c.s.-ccmrb-program-evaluation-2020-2021

Central Colorado Mountains River Basins Weather Modification Program Cloud Seeding Report for the 2020-2021 Winter Season Sponsoring Organizations: Ski Area of Winter Park Front Range

Central Colorado Mountains River Basins Weather Modification Program

Cloud Seeding Report for the 2020-2021

Winter Season Sponsoring Organizations:

Ski Area of Winter Park Front Range Water Council Colorado River Water Conservation District Colorado Water Conservation Board California Six Agency Committee Central Arizona Water Conservation District Southern Nevada Water Authority

Metropolitan Water District of Southern California

November 8, 2020 – April 19, 2021

*Original State Permit extended through end of April 2021

Program Conducted and Report Prepared by:

Mike Hjermstad Eric Hjermstad Larry Hjermstad Alisa Hjermstad WESTERN WEATHER CONSULTANTS, LLC

P.O BOX 58 DURANGO, COLORADO 81302

August 2021 PERMIT # 2017-02 CONTRACT # CA20045-A

TABLE OF CONTENTS:

EXECUTIVE SUMMARY - PAGE 03

INTRODUCTION - PAGE 04

PROJECT INFORMATION - PAGE 06

FORECAST-GUIDED OPERATIONAL PROCEDURES - PAGE 13

OPERATIONAL SUMMARY - PAGE 21

LEASED REMOTE OPERATIONS - PAGE 38

PROCEDURES AND METHODOLOGY FOR ESTIMATING PRECIPITATION INCREASES - PAGE 40

EVALUATION OF SEEDING RESULTS AND EFFECTIVENESS - PAGE 43 RECOMMENDATIONS - PAGE 49

Images:

Image 1 Seeding Response Model - PAGE 43

Image 2 Proof of Insurance - PAGE 52

Figures and Charts:

Images and Graphs associated with operations - PAGES 14-37

Tables:

Table A Generator Locations - PAGE 09

Table B Seeding Criteria- PAGE 10

Table C Summary of Operations - PAGE 23

Table D Estimated Project Increases - PAGE 44

Table E Estimated Runoff Increase by Sub-basin - PAGE 48

Maps:

Map 1 CCMRB Program Target Area - PAGE 05

Map 2 Estimate Precipitation Increase - PAGE 47

Appendices:

Appendix A: Summary by Seeding Event - PAGE 53

Appendix B: Emergency Management - PAGE 117

Appendix C: 2020-21 Target vs Control Report - PAGE 128

2021, was seeded during this extension

Available snowpack data was evaluated by WWC to estimate cloud seeding program effectiveness Results suggest the CCMRB Program activities produced an additional 94,413 to 112,652 AF of water within the target area This range is based on 12% less and 5% more than a “best estimate” of 107,288 AF of volumetric snow water equivalent increase This enhancement resulted in an estimated additional 7 to 17 inches

of snowfall assuming a 10 to 1 snow to water ratio

The estimated increased water yield related to direct cloud seeding expenditures indicates the cost per acre-foot (AF) of water is between $2.54/AF to $3.03/AF, with the

“best estimate” cost of $2.67/AF

INTRODUCTION

This report details the results of the 2020-21 Central Colorado Mountains River Basins Weather Modification Program (CCMRB Program) The first cloud seeding operation was on November 8, 2020, and the last operation was on April 19, 2021 Within this timeframe, there were 32 cloud seeding events which covered 47 days and utilized 2,025.33 hours In addition to the contracted hours there were 252.67 seeding hours provided to the CCMRB Program using two leased DRI remote generators funded by the State and Lower Basin The CCMRB Program uses 17 manually operated cloud nucleating generators and 4 remotely operated generators DRI also operates 2 more remote generators for Winter Park This was the ninth consecutive season for the CCMRB Program

The objective of the CCMRB Program is to increase precipitation through the augmentation of natural precipitation within the project Target Area (Map 1) to improve early season snowpack for ski resort activities and increase the high elevation snowpack which helps replenish the water supply to the Upper Colorado River Basin

The operational technology and procedures used in the CCMRB Program are consistent with other permitted snowpack augmentation programs operated in Colorado Specifically, the CCMRB Program is informed and guided by experience gained from managing and operating various cloud seeding programs over the years This includes the Climax and Wolf Creek Colorado State University research programs (Mielke, 1981), and the observations and experiences gained from more than 45 winters of seeding operations in the Central Colorado and San Juan Mountains under the sponsorship of various entities

The CCMRB Program “Target Area”, as shown in Map 1, is the Upper Colorado River Basin, generally above 8,500 feet, in Pitkin, Summit, Eagle and Grand Counties, with an exclusion area in the Tenmile Creek basin The Upper Colorado River sub basins that are being seeded are the Fryingpan/Roaring Fork, Eagle, Blue River, Williams Fork and the Fraser River basin The CCMRB Program is designed and carefully operated to only impact the defined and permitted Target Area

The following map shows the Target Area along with manual generator locations (Red Stars = CCMRB, Blue Triangles = Vail, Purple Diamonds = Shared Generator Locations, Yellow Flags = SNOTEL sites and Red Pentagons = Desert Research Institute’s (DRI) Remote Generators)

Map 1 Target Areas:

CCMRB Program = Blue Line Light Blue shading

Map 1 Vail & Beaver Creek Program = Red Line within Blue shading

Project Information

Data Services

WWC monitors and evaluates the weather conditions throughout the target area within the contracted operating period for time periods of positive cloud seeding potential The weather data utilized is sourced from the following: The National Weather Service (NWS), University of Wyoming, Pennsylvania and Texas A&M Weather, National Center for Atmospheric Research (NCAR), and National Oceanic and Atmospheric Administration (NOAA) Pivotalweather.com is used for short and long-range model forecasts Information from the Natural Resources Conservation Service (NRCS) website

is used to monitor snowpack in the Target Area, as recorded by the network of SNOTELs

in Colorado and detailed analyses of snow accumulation are completed using these measurements

Additional sources of information were used from the Colorado Department of Transportation (CDOT) to monitor road conditions and concerns, as well as from the Colorado Avalanche Information Center (CAIC) for Weather Research Forecasting (WRF) point forecasts, and to understand the avalanche and potential avalanche conditions in and around the Target Area

