WMOD00156

• Applicant: Valley Grovers
• Sponsor Name: Western Weather Consultants
• Project Name: San Luis Valley
• Date: 5/1/1976
• Weather Modification - Doc Type: Report

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InterpretatIon of the results of this Cloud S8eriIng Program.

Since thIs program was operated for only three of the sIx month 1975-76
winter season and only two months of r~cordIng precIpItatIon gauge data
were collected, no sophIsticated statistical evaluation of the precip-
itation data is realistically feasible. However, during the operation
of the pro~ram, a monthly analysis was made of the Soil Conservation
Service ( S.C.S. ) snowcourse observations at about 30 sites in the San
Juan >J[0untAins in Southwestern Colorade. Fourteen of these snowcourse
sites were within the bJunds of the Projest Seeding Area and fifteen
other sites were in the San Juan I'ountains surrounding the Pro,iect Area.
The Project Area and surrounding area sn,wcourse s~tes are listed below:

Project Area
Snowcourse SItes

Silver Lakes
SU'11mitville
Cumbres
Platoro
River Springs
Wolf Creek Summit
l{olf Creek Pass
Upper Rid Grande
Santa Maria
Porcupine
Pool Table
Pass Creek
Love Lake
Lake Humphrey

Surrounding Area
Snowcourse Sites

Cochetopa Pass
I~onarch Pass
Lake City
Ironton Park
Red MountaIn Pass
LIzzard Head Pass
Silverton Sub Stn.
Molas Lake
Spud Mountain
Cascade
Lemon Dam
Upper San Juan
Chamita
Chama Di Tide
Payrole

An: analysis of these snowcourse sites on the first of February indicated
that in the Project Seeding Area, the average snowpack was 76% of normal
based-Upon the 1958-1972 fifteen year average derived by the S.C.S. The
average snowpack in the San Juan Mountains surrounding the Project Area
was 84% of the fifteen year normal.

An analysis of the snowpacks on these same snowcourse sites on the first
of ray, following the three month seeding program, indicated that in the
Project Seeding Area the average snowpack had increased to 132% of~he
fifteen year normal. The average snowpack in the San Juan MountaIns
surrounding the Project Area had increAsed to 100% of normal during this
same three m,nth oeriod.

FIgure 2 shows a olot and analysis of the three month (Feb. to May)
change in the sno;mack thr"ughout the San Juan l1"untain Region. The two
areas of maximum increase in snowoack for this three month veriod are
located in the mid to uoper elevations in the Pr0ject Area. The two
areas of minimum increase (decrease) in snowoack are low elevation sites
that had lost their February snowpack by the May 1, 1976 observation date.

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