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<br />III. Technique Development on Skywater Projects <br /> <br />Park Range Atmospheric Water Resources Program <br /> <br />The Park Range Atmospheric Water Resources Program, which was <br />conducted from 1964 to 1966 in northern Colorado, was the first <br />major Skywater fi el d program desi gned to determi ne to \l/hat extent <br />the precipitation in a mountainous region could be increased by <br />artifi ci a 1 nucl eati on of moi sture-beari ng cloud formations. <br />E. Bollay Associates, Inc., 4/ made field comparisons of precipita- <br />tion measurement equipment at Steamboat Springs, C010rcldo, before <br />establishing a network of sensors. The comparison was made between <br />shielded and unshielded snow boards at different heights, a com- <br />pressed scale weighing gage, a snow pillow, a heated tiipping-bucket <br />gage, and optical snow rate gages. Figure 1 shows the heated <br />tipping-bucket snow rate sensor which was modified with an expanded <br /> <br />aperture, 0.46 m2 (5 ft2), and a I-kilowatt thermostatically <br />controlled heater. The gage operated accurately and reliably in the <br />range of from 0.50~ to 3.810 nun (0.02 to 0.15 in) of water per hour, <br />but difficulties were encountered at the higher intensities. The <br />optical snow rate gage shown in figure 2 consists of a light source <br />and detector operating over a 0.91-meter (3-foot) transmission path. <br />Snowflakes falling through the light beam produce an a-c signal <br />which is amplified and smoothed before recording. An optical snow <br />rate sensor was used at each measurement station to gather data at <br />short time intervals to study the effects of the pulse-.type release <br />of seeding material. . <br /> <br />Washichek and McAndrew 5/ in a report to the Western Snow Conference <br />in 1967 discussed the operation of six snow pillows on the Park <br />Range Program. Numerous problems were encountered with the 3.66-meter <br />(12-foot) diameter pillows including leaking, bridging~ and water <br />enteri ng the battery and transducer boxes. Al though sc1ti sfactory <br />operation of snow pillows was not achieved on this program, some <br />optimism was expressed for th~ir future use. <br /> <br />Bridger Range Cloud Seeding Experiment <br /> <br />Montana State Uni versi ty 6/ conducted a wi nter cloud sE!edi ng experi- <br />ment for the Bureau of Reel amati on in the Sri dger RangE! of southwestern <br />Montana from 1969 to 1972. During the first winter operation, several <br />types of sensors were compared in different size and shaped clearings. <br />Th~ sensors compared included: nonrecording, nonshielded gages of <br />differing orifice size and shape; a shielded weighing gage; a heated <br />tipping-bucket gage; a 3.U5-meter (10-foot) diameter snow pillow; <br />and snow boards. Sensors were checked daily. Wind speed and <br /> <br />.~ <br /> <br />2 <br />