From the above listed data sites, WWC reviews, and archives, as needed, weather data such as: surface and upper air data, synoptic surface maps, significant level maps, model forecast data, rawinsonde data, satellite and radar data, surface observations, webcam images, and other forecast aids These data assist in selecting favorable storms for modification and compliance with suspension criteria

Snowpack Suspension Criteria

Pursuant to the State of Colorado issued permit, seeding operations can only occur within the targeted mountain regions under ‘normal’ conditions The comparative normal for these snow observation sites is the last 30-year average updated every 10 years as last published by the NRCS for the 1981 to 2010 time period Historical evaluation of Snow Water Equivalent (SWE) content has indicated that flooding and stream channel capacities can be exceeded when late winter SWE reaches or exceeds 155% of median

More substantial flooding problems can be anticipated when Mid-winter snowpack is more than 175% of median Since the CCMRB Program is designed for reasonable levels of snowpack enhancement and consistent with permit requirements, CCMRB seeding operations will be suspended in seeding areas when one or more of the following SWE conditions are observed: 175% of median on December 1st, 175% of median on January 1st, 165% of median on February 1st, 155% of median average on March 1st and 145%

of median on April 1st

Additionally, seeding operations may be suspended due to high avalanche hazard levels and as such, seeding must be suspended when avalanche hazard levels are triggered for highway corridors, as determined by the CAIC and the NWS “Hazardous Weather Statements”

Specifically, “the permit holder must suspend all weather modification operations whenever one of the following is issued that impacts any part of the Target Area:

a An urban or small stream flood advisory

b A blizzard warning

c A flash flood warning; or

d A severe thunderstorm warning

Operations may resume after these statements have expired.”

WWC corresponds with the county emergency managers within the Target Area counties and adjacent counties prior to the first seeding operation of the seeding season

If at any time an emergency manager determines that additional snowfall would hinder any emergency procedure, operations are to be suspended in such areas as needed to avoid impairing emergency operations On October 27th, 2020, emergency managers were informed via email as to the start date of the 2020-21 seeding season in the Central Rocky Mountains This correspondence letter can be viewed in the Emergency Management Coordination section of the report Appendix B

Seeding Operations, Equipment and Threshold Criteria

WWC enhances the snowpack within the Target Area by producing silver iodide crystals (artificial ice nuclei) from a network of approximately 17 manually operated ground-based generators using a 4% silver iodide and 1.25% sodium iodide solution in acetone

Additionally, there are two remote generators and two leased remote generators in the CCMRB, these use a 2% silver iodide solution The solution from both types of generators is vaporized

in a propane flame at a rate of 5 to 25 grams per hour into a chosen weather system that has a cloud base temperature ranging from -5°C to -16°C and a cloud base at least 500 feet below the height

of the mean mountain crest

Separately, there are 2 remotely operated generators used for seeding Winter Park in the CCMRB Program and are operated

by Desert Research Institute (DRI) Although, DRI coordinates seeding operations with WWC by sending out seeding updates via email as the remotes are turned on and off, remote operations and associated seasonal results are reported separately from this report Open communication between DRI and WWC are made consistently to address any concerns related to suspensions, operations, or extensions to the Program

Table A lists all the generator sites within the CCMRB Program seeding region

Table A CCMRB Program Generator Locations 2020-2021

These generators produce tiny silver iodide crystals and distribute them over the Target Area using favorable wind flows during selected storms to produce increased precipitation over the target area An analysis of low-level wind fields, cloud characteristics, stability parameters, terrain features, and synoptic meteorological features help determine which network of generators will best seed the cloud system over the project area for each seeding opportunity This analytical technique allows for

DBB Wolcott Divide Vail/CCMRB 8194

BC REM Beaver Creek CCMRB-REM3 9512

OC-REM Otter Creek CCMRB-REM6 8080

adjusting the seeding network as new weather information becomes available After the best network of generators is determined to seed a storm, the generator operators are telephoned and instructed to turn on their generators at a specific time, operate at a specific burn rate, and turn the generators off at a specific time These instructions are subject to change by another phone call from the program operators at WWC Continuous monitoring of weather data by of the weather forecasters allows for adjustments related to changing conditions related to criteria of the seeding operation Table B presents the “Seeding Criteria” used by WWC

Table B

Western Weather Consultants Seeding Criteria for Winter Cloud Systems

Seeding Potential and Evaluation

In addition to the specific meteorological criteria utilized to identify a potentially suitable weather event for seeding over the target area in Table B, WWC evaluates the augmentation potential for each weather event selected for seeding The three equally weighted primary factors are used to evaluate the augmentation potential of a weather event: 1.) the average 24-hour wind direction, 2.) the potential total amount of expected

• Cloud bases are at least 500 feet below the mean mountain barrier crest of the Target

Area and are forecast to move lower in elevation from the onset of seeding and

continue throughout the seeding period The weather system has clouds that are

forecast to have vertical heights and moisture content capable of producing natural

precipitation

• Temperatures at the height of 500 feet below the mean mountain crest within the

Target Area are -5°C (23°F.) or colder and are forecast to become colder if at -5°C

• Wind directions and speeds from the surface to cloud-base are observed and forecast

to favor the movement into the intended Target Area of the silver iodide nuclei being

released from the ground-based generator sites

• There are no stable regions or atmospheric inversions between the surface and

cloud-base that would prevent the vertical dispersion of the silver iodide particles from the

surface to at least the -5°C (23°F.) level or colder within the cloud system

• The temperature at approximately 10,000 feet (700 MB) is warmer than -16°C

(3°F.)

precipitation or precipitable water forecast for a specific weather event and 3.) the duration of that weather event

The 24-hour average wind direction has been correlated with the 24-hour seeded precipitation amount reported at observation sites in the target area These augmentation potentials are based upon research that WWC completed in 1976 on data from the Colorado River Basin Pilot Project (CRBPP) and later in a separate study of the Vail Seeding Program in 2001 On average, these studies indicated that average wind directions during 24-hour seeded portions of weather systems moving into the Colorado Target Region from the indicated directions below had increases in precipitation as indicated below:

