Monday, July 31, 2017

Projecting Climate Change Impacts on Water Resources in Regions of Complex Topography: A Case Study of the Western United States and Southern California

This is the talk given by Jeremy Pal (GS) in Trento on July 26, 2017. He talked about the impact of climate change and  land use on California water resources. Actually the work he presented is part of the awarded Master Thesis of Brianna Pagàn (see last slides).
The talk presents in a plane way the issue related to water resources management of South California, Los Angeles area. It then uses an impressive set of modeling tools to pass from climate and land use changes to water availability. You can enjoy the video and get the slides too.
Here it is the abstract of the talk:
The Western United States and California have a greater potential vulnerability to climate change impacts on water resources due to a heavy reliance on snowmelt driven streamflow. California, the most agriculturally productive and populous region in the United States, depends on a complex and extensive water storage and conveyance system to supply water primarily for irrigation, municipal and industrial use and hydropower generation. This study provides an integrated approach to assess the impacts of climate change on the hydrologic cycle and extremes for all Southern Californian water supply basins:  Owens Valley, Mono Lake, Colorado River, Sacramento River, San-Joaquin River, and Tulare Lake basins. An 11-member ensemble of coupled atmosphere-ocean global climate models is first dynamically downscaled using a regional climate model and then statistically downscaled to force a hydrological model resulting in 4-km high-resolution output for the Contiguous United States. Greenhouse gas concentrations are prescribed according to historical values for the period 1976-2005 and to the IPCC Representative Concentration Pathway 8.5 for the near term future period 2021-2050. Precipitation is projected to remain the same or slightly increase by mid-century; however, rising temperatures result in a repartitioning of precipitation type towards more rainfall and therefore a reduced snowpack and earlier snowmelt. In addition to these hydrological changes, daily annual maximum runoff and precipitation events are projected to significantly increase in intensity and frequency such that future return periods change to become substantially more common. More specifically, the current daily annual maximum runoff 10-, 25-, and 50-, and 100-year events are projected to become approximately two to ten times more likely in the future. Furthermore, annual cumulative runoff volumes are projected to increase for high flow years and in contrast decrease for low flow years reducing the reliability of the system. While the escalating likelihood of drought reduces water supply availability, earlier snowmelt and significantly more intense winter precipitation events increases flood risk requiring winter releases from reservoirs for flood control purposes. All of these factors, coupled with projected increases in population, are likely to decrease supply during the higher demand drier months necessitating multiyear storage solutions for urban and agricultural regions as well as improved infrastructure and measures for flood control.

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