WMOD00307 ‎(2)‎

• Title: Evalutation of Operational Cloud Seeding in Western Kansas - Final Report
• Date: 11/1/1987
• State: KS
• Weather Modification - Doc Type: Report

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EV ALVA TION OF OPERATIONAL CLOUD SEEDING IN W&~"TERN
KANSAS

1. INTRODUCTION, SUMMARY, AND CONCLUSIONS

In 1975, agricultural interests in southwestern Kansas organized a weather modification program
to sec~ summer clouds for the purposes of increasing rainfall and suppress~g crop-hail damage.
1be project has continued each year since then, although the project area has: varied as individual
counties elected to participate or not to participate on a yearly basis (figure 1.1). For its first few
yean>, the project was called the "Muddy Road" Project. More recently it, has been Cluled the
Western Kansas Weather ModifICation Project. Administrative suppon for the project is provided
by the Western Kansas Groundwater Management District No.1, headquaftered in Scott City,
Kansas.

The project has been conducted each year during the growing season, which extends from late
April to September. The actual starting and stopping dates vary from year: to year. Se:eding is
carried out each year by several aircraft equipped with one or more types of s~ing devi<:e5. The
silver iodide generators used have included both liquid-fueled generators burning solutions of
silver iodide in acetone and solid (pyrotechnic) generators. Most of tne seeding has been
conducted in updrafts below the bases of convective clouds. During some years, high
performance aircraft capable of cloud-top seeding have been available. The high perlormance
aircraft are equipped with racks for droppable pyrotechnics, dry ice dispensers, lOr both.
Additional information on seeding operations is provided in section 2.

The project has operated on the assumption that additional ice particles pr~ced in the clouds hy
the seeding agents would grow into snowflakes, graupel panicles (sometimes 'called snow pellets),
or small hail, and then melt to raindrops during their fall to the ground. It was reasoned that this
process would tend to increase SUI1}ll1er rainfall and would also, by increaSing the numbers of
frozen precipitation particles, tend to reduce their sizes and thereby decrease the probabililty of any
of tbm1 reaching the ground as hailstones before completely melting to raindxops (the competing
emblYo concept of hail suppression).

Since lenS, the operators of the project have recognized the impolUJllce of ev8tuating the effects of
their operations. Some generally inconclusive analyses of the rainfall data have been published hy
scientists of the illinois State Water Survey (Hsu and Chen [1] and Huff et aJ.. [2]). In 1985, the
Kansas Water Office asked the Bureau of Reclamation's Southwest Regional Office in Amarillo,
Texas, for assistance in evaluating the project. The Southwest Region in turn requested the
Bureau's Engineering and Research Center in Denver, Colorado, to conduct ~ evaluation. Work
got underway in the DARR (Division of Atmospheric Resources Research) in the fall of 1985
under a plan calling for the evaluation to extend through September 1987. 111lis report sununarizes
the evaluation and sets forth the conclusions reached.

The basic approach followed was to acquire rainfall and hail data for the t8l.'get area and a large
surrounding study area and then examine these data for changes that could be attribute:d to the
projc.'Ct activities. In addition, copies of logs of seeding activities were obtairied from the Western
Kansas Groundwater Management District No. 1 so that information about the: location and amount
of seeding could be compared with the rain and hail data. Details are provided in later sections of
dUsJ~pon. '

Daily rainfall data were obtained from the National Climatic Center in Asheville, Nonh Carolina.
Crop-hail loss data were obtained from the Crop-Hail1nsurance Actuarial AssOCiation of Chicago,