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Tahoe-Truckee Cloud Seeding Project

Tahoe-Truckee Cloud Seeding Project. Water Year 2016. DRI Cloud seeding generator : on ( Sierra Crest). 9-21-16: WRWC Agenda Item 9. Cloud Seeding Winter C louds. Cloud Seeding Winter C louds.

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Tahoe-Truckee Cloud Seeding Project

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  1. Tahoe-Truckee Cloud Seeding Project Water Year 2016 DRI Cloud seeding generator: on (Sierra Crest) 9-21-16: WRWC Agenda Item 9

  2. Cloud Seeding Winter Clouds

  3. Cloud Seeding Winter Clouds • Introduce ice forming aerosols into to liquid water cloud layers colder than +23oF and warmer than +5oF. • Aerosols form embryonic ice crystals. • Ice crystals will collect and freeze cloud drops forming snow that falls as increased precipitation. • Increasing evidence suggests that pollution upstream of the Sierra is reducing precipitation efficiency over the Sierra (e.g. Rosenfield et. al. 2008) Freezing fog/ low clouds (water clouds) Introduce ice and form snowflakes Create additional snowfall

  4. How do we know these clouds are present? Icing: Indicator these non or reduced snowy clouds (with small liquid drops) are present.

  5. Does cloud seeding work? • Cloud seeding can increase snowfall by up to 15% and stream flows up to 8% (peer reviewed scientific publications) • Snowy Precipitation Enhancement Research Project (Snowy Mountains, Australia) • 14% increase in snow • Statistical and trace chemical evidence(Manton et al. 2011) • Southern California Edison (Sierra Nevada) • 4.7% median increase in seeded watershed stream flow (95% confidence) • 68 years of stream flow data (Gornbein 2010) • Wyoming Weather Modification Pilot Project (Medicine Bow/Sierra Madre, WY) • 5 to 15% snow(data corrected) • Statistical, physical, trace chemical and modeling evidence • (Breed et al. 2014)

  6. Are there safeguards built into cloud seeding projects? Yes! Numerous environmental impact studies have been conducted and shown no negative impacts. Many suspension criteria are built into operational projects (e.g flood); - warm storms - snowpack exceeds 150% of the average in midseason, and 140% late in the season seeding operations are suspended.

  7. Does cloud seeding have any significant negative environmental effects?No! • Silver Iodide (AgI) is the primary seeding agent • Occurs in nature (Silver State) • Insoluble in water (remains a solid at high and low temperatures) • No molecular charge (stable won’t disassociate) • Less than 1 oz released per hour by DRI generators – dispersed over hundreds of sq. miles • Not bioavailable (is not biologically available to the ecosystem) • The amounts found in the seeded snow typically 50 parts per trillion (50/1000000000000) or less (Huggins 2015) • Not detectable in soil/runoff or water bodies even after 50 years of cloud seeding. Background 1 part per million. (Mokelumne; Stone 2006) • http://www.weathermodification.org/images/AGI_toxicity.pdf

  8. WY 2016 Tahoe-Truckee network CSG

  9. Identification of cloud seeding weather • Subfreezing liquid clouds • DRI Barker webcam • Aircraft icing reports • Alpine/Squaw webcam • Cloud heights • Surface stations (SLC, TRK) • Webcams • Weather models • Temperatures • Mountain stations/models • Stability (mixing height) • Models/mountain stations • Winds • Models/mountain stations

  10. Tahoe-Truckee Project Summary WY2016 • 38cloud seeding events • 1094total generator hours • 95% seeding efficiency • Estimated additional water added to watershed (19,021 acre-feet (AF))* • Costs $16.25 acre-ft * 6.1 billion gallons (if all added to river enough for 45,240 Truckee Meadows Households

  11. Tahoe-Truckee Winter Summary Storms by month Hours by month

  12. Lake Tahoe height over past year Lake Tahoe Natural Rim Max height 3.89’ without seeding, 15% less storage for year Natural rim reached 10 days later without seeding

  13. WRWC Sponsored Snow Gauges WY2016 Target Control

  14. Validation using gauges control control target target Seeded cases by month Unseeded cases by month

  15. Validation using gaugesOne tailed T-test for equal means Ratios Ratios Eliminate October and May due to sample size issues and unfair advantage to seeded area Greater than 95% confidence that there was a positive seeding effect

  16. New gauges available for WY2017

  17. Potential Partners NV-GOED – UAS project (WY2016) $400K -develop technology (DRI- wx modeling, validation) - UAS project (WY2017) $350K - conduct UAS flights over the northern Truckee watershed, additional wx modeling and validation SMUD – Aircraft project ($250K) - Study cloud seeding plumes in GOED modeling - Work with project this winter doing storm plume tests - If positive results - propose co-funded project for WY2018 State of Nevada – (Potential $680K) - restore state funded program for WY2018 Ski Resorts - met with CEO Squaw, set up basin wide ski resort meeting - meeting at NSAA to educate (Tahoe resorts present) Drone America Cloud Seeding Test aircraft – testing the flare racks

  18. Summary • Water Year 2016 above average 19,021 acre-ft (6.1 billion gallons) • Costs $16.25 acre-ft • Upgrades (cameras, snow gauges, models) improved forecasting and validation • Several potential partners identified • some additional cloud seeding and validation already funded by GOED.

  19. Thank You ! Any questions/comments?

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