Tuesday, December 4, 2012

Tuolumne climate change sensitivity

Earlier this year, the SFPUC completed a report on the potential changes (increase or decrease) in Tuolumne River inflows to Hetch Hetchy Reservoir with anticipated changes in climate.  The study used modeled temperature and precipitation data from a range of previously modeled climate change scenarios.  While the likelihood of any particular climate future was not assessed, and the report doesn't seek to address potential water supply impacts of climate change, the simulated 2040, 2070, and 2100 hydrologic conditions show a progressively altered snow and runoff regime in the watershed. Snow accumulation is reduced and snow melts earlier in the spring. Fall and early winter runoff increases while late spring and summer runoff decreases, and these changes become more significant at the later time periods. Total runoff is projected to decrease under the climate change scenarios evaluated, in some cases marginally and others significantly. The consequences of these potential changes for UTREP efforts is unknown at this time, but will be considered in our ongoing instream flow work.

Monday, December 3, 2012

Sunday, December 2, 2012

Clavey confluence timelapse

This past spring, UC Davis researchers installed time lapse cameras, water stage recorders, and temperature monitoring equipment in both the mainstem Tuolumne River (regulated by Hetch Hetchy Project facilities - particularly Holm Powerhouse) and the Clavey River (an unregulated tributary to the Tuolumne) near their confluence.  Video gurus at UC Davis then layered the time lapse video, stage, and temperature data of both rivers, providing a visual comparison of temperature and hydrology dynamics in the regulated and unregulated streams. This work is part of a larger UC Davis effort to learn more about how tributaries and stream confluences affect hydrology and geomorphology.  Watch the video in HD on Vimeo for best effect, and to learn more about how the video and data were compiled.

Time Lapse Hydrography - Tuolumne and Clavey Rivers 2012 with Temperatures from Center for Watershed Sciences on Vimeo.