih -Chieh, Naz, Bibi S., Mei, Rui, and Pal, Jeremy S. Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century. United States: N. p., 2016. Web. doi:10.1088/1748-9326/11/9/094026.
Pagán, Brianna R., Ashfaq, Moetasim, Rastogi, Deeksha, Kendall, Donald R., Kao, Shih -Chieh, Naz, Bibi S., Mei, Rui, & Pal, Jeremy S. Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century. United States. doi:10.1088/1748-9326/11/9/094026.
Pagán, Brianna R., Ashfaq, Moetasim, Rastogi, Deeksha, Kendall, Donald R., Kao, Shih -Chieh, Naz, Bibi S., Mei, Rui, and Pal, Jeremy S. 2016. "Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century". United States. doi:10.1088/1748-9326/11/9/094026.
@article{osti_1325599,
title = {Extreme hydrological changes in the southwestern US drive reductions in water supply to Southern California by mid century},
author = {Pagán, Brianna R. and Ashfaq, Moetasim and Rastogi, Deeksha and Kendall, Donald R. and Kao, Shih -Chieh and Naz, Bibi S. and Mei, Rui and Pal, Jeremy S.},
abstractNote = {The Southwestern United States has a greater vulnerability to climate change impacts on water security due to a reliance on snowmelt driven imported water. The State of California, which is the most populous and agriculturally productive in the United States, depends on an extensive artificial water storage and conveyance system primarily for irrigated agriculture, municipal and industrial supply and hydropower generation. Here we take an integrative high-resolution ensemble approach to examine near term climate change impacts on all imported and local sources of water supply to Southern California. While annual precipitation is projected to remain the same or slightly increase, rising temperatures result in a shift in precipitation type towards more rainfall, reducing cold season snowpack and earlier snowmelt. Associated with these hydrological changes are substantial increases in both dry and flood event frequency and intensity. On one hand, the greater probability of drought decreases imported water supply availability. On the other hand, earlier snowmelt and significantly stronger winter precipitation events pose increased flood risk requiring water releases from reservoirs for flood control, also potentially decreasing water availability. As a result, lack of timely local water resource expansion coupled with climate change projections and population increases may leave the area in extended periods of shortages.},
doi = {10.1088/1748-9326/11/9/094026},
journal = {Environmental Research Letters},
number = 9,
volume = 11,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1088/1748-9326/11/9/094026

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  • The Southwestern United States has a greater vulnerability to climate change impacts on water security due to a reliance on snowmelt driven imported water. The State of California, which is the most populous and agriculturally productive in the United States, depends on an extensive artificial water storage and conveyance system primarily for irrigated agriculture, municipal and industrial supply and hydropower generation. Here we take an integrative high-resolution ensemble approach to examine near term climate change impacts on all imported and local sources of water supply to Southern California. While annual precipitation is projected to remain the same or slightly increase,more » rising temperatures result in a shift in precipitation type towards more rainfall, reducing cold season snowpack and earlier snowmelt. Associated with these hydrological changes are substantial increases in both dry and flood event frequency and intensity. On one hand, the greater probability of drought decreases imported water supply availability. On the other hand, earlier snowmelt and significantly stronger winter precipitation events pose increased flood risk requiring water releases from reservoirs for flood control, also potentially decreasing water availability. As a result, lack of timely local water resource expansion coupled with climate change projections and population increases may leave the area in extended periods of shortages.« less
  • Twenty-year return value of annual and seasonal maxima of daily precipitation are calculated from a set of transiently forced coupled general circulation model simulations. The magnitude and pattern of return values are found to be highly dependent on the seasonal cycle. A similar dependence is found for projected future changes in return values. The correlation between the spatial pattern of return value changes and mean precipitation changes is found to be low. Hence, the changes in mean precipitation do not provide significant information about changes in precipitation extreme values.
  • This study examines an ensemble of climate change projections simulated by a global climate model (GCM) and downscaled with a region climate model (RCM) to 40 km spatial resolution for the western North America. One control and three ensemble future climate simulations were produced by the GCM following a business as usual scenario for greenhouse gases and aerosols emissions from 1995 to 2100. The RCM was used to downscale the GCM control simulation (1995-2015) and each ensemble future GCM climate (2040-2060) simulation. Analyses of the regional climate simulations for the Georgia Basin/Puget Sound showed a warming of 1.5-2oC and statisticallymore » insignificant changes in precipitation by the mid-century. Climate change has large impacts on snowpack (about 50% reduction) but relatively smaller impacts on the total runoff for the basin as a whole. However, climate change can strongly affect small watersheds such as those located in the transient snow zone, causing a higher likelihood of winter flooding as a higher percentage of precipitation falls in the form of rain rather than snow, and reduced streamflow in early summer. In addition, there are large changes in the monthly total runoff above the upper 1% threshold (or flood volume) from October through May, and the December flood volume of the future climate is 60% above the maximum monthly flood volume of the control climate. Uncertainty of the climate change projections, as characterized by the spread among the ensemble future climate simulations, is relatively small for the basin mean snowpack and runoff, but increases in smaller watersheds, especially in the transient snow zone, and associated with extreme events. This emphasizes the importance of characterizing uncertainty through ensemble simulations.« less