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Update on Wintertime Snowfall Augmentation in the Western U. S.

Update on Wintertime Snowfall Augmentation in the Western U. S. NWRA Annual Meeting Emerging Water Augmentation Strategies 7 March 2012. Arlen Huggins Associate Research Scientist Division of Atmospheric Sciences Desert Research Institute Reno, Nevada.

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Update on Wintertime Snowfall Augmentation in the Western U. S.

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  1. Update on Wintertime Snowfall Augmentationin the Western U. S. NWRA Annual Meeting Emerging Water Augmentation Strategies 7 March 2012 Arlen Huggins Associate Research Scientist Division of Atmospheric Sciences Desert Research Institute Reno, Nevada

  2. Winter Cloud Seeding for Snow/Water Augmentation • Conceptual model for winter cloud seeding • Current research activities • Randomized experiments • Physical studies • Hydrologic modeling • Operational projects in the western U.S. • Upper Colorado River Basin Projects • Colorado, Utah, and Wyoming • Upper and Lower Basin interaction • Summary of snow augmentation status

  3. Conceptual Diagram of Orographic Cloud Seeding Ground-based seeding with silver iodide -10C -5C

  4. Recent Research • Australian Snowy Mountain Project • Funded by Australian government and conducted by Snowy Hydro • 5-year study with randomized seeding of a single target • Published results showed a statistically significant 14% increase in target precipitation for “seeded” events • U. of Wyoming airborne radar study • Radar signal increase noted during seeding periods • Radar signal increase corresponds to a significant precipitation rate increase

  5. Recent Research • WY Weather Modification Pilot Project • Dual-target experiment: one target randomly seeded when cloud conditions are similar over both targets – 4-hour experimental units (EUs) • 121 EUs to date; requesting funding for an additional two years – funded by state of WY • Statistical evaluation of paired seed vs. no-seed precipitation values – 200+ EUs desired • Targeting and environmental assessment using trace chemistry techniques • Unique use of atmospheric modeling for forecasting and evaluation of seeding events • Hydrologic modeling to assess impact of seeding on streamflow in the North Platte RB • U. of WY airborne radar study being repeated • NSF funding (~$1M budget) with more ground based instrumentation • Attempting to verify earlier findings

  6. UW Cloud Radar • 3 mm (95 GHz, W-band), dual-polarization • pulse width: 250-500 ns • max range: 3-10 km • volume resolution @ 3 km range: < 40 m • minimum detectable signal (@ 1 km): ~-30 dBZ • Cloud droplets are much smaller than ice crystals, thus in a mixed-phase cloud, reflectivity is dominated by ice crystals. UW Cloud Lidar • non-coherent eyesafe backscatter lidar • up & down (down only for 4 out of 7 flights) • backscatter power & depolarization ratio • attenuated by cloud layers • lidar & radar can be combined to estimate cloud properties

  7. WWMPP model output of seeding plume trajectories, winds and cloud water content

  8. Weather station controls dispenser Plume of ice crystals Seeding materials & delivery methods

  9. Research on Wintertime Cloud Seeding in Mountainous Terrain • Has verified all the links in the chain of the cloud seeding conceptual model • Has verified ice crystal and precipitation enhancement through physical observations • Has shown evidence of precipitation enhancement through statistical evaluations • Has revealed situations when cloud seeding is ineffective • Does not have all the answers to every meteorological situation where cloud seeding is applied

  10. Operational Cloud Seeding Projects

  11. Nevada Cloud Seeding Projects • Tahoe funded by TMWA and WRWC • Walker Basin funded by BOR (Desert Terminal Lakes Project) • NE Nevada funded by SNWA

  12. Utah Projects Cost share between state and local water groups Cost ~ $370K Est. snow water increase > 150 AF

  13. Colorado Projects in WY2011 – Local Funding plus CWCB/LCRB grants

  14. Areas with snowfall augmentation potential in the UCRB 1967-1968 Runoff Augmentation Estimates 10% increase 1.3 – 1.9 MAF Hunter (USBR, 2005) 2-year SNODAS w/+10% 0.6 – 1.1 MAF Griffith/Solak (NAWC, 2006) NWS Runoff Model 5-15% increase 0.6 – 1.6 MAF

  15. Collaboration between Upper and Lower CRB States in Snow Augmentation Projects • Cooperative agreement between (CO, UT and WY) and (AZ, CA and NV) – in place since 2006 • LCRB funding to: • Extend operations in existing projects in UT & CO • Add new equipment (seeding and observing) in UT & CO • Add additional research equipment (WY) • Apply modeling, physical evaluations, etc. to ongoing projects

  16. Summary of Water Augmentation by Wintertime Cloud Seeding • A reasonably healthy research component • Steady number of operational projects • Funded mainly by state, regional and local water agencies + power companies • Augmentation strategy used for over 50 years • Project evaluations indicate benefits justify costs • Operations being enhanced by interstate/basin cooperative agreements • Instrumentation and modeling advances have improved operational efficiency – room for further improvement • Hydrologic modeling used more to assess water augmentation aspect and its economic, political and environmental benefits

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