North-Northwest - precipitation increases of 33%

Northwest - precipitation increases of 25%

West - precipitation increases of 12%

Southwest - precipitation increases of 8%

South - precipitation increases of 5%

The second augmentation factor is the total forecasted precipitation for a targeted weather event Southerly weather events, meaning storms moving into the region with a southerly wind component usually have warmer cloud base temperatures and can hold greater amounts of precipitable water in the cloud system These Southerly storm systems can regularly produce two to three inches of equivalent water in the snowfall from this type of system over one to two days A 5% increase in augmented precipitation will add 0.10 to 0.15 inches of additional water in the snowpack The climatology of Colorado’s winter storms indicated that the mountain regions normally receive about 7 to

8 of these southerly storm types over the winter which produces about 70% of the total water in a winter’s snowpack that is potentially available for the spring runoff (Rasmussen, 1968)

A Northerly weather system, meaning any storm with a Northerly wind component may only have around a half inch of precipitable water it produces over a 24-hour duration with an assumed 25% augmentation multiplier, this system will add an additional 0.13

inches of water in the snow total that it produces The climatology of Colorado’s winter storms indicates that the target area receives about 20 of these Northerly storms on average over the winter which produces about the other 30% of the total water in the seasonal snowpack potentially available for the spring runoff (Rasmussen, 1968)

The third augmentation factor for a specific weather event over the CCMRB is related to duration the storm system will produce precipitation over the target area A weather system that would produce significant precipitation amounts for 24 hours would

be given the highest augmentation potential rating of five (5) for seeding operations if all other criteria factors are favorable A weather system that has less potential and projected to produce about half of the desired precipitation amounts in a shorter duration

of less than a days’ time or the full expected precipitation amount over a day and a half’s time would be rated a three (3) A rating of four (4) would have some or all the three factors between the (3) and (5) ratings It is preferable to seed weather systems that have a rating for seeding potential of (3) or greater for each of the selected seeding operations All the weather systems seeded from November 8, 2020, through April 19,

2021, have been given an augmentation potential rating and can be viewed on Table C (page 23)

Evaluation of this project and operational features of the CCMRB Program are based upon the findings and experience learned through operating the U.S Bureau of Reclamation’s CRBPP in the upper San Juan River Basin (Colorado River Basin Pilot Project (research randomized seeding program), June 1976) The placement of ground-based generators, identification of storm systems with favorable modification potential and concern for public safety and awareness through reasonable operations are some of the refinements incorporated into this wintertime weather modification program The evaluation results of this Program are consistent with research findings from the San Juan CRBPP Program in1976 and the Vail Operational Evaluation, completed by WWC in March 2001 (Vail/Beaver Creek operational seeding program using both 10-and 16-year data sets from two separate precipitation information sources)

In summary, based upon the findings of the San Juan CRBPP Program and the Vail Operational Evaluation, precipitation increases ranging from approximately 10 to 20

percent of the total wintertime precipitation can be expected from optimal cloud seeding operations

Forecast-Guided Operational Procedures

The Global Forecast System (GFS) model produced by the National Centers for Environmental Prediction (NCEP) forecast provides a meteorological outlook up to 84 hours in the future This forecast model helps with early identification of approaching storm system that may be seedable As seedable storms are identified, WWC initiates the operational procedure in the following order: First, comparisons are made to the North American Mesoscale Forecast System (NAM) model forecast, High-Resolution Rapid Refresh (HRRR) model forecast and WRF model forecast for similarities Next, care is taken to make sure there are no suspension criteria restrictions that would affect the chance for any seeding operations If there are no restrictions the storm will then closely

be followed as the storm approaches the target area, monitoring the storm’s characteristics and seeding potential to ensure it will meet the seeding criteria for the initiation of seeding Once it is determined that a storm can be seeded, we will once again check the CAIC website to ensure no restrictions have been issued, then commence with seeding

Figure 1

Figure 1 This is an example of an hourly forecast chart from Pivotalweather.com showing around three tenths of an

inch of precipitation forecast to fall in the Target Areas

As an example, Figure 1 shows a HRRR 1-hour forecast from Pivotalweather.com with projected surface precipitation in the target areas The colored precipitation legend indicates projected precipitation amounts in the target areas are between 0.1 and 0.3 inches for a one-hour period between 8:00 PM and 9:00 PM Wind direction and speed

as well as temperature increments of two degrees are available at the 700 MB elevation

to aide in decision making Pivotalweather.com also provides NAM, GFS, RDPS and other model analysis as well as point Skew-T and Upper Air plot data

Figure 2

Figure 2 Example of a point forecast based on the WRF model from the CAIC website for Breckenridge Ski Area

Timeline charts, like the one from the CAIC website in Figure 2, are helpful in providing a quick look at conditions over a specific point (e.g., Breckenridge Ski Area) This WRF chart shows forecast precipitation, 700 MB temperatures, -5°C height, and

700 MB wind speed and direction

The CAIC has been helpful in working with the cloud seeding industry by providing specific data tailored to the needs of cloud seeding on their website They provide hourly forecast data based on the WRF model pinpointed to the individual target areas NAM and GFS forecast data are also available as a point forecast for the individual target areas The point forecast data provided by the CAIC is also available in a text format Other valuable information found on the CAIC website is the surface weather data that can be used in verifying temperatures, relative humidity values and precipitation in the target areas The CAIC Forecast Sounding tool provides a skew-t diagram for each of the point forecast locations

The CAIC also provides avalanche suspension information WWC will suspend seeding operations when data available from the CAIC, and, in conjunction with CDOT, determine that the highway transportation system is in danger of avalanches that would

be hazardous to the public Figure 3 is an example of suspension data provided by the CAIC The website provides a categorical hazard rating, None/ Notice (green), Caution (yellow) and Warning (red), for mountain passes within the V/BC Program Target Area Each mountain pass includes the date issued and a color-coded rating In cases where two hazard ratings are listed the CAIC is indicating they are expecting the hazard to advance to the next level of hazard in the next 12 to 24 hours if conditions persist In the example below the CAIC is expecting Loveland Pass East to change from Notice (green)

to Warning (red) in the next 12 to 24 hours from the time the hazard rating was issued (12-12-2019 6:52 AM) completely bypassing the Caution hazard rating (yellow)

Figure 3

Figure 3 An example of a Highway Summary from the CAIC website indicating seeding in the Loveland Pass East

area has reached a “Caution” status

The NRCS website also provides a map indicating “seed/no seed” suspension data based on snowpack values listed by the SNOTEL network in Colorado

