Laserfiche WebLink
<br />-~ <br /> <br />the Boise target and its upwind controls. No known contamination occurred in the Boise <br />controls because of upwind seeding, and no seeding is known to have occurred in the Boise <br />drainage for the 30-year period prior to the 1993 winter. <br /> <br />Some potential control sites for the other two targets conceivably could have been affected <br />by the Boise target seeding and/or by the widespread operational seeding in Utah. Much or <br />all of the high terrain in Utah just south of the Idaho border has been seeded in recent <br />winters, which could affect both target and control areas in southeastern Idaho. Moreover, <br />the Bear River drainage has been seeded frequently in the past (Griffith et al., 1983), <br />including during the 1988-1989 and 1989-1990 winters. The frequent seeding has reduced <br />the number of nonseed.ed winters available for comparison. For all these reasons the Boise <br />seeding signal, if it exists, should be the most detectable. <br /> <br />5. SNOWPACK SNOW WATER EQUIVALENT OBSERVATIONS <br /> <br />The Idaho cloud seeding program was intended to increase the high elevation snowfall, <br />resulting in a snowpack with higher SWE, which could result in more spring and summer <br />streamflow. Accordingly, measurements of high el19vation SWE are of prime interest in <br />evaluating the seeding. <br /> <br />5.1 Sampling Methods <br /> <br />The SCS has operated a large network of manually-sampled snow courses in the mountains <br />of Idaho and nearby States for several decades. More recently, snow pillows have been <br />incorporated into the observing network. Since about 1980, a radio-telemetry system known <br />as SNOTEL has been become increasing important. The system currently provides daily <br />measurements of SWE from snow pillows, of precipitation from gauges, and of maximum, <br />minimum, and average air temperature. <br /> <br />At several locations, snow courses continued to be manually sampled on a monthly or bi- <br />monthly basis while similar observations were obtained nearby with the SNOTEL system. <br />The approach has been to attempt to demonstrate a good relationship between the two <br />methods over a period of approximately a decade. Once that relationship was established, <br />the snow course was discontinued and future measurements were made automatically by <br />SNOTEL. Accordingly, the snow course has been discontinued at most paired snow course <br />and snow pillow sites. Older snow course data have been adjusted with the relationship <br />established between the two methods so the measurements appear to be from one site. In <br />reality, many SCS snow observing sites are now a hybrid, consisting of estimates based on <br />snow course measurements prior to approximately 1980, and on snow pillow measurements <br />since whenever the pilJlow was installed. <br /> <br />7 <br />