WMOD00315 ‎(2)‎

• Title: Colorado River Augmentation Demonstration Program - Technical Report January 1983 - March 1985
• Date: 4/1/1986
• Weather Modification - Doc Type: Report

SECTION 3
PRECIPITATION INVESTIGATIONS

3.1 Precipitation Gauge
Networks

Limited precipitation gauge networks were operated in the
Grand Mesa area for several purposes during the winter
months of November through March, from January 1983 to
date. Some of the studies concerned the adequacy of the
gauges themselves through intercomparisons with snow-
boards and other gauge types. Other studies considered the
statistics on snowfall intensities, amounts, durations, and fre-
quencies of occurrence relative to meteorological factors of
wind, cloud structure, and cloud top temperature. Gauges
were also used to indicate storm intensity in supe'rcooled
liquid water studies (13). The spatial variations and site cor-
relations were studied to help in the design of future seeding
experiments.

Gauges were located at sites in small clearings of a coniferous
forest, and were further protected from wind effects by Alter-
II wind shields. The sites were accessible, and were serviced
at intervals of 1 week to 1 month, depending on gauge

capacity, clock speeds, and total precipitation accumulated
between servicings.

Three different gauge orifice sizes were studied, the standard
8-inch-dlameter, and gauges with areas two and five times
greater. Clocks supplied daily or weekly rotations for the
charts, which were calibrated in inches. The standard 12-
inch gauge capacity was reduced by factors of two and five
for the larger orifices. A 30-inch capacity gauge was also
tested. Table 3-1 shows the site locations and equipment
combination deployment for the three winter seasons. Be-
cause of the predominance of English units associated with
the dimensions and data from these gauges, such units will
be used in this section In preference to the metric units used
In the other sections.

The Uncompahgre Plateau site was chosen to test its poten-
tial for an upwind control for Grand Mesa. The West Arm
site was chosen as the farthest-west location on the Mesa
that still had adequate tree cover and for its potential as an
upwind control for seeding experiments. The GMQ-West and
-East sites were located near the center of the Mesa where

Table 3-1 - Precipitation gauge sites, and types of gauges by season. 1

Site Latitude Longitude Elevation, Years
feet 1982-83 1983-84 1984-85
Uncompahgre Plateau 38050'05" 108047'32" 9,420 11 w30
11w6
West Arm 39001'39" 108010'27" 10,120 l1w6
11w6
Land's End 39001'38" 108003'52" 10,620 18d2
Mesa Lakes Resort 39002'43" 108005'10" 9,800 11w6
Mesa Lakes 39003'14" 108004'08" 10,050 18d2
GMO West 39002'09" 108001'48" 10,810 18d2 ' 18d2
11d6 11w6
11 w30
8w12
GMO East 39002'49" 108000'52" 10,810 18d2
11w6
Radar-Radiometer 39002'20" 108002'15" 10,410 11d6 18d2
Alexander Lake Lodge 39002'33" 107057'45" 10,290 11d6
Ward Creek 39000'20" 107058'32" 9,560 18d2

'Key to gauge types:
First number denotes orifice diameter: 8 Is 8-lnch (20.3-cm), Ills 11.3-lnch (28.7-cm), and 18 Is 17.9-inch (45.5-cm).
The d or w denotes chart speed, with d = daily rotation and w = weekly rotation.
Second number denotes gauge capacity: 2 Is 2.4 Inches (61 mm), 6 Is 6 Inches (152 mm), 12 Is 12 Inches (305 mm), and 30 Is 30 111ches (762 mm).
For example, lld6 Is a 11.3-lnch (28.7-cm) diameter orifice using daily rotation, and has a 6-lnch (152-mm) capacity.

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