Figure 4

Figure 4 Map provided by the NRCS that WWC uses as seed / no seed indicator for Snowpack suspension criteria

Figure 4 is an example of the maps provided by the NRCS that WWC uses as seed/no seed indicator based upon our suspension criteria relative to the snowpack conditions throughout Colorado In the example, the green icons indicate “Seed”, yellow icons indicate “Seed with Caution” and red icons indicate “Do Not Seed Daily basin wide reports are also available from the NRCS that are used to determine if snowpack thresholds have been approached or exceeded, Figure 5

In the example, the first column is the SNOTEL name followed by its elevation, actual SWE, median SWE and the percent of median SWE The last 3 columns are the same, but for precipitation

Figure 5

Figure 5 An example of a report from the NRCS showing the Roaring Fork River Basin

WWC approaches the snowpack suspension in two ways First, if there is a Basin wide suspension WWC will not conduct any seeding within that basin Second, if there

is a partial suspension within a basin such that a sub-basin remains below the snowpack suspension criteria with another sub-basin snowpack reading that is reporting SWE above suspension criteria levels WWC would only seed into the areas where snowpack levels were below the criteria levels and will not seed into any area above the criteria level

The CDOT website is also monitored routinely to check road conditions and verify precipitation in the target areas Figure 6 is an example of a CDOT still cam photo that documents precipitation in the target area The image is of the parking lot on Berthoud Pass Snow has covered the pavement and the visual of snow falling onto the hills in the background help us see that there is precipitation in the area

Figure 6

Figure 6 Image is from the CDOT website and shows accumulated snow on Ute Pass

In 2020-21, only a few sub-areas (as indicated by point information that exceeded threshold levels provided by SNOTELs) in the CCMRB Program target area were avoided during seeding events As the snowpack subsided or suspension values changed, seeding continue in these sub-areas There were no basin wide suspensions due to snowpack concerns as noted by the NRCS Moderate avalanche concerns were implied

by the CAIC Cloud Seeder information site during the season but were not high enough

to suspend seeding operations

Operational Summary

Within this section, a brief monthly review is given indicating the climatological conditions, including any conditions or concerns that may have influenced the timing or operating of any part of the generator network during the 166-day permitted seeding season Included with this review are graphs and images to illustrate monthly precipitation totals The Permit for the CCMRB Program allows for seeding from November 1 through April 15th An extension, allowing WWC and DRI to seed into Winter Park and the CCMRB target area through the end of April was granted by the CWCB WWC Operations began for the CCMRB on November 8, 2020, and ended on April 19,

2021, covering 47 seeding days within this timeframe

Appendix A provides a brief meteorological table of each seeding event SNOTEL and Ski Area precipitation data and “Proof of Precipitation” are included to depict the regional coverage of each storm Not every storm that passed over the Target Area was seeded since not every storm met our seeding criteria Appendix A also includes a list of generators used to seed each event Included are the actual on and off times for each generator, the number of hours each generator operated, as well as the amount of silver iodide dispensed by each generator The totals of hours are displayed at the bottom of the generator operations list It should be noted that some generators are shared between programs Generator names such as CCMRB 16 would indicate the generator

is only used to seed for the CCMRB Program Generators denoted like V15 would indicate that that generator is in place for the Vail and Beaver Creek Program but can be used to seed for the CCMRB Program as well Only the hours of seeding for the CCMRB Program will be shown on the generator operational list Table C includes the dates of the seeding operations, Storm Potential Rating (SPR), number of days and generators utilized per operation, total number of hours the generators operated for seeding and the total output of silver iodide used for the Target Area for each event

Summary of 2020-21 Seeding Operations by Month

November had warmer than normal temperatures and slightly less than average precipitation in 2020 There were four seeding events over five days throughout November to start the season

With near average temperatures and near average precipitation, December had eight storms over eleven days that were seedable

January started off slow and warm, but still accounted for five seeding events covering six days February had seven seeding events over eleven days with a new storm passing through about every three to five days By the end of February, the snowpack across Central Colorado was looking good as the month finished up above average in precipitation Only having a close to average snowpack during the season, there had been no suspensions from seeding in any part of the CCMRB Program Target area However, we did avoid directly targeting a few locations as snowpack levels approached suspension levels

March had a total of six seeded storms over eleven days The month ended with average temperatures and precipitation Unfortunately, the overall weather pattern in April only allowed for a total of two seeding events as average temperatures and below-average precipitation defined the month Therefore, an extension to the CCMRB Program’s seeding permit was granted for the continuation of cloud seeding activities through the end of April The final seeding event of the season occurred on April 19,

2021

Overall, the 2020-21winter was characterized by above average temperatures and normal precipitation, resulting in the Central Colorado Mountains having a near average snowpack There is potential to have a few more remotely controlled generators added

to the Program to increase seeding opportunities in areas with a few year-round residents

or where manually operated generators cannot be placed moving into the 2021-22 winter season

TABLE C Operational Summary for 2020-2021 Seeding Season

CCMRB Program

*SPR = Storm Potential Rating as described on page 13.

The site names used by the NRCS to collect SWE amounts used in providing the monthly basin reports for the UCRB are shown in Figure 7

