WMOD00249

• Contract/Permit #: #97-3
• Applicant: Western Kansas Groundwater
• Project Name: Kansas Weather Modification
• Date: 1/1/1997
• Weather Modification - Doc Type: Public Hearing

Step 4:

The control area average season precipitation for the 1941-1970 time
period was calculated by adding the 30 annual control area averages,
calculated in Step 2, and dividing by 30.

Step 5:

The target area average seasonal precipitation was calculated for the 1941-
1970 and the 1979-1993 time periods, as described in Steps 3 and 4 for
the control area.

If the (1979-1993 target area average seasonal precipitation) minus the (1941-1970
historical target area average seasonal precipitation) exceeds the similar calculated value
for the control area, then it would appear likely that weather modification activities in
the target area have had a positive effect.

If Tl = the 1979-1993 target area average seasonal precipitation, TZ = the 1941-1970
historical target area average seasonal precipitation and C 1 and C2 represent the
corresponding control area averages, then the estimated change in the target area average
seasonal precipitation due to weather modification activities, is calculated by:

Y = (T 1 - TZ) - (Cl - CZ)'

Precipitation Evaluation Results

The results of the analysis of precipitation data are presented in Table 1. It may be seen
from Table I that the average seasonal precipitation for the target area was slightly less
at 11.38 inches for the cloud seeding period from 1979-1993, in comparison to 11.63
inches for the pre-cloud seeding time period of 1941-1970. In contrast, the average
seasonal precipitation for the control area was slightly higher at 12.00 inches for the
cloud seeding period from 1979-1993, in comparison to 11.54 inches in the pre-cloud
seeding time period of 1941-1970. The estimated change in the target area average
seasonal precipitation, in inches, due to weather modification activities is determined
from Table 1 as (11.38 - 11.63) - (lZ.00 - 11.54) = (-0.25) - (0.46) = -0.71 inches.
Hence, it would appear from this table that the cloud seeding activities may have had a
small negative impact on average seasonal rainfall in the target area during the 1979-1993
time period.

Economic Silmificance

A linear regression analysis was roD to determine if there was a statistically significant
linear relationship between the average seasonal precipitation and annual crop values in
the target area during the 1979-1993 time period. It was found that less than 10 percent
of the variability in crop values could be explained by average seasonal precipitation,
which was far from being a statistically significant relationship. Hence, it was concluded
that the estimated change of -0.71 inches in the amount of average seasonal rainfall due
to cloud seeding activities was of no practical economic significance. Apparently other
factors, such as intensity of rainfall events, soil moisture level, timing of rainfall events
with crop moisture needs and seasonal temperatures may be Int'.-::h more important factors
in determining crop value than simply the average seasonai precipitation.

11