Number of Number of Hours Hours Hours Total AGI AGI AGI AGI

From To Days Generators SPR CCMRB Key/Brk WP Hours CCMRB Key/Brk WP Total

11/8/2020 20:30 11/8/2020 22:00 1 1 5 1.50 0.00 0.00 1.50 28.50 0.00 0.00 28.5 11/9/2020 23:00 11/10/2020 23:00 2 1 2 24.00 0.00 0.00 24.00 456.00 0.00 0.00 456 11/14/2020 2:00 11/14/2020 12:00 1 14 5+ 69.50 0.00 0.00 69.50 803.00 0.00 0.00 803 11/24/2020 3:00 11/24/2020 14:00 1 6 5+ 45.50 0.00 0.00 45.50 697.00 0.00 0.00 697 12/1/2020 6:00 12/1/2020 12:00 1 7 5+ 26.50 0.00 0.00 26.50 292.00 0.00 0.00 292 12/11/2020 8:00 12/11/2020 18:00 1 11 4 63.83 0.00 0.00 63.83 804.50 0.00 0.00 804.5 12/12/2020 8:15 12/12/2020 22:00 1 17 4 129.25 0.00 0.00 129.25 1346.50 0.00 0.00 1346.5 12/14/2020 16:00 12/14/2020 22:00 1 1 5 6.00 0.00 0.00 6.00 114.00 0.00 0.00 114 12/17/2020 22:00 12/18/2020 9:00 2 2 2 22.00 0.00 0.00 22.00 264.00 0.00 0.00 264 12/22/2020 15:45 12/22/2020 22:30 1 12 5+ 55.25 0.00 0.00 55.25 588.50 0.00 0.00 588.5 12/26/2020 21:00 12/27/2020 9:00 2 10 5 83.75 0.00 0.00 83.75 1054.00 0.00 0.00 1054 12/28/2020 17:00 12/29/2020 8:30 2 3 3 35.33 0.00 0.00 35.33 441.08 0.00 0.00 441.0833 1/5/2021 7:00 1/5/2021 21:00 1 13 5 98.75 0.00 7.00 105.75 1030.25 0.00 70.00 1100.25 1/16/2021 4:00 1/16/2021 6:00 1 1 5 2.00 0.00 0.00 2.00 38.00 0.00 0.00 38 1/17/2021 20:30 1/18/2021 9:30 2 7 5 40.50 0.00 14.00 54.50 515.75 0.00 168.00 683.75 1/26/2021 12:00 1/26/2021 20:15 1 11 5 36.75 0.00 6.00 42.75 405.75 0.00 60.00 465.75 1/30/2021 5:00 1/30/2021 11:00 1 4 5 19.00 0.00 0.00 19.00 226.00 0.00 0.00 226 2/3/2021 17:45 2/4/2021 10:00 2 18 5+ 199.00 0.00 2.00 201.00 2093.50 0.00 20.00 2113.5 2/5/2021 8:30 2/5/2021 20:30 1 13 5+ 96.50 0.00 0.00 96.50 1091.00 0.00 0.00 1091 2/9/2021 17:45 2/10/2021 7:30 2 2 2 23.75 0.00 0.00 23.75 237.50 0.00 0.00 237.5 2/12/2021 6:00 2/13/2021 9:30 2 10 4 157.25 0.00 0.00 157.25 1887.00 0.00 0.00 1887 2/15/2021 19:00 2/16/2021 16:00 2 8 5 35.25 0.00 0.00 35.25 397.50 0.00 0.00 397.5 2/20/2021 15:00 2/20/2021 23:15 1 13 5+ 72.25 0.00 0.00 72.25 787.75 0.00 0.00 787.75 2/27/2021 3:30 2/27/2021 8:00 1 2 5 7.00 0.00 0.00 7.00 133.00 0.00 0.00 133 3/4/2021 6:00 3/4/2021 20:45 1 14 5+ 146.92 0.00 0.00 146.92 1781.67 0.00 0.00 1781.667 3/9/2021 21:00 3/10/2021 8:00 2 11 4 88.50 0.00 0.00 88.50 1090.00 0.00 0.00 1090 3/13/2021 16:00 3/14/2021 21:00 2 17 5 232.25 0.00 0.00 232.25 2803.00 0.00 0.00 2803 3/21/2021 1:00 3/23/2021 19:00 3 4 4 23.00 0.00 0.00 23.00 311.00 0.00 0.00 311 3/26/2021 16:00 3/26/2021 21:00 1 3 4+ 12.75 0.00 0.00 12.75 153.00 0.00 0.00 153 3/29/2021 20:30 3/30/2021 7:30 2 6 5+ 61.00 0.00 0.00 61.00 610.00 0.00 0.00 610 4/15/2021 16:45 4/16/2021 6:00 2 11 5+ 61.50 0.00 0.00 61.50 720.50 0.00 0.00 720.5 4/19/2021 17:00 4/19/2021 22:00 1 4 5+ 20.00 0.00 0.00 20.00 240.00 0.00 0.00 240

47 1996.33 0 29 2025.33 23441.25 0 318 23759.25

Figure 7

Figure 7 NRCS Chart showing UCRB snowpack summary providing site names used to define the UCRB

Basin Site Name Elev (ft)

Snow Water Equivalent Percent of Current

(in)

Today's Median (in)

Median Peak (in)

Median Peak Date Today's Median Median Peak

UPPER COLORADO RIVER BASIN

Arapaho Ridge 10960 5.3 5.7 R 22.4 R May 10 93 24 Beaver Ck Village 8500 0.8 2.3 R 12.5 R Apr 02 35 6 Berthoud Summit 11300 2.6 3.7 21.8 Apr 29 70 12 Bison Lake 10880 3.8 6.3 28.2 May 06 60 13 Buffalo Park 9240 4.1 3.0 C 12.5 C Apr 25 137 33 Chapman Tunnel 10110 2.3 N/A N/A N/A * * Copper Mountain 10550 1.7 3.2 15.4 Apr 28 53 11 Elliot Ridge 10520 1.9 N/A N/A N/A * * Fool Creek 11150 5.1 N/A N/A N/A * * Fremont Pass 11400 4.3 4.0 18.6 May 07 108 23 Grizzly Peak 11100 3.6 3.8 17.1 Apr 12 95 21 High Lonesome 10620 2.0 N/A N/A N/A * * Hoosier Pass 11400 3.4 4.2 16.0 Apr 25 81 21 Independence Pass 10600 2.3 4.5 16.5 Apr 09 51 14 Ivanhoe 10400 3.5 3.4 C 14.9 C Apr 28 103 23 Jones Pass 10400 1.8 3.0 C 15.6 C Apr 26 60 12 Kiln 9600 1.0 2.5 11.8 Apr 06 40 8 Lake Irene 10700 3.6 5.0 24.9 Apr 07 72 14 Lynx Pass 8880 2.0 2.3 11.1 Apr 08 87 18

Mc Clure Pass 9500 0.0 3.3 16.3 Apr 05 0 0 Mccoy Park 9480 1.0 3.0 R 16.1 R Apr 02 33 6 Mesa Lakes 10000 0.7 3.7 18.3 Apr 16 19 4 Middle Fork Camp 8940 0.7 2.4 R 11.9 R Apr 14 29 6 Nast Lake 8700 0.9 1.0 7.3 Mar 31 90 12 North Lost Trail 9200 1.2 3.1 16.5 Apr 03 39 7 Phantom Valley 9030 2.5 2.0 9.3 Apr 01 125 27 Schofield Pass 10700 6.3 7.5 33.7 Apr 16 84 19 Stillwater Creek 8720 1.8 1.5 7.2 Mar 19 120 25

November 2020 Seeding Operations

Warmer temperatures are typically observed in the onset of storms through November These warm temperatures can delay the start of seeding and/or prevent the opportunity to seed in some cases NOAA reported that November 2020 was above too much above average in temperatures and below average to average for precipitation In

November there were four seeding events covering five calendar days using 140.50 seeding hours, Table C The 2020-2021 seeding season started out with a ridge of high pressure centered over Colorado for the first seven days of the month After a dry summer and fall the NRCS reported 90% of median snowpack of the Snow Water Equivalent (SWE) in the Upper Colorado River Basin (UCRB) as per the November 1,

2020, NRCS SNOTEL snow/precipitation update report, thanks to a late October snowstorm, however, as stated on their report, this analysis may not be a valid measure

of the actual conditions for the start of November

Figure 8 represents conditions in the Colorado River Basin Headwaters as of the morning of the 2nd of November with snowpack at 78% of median and a comparison to the previous three water years

Figure 8

Figure 8 NRCS Chart showing CRB snowpack summary Nov 2 , 2020.

A series of low-pressure troughs arrived the evening of the 7th with the leading trough too warm for seeding to be effective A second wave arrived in the early hours of the 8th with colder temperatures allowing remote generators to seed for a few hours The third wave passed the area the evening of the 8th to the morning of the 9th Another mid-level trough arrived early morning on the 14th and was seeded until noon when temperatures became too cold for seeding The Berthoud Summit SNOTEL site reported

an increase of 1.9 inches of SWE in the first half of November from 1.2 to 3.1 inches of SWE with three days reporting a SWE increase of 0.30 inches or more Precipitation values also increased 2.5 inches from 1.5 to 4.0 as noted by readings the morning of November 16, 2020 Similarly, at the Chapman Tunnel SNOTEL site SWE values increased by 1.3 inches through the morning of the 16th Precipitation and SWE through

the middle of the month of November were 80% of average precipitation and 101% of median SWE across the UCRB via the NRCS November 16, 2020, SNOTEL Snow/Precipitation Update Report for the Upper Colorado River Basin for the Upper Colorado Headwaters Figure 9 below represents conditions in the Colorado River Basin Headwaters as of the morning of the 15th of November with snowpack at 94% of median and a comparison to the previous three water years

Figure 9

Figure 9 NRCS Chart showing CRB snowpack summary Nov 15, 2020.

The second half of November brought less precipitation to the area than the first half From mid-November through the end of the month there was one day reporting an increase of precipitation of 0.30 or more at the Berthoud Summit SNOTEL site

By the end of November, the snowpack in the UCRB dropped to 76% of median SWE and total precipitation was at 70% of average as described in the December 1, 2020, NRCS report Berthoud Summit and Chapman Tunnel SNOTEL’s ended the month with SWE values increasing from 3.1 to 4.1 at Berthoud Summit and from 2.1 to 2.9 inches at Chapman Tunnel for the month

On the Snow (OTS) is one of many websites that reports daily snowfall for ski resorts across the world Archived daily snowfall is also accessible on the OTS website which makes it one we like to use for ski area snowfall data, and this website tends to be more accurate and timelier with their reporting OTS showed that ski resorts in the Central Colorado Mountains target area had reported mid-Mountain base snow amounts in the range of 17 to 20-inch depths on November 30, 2020

December 2020 Seeding Operations

With a poor start to the winter season, the weather seemed to pick up a bit in December as a series of storms arrived after the 10th through the end of the month

mid-December 2020 was near average for temperatures and near average for precipitation

as reported by NOAA December had eight seeding events, covering eleven calendar days utilizing 421.92 seeding hours, Table C

Of the first 15 days of December, six days reported SWE increase at the Berthoud Summit SNOTEL site with 2 days reporting an increase of 0.30 inches or more The total increase in precipitation in over this timeframe was 1.2 inches with SWE values increasing

by 1.1 inches The first 15 days at the Chapman Tunnel SNOTEL received 0.8 inches of precipitation and 0.8 of an inch SWE The mid-December snowpack in the UCRB had dropped to 73% of median and the total precipitation was at 67% of average as per the NRCS December 16, report Figure 10 represents conditions in the Colorado River Basin

as of the morning of December 15, at 72% of median SWE

Figure 10

Figure 10 NRCS Chart showing UCRB snowpack summary

The second half of December began a somewhat daily increase in SWE that lasted through the end of the month From the 16th through the end of the month the Berthoud Summit SNOTEL site reported a precipitation increase of 2.0 inches and SWE increased

by also 2.0 inches, the Chapman Tunnel SNOTEL site reported a precipitation increase

of 1.8 inches and SWE increased by also 1.4 inches Four seeding operations took place the second half of December

The snowpack in December a little higher than mid-month with 77% of median snowpack in the UCRB and the total precipitation at 70% of average as described in the January 1, 2021, NRCS report Ski resorts in the Central Colorado Mountains reported base snow amounts in the range of 25 to 37-inch depths via the OTS daily web report on December 31, 2020

January 2021 Seeding Operations

In January, the weather pattern was repeating December’s pattern with little precipitation the first half and precipitation every two or three days in the second half

Above average Temperatures and Below average precipitation resulted in five seeding events covering six calendar days in January using 224.00 seeding hours as shown on Table C

The first half of January provided one seeding opportunity on the 5th that produced

a bit precipitation in the Berthoud Summit SNOTEL area An increase of 0.4 inch of precipitation and 0.3 inches of SWE was recorded between the 5th and 6th at the Berthoud Summit SNOTEL. The Chapman Tunnel SNOTEL had an increase of 0.1 inches precipitation and SWE Overall, the first half of January continued to depart the normal average of precipitation and SWE The January 16, 2021, NRCS SWE report values had remained constant in the UCRB at 70% of median SWE and stayed at 65% average for precipitation

The NRCS chart in Figure 11, shows the January 1, 2021, total snowpack was at 78% of average when compared to the historical regional averages of UCRB snowpack from 1987 to 2021 for the same date In the 35 years of available data, on January 1 from 1987 to January 1, 2021, only one year was at or below 60%, ten years are between 61% and 80%, eleven years are between 81% and 100% and thirteen years are at or above 101%

Figure 11

Figure 9 Snowpack percentages for the region on January 1st from 1987 to Jan 1, 2021

From the middle to the end of the month there was a slight change to the weather pattern and more frequent storms began to enter the region Four additional storms were seeded after mid-month covering five calendar days An additional 1.5 inches of precipitation and 1.2 inches of SWE were recorded over the second half of January as

reported by the Berthoud Summit SNOTEL Precipitation and SWE reports at Chapman Tunnel SNOTEL showed a gain of just over a half inch of precipitation and SWE

The February 1, 2021, NRCS report shows that the UCRB ended at 72% of median snowpack and 67% of average total precipitation to end the month of January Ski resorts

in the Central Colorado Mountains reported base snow amounts in the range of 31 to inch depths based on the January 31, 2021, daily snow reports from OTS, ten inches less than a year ago

48-February 2021 Seeding Operations

February in central Colorado had average temperatures and average to above average precipitation as reported by NOAA The month of February started out with a

nice storm on the 3rd into the 4th followed by a few small storms to end the first week From the 8th to the 12th unseasonal warm weather took its toll on SWE values, a more consistent pattern of storms moved over north central Colorado mountains mid-February

to the end of the month Seeding was done over seven cloud seeding events covering eleven calendar days using 593.00 seeding hours, Table C

The NRCS chart in Figure 12, shows a comparison of historical regional averages

of UCRB snowpack from 1968 to 2021 on February 1

Figure 12

Figure 10 Chart shows snowpack percentages for the UCRB region on February 1st from 1968 to present

For this date, the snowpack value was at 72% of average when compared to the historical regional averages of UCRB snowpack from 1987 to 2021 for the same date In

53 years, on February 1 from 1968 to February 1, 2021, twelve years were below 80%, twenty-six years were over 101% and sixteen years were between 81% and 100% of average snowpack

February’s snowpack started to show some improvement after the first half of the month The NRCS February 14, 2021, report showed the UCRB was up to 90% median SWE and 81% average precipitation Berthoud Summit and Chapman Tunnel SNOTELs both showed gains in SWE and precipitation At Berthoud values has risen by 3.1 inches

of precipitation and 2.0 of an inch SWE, while at Chapman Tunnel there were increases

of 3.1 inches precipitation and 2.9 inches SWE

After three short seeding events that met seeding criteria February ended with slightly lower numbers than it had mid-month with total SWE and precipitation values for the UCRB SWE values were at 86% of median and total precipitation was at 79% of average based on the March 1, 2021, NRCS report The Berthoud Summit SNOTEL went from 10.8 inches of precipitation on the first of the month to 15.6 inches at months end gaining 4.8 inches of precipitation and SWE values increased 3.6 inches SWE from 9.1 to 12.7 in February Month end values at Chapman Tunnel SNOTEL went from 6.4 inches of precipitation on the first of the month to 10.8 inches gaining 4.4 inches of precipitation and SWE values increased 4.2 inches SWE from 5.8 to 10.0 inches Ski resorts in the Central Colorado Mountains reported on February 28, 2021, base snow amounts in the range of 41 to 58-inch depths according to OTS

March 2021 Seeding Operations

Average temperatures and average precipitation were reported by NOAA in March

March had six seeding events covering eleven calendar days using 564.42 seeding hours, Table C In the first ten days of the month only one storm brought in notable moisture to the area on the 4th into the 5th when about a half inch of precipitation arrived

in the region Around mid-month storms started arriving every few days bringing much needed precipitation to the area

The NRCS chart in Figure 13 shows that the March 1, 2021, snowpack was 84%

of the long-term average in comparison to historical regional averages of UCRB snowpack from 1968 to 2021 on March 1 In 53 years less 1981, on March 1 from 1968

to March 1, 2021, eight years were below 80%, twenty-four years were over 101% and twenty-one years were between 80% and 100%

Figure 13

Figure 13 Chart shows snowpack percentages for the region on March 1st from 1968 to present

With five days reporting SWE increases the first fifteen days of the month, 2.5 inches of precipitation and 2.6 inches SWE were recorded at the Berthoud Summit SNOTEL and at Chapman Tunnel 1.6 inches of precipitation and 1.5 inches of SWE were measured in that time

By the middle of March SWE values had a slight up-tick for the most part and the NRCS March 16, 2021, report showed the UCRB had slightly risen to 89% of median SWE and 82% average precipitation

The second half of March had three seeding events towards the end of the month that met seeding criteria Berthoud Summit SNOTEL reporting 15.6 inches on the 16th

and 18.0 inches on the 31st gaining 2.4 of inches of SWE and the same amount of precipitation during that time At the end of March, snowpack values in the UCRB had not budged, remaining at 89% of median and total precipitation about 82% of average reported by the NRCS on April 1, 2021 The last records in March the ski resorts recorded

in the Central Colorado Mountains had base snow amounts in the range of 54 to 83-inch depths as reported by OTS

April 2021 Seeding Operations

Storms continued to pass over Colorado in April, near average temperatures and below to well below average precipitation led to many of the storms being too warm for

seeding with silver iodide, however a couple had cold enough temperatures for good seeding On April 19, the final cloud seeding event took place closing out the season as temps remained mostly warm and storm durations were very short for productive seeding April had two seeding events covering three calendar days using 81.5 seeding hours (see Table C)

A seeding extension through the end of April was requested for, and granted by, the CWCB allowing for continued seeding in the CCMRB target area and into Winter Park from the two DRI remote generators

The NRCS chart shown in Figure 14 depicts the monthly average snowpack at 90% of the long-term average in comparison to the historical regional averages of UCRB snowpack from 1968 to 2021 on April 1

Figure 14

Figure 14 Chart shows snowpack percentages for the region on April 1st from 1968 to present

In 53 years, on April 1 from 1968 to April 1, 2021, nine years were below 80%, twenty-six years were 101% or more and nineteen years were between 80% and 100%

By the end of the seeding season in April SWE values were lowering and the UCRB had settled to 80% of median SWE and 79% average precipitation as reported by the NRCS on April 20, 2021

The last records in April the ski resorts recorded in the Central Colorado Mountains had base snow amounts in the range of 43 to 73-inch depths as reported by OTS

Remote Operations

For the 2020-2021 winter season the CWCB and LCRB leased two Desert Research Institute’s (DRI) remote generators The YMCA and Otter Creek remotes were used for seeding in the CCMRB Program independent from the generators contracted with WWC Maintenance and supplying of consumables were provided by DRI while WWC conducted operations of these remotes along with the manually operated generator network

Listed below are the run logs for the YMCA and Otter Creek DRI remote generators:

YMCA Remote Operations

Start Day Time Stop Day Time Hrs Rate Output 11/9/2020 16:20 11/9/2020 19:00 2.67 23 61.33 11/14/2020 3:00 11/14/2020 10:00 7.00 23 161.00 11/24/2020 3:00 11/24/2020 14:00 11.00 23 253.00 12/1/2020 6:00 12/1/2020 10:15 4.25 23 97.75 12/11/2020 9:50 12/11/2020 10:00 0.17 23 3.83 12/14/2020 18:10 12/14/2020 22:10 4.00 23 92.00 12/18/2020 9:00 12/18/2020 11:00 2.00 23 46.00 12/26/2020 22:00 12/27/2020 4:00 6.00 23 138.00 1/5/2021 9:00 1/5/2021 15:00 6.00 23 138.00 1/16/2021 4:00 1/16/2021 6:00 2.00 23 46.00 1/17/2021 20:30 1/18/2021 3:00 6.50 23 149.50 1/30/2021 4:45 1/30/2021 7:15 2.50 23 57.50 2/3/2021 20:15 2/4/2021 2:15 6.00 23 138.00 2/5/2021 11:00 2/5/2021 17:00 6.00 23 138.00 2/12/2021 17:00 2/13/2021 6:00 13.00 23 299.00 2/20/2021 16:20 2/20/2021 22:20 6.00 23 138.00 2/27/2021 2:00 2/27/2021 8:00 6.00 23 138.00 3/4/2021 10:00 3/4/2021 17:00 7.00 23 161.00 3/14/2021 7:00 3/14/2021 18:00 11.00 23 253.00

Otter Creek Remote

There were a few seeding opportunities missed throughout the season due to a few technical issues and running out of propane in the middle and then again at the end

of the seeding season The reason that both sites ran out of propane was due to the late install of the remotes and the lack of propane tank availability caused by the wildfires in the fall of 2020 leading us to use temporary 100lb tanks Installing 250- or 500-gallon propane tanks at these locations is planned for this fall leading into the 2021-22 season

Start Day Time Stop Day Time Hrs Rate Output 11/9/2020 23:00 11/10/2020 3:00 4.00 23 92.00 11/14/2020 3:50 11/14/2020 10:50 7.00 23 161.00 11/24/2020 2:00 11/24/2020 14:00 12.00 23 276.00 12/1/2020 6:00 12/1/2020 10:15 4.25 23 97.75 12/1/2020 15:00 12/1/2020 17:00 2.00 23 46.00 12/11/2020 9:30 12/11/2020 14:00 4.50 23 103.50 12/18/2020 9:00 12/18/2020 11:00 2.00 23 46.00 12/22/2020 16:00 12/22/2020 21:00 5.00 23 115.00 12/26/2020 22:00 12/27/2020 6:00 8.00 23 184.00 1/5/2021 9:00 1/5/2021 16:00 7.00 23 161.00 1/16/2021 4:00 1/16/2021 6:00 2.00 23 46.00 1/17/2021 20:40 1/18/2021 4:00 7.33 23 168.67 1/30/2021 4:30 1/30/2021 7:30 3.00 23 69.00 2/5/2021 9:00 2/5/2021 17:00 8.00 23 184.00 2/12/2021 17:00 2/13/2021 6:00 13.00 23 299.00 2/3/2021 20:30 2/4/2021 4:00 7.50 23 172.50 2/5/2021 11:00 2/5/2021 17:00 6.00 23 138.00 2/12/2021 17:00 2/13/2021 6:00 13.00 23 299.00 2/27/2021 2:00 2/27/2021 8:00 6.00 23 138.00 3/4/2021 10:00 3/4/2021 17:00 7.00 23 161.00 3/14/2021 8:00 3/14/2021 19:00 11.00 23 253.00 3/21/2021 1:00 3/21/2021 5:00 4.00 23 92.00

Procedures and Methodology for Estimating Precipitation Increases

A Weather Modification Act was enacted by the State of Colorado in 1972 The early versions of this Act required permit holders to provide program participants with an annual estimate of the precipitation increases produced by the permitted seeding program For this reason, WWC developed the detailed process used to evaluate the results of seeding activities This Act went through various amendments and was extended for a seven-year period in 2011 following the completion of the Sunset Review Earlier rules and regulations were revised effective July 1, 2012 Article 12 of the 2012 revised rules and regulations, annual reports state: “The permit holder must compile annual reports in accordance with section 36-20-117(3), C.R.S (2011) Annual reporting for ground-based winter operations shall include, at a minimum, target versus control analysis of precipitation or snow water equivalent.”

North American Weather Consultants (NAWC), with headquarters in Sandy, Utah, developed a Target vs Control evaluation methodology for the CCMRB Program for Water Year 2013 For Water Year 2020-21, NAWC’s services were obtained for the required annual evaluation NAWC’s Target vs Control Report for the CCMRB Program for WY2020-21 is attached as an appendix to this report

In addition, a separate WWC evaluation was utilized for estimating the precipitation increases produced by cloud seeding for the 2020-21 winter This evaluation has been used in previous reports and is based on two separate seeding program research analyses conducted by WWC (Colorado River Basin Pilot Project (research randomized seeding program), June 1976; and 10-and 16-year data sets from two separate precipitation sources for the Vail/Beaver Creek operational seeding program March 2001)

The two evaluation programs were conducted over the Colorado Mountains utilizing similar seeding applications and weather event identification criteria Both analyses produced similar seeding response results The research analyses utilized a conservative estimate of the seeding responses to the associated prevailing wind direction